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  • 1.
    Aasa, Jenny
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Cancer Risk Assessment of Glycidol: Evaluation of a Multiplicative Risk Model for Genotoxic Compounds2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Humans are exposed to chemical compounds in everyday life, both from the environment and from endogenous processes. Some compounds constitute a risk for cancer development. One such compound is glycidol, which is genotoxic and an animal carcinogen. It is the model compound of this work, partly due to its presence in food. Glycidol, often together with 3-monochloropropane-1,2-diol (3-MCPD), occurs in the form of esters particularly in refined cooking oils, which are used in a variety of food products. The esters are hydrolyzed in the gastrointestinal tract to form glycidol (and 3-MCPD).

    The aim of the thesis has been to evaluate an approach for cancer risk estimation of genotoxic carcinogens based on a multiplicative (relative) risk model and genotoxic potency. Further, the aim was to estimate the cancer risk for exposure to glycidol via food. Measurement of the internal doses (concentration × time) of glycidol in the studied biological systems, including humans, has been crucial. Glycidol is electrophilic and forms adducts with nucleophilic sites in proteins and DNA. The doses of glycidol were quantified by mass spectrometry: in vivo from adduct levels to hemoglobin (Hb); in vitro from adducts to cob(I)alamin.

    The first part of the thesis concerns the genotoxic potency (genotoxic response per internal dose) of glycidol, measured in vitro by mutation studies and in vivo by micronuclei as a biomarker for genotoxicity (short-term studies in mice). The results were compared to that of ionizing radiation, used as a standard, to estimate the relative genotoxic potency of glycidol: 10 and 15 rad-equ./mMh from mutations and micronuclei, respectively. No induction of micronuclei was observed for the related compound 3-MCPD.

    Tumor incidence from published carcinogenicity studies of glycidol in mice and rats, together with the measured in vivo doses, was evaluated with the relative cancer risk model. A good agreement between predicted and observed tumor incidence was shown, and no significant difference of the obtained cancer risk coefficients (risk per dose) between mice (5.1 % per mMh) and rats (5.4 % per mMh) was observed. The overall results support that the relative risk coefficient (β) is independent of sex, tumor site, and species, and indicated that it can be transferred also to humans. The doubling dose, expressed as 1/β, is the dose that is required to double the background tumor incidence. The mean of the doubling doses from mice and rats (19 mMh) was assumed valid for risk estimation for humans. Transfer of β of glycidol to rad-equ. via its relative genotoxic potency showed a risk coefficient in agreement with the relative cancer risk coefficient of ionizing radiation.

    In the final work, the lifetime (70 years) in vivo doses of glycidol were calculated from measured Hb adduct levels in blood from 50 children and 12 adults, and compared to the doubling dose. A fivefold variation was observed in the in vivo doses. The estimated lifetime excess cancer risk from glycidol exceeds 1/1000. This is much higher than what is considered as an acceptable risk.

    To conclude, the multiplicative (relative) risk model together with relative genotoxic potency is promising to use in an approach for cancer risk estimation and in line with 3R (reduce-refine-replace) initiatives.

  • 2.
    Aasa, Jenny
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Abramsson-Zetterberg, Lilianne
    Carlsson, Henrik
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Törnqvist, Margareta
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    The genotoxic potency of glycidol established from micronucleus frequency and hemoglobin adduct levels in mice2017In: Food and Chemical Toxicology, ISSN 0278-6915, E-ISSN 1873-6351, Vol. 100, p. 168-174Article in journal (Refereed)
    Abstract [en]

    Glycidol is a genotoxic animal carcinogen that has raised concern due to its presence in food, as glycidyl fatty acid esters. Here we investigated the genotoxicity of glycidol in BalbC mice (0-120 mg/kg) by monitoring the induction of micronuclei in peripheral blood as a marker of chromosomal damage. The scoring of the micronuclei was assessed by flow cytometry. In the treated mice, the internal dose of glycidol, expressed as area under the concentration-time curve, AUC (mol x L-1 x h; Mh), was measured by dihydroxypropyl adducts to hemoglobin (Hb). The study showed that glycidol induced linear dose dependent increases of Hb adducts (20 pmol/g Hb per mg/kg) and of micronuclei frequencies (12 parts per thousand per mMh). Compared to calculations based on administered dose, an improved dose-response relationship was observed when considering internal dose, achieved through the applied combination of sensitive techniques used for the scoring of micronuclei and AUC estimation of glycidol in the same mice. By comparing with earlier studies on micronuclei induction in mice exposed to ionizing radiation we estimated the radiation dose equivalent (rad-eq.) of glycidol to be ca 15 rad-eq./mMh.

  • 3.
    Aasa, Jenny
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Törnqvist, Margareta
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Abramsson-Zetterberg, Lilianne
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. National Food Agency, Sweden.
    Measurement of micronuclei and internal dose in mice demonstrates that 3-monochloropropane-1,2-diol (3-MCPD) has no genotoxic potency in vivo2017In: Food and Chemical Toxicology, ISSN 0278-6915, E-ISSN 1873-6351, Vol. 109, p. 414-420Article in journal (Refereed)
    Abstract [en]

    In this study 3-monochloropropane-1,2-diol (3-MCPD), a compound that appears as contaminant in refined cooking oils, has been studied with regard to genotoxicity in vivo (mice) with simultaneous measurement of internal dose using state-of-the-art methodologies. Genotoxicity (chromosomal aberrations) was measured by flow cytometry with dual lasers as the frequency of micronuclei in erythrocytes in peripheral blood from BalbC mice intraperitoneally exposed to 3-MCPD (0, 50, 75, 100, 125 mg/kg). The internal doses of 3-MCPD in the mice were calculated from N-(2,3-dihydroxypropyl)-valine adducts to hemoglobin (Hb), quantified at very low levels by high-resolution mass spectrometry.

    Convincing evidence for absence of genotoxic potency in correlation to measured internal doses in the mice was demonstrated, despite relatively high administered doses of 3-MCPD. The results are discussed in relation to another food contaminant that is formed as ester in parallel to 3-MCPD esters in oil processing, i.e. glycidol, which has been studied previously by us in a similar experimental setup. Glycidol has been shown to be genotoxic, and in addition to have ca. 1000 times higher rate of adduct formation compared to that observed for 3-MCPD. The conclusion is that at simultaneous exposure to 3-MCPD and glycidol the concern about genotoxicity would be glycidol.

  • 4.
    Aasa, Jenny
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Törnqvist, Margareta
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Granath, Fredrik
    Cancer risk estimation of glycidol based on rodent carcinogenicity studies, a multiplicative risk model and in vivo dosimetryManuscript (preprint) (Other academic)
    Abstract [en]

    Here we evaluate a multiplicative (relative) risk model for more reliable cancer risk estimations of genotoxic compounds. According to this model, cancer risk is proportional to background tumor incidence and to internal dose of the genotoxic compound. A relative risk coefficient is considered to be common across species, sex, and tumor sites. The model has previously been shown to be successfully applied to rodent carcinogenicity data for a few genotoxic compounds. The aim of the present study was to evaluate this risk model for glycidol, a common food contaminant. Tumor data from published glycidol carcinogenicity studies in mice and rats were evaluated with the model, using internal doses estimated from hemoglobin adduct measurements in blood of B6C3F1 mice and Sprague Dawley rats treated with glycidol in short-term exposure studies.

    The evaluation demonstrated that the relative risk model is valid for glycidol. A good agreement between predicted and observed tumor incidence was demonstrated in the animals, supporting a relative risk coefficient that is independent of species, sex, and tumor site. There was no significant difference of the risk coefficients between mice (5.1 % per mMh) and rats (7.1 % per mMh) when the internal doses of glycidol were considered. Altogether, this mechanism-based risk model gives a common and more reliable risk coefficient which could be extrapolated to humans via internal dose measurements, and by considering the background cancer incidence.

  • 5.
    Aasa, Jenny
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Vare, Daniel
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Motwani, Hitesh V.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Jenssen, Dag
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Törnqvist, Margareta
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Quantification of the mutagenic potency and repair of glycidol-induced DNA lesions2016In: Mutation research. Genetic toxicology and environmental mutagenesis, ISSN 1383-5718, E-ISSN 1879-3592, Vol. 805, p. 38-45Article in journal (Refereed)
    Abstract [en]

    Glycidol (Gly) is an electrophilic low-molecular weight epoxide that is classified by IARC as probably carcinogenic to humans. Humans might be exposed to Gly from food, e.g. refined vegetable oils, where Gly has been found as a food process contaminant. It is therefore important to investigate and quantify the genotoxicity of Gly as a primary step towards cancer risk assessment of the human exposure. Here, quantification of the mutagenic potency expressed per dose (AUC: area under the concentration time curve) of Gly has been performed in Chinese hamster ovary (CHO) cells, using the HPRT assay. The dose of Gly was estimated in the cell exposure medium by trapping Gly with a strong nucleophile, cob(I)alamin, to form stable cobalamin adducts for analysis by LC-MS/MS. Gly was stable in the exposure medium during the time for cell treatment, and thus the dose in vitro is the initial concentration x cell treatment time. Gly induced mutations in the hprt-gene at ante of 0.08 +/- 0:01 mutations/10(5) cells/mMh. Through comparison with the effect of ionizing radiation in the same system a relative mutagenic potency of 9.5 rad-eq./mMh was obtained, which could be used for comparison of genotoxicity of chemicals and between test systems and also in procedures for quantitative cancer risk assessment. Gly was shown to induce strand breaks, that were repaired by base excision repair. Furthermore, Gly-induced lesions, present during replication, were found to delay the replication fork elongation. From experiments with repair deficient cells, homologous recombination repair and the ERCC1-XPF complex were indicated to be recruited to support in the repair of the damage related to the stalled replication elongation. The type of DNA damage responsible for the mutagenic effect of Gly could not be concluded from the present study.

  • 6.
    Aasa, Jenny
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Vryonidis, Efstathios
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Abramsson-Zetterberg, Lilianne
    Törnqvist, Margareta
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Internal dose of glycidol in children and estimation of associated cancer riskManuscript (preprint) (Other academic)
    Abstract [en]

    Children are more susceptible to exposures to harmful compounds compared to adults. Monitoring of the actual exposures in vivo is important to enable risk mitigation actions. The general population, including children, is exposed to the carcinogen glycidol through food. A possible exposure source to glycidol is food containing refined cooking oils where it is present as a process-induced contaminant in the form of fatty acid esters.

    In the present study internal (in vivo) doses of the genotoxic and carcinogenic compound glycidol have been determined in a cohort of 50 children and in a reference group of 12 adults (non-smokers and smokers). The lifetime in vivo doses of glycidol have been calculated from the levels of the hemoglobin (Hb) adduct N-(2,3-dihydroxypropyl)-valine in blood samples from the subjects, demonstrating about a 5-fold variation between the children (71–322 µMh). This variation is likely due to different dietary habits and/or different genotypes/phenotypes of the enzymes involved in the detoxification of glycidol. Data from the adults indicate that the non-smoking subjects are exposed to about the same level as the children, whereas the smoking subjects have about double levels, likely due to the presence of glycidol in tobacco smoke. The estimated exposure to glycidol in the children is higher than those estimated by European Food Safety Authority.

    The calculated relative cancer risk increment due to glycidol exposure demonstrated an unacceptable risk for all subjects. The excess lifetime risk based on the estimated lifetime in vivo doses of glycidol exceeded 1/1000, which should be compared to a generally applied acceptable lifetime risk level of 1/100 000. A small contribution to the internal dose of glycidol from other precursors to the measured Hb adduct, and corresponding contribution to estimated risks from intake of glycidol from food cannot though be excluded.

  • 7. Abbas, Sk Jahir
    et al.
    Ramacharyulu, P. V. R. K.
    Lo, Hsin-Hsi
    Ali, Sk Imran
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ke, Shyue-Chu
    A catalytic approach to synthesis of PLP analogs and other environmental protocols in a single handed CaO/TiO2 green nanoparticle2017In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 210, p. 276-289Article in journal (Refereed)
    Abstract [en]

    As our precursory stage we have focus straight forward on clean catalytic approach for the production of C3 substituted pyridoxal-5 '-phosphate analogues of vitamin B6, and other environmental protocols like photocatalytic activity, green fossil fuels and c-c coupling using efficient biocompatible eggshell related unrivalled materials which show versatility of the catalytic effect on different inorganic support. The eggshell immobilized nanoparticles have encouraging relevance in creation of new molecules and can advantageously be studied by various spectroscopic, thermal and elemental analyses like powder X-ray diffraction (XRD), Raman spectroscopy, UV-vis, Scanning electron microscopy (SEM), Energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) surface area analysis. The elucidate nature of nanoparticles offer: more active site acts as lewis acid, vacancies on the catalyst surface and good to better yield of C3 substituted deoxy and 2-nor deoxy coenzyme pyridoxine (PN), coupling products propargylamines (PA), photo degrading enhancement of MB and nucleophilic substituted fatty acid (BD). This enzyme cofactor explore molecular synthons to synthetic equivalent: 3-deoxy and 2-nor-3-deoxy pyridoxal (PL), pyridoxal oxime (P0), pyridoxamine (PM) and mono phosphate derivative of 3-deoxyPM, 3-deoxyPL respectively and chemistry of selective oxidation and schiff base mechanism was studied and complemented through combined experimental and theoretical molecular orbital calculation consequently. The heterogeneous catalyst has strong selective ability towards selective reducing pyridine diester, bioactive intermediates substances and holds vast potential towards separation for the photogenerated electron-hole pairs and renewable, nontoxic, biodegradable green fossil fuels. The catalyst including environmental concern is reapplicable and strong impressive that can unfold the space of worthy metal component widely and facilitate the scope to take a vital role in different fileds like catalysis, biochemistry, nanoscience, energy and materials science.

  • 8.
    Abbasi, Alireza
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Structural and Spectroscopic Studies of Solvated Metal Ions2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Crystallographic and spectroscopic studies have been performed of structures, coordination and chemical bonding for series of trivalent metal ions solvated by two oxygen-coordinating solvents, water and dimethyl sulfoxide (DMSO). The hydrated scandium(III) and lanthanoid(III) ions, La to Lu, are surrounded by tricapped trigonal prisms of aqua ligands in the isomorphous series of trifluoromethanesulfonates, [M(H2O)n](CF3SO3)3. For the smallest ions, M = Er, Tm, Yb, Lu, Sc, the hydration numbers decrease, n = 8.96(5), 8.8(1), 8.7(1), 8.5(1), 8.0(1), respectively, with decreasing size of the ion. The crystal structures at ambient temperature indicate randomly distributed vacancies of the capping oxygen atoms, and 2H solid-state NMR of the diamagnetic [M(H2O)n](CF3SO3)3, M = Sc, Lu, Y and La compounds revealed increasing mobility of the water ligands in the coordination sphere with increasing temperature, also for the fully nonahydrated LaIII and YIII ions. The stretching force constants of the Ln-O bonds, evaluated from vibrational spectroscopy, increased from 0.81 to 1.16 N cm-1 for the Ln-6O trigonal prism in a smooth correlation with the bond distances from La to Lu. For the capping Ln-3O bonds the increase from 0.49 to 0.65 N cm-1 reflects the increased ligand-ligand repulsion with decreasing ion size. This is also the reason for the water deficiency of the Er, Tm, Yb, Lu and Sc salts, and for [Sc(H2O)8.0](CF3SO3)3 the repulsion induced a phase transition at about 185 K that, by low temperature crystallography, was found to distort the coordination of water molecules toward a monocapped trigonal prism around the scandium(III) ion.

    All crystal structures of the octakis(dimethyl sulfoxide)lanthanoid(III) iodides comprise discrete [Ln(dmso)8]3+ complexes surrounded by iodide ions. The lanthanum(III) and praseodymium(III) compounds crystallize in the orthorhombic space group Pbca with more efficient packing than for the heavier and smaller ions in the lanthanoid series, which crystallize in the monoclinic space group P21/n. The group 13 metal ions, aluminium(III), gallium(III), indium(III), thallium(III), and also scandium(III) of group 3, form crystalline hexakis(dimethyl sulfoxide) solvates in the space group R 3, with octahedral MO6 coordination entities, which are increasingly compressed along one threefold axis for increasing ionic size. EXAFS measurements on the solvated ions display similar M-O bond distances in dimethyl sulfoxide solution as in the solid solvates. For all the solid dimethyl sulfoxide solvates the strength and nature of the metal-oxygen bond has been evaluated by normal coordinate analysis of vibrational spectra, and correlated with the S-O stretching vibrational mode.

    Distortions from regular octahedral six coordination are discussed for the hydrated isoelectronic soft mercury(II) and thallium(III) ions in the solid bisaquamercury(II) and trisaquatallium(III) trifluoromethanesulfonates, in terms of pseudo Jahn-Teller effects (PJTE). Mercury(II), generally more strongly influenced by PJTE distortions, displays a 2 + 4 Hg-O coordination forming chains that are held together in sheets by hydrogen bonds and in layers by van der Waals interactions, which explain the fragile structure of the crystals.

  • 9. Abbasi, Alireza
    et al.
    Damian Risberg, Emiliana
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Mink, Janos
    Persson, Ingmar
    Sandström, Magnus
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Sidorov, Yurii V.
    Skripkin, Mikhail Yu.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Ullström, Ann-Sofi
    Crystallographic and Vibrational Spectroscopic Studies of Octakis(dimethyl sulfoxide)lanthanoid(III) Iodides2007In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 46, no 19, p. 7731-7741Article in journal (Refereed)
    Abstract [en]

    The octakis(DMSO) (DMSO = dimethylsulfoxide) neodymium(III), samarium(III), gadolinium(III), dysprosium(III), erbium(III), and lutetium(III) iodides crystallize in the monoclinic space group P21/n (No. 14) with Z = 4, while the octakis(DMSO) iodides of the larger lanthanum(III), cerium(III), and praseodymium(III) ions crystallize in the orthorhombic space group Pbca (No. 61), Z = 8. In all [Ln(OS(Me2)8]I3 compounds the lanthanoid(III) ions coordinate eight DMSO oxygen atoms in a distorted square antiprism. Up to three of the DMSO ligands were found to be disordered and were described by two alternative configurations related by a twist around the metal−oxygen (Ln−O) bond. To resolve the atomic positions and achieve reliable Ln−O bond distances, complete semirigid DMSO molecules with restrained geometry and partial occupancy were refined for the alternative sites. This disorder model was also applied on previously collected data for the monoclinic octakis(DMSO)yttrium(III) iodide. At ambient temperature, the eight Ln−O bond distances are distributed over a range of about 0.1 Å. The average value increases from Ln−O 2.30, 2.34, 2.34, 2.36, 2.38, 2.40 to 2.43 Å (Ln = Lu, Er, Y, Dy, Gd, Sm, and Nd) for the monoclinic [Ln(OSMe2)8]I3 structures, and from 2.44, 2.47 to 2.49 Å (Ln = Pr, Ce, and La) for the orthorhombic structures, respectively. The average of the La−O and Nd−O bond distances remained unchanged at 100 K, 2.49 and 2.43 Å, respectively. Despite longer bond distances and larger Ln−O−S angles, the cell volumes are smaller for the orthorhombic structures (Ln = Pr, Ce, and La) than for the monoclinic structure with Ln = Nd, showing a more efficient packing arrangement. Raman and IR absorption spectra for the [Ln(OS(CH3)2)8]I3 (Ln = La, Ce, Pr, Nd, Gd, Tb, Dy, Er, Lu, and Y) compounds, also deuterated for La and Y, have been recorded and analyzed by means of normal coordinate methods. The force constants for the Ln−O and S−O stretching modes in the complexes increase with decreasing Ln−O bond distance and show increasing polarization of the bonds for the smaller and heavier lanthanoid(III) ions.

  • 10. Abbasi, Alireza
    et al.
    Geranmayeh, Shokoofeh
    Skripkin, Mikhail Y.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Potassium ion-mediated non-covalent bonded coordination polymers2012In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, no 3, p. 850-859Article in journal (Refereed)
    Abstract [en]

    Crystal structures and vibrational spectra of three related network-forming coordination complexes have been studied. Two novel thermodynamically stable pseudo-polymorphic solvated rhodium chloro compounds, [cis-RhCl4(DMSO-kappa S)(2)K](n), 1, and [cis-RhCl4(DMSO-kappa S)(2)K center dot 3H(2)O](n), 2, and one metastable compound [trans-RhCl4(DMSO-kappa S)(2)K center dot 0.25H(2)O](n), 3, crystallize at ambient temperature in the orthorhombic space group P2(1)2(1)2(1) for 1, and the monoclinic space groups P2(1)/n and P2(1)/c for 2 and 3, respectively. All three structures contain [RhCl4(DMSO-kappa S)(2)]-complexes in which the rhodium(III) ions bind to two dimethyl sulfoxide (DMSO) sulfur atoms and four chloride ions in distorted octahedral coordination geometries. The complexes are connected in networks via potassium ions interacting with the Cl- and the DMSO oxygen atoms. As the sum of Shannon ionic radii of K+ and Cl- exceeds the K-Cl distances in compounds under study, these compounds can be described as Rh-Cl-K coordination polymers with non-covalent bonding, which is not common in these systems, forming 1- and 2-D networks for 1/2 and 3, respectively. The 2-D network with nano-layered sheets for compound 3 was also confirmed by TEM images. Further evaluation of the bonding in the cis- and trans-[RhCl4(DMSO-kappa S)(2)](-) entities was obtained by recording Raman and FT-IR absorption spectra and assigning the vibrational frequencies with the support of force-field calculations. The force field study of complexes reveals the strong domination of trans-effect (DMSO-kappa S > Cl) over the effect of non-covalent bonding in coordination polymeric structures. The comparison of calculated RhCl, RhS and SO stretching force constants showed evidence of K+-ligand interactions whereas direct experimental evidences of K+-Cl- interaction were not obtained because of strong overlap of the corresponding spectral region with that where lattice modes and Rh-ligand bendings appear.

  • 11. Abbasi, Alireza
    et al.
    Skripkin, Mikhail Yu.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Torapava, Natallia
    Ambidentate coordination of dimethyl sulfoxide in rhodium(III) complexes2011In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 40, no 5, p. 1111-1118Article in journal (Refereed)
    Abstract [en]

    The two dimethyl sulfoxide solvated rhodium(III) compounds, [Rh(dmso-kappa O)(5)(dmso-kappa S)](CF(3)SO(3))(3) (1 & 1* at 298 K and 100 K, respectively) and [Rh(dmso-kappa O)(3)(dmso-kappa S)(2)Cl](CF(3)SO(3))(2) (2), crystallize with orthorhombic unit cells in the space group Pna2(1) (No. 33), Z = 4. In the [Rh(dmso)(6)](3+) complex with slightly distorted octahedral coordination geometry, the Rh-O bond distance is significantly longer with O trans to S, 2.143(6) angstrom (1) and 2.100(6) angstrom (1*), than the mean Rh-O bond distance with O trans to O, 2.019 angstrom (1) and 2.043 angstrom (1*). In the [RhCl(dmso)(5)](3+) complex, the mean Rh-O bond distance with O trans to S, 2.083 angstrom, is slightly longer than that for O trans to Cl, 2.067(4) angstrom, which is consistent with the trans influence DMSO-kappa S > Cl > DMSO-kappa O of the opposite ligands. Raman and IR absorption spectra were recorded and analyzed and a complete assignment of the vibrational bands was achieved with support by force field calculations. An increase in the Rh-O stretching vibrational frequency corresponded to a decreasing trans-influence from the opposite ligand. The Rh-O force constants obtained were correlated with the Rh-O bond lengths, also including previously obtained values for other M(dmso)(6)(3+) complexes with trivalent metal ions. An almost linear correlation was obtained for the MO stretching force constants vs. the reciprocal square of the MO bond lengths. The results show that the metal ion-oxygen bonding of dimethyl sulfoxide ligands is electrostatically dominated in those complexes and that the stretching force constants provide a useful measure of the relative trans-influence of the opposite ligands in hexa-coordinated Rh(III)-complexes.

  • 12.
    Abdel Rehim, Abbi
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Abdel Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Screening and determination of drugs in human saliva utilizing microextraction by packed sorbent and liquid chromatography-tandem mass spectrometry2013In: BMC Biomedical chromotography, ISSN 0269-3879, E-ISSN 1099-0801, Vol. 27, no 9, p. 1188-1191Article in journal (Refereed)
    Abstract [en]

    This study presents a new method for collecting and handling saliva samples using an automated analytical microsyringe and microextraction by packed syringe (MEPS). The screening and determination of lidocaine in human saliva samples utilizing MEPS and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were carried out. An exact volume of saliva could be collected. The MEPS C-8-cartridge could be used for 50 extractions before it was discarded. The extraction recovery was about 60%. The pharmacokinetic curve of lidocaine in saliva using MEPS-LC-MS/MS is reported.

  • 13.
    Abdelhamid, Hani Nasser
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lanthanide Metal-Organic Frameworks and Hierarchical Porous Zeolitic Imidazolate Frameworks: Synthesis, Properties, and Applications2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents the synthesis, properties, and applications of two important classes of metal-organic frameworks (MOFs); lanthanide MOFs and hierarchical porous zeolitic imidazolate frameworks (ZIFs). The materials have been characterized using a wide range of techniques including diffraction, imaging, various spectroscopic techniques, gas sorption, dynamical light scattering (DLS) and thermogravimetric analysis (TGA).

    In Chapter 1, the unique features of MOFs and ZIFs as well as their potential applications are summarized. In Chapter 2, different characterization techniques are presented.

    Chapter 3 describes a family of new isoreticular lanthanide MOFs synthesized using tri-topic linkers of different sizes, H3L1-H3L4, denoted SUMOF-7I-IV (Ln) (SU; Stockholm University, Ln = La, Ce, Pr, Nd, Sm, Eu and Gd, Paper I). The SUMOF-7I-III (Ln) contain permanent pores and exhibit exceptionally high thermal and chemical stability. The luminescence properties of SUMOF-7IIs are reported (Paper II). The influences of Ln ions and the tri-topic linkers as well as solvent molecules on the luminescence properties are investigated. Furthermore, the potential of SUMOF-7II (La) for selective sensing of Fe (III) ions and the amino acid tryptophan is demonstrated (Paper III). 

    Chapter 4 presents a simple, fast and scalable approach for the synthesis of hierarchical porous zeolitic imidazolate framework ZIF-8 and ZIF-67 using triethylamine (TEA)-assisted approach (Paper IV). Organic dye molecules and proteins are encapsulated directly into the ZIFs using the one-pot method. The photophysical properties of the dyes are improved through the encapsulation into ZIF-8 nanoparticles (Paper IV). The porosity and surface area of the ZIF materials can be tuned using the different amounts of dye or TEA. To further simplify the synthesis of hierarchical porous ZIF-8, a template-free approach is presented using sodium hydroxide, which at low concentrations induces the formation of zinc hydroxide nitrate nanosheets that serve as in situ sacrificial templates (Chapter 5, Paper V). A 2D leaf-like ZIF (ZIF-L) is also obtained using the method. The hierarchical porous ZIF-8 and ZIF-L show good performance for CO2 sorption.

  • 14.
    Abdelhamid, Hani Nasser
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bermejo-Gómez, Antonio
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    A water-stable lanthanide metal-organic framework for fluorimetric detection of ferric ions and tryptophan2017In: Microchimica Acta, ISSN 0026-3672, E-ISSN 1436-5073, Vol. 184, no 9, p. 3363-3371Article in journal (Refereed)
    Abstract [en]

    The preparation of a highly water stable and porous lanthanide metal-organic framework (MOF) nanoparticles (denoted SUMOF-7II; SU refers to Stockholm University) is described. SUMOF-7II was synthesized starting from the tritopic linker of 2,4,6-tri-p-carboxyphenyl pyridine (H3L2) and La(III) as metal clusters. SUMOF-7II forms a stable dispersion and displays high fluorescence emission with small variation over the pH range of 6 to 12. Its fluorescence is selectively quenched by Fe(III) ions compared to other metal ions. The intensity of the fluorescene emission drops drops linearly in 16.6–167 μM Fe(III) concentration range, and Stern-Volmer plots are linear. The limit of detection (LOD) is 16.6 μM (at an S/N ratio of >3). This indicator probe can also be used for selective detection of tryptophan among several amino acids. Compared to the free linker H3L2, SUMOF-7II offers improved sensitivity and selectivity of the investigated species.

  • 15.
    Abdelhamid, Hani Nasser
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Huang, Zhehao
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    El-Zhory, Ahmed M.
    Haoquan, Zheng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    A Fast and Scalable Approach for Synthesis of Hierarchical Porous Zeolitic Imidazolate Frameworks and One-Pot Encapsulation of Target Molecules2017In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 56, no 15, p. 9139-9146Article in journal (Refereed)
    Abstract [en]

    A trimethylamine (TEA)-assisted synthesis approach that combines the preparation of hierarchical porous zeolitic imidazolate framework ZIF-8 nanoparticles and one-pot encapsulation of target molecules is presented. Two dye molecules, rhodamine B (RhB) and methylene blue (MB), and one protein (bovine serum albumin, BSA) were tested as the target molecules. The addition of TEA into the solution of zinc nitrate promoted the formation of ZnO nanocrystals, which rapidly transformed to ZIF-8 nanoparticles after the addition of the linker 2-methylimidazole (Hmim). Hierarchical porous dye@ZIF-8 nanoparticles with high crystallinity, large BET surface areas (1300–2500 m2/g), and large pore volumes (0.5–1.0 cm3/g) could be synthesized. The synthesis procedure was fast (down to 2 min) and scalable. The Hmim/Zn ratio could be greatly reduced (down to 2:1) compared to previously reported ones. The surface areas, and the mesopore size, structure, and density could be modified by changing the TEA or dye concentrations, or by postsynthetic treatment using reflux in methanol. This synthesis and one-pot encapsulation approach is simple and can be readily scaled up. The photophysical properties such as lifetime and photostability of the dyes could be tuned via encapsulation. The lifetimes of the encapsulated dyes were increased by 3–27-fold for RhB@ZIF-8 and by 20-fold for MB@ZIF-8, compared to those of the corresponding free dyes. The synthesis approach is general, which was successfully applied for encapsulation of protein BSA. It could also be extended for the synthesis of hierarchical porous cobalt-based ZIF (dye@ZIF-67).

  • 16.
    Abdelhamid, Hani Nasser
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Assuit University, Egypt .
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Template-free and room temperature synthesis of hierarchical porous zeolitic imidazolate framework nanoparticles and their dye and CO2 sorption2018In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 20, no 5, p. 1074-1084Article in journal (Refereed)
    Abstract [en]

    Hierarchical porous zeolitic imidazolate framework ZIF-8 nanoparticles have been synthesized using zinc nitrate, 2-methylimidazole (Hmim), and sodium hydroxide. Zinc hydroxide nitrate nanosheets were formed as intermediates that further transformed to hierarchical porous ZIF-8 after the addition of Hmim. These intermediates serve as in situ sacrificial templates and promote the formation of hierarchical porous ZIF-8 without the need for any other templates. The surface area and mesoporosity of the materials can be tuned by adjusting the concentration of NaOH. This method offers a fast and template-free approach for the synthesis of pure hierarchical porous ZIF-8 at room temperature with tunable porosity. The approach has been applied to synthesize two-dimensional ZIF leaf-like materials, ZIF-L. The synthesis of ZIF-8 and ZIF-L can be scaled up with high yields (>80%). The resulting ZIF-8 and ZIF-L materials show very good CO2 sorption properties. ZIF-8 nanoparticles show fast (<5 min), selective, and high efficiency (>95%) uptake of methyl blue in aqueous solution both without and in the presence of other dyes. The results open a new avenue for the understanding of the self-assembly and the formation of hierarchical porous ZIFs.

  • 17.
    Abdelhamid, Hani
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Wilk-Kozubek, Magdalena
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ahmed, M. El-Zohry
    Valiente, Alejandro
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bermejo-Gomez, Antonio
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mudring, Anja-Verena
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Luminescence Properties for a Family of Highly Stable Lanthanide Metal-Organic FrameworksManuscript (preprint) (Other academic)
  • 18.
    Abdelhamid, Hani
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Template-Free Synthesis of Hierarchical Porous Zeolitic Imidazole Frameworks Nanoparticles and their CO2 SorptionManuscript (preprint) (Other academic)
  • 19.
    Abdel-Magied, Ahmed F.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Arafa, Wael A. A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Laine, Tanja M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Shatskiy, Andrey
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Substituent Effects in Molecular Ruthenium Water Oxidation Catalysts Based on Amide Ligands2017In: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899, Vol. 9, no 9, p. 1583-1587Article in journal (Refereed)
    Abstract [en]

    The production of clean and sustainable energy is considered as one of the most urgent issues for our society. Mastering the oxidation of water to dioxygen is essential for the production of solar fuels. A study of the influence of the substituents on the catalytic activity of a series of mononuclear Ru complexes (2a-e) based on a tetradentate ligand framework is presented. At neutral pH, using [Ru(bpy)(3)](PF6)(3) (bpy=2,2'-bipyridine) as the terminal oxidant, a good correlation between the turnover frequency (TOF) and the Hammett sigma(meta) parameters was obtained. Additionally, a general pathway for the deactivation of Ru-based catalysts 2a-e during the catalytic oxidation of water through poisoning by carbon monoxide was demonstrated. These results highlight the importance of ligand design for fine-tuning the catalytic activity of water oxidation catalysts.

  • 20.
    Abdel-Magied, Ahmed F.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Shatskiy, Andrey
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Liao, Rong-Zhen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Laine, Tanja M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Arafa, Wael A. A.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. University Fayoum, Egypt.
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kärkäs, Markus D.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Bjorn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Chemical and Photochemical Water Oxidation Mediated by an Efficient Single-Site Ruthenium Catalyst2016In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 9, no 24, p. 3448-3456Article in journal (Refereed)
    Abstract [en]

    Water oxidation is a fundamental step in artificial photosynthesis for solar fuels production. In this study, we report a single-site Ru-based water oxidation catalyst, housing a dicarboxylate-benzimidazole ligand, that mediates both chemical and light-driven oxidation of water efficiently under neutral conditions. The importance of the incorporation of the negatively charged ligand framework is manifested in the low redox potentials of the developed complex, which allows water oxidation to be driven by the mild one-electron oxidant [Ru(bpy)(3)](3+) (bpy = 2,2'-bipyridine). Furthermore, combined experimental and DFT studies provide insight into the mechanistic details of the catalytic cycle.

  • 21. Abdel-Rehim, Abbi
    et al.
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Advantages of Saliva Sampling in Bioanalysis Using Microextraction by Packed Sorbent and Dried Saliva Spot with LC-MS-MS2014In: LC GC Europe, ISSN 1471-6577, Vol. 27, no 10, p. 529-531Article in journal (Refereed)
    Abstract [en]

    Saliva offers a fast and non-invasive sampling matrix for determining drug concentration levels, making it a suitable alternative to plasma and blood. During the analysis of biological samples attention is focused on sample pre-treatment. In addition, liquid chromatography coupled to tandem mass spectrometry (LC-MS-MS) is often the method of choice in bioanalysis because of the good selectivity and good sensitivity of the technique. In this article, two sample handling and sample preparation methods for saliva samples are presented and discussed. The first method is microextraction by packed sorbent (MEPS), and the second method is dried saliva spot (DSS). Both methods were applied for determining the presence of lidocaine in saliva.

  • 22. Abdel-Rehim, Abbi
    et al.
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dried saliva spot as a sampling technique for saliva samples2014In: BMC Biomedical chromotography, ISSN 0269-3879, E-ISSN 1099-0801, Vol. 28, no 6, p. 875-877Article in journal (Refereed)
    Abstract [en]

    For the first time, dried saliva spot (DSS) was used as a sampling technique for saliva samples. In the DSS technique 50 L of saliva was collected on filter paper and the saliva was then extracted with an organic solvent. The local anesthetic lidocaine was used as a model compound, which was determined in the DSS using liquid chromatography and mass spectrometry. The results obtained for the determination of lidocaine in saliva using DSS were compared with those from a previous study using a microextraction by packed sorbent syringe as the sampling method for saliva. This study shows that DSS can be used for the analysis of saliva samples. The method is promising and very easy in terms of sampling and extraction procedures. The results from this study are in good agreement with those from our previous work on the determination of lidocaine in saliva. DSS can open a new dimension in the saliva handling process in terms of sampling, storing and transport.

  • 23.
    Abdel-Rehim, Abbi
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Evaluation of microextraction by packed sorbent and micro-liquid chromatography-tandem mass spectrometry as a green approach in bioanalysis2013In: BMC Biomedical chromotography, ISSN 0269-3879, E-ISSN 1099-0801, Vol. 27, no 10, p. 1225-1233Article in journal (Refereed)
    Abstract [en]

    In this study the use of micro-liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was investigated in routine bioanalysis application for separation and quantification of pro-drug AZD6319 (developed for aldezheimer treatment). Microextraction by packed sorbent (MEPS) was used as sample clean-up method. The focus of this study was put on the evaluation of the usability of smaller column diameters such as 1.0 and 0.3mm instead of 2.1mm in bioanalysis application to reduce solvent consumption and sample volumes. Solvent consumption was reduced by 80% when a 1.0mm column was used compared with 2.1mm column. Robustness of the micro-columns in terms of accuracy and precision was investigated. The application of LC-MS/MS for the quantitative analysis of AZD6319 in plasma samples showed good selectivity, accuracy and precision. The coefficients of determination (R-2) were >0.998 for all runs using plasma samples on the studied micro-columns. The inter-day accuracy values for quality control samples ranged from 99 to 103% and from 96 to 105% for 0.3x50mm and 1.0x50mm columns, respectively. The inter-day precision values ranged from 4.0 to 9.0% and from 4.0 to 8.0% for 0.3x50 and 1.0x50mm columns, respectively. In addition the sensitivity was increased by three times using a 1.0mm column compared with 2.1mm. Furthermore, robustness of the micro-columns from different manufacturers was investigated.

  • 24.
    Abebe, Mihret
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bacsik, Zoltan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Spherical and Porous Particles of Calcium Carbonate Synthesized with Food Friendly Polymer Additives2015In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 15, no 8, p. 3609-3616Article in journal (Refereed)
    Abstract [en]

    Porous calcium carbonate particles were synthesized by adding solutions of Ca2+ to solutions of CO32- containing polymeric additives. Under optimized conditions well-defined aggregates of the anhydrous polymorph vaterite formed. A typical sample of these micrometer-sized aggregates had: a pore volume of 0.1 cm(3)/g, a pore width of similar to 10 nm, and a specific surface area of similar to 25-30 m(2)/ g. Only one mixing Order (calcium to carbonate) allowed the formation of vaterite, which was ascribed to the buffering capacity and relatively high pH of the CO32- solution. Rapid addition of the calcium chloride solution and rapid stirring promoted the formation of vaterite, due to the high supersaturation levels achieved. With xanthan gum, porous and micrometer-sized vaterite aggregates could be synthesized over a wide range of synthetic conditions. For the Other food grade polymers, hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), and sodium carboxyl methylcellulose, several intensive and extensive synthetic parameters had to be optimized to obtain pure vaterite and porous aggregates. HPMC and MC allowed well-defined spherical micrometer-sited particles to form. We expect that these spherical and porous particles of vaterite could be relevant to model studies as well as a controlled delivery of particularly large molecules.

  • 25.
    Abelein, Axel
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Jarvet, Jüri
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. The National Institute of Chemical Physics and Biophysics, Estonia.
    Barth, Andreas
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Gräslund, Astrid
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Danielsson, Jens
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Ionic Strength Modulation of the Free Energy Landscape of A beta(40) Peptide Fibril Formation2016In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 138, no 21, p. 6893-6902Article in journal (Refereed)
    Abstract [en]

    Protein misfolding and formation of cross-beta structured amyloid fibrils are linked to, many neurodegenerative disorders. Although recently developed,quantitative approaches have started to reveal the molecular nature of self-assembly and fibril formation of proteins and peptides, it is yet unclear how these self-organization events are precisely modulated by microenvironmental factors, which are known to strongly affect the macroscopic aggregation properties. Here, we characterize the explicit effect of ionic strength on the microscopic aggregation rates of amyloid beta peptide (A beta 40) self-association, implicated in Alzheimer's disease. We found that physiological ionic strength accelerates A beta 40 aggregation kinetics by promoting surface-catalyzed secondary nucleation reactions. This promoted catalytic effect can be assigned to shielding of electrostatic repulsion between Monomers on the fibril surface or between the fibril surface itself and monomeric peptides. Furthermore, we observe the formation of two different beta-structured states with =similar but distinct spectroscopic features, which can be assigned to an off-pathway immature state (F-beta*) and a mature stable State (F-beta), where salt favors formation of the F-beta fibril morphology. Addition of salt to preformed F-beta* accelerates transition to F-beta, underlining the dynamic nature of A beta 40 fibrils in solution. On the basis of,these results we suggest a model where salt decreases the free-energy barrier for A beta 40 folding to the F-beta state, favoring the buildup of the mature fibril morphology while omitting competing, energetically less favorable structural states.

  • 26. Abrahamsson, Maria
    et al.
    Wolpher, Henriette
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johansson, Olof
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Larsson, Jan
    Kritikos, Mikael
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Structural Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Structural Chemistry.
    Norrby, Per-Ola
    Bergquist, Jonas
    Sun, Licheng
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hammarström, Leif
    A New Strategy for Improvement of Photophysical Properties in Ruthenium(II) Polypyridyl Complexes. Synthesis, Photophysical and Electrochemical characterisation of Six Mononuclear Ruthenium(II) Bisterpyridine Type Complexes2005In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 44, no 9, p. 3215-3225Article in journal (Refereed)
    Abstract [en]

    The synthesis and characterization of six ruthenium(II) bistridentate polypyridyl complexes is described. These were designed on the basis of a new approach to increase the excited-state lifetime of ruthenium(II) bisterpyridine-type complexes. By the use of a bipyridylpyridyl methane ligand in place of terpyridine, the coordination environment of the metal ion becomes nearly octahedral and the rate of deactivation via ligand-field (i.e., metal-centered) states was reduced as shown by temperature-dependent emission lifetime studies. Still, the possibility to make quasi-linear donor−ruthenium−acceptor triads is maintained in the complexes. The most promising complex shows an excited-state lifetime of τ = 15 ns in alcohol solutions at room temperature, which should be compared to a lifetime of τ = 0.25 ns for [Ru(tpy)2]2+. The X-ray structure of the new complex indeed shows a more octahedral geometry than that of [Ru(tpy)2]2+. Most importantly, the high excited-state energy was retained, and thus, so was the potential high reactivity of the excited complex, which has not been the case with previously published strategies based on bistridentate complexes.

  • 27. Abu-Bakr, Sherifa M.
    et al.
    Bassyouni, Fatma A.
    Rehim, Mohamed Abdel
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Pharmacological evaluation of benzimidazole derivatives with potential antiviral and antitumor activity2012In: Research on chemical intermediates (Print), ISSN 0922-6168, E-ISSN 1568-5675, Vol. 38, no 9, p. 2523-2545Article, review/survey (Refereed)
    Abstract [en]

    In recent years the synthesis of benzimidazole and its derivatives has attracted the attention of many organic chemists because of the compounds' interesting biological activity and the crucial importance of the benzimidazole unit in the function of these biologically important molecules. Benzimidazole-based polyheterocyclic compounds have several interesting biological properties. Simple synthetic strategies leading to benzimidazole-based fused polyheterocyclic systems and the antiviral and anticancer biological activity of the compounds are surveyed in this review article.

  • 28.
    Abuzooda, Thana
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Amini, Ahmad
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Graphite-based microextraction by packed sorbent for online extraction of beta-blockers from human plasma samples2015In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 992, p. 86-90Article in journal (Refereed)
    Abstract [en]

    In the present work a new graphitic material (Carbon-XCOS) was used as a sorbent for microextraction by packed sorbent (MEPS).The beta-blockers metoprolol and acebutolol in plasma samples were extracted and detected online using Carbon-MEPS syringe and liquid chromatography and tandem mass spectrometry (LC-MS/MS). Factors affecting the MEPS performance such as conditioning, washing and elution solutions were investigated. The validation of the bioanalytical method was performed using human plasma. The standard curve ranged from 10 to 2000 nM and the lower limit of quantification (LLOQ) was set to 10 nM. The method validation showed good accuracy and precision for the quality control (QC) samples at three concentration levels (30, 800 and 1600 nM). The accuracy values of the QC samples were in the range of 86-108% (n = 18). The precision values of intra- and inter-day for QC samples ranged from 4.4% to 14.4% (RSD) for the both studied analytes. The coefficient of determination (R-2) values were >= 0.999 (n = 3).

  • 29. Achari, Muthuraaman Bhagavathi
    et al.
    Elumalai, Viswanathan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Vlachopoulos, Nick
    Safdari, Majid
    Gao, Jiajia
    Gardner, James M.
    Kloo, Lars
    A quasi-liquid polymer-based cobalt redox mediator electrolyte for dye-sensitized solar cells2013In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, no 40, p. 17419-17425Article in journal (Refereed)
    Abstract [en]

    Recently, cobalt redox electrolyte mediators have emerged as a promising alternative to the commonly used iodide/triiodide redox shuttle in dye-sensitized solar cells (DSCs). Here, we report the successful use of a new quasi-liquid, polymer-based electrolyte containing the Co3+/Co2+ redox mediator in 3-methoxy propionitrile solvent in order to overcome the limitations of high cell resistance, low diffusion coefficient and rapid recombination losses. The performance of the solar cells containing the polymer based electrolytes increased by a factor of 1.2 with respect to an analogous electrolyte without the polymer. The performances of the fabricated DSCs have been investigated in detail by photovoltaic, transient electron measurements, EIS, Raman and UV-vis spectroscopy. This approach offers an effective way to make high-performance and long-lasting DSCs.

  • 30.
    Adolfsson, Erik
    Stockholm University.
    Phase Stability and Preparations of Oxide-Apatite Composites1999Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the preparation of bioactive composites containing hydroxyapatite, Ca5(PO4)3(OH), and an oxide it has been a problem to prevent the hydroxyapatite from decomposing in the sintering process. This is because H2O is evolved when hydroxyapatite is heated, implying that the occupied OH- positions in hydroxyapatite structure are partly replaced by vacancies and O2- ions. The thermal stability of hydroxyapatite was found to depend on the fraction of vacancies and O2- ions present. The decomposition of the hydroxyapatite is initiated when a critical fraction of the OH- ions has been lost, and it is not specifically related to the temperature applied or atmosphere used. The decomposition temperature of hydroxyapatite and fluoride-containing apatite, Ca5(PO4)3(OH)1-xFx, in the presence of alumina has been studied and found to increase with increasing x value in Ca5(PO4)3(OH)1-xFx. By combining this observation with thermogravimetric studies of hydroxyapatite and Ca5(PO4)3OH1-xFxsamples, it was concluded that the decomposition of hydroxyapatite in the presence of alumina can be described by the following reactions:

    Ca5(PO4)3(OH) --> Ca5(PO4)3(OH)1-xOx/2 + x/2 H20

    2 Ca5(PO4)3(OH)1-xOx/2+ Al2O3 --> 3 Ca3(PO4)2 + CaAl2O4 + (1-x) H2O

    With the use of a closed system for sintering the aluminañapatite composites, the loss of water can be reduced. The equilibrium in the first reaction will then be shifted to the left, and the second reaction will not occur. This implies that a higher sintering temperature can be used to densify an aluminañhydroxyapatite composite. Accordingly, composites of alumina and zirconia, respectively, with hydroxyapatite could be hot isostatically pressed (HIPed) in a closed system at 1200oC and at a pressure of 160 MPa without any detectable decomposition of the hydroxyapatite. Another way to avoid excess formation of vacancies is to replace some of the OH-ions with F-. This implies that the equilibrium in the first reaction given above is shifted to the left, thus improving the thermal stability of the apatite.

    The main result of this thesis work is a more detailed understanding of the reaction between the oxide and hydroxyapatite, which has made it possible to prepare densified oxide-hydroxyapatite composites without decomposition of the hydroxyapatite phase.

  • 31. Adolfsson, Erik
    et al.
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Effects of granule density on strength and granule related defects in zirconia2012In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 32, no 11, p. 2653-2659Article in journal (Refereed)
    Abstract [en]

    A suspension of zirconia powder (TZ3YSE) with a solids loading of 50 vol% was prepared by ball milling. Binders were added and some of the suspension was diluted to 40, 30 and 20 vol% before freeze granulation was performed. A spray dried material (TZ3YSEB) was used as a reference. The pore size distribution of the different granules was evaluated and from the microstructure it was shown that inhomogeneities were present in both the freeze granulated as well as in the spray dried granules. In addition, the density, microstructure as well as the strength of sintered materials prepared from the granules were studied. The results showed that a high green density or sintered density was not sufficient in order to achieve a high strength material. It was further shown that the strength was significantly influenced by the granule density and not by the inhomogeneities found in the granules.

  • 32.
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Transition metal-catalyzed epoxidation of alkenes2010In: Modern Oxidation Methods / [ed] Jan-Erling Bäckvall, Weinheim: Wiley-VCH Verlag GmbH & Co. KGaA , 2010, 2, p. 37-84Chapter in book (Other academic)
  • 33.
    Adrian Meredith, Jenny
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Design and Synthesis of Inhibitors Targeting the Aspartic Proteases HIV-1 PR and BACE-12009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes the synthesis of molecules designed for inhibition of two aspartic proteases, viral HIV-1 PR and human BACE-1. It also reports on the structure activity relationships of the targeted enzyme inhibitors.

    It is estimated that currently 33 million people are infected with HIV, the causative agent of AIDS. The virus targets T-lymphocytes and macrophages of the human immune system. The HIV-1 PR plays an important role in the viral replication, and by inhibiting the enzyme the disease progression can be slowed down or even halted.

    Herein is reported the design and synthesis of a series of HIV-1 PR inhibitors with novel P2 substituents of which several inhibit the enzyme in the nanomolar range. The aim of the second work was to further develop the inhibitors by the introduction of fluorine. Several attempts were performed to fluorinate different P2-substituents.

    Alzheimer’s disease (AD) is neurodegenerative, progressive and fatal disorder of the brain. It is associated with accumulation of plaques and tangles that cause impairment and functional decline of brain tissue which result in loss of memory and cognition. The plaques are mainly constituted of amyloid-β peptides that are generated in two steps from the amyloid precursor protein (APP). The cleavage sequence is initiated by the aspartic protease BACE-1, which makes the enzyme a key target in the effort of finding a therapy that aim to slow down the progression of AD.

    Herein are enclosed the development of two series of potent BACE-1 inhibitors. In the first work a synthetic strategy was developed to truncate a previously reported hydroxyethylene core structure in order to generate more drug-like inhibitors. This generated a series of truncated inhibitors where two amide bonds have been replaced with an ether - or alternatively a secondary amine linkage. A number of these inhibitors show potency against BACE-1. In the second part of the work the aim was investigate the effect of alterations in the P1 position. Five scaffolds with new P1 substituents were designed, synthesized and coupled with two different P2-P3 substituents. This resulted in a series of potent inhibitors that inhibit BACE-1 in the nanomolar range.

  • 34. Afewerki, Samson
    et al.
    Alimohammadzadeh, Rana
    Osong, Sinke H.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Engstrand, Per
    Córdova, Armando
    Sustainable Design for the Direct Fabrication and Highly Versatile Functionalization of Nanocelluloses2017In: Global Challenges, ISSN 2056-6646, Vol. 1, no 7, article id 1700045Article in journal (Refereed)
    Abstract [en]

    This study describes a novel sustainable concept for the scalable direct fabrication and functionalization of nanocellulose from wood pulp with reduced energy consumption. A central concept is the use of metal-free small organic molecules as mediators and catalysts for the production and subsequent versatile surface engineering of the cellulosic nanomaterials via organocatalysis and click chemistry. Here, organoclick chemistry enables the selective functionalization of nanocelluloses with different organic molecules as well as the binding of palladium ions or nanoparticles. The nanocellulosic material is also shown to function as a sustainable support for heterogeneous catalysis in modern organic synthesis (e.g., Suzuki cross-coupling transformations in water). The reported strategy not only addresses obstacles and challenges for the future utilization of nanocellulose (e.g., low moisture resistance, the need for green chemistry, and energy-intensive production) but also enables new applications for nanocellulosic materials in different areas.

  • 35. Afewerki, Samson
    et al.
    Breistein, Palle
    Deiana, Luca
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dziedzic, Pawel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ibrahem, Ismail
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalytic enantioselective β -alkylation of α,β-unsaturated aldehydes by combination of transition-metal- and aminocatalysis: Total synthesis of bisabolane sesquiterpenes2011In: Chemistry: a European Journal, ISSN 0947-6539, Vol. 17, no 32, p. 8784-8788Article in journal (Refereed)
  • 36. Afewerki, Samson
    et al.
    Ibrahem, Ismail
    Rydfjord, Jonas
    Breistein, Palle
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Direct Regiospecific and Highly Enantioselective Intermolecular α-Allylic Alkylation of Aldehydes by a Combination of Transition-Metal and Chiral Amine Catalysts2012In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, no 10, p. 2972-2977Article in journal (Refereed)
    Abstract [en]

    The first direct intermolecular regiospecific and highly enantioselective a-allylic alkylation of linear aldehydes by a combination of achiral bench-stable Pd0 complexes and simple chiral amines as co-catalysts is disclosed. The co-catalytic asymmetric chemoselective and regiospecific a-allylic alkylation reaction is linked in tandem with in situ reduction to give the corresponding 2-alkyl alcohols with high enantiomeric ratios (up to 98:2 e.r.; e.r.=enantiomeric ratio). It is also an expeditious entry to valuable 2-alkyl substituted hemiacetals, 2-alkyl-butane-1,4-diols, and amines. The concise co-catalytic asymmetric total syntheses of biologically active natural products (e.g., Arundic acid) are disclosed.

  • 37.
    Afewerki, Samson
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Mid-Sweden University, Sweden.
    Ma, Guangning
    Ibrahem, Ismail
    Liu, Leifeng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Mid-Sweden University, Sweden.
    Highly Enantioselective Control of Dynamic Cascade Transformations by Dual Catalysis: Asymmetric Synthesis of Polysubstituted Spirocyclic Oxindoles2015In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 5, no 2, p. 1266-1272Article in journal (Refereed)
    Abstract [en]

    The highly enantioselective (up to >99.5:0.5 er) synthesis of polysubstituted spirocyclic oxindoles with four new contiguous stereocenters, including the spiro all-carbon quaternary center, is disclosed. It is accomplished by the highly stereoselective control of a dynamic conjugate/intramolecular allylic alkylation relay sequence based on the synergistic cooperation of metal and chiral amine catalysts in which the careful selection of organic Nand, metal complex, and chiral amine is essential. The intermolecular C-C bond-forming step occurred only when both the metal and chiral amine catalysts were present.

  • 38. Afzal, Muhammad
    et al.
    Saleemi, Mohsin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). KTH Royal Institute of Technology, Sweden.
    Wang, Baoyuan
    Xia, Chen
    Zhang, Wei
    He, Yunjuan
    Jayasuriya, Jeevan
    Zhu, Bin
    Fabrication of novel electrolyte-layer free fuel cell with semi-ionic conductor (Ba0.5Sr0.5Co0.8Fe0.2O3-delta- Sm0.2Ce0.8O1.9) and Schottky barrier2016In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 328, p. 136-142Article in journal (Refereed)
    Abstract [en]

    Perovskite Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) is synthesized via a chemical co-precipitation technique for a low temperature solid oxide fuel cell (LTSOFC) (300-600 degrees C) and electrolyte-layer free fuel cell (EFFC) in a comprehensive study. The EFFC with a homogeneous mixture of samarium doped ceria (SDC): BSCF (60%:40% by weight) which is rather similar to the cathode (SDC: BSCF in 50%:50% by weight) used for a three layer SOFC demonstrates peak power densities up to 655 mW/cm(2), while a three layer (anode/ electrolyte/cathode) SOFC has reached only 425 mW/cm(2) at 550 degrees C. Chemical phase, crystal structure and morphology of the as-prepared sample are characterized by X-ray diffraction and field emission scanning electron microscopy coupled with energy dispersive spectroscopy. The electrochemical performances of 3-layer SOFC and EFFC are studied by electrochemical impedance spectroscopy (EIS). As-prepared BSCF has exhibited a maximum conductivity above 300 S/cm at 550 degrees C. High performance of the EFFC device corresponds to a balanced combination between ionic and electronic (holes) conduction characteristic. The Schottky barrier prevents the EFFC from the electronic short circuiting problem which also enhances power output. The results provide a new way to produce highly effective cathode materials for LTSOFC and semiconductor designs for EFFC functions using a semiconducting-ionic material.

  • 39. Agasti, Soumitra
    et al.
    Maity, Soham
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Maiti, Debabrata
    Palladium-Catalyzed Synthesis of 2,3-Disubstituted Benzofurans: An Approach Towards the Synthesis of Deuterium Labeled Compounds2015In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 357, no 10, p. 2331-2338Article in journal (Refereed)
    Abstract [en]

    Palladium-catalyzed oxidative annulations between phenols and alkenylcarboxylic acids produced a library of benzofuran compounds. Depending on the nature of the substitution of the phenol precursor, either 2,3-dialkylbenzofurans or 2-alkyl-3-methylene-2,3-dihydrobenzofurans can be synthesized with excellent regioselectivity. Reactions between conjugated 5-phenylpenta-2,4-dienoic acids and phenol gave 3-alkylidenedihydrobenzofuran alkaloid motifs while biologically active 7-arylbenzofuran derivatives were prepared by starting from 2-phenylphenols. More interestingly, selective incorporation of deuterium from D2O has been discovered, which offers an attractive one-step method to access deuterated compounds.

  • 40.
    Aggarwal, Varinder K.
    et al.
    Bristol University.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry. University of Bristol, Bristol, UK.
    Enantioselective α-arylation of cyclohexanones with diaryl iodonium salts: Application to the synthesis of (-)-epibatidine.2005In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 44, no 34, p. 5516-5519Article in journal (Refereed)
    Abstract [en]

    The direct asym. α-arylation of prochiral ketones has been effected using chiral lithium amide bases and diaryl iodonium salts. The methodol. has been employed in a short total synthesis of the alkaloid (-)-epibatidine. [on SciFinder(R)]

  • 41.
    Agosta, Lorenzo
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Brandt, Erik G.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lyubartsev, Alexander P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Diffusion and reaction pathways of water near fully hydrated TiO2 surfaces from ab initio molecular dynamics2017In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 147, no 2, article id 024704Article in journal (Refereed)
    Abstract [en]

    Ab initio molecular dynamics simulations are reported forwater-embedded TiO2 surfaces to determine the diffusive and reactive behavior at full hydration. A three-domain model is developed for six surfaces [rutile (110), (100), and (001), and anatase (101), (100), and (001)] which describes waters as hard (irreversibly bound to the surface), soft (with reduced mobility but orientation freedom near the surface), or bulk. The model explains previous experimental data and provides a detailed picture of water diffusion near TiO2 surfaces. Water reactivity is analyzed with a graph-theoretic approach that reveals a number of reaction pathways on TiO2 which occur at full hydration, in addition to direct water splitting. Hydronium (H3O+) is identified to be a key intermediate state, which facilitates water dissociation by proton hopping between intact and dissociated waters near the surfaces. These discoveries significantly improve the understanding of nanoscale water dynamics and reactivity at TiO2 interfaces under ambient conditions.

  • 42.
    Agrawal, Santosh
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lenormand, Maud
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Selective Alkylation of (Hetero)Aromatic Amines with Alcohols Catalyzed by a Ruthenium Pincer Complex2012In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 14, no 6, p. 1456-1459Article in journal (Refereed)
    Abstract [en]

    A readily available pincer ruthenium(II) complex catalyzes the selective monoalkylation of (hetero)aromatic amines with a wide range of primary alcohols (including pyridine-, furan-, and thiophene-substituted alcohols) with high efficiency when used in low catalyst loadings (1 mol %). Tertiary amine formation via polyalkylation does not occur, making this ruthenium system an excellent catalyst for the synthesis of sec-amines.

  • 43.
    Agrawal, Santosh
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martínez-Castro, Elisa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Marcos, Rocio
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Readily Available Ruthenium Complex for Efficient Dynamic Kinetic Resolution of Aromatic alpha-Hydroxy Ketones2014In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 16, no 8, p. 2256-2259Article in journal (Refereed)
    Abstract [en]

    A ruthenium complex formed from commercially available [Ru(p-cymene)Cl-2](2) and 1,4-bis(diphenylphosphino)butane catalyzes the racemization of aromatic alpha-hydroxy ketones very efficiently at room temperature. The racemization is fully compatible with a kinetic resolution catalyzed by a lipase from Pseudomonas stutzeri. This is the first example of dynamic kinetic resolution of alpha-hydroxy ketones at ambient temperature in which the metal and enzyme catalysts work in concert in one pot at room temperature to give quantitative yields of esters of alpha-hydroxy ketones with very high enantioselectivity.

  • 44.
    Agthe, Michael
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Crystallization on the Mesoscale: Self-Assembly of Iron Oxide Nanocubes into Mesocrystals2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Self-assembly of nanoparticles is a promising route to form complex, nanostructured materials with functional properties. Nanoparticle assemblies characterized by a crystallographic alignment of the nanoparticles on the atomic scale, i.e. mesocrystals, are commonly found in nature with outstanding functional and mechanical properties. This thesis aims to investigate and understand the formation mechanisms of mesocrystals formed by self-assembling iron oxide nanocubes.

    We have used the thermal decomposition method to synthesize monodisperse, oleate-capped iron oxide nanocubes with average edge lengths between 7 nm and 12 nm and studied the evaporation-induced self-assembly in dilute toluene-based nanocube dispersions. The influence of packing constraints on the alignment of the nanocubes in nanofluidic containers has been investigated with small and wide angle X-ray scattering (SAXS and WAXS, respectively). We found that the nanocubes preferentially orient one of their {100} faces with the confining channel wall and display mesocrystalline alignment irrespective of the channel widths. 

    We manipulated the solvent evaporation rate of drop-cast dispersions on fluorosilane-functionalized silica substrates in a custom-designed cell. The growth stages of the assembly process were investigated using light microscopy and quartz crystal microbalance with dissipation monitoring (QCM-D). We found that particle transport phenomena, e.g. the coffee ring effect and Marangoni flow, result in complex-shaped arrays near the three-phase contact line of a drying colloidal drop when the nitrogen flow rate is high. Diffusion-driven nanoparticle assembly into large mesocrystals with a well-defined morphology dominates at much lower nitrogen flow rates. Analysis of the time-resolved video microscopy data was used to quantify the mesocrystal growth and establish a particle diffusion-based, three-dimensional growth model. The dissipation obtained from the QCM-D signal reached its maximum value when the microscopy-observed lateral growth of the mesocrystals ceased, which we address to the fluid-like behavior of the mesocrystals and their weak binding to the substrate. Analysis of electron microscopy images and diffraction patterns showed that the formed arrays display significant nanoparticle ordering, regardless of the distinctive formation process. 

    We followed the two-stage formation mechanism of mesocrystals in levitating colloidal drops with real-time SAXS. Modelling of the SAXS data with the square-well potential together with calculations of van der Waals interactions suggests that the nanocubes initially form disordered clusters, which quickly transform into an ordered phase.

  • 45.
    Agthe, Michael
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Høydalsvik, Kristin
    Mayence, Arnaud
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Karvinen, Petri
    Liebi, Marianne
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nygård, Kim
    Controlling Orientational and Translational Order of Iron Oxide Nanocubes by Assembly in Nanofluidic Containers2015In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, no 45, p. 12537-12543Article in journal (Refereed)
    Abstract [en]

    We demonstrate that spatial confinement can be used to control the orientational and translational order of cubic nanoparticles. For this purpose we have combined X-ray scattering and scanning electron microscopy to study the ordering of iron oxide nanocubes that have self-assembled from toluene-based dispersions in nanofluidic channels. An analysis of scattering vector components with directions parallel and perpendicular to the slit walls shows that the confining walls induce a preferential parallel alignment of the nanocube (100) faces. Moreover, slit wall separations that are commensurate with an integer multiple of the edge length of the oleic acid-capped nanocubes result in a more pronounced translational order of the self-assembled arrays compared to incommensurate confinement. These results show that the confined assembly of anisotropic nanocrystals is a promising route to nanoscale devices with tunable anisotropic properties.

  • 46.
    Agthe, Michael
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Plivelic, Tomas S.
    Labrador, Ana
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Salazar-Alvarez, German
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Following in Real Time the Two-Step Assembly of Nanoparticles into Mesocrystals in Levitating Drops2016In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 16, no 11, p. 6838-6843Article in journal (Refereed)
    Abstract [en]

    Mesocrystals composed of crystallographically aligned nanocrystals are present in biominerals and assembled materials which show strongly directional properties of importance for mechanical protection and functional devices. Mesocrystals are commonly formed by complex biomineralization processes and can also be generated by assembly of anisotropic nanocrystals. Here, we follow the evaporation-induced assembly of maghemite nanocubes into mesocrystals in real time in levitating drops. Analysis of time-resolved small-angle X-ray scattering data and ex situ scanning electron microscopy together with interparticle potential calculations show that the substrate-free, particle-mediated crystallization process proceeds in two stages involving the formation and rapid transformation of a dense, structurally disordered phase into ordered mesocrystals. Controlling and tailoring the particle-mediated formation of mesocrystals could be utilized to assemble designed nanoparticles into new materials with unique functions.

  • 47.
    Agthe, Michael
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Wetterskog, Erik
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Following the Assembly of Iron Oxide Nanocubes by Video Microscopy and Quartz Crystal Microbalance with Dissipation Monitoring2017In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, no 1, p. 303-310Article in journal (Refereed)
    Abstract [en]

    We have studied the growth of ordered arrays by evaporation-induced self-assembly of iron oxide nanocubes with edge lengths of 6.8 and 10.1 nm using video microscopy (VM) and quartz crystal microbalance with dissipation monitoring (QCM-D). Ex situ electron diffraction of the ordered arrays demonstrates that the crystal axes of the nanocubes are coaligned and confirms that the ordered arrays are mesocrystals. Time-resolved video microscopy shows that growth of the highly ordered arrays at slow solvent evaporation is controlled by particle diffusion and can be described by a simple growth model. The growth of each mesocrystal depends only on the number of nanoparticles within the accessible region irrespective of the relative time of formation. The mass of the dried mesocrystals estimated from the analysis of the bandwidth-shift-to-frequency-shift ratio correlates well with the total mass of the oleate-coated nanoparticles in the deposited dispersion drop.

  • 48.
    Agthe, Michael
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Wetterskog, Erik
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Following the mesocrystal growth of self-assembling iron oxide nanocubes by video microscopy and quartz crystal microbalance with dissipation monitoringManuscript (preprint) (Other academic)
  • 49.
    Agthe, Michael
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Wetterskog, Erik
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mouzon, Johanne
    Salazar-Alvarez, German
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Dynamic growth modes of ordered arrays and mesocrystals during drop-casting of iron oxide nanocubes2014In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 16, no 8, p. 1443-1450Article in journal (Refereed)
    Abstract [en]

    The growth modes of self-assembled mesocrystals and ordered arrays from dispersions of iron oxide nanocubes with a mean edge length of 9.6 nm during controlled solvent removal have been investigated with a combination of visible light video microscopy, atomic force microscopy and scanning electron microscopy. Mesocrystals with translational and orientational order of sizes up to 10 mu m are formed spontaneously during the final, diffusion-controlled, drop-casting stage when the liquid film is very thin and the particle concentration is high. Convection-driven deposition of ordered nanocube arrays at the edge of the drying droplet is a manifestation of the so called coffee-ring effect. Dendritic growth or fingering of rapidly growing arrays of ordered nanocubes could also be observed in a transition regime as the growth front moves from the initial three-phase contact line towards the centre of the original droplet.

  • 50.
    Ahlford, Katrin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Asymmetric transfer hydrogenation of ketones: Catalyst development and mechanistic investigation2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The development of ligands derived from natural amino acids for asymmetric transfer hydrogenation (ATH) of prochiral ketones is described herein. In the first part, reductions performed in alcoholic media are examined, where it is found that amino acid-derived hydroxamic acids and thioamides, respectively, are simple and versatile ligands that in combination with [RhCp*Cl2]2 efficiently catalyze this particular transformation. Selectivities up to 97% ee of the corresponding secondary alcohols are obtained, and it is furthermore observed that the two different ligand classes, albeit based on the same amino acid scaffold, give rise to products of opposite configuration.

    The highly interesting enantioswitchable nature of the two abovementioned catalysts is studied in detail by mechanistic investigations. A structure/activity correlation analysis is performed, which reveals that the diverse behavior of the catalysts arise from different interactions between the ligands and the metal. Kinetic studies furthermore stress the catalyst divergence, since a difference in the rate determining step is established from initial rate measurements. In addition, rate constants are determined for each step of the overall reduction process.

    In the last part, catalyst development for ATH executed in water is discussed. The applicability of hydroxamic acid ligands is further extended, and catalysts based on these compounds are found to be efficient and compatible with aqueous conditions. The structurally even simpler amino acid amide is also evaluated as a ligand, and selectivities up to 90% ee are obtained in the reduction of a number of aryl alkyl ketones. The very challenging reduction of dialkyl ketones is moreover examined in the Rh-catalyzed aqueous ATH, where a modified surfactant-resembling sulfonylated diamine is used as ligand, and the reaction is carried out in the presence of SDS-micelles. A positive effect is to some extent found on the catalyst performance upon addition of phase-transfer components, especially regarding the catalytic activity in the reduction of more hydrophobic substrates.

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