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  • 1.
    Almqvist, Jonas
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Structural modeling of membrane transporter proteins2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A fundamental process of all living organisms - the transport of molecules across cellular membranes through membrane transport proteins - is investigated.

    After a brief review of general properties of biological membranes follows a recollection of the major methods of membrane transport that Nature utilizes (Chapter 1). This is followed by a description of important experimental (Chapter 2) and theoretical methods (Chapter 3) for structural studies of membrane proteins. The findings on membrane protein transport in papers I-IV are then summarized (Chapter 4) and important findings are discussed. The remaining text is a discussion on relevant theoretical and experimental methods.

  • 2.
    Bayat, Narges
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Lopes, Viviana R.
    Schoelermann, Julia
    Dahl Jensen, Lasse
    Cristobal, Susana
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Vascular toxicity of ultra-small TiO2 nanoparticles and single walled carbon nanotubes in vitro and in vivo2015In: Biomaterials, ISSN 0142-9612, E-ISSN 1878-5905, Vol. 63, p. 1-13Article in journal (Refereed)
    Abstract [en]

    Ultra-small nanoparticles (USNPs) at 1-3 nm are a subset of nanoparticles (NPs) that exhibit intermediate physicochemical properties between molecular dispersions and larger NPs. Despite interest in their utilization in applications such as theranostics, limited data about their toxicity exist. Here the effect of TiO2-USNPs on endothelial cells in vitro, and zebrafish embryos in vivo, was studied and compared to larger TiO2-NPs (30 nm) and to single walled carbon nanotubes (SWCNTs). In vitro exposure showed that TiO2-USNPs were neither cytotoxic, nor had oxidative ability, nevertheless were genotoxic. In vivo experiment in early developing zebrafish embryos in water at high concentrations of TiO2-USNPs caused mortality possibly by acidifying the water and caused malformations in the form of pericardial edema when injected. Myo1C involved in glomerular development of zebrafish embryos was upregulated in embryos exposed to TiO2-USNPs. They also exhibited anti-angiogenic effects both in vitro and in vivo plus decreased nitric oxide concentration. The larger TiO2-NPs were genotoxic but not cytotoxic. SWCNTs were cytotoxic in vitro and had the highest oxidative ability. Neither of these NPs had significant effects in vivo. To our knowledge this is the first study evaluating the effects of TiO2-USNPs on vascular toxicity in vitro and in vivo and this strategy could unravel USNPs potential applications.

  • 3. Dong, Yihui
    et al.
    Ji, Xiaoyan
    Laaksonen, Aatto
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Nanjing Tech University, China; Uppsala University, Sweden; Petru Poni Institute of Macromolecular Chemistry, Romania.
    Cao, Wei
    An, Rong
    Lu, Linghong
    Lu, Xiaohua
    Determination of the small amount of proteins interacting with TiO2 nanotubes by AFM-measurement2019In: Biomaterials, ISSN 0142-9612, E-ISSN 1878-5905, Vol. 192, p. 368-376Article in journal (Refereed)
    Abstract [en]

    Detecting the small amounts of proteins interacting effectively with the solid film electrodes surface still remains a challenge. To address this, in this work, a new approach was proposed by the combination of the adhesion forces and the molecular interaction measured with AFM. Cytochrome c (Cyt C) interacting effectively with TiO2 nanotube arrays (TNAs) was chosen as a probe. The amounts of Cyt C molecules interacting effectively on TNAs surface (C-TNA) range from 5.5x10(-12) to 7.0x10(-12) mol/cm(2) (68.2-86.8 ng/cm(2)) and they are comparable with the values obtained by the electrochemistry method in the literature, in evidence of the accuracy of this AFM-based approach. The reliability of the proposed approach was further verified by conducting Surface Enhanced Raman Scattering (SERS) measurements and estimating the enhancement factor (EF). This interaction-based AFM approach can be used to accurately obtain the small amounts of adsorbed substances on the solid film electrodes surface in the applications such as biosensors, biocatalysis, and drug delivery, etc.

  • 4.
    Ericsson, Ulrika
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    A structural genomics pilot project: methods and applications2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    With the availability of many completely sequenced genomes, scientific research has shifted from genes to the products of the genes, the proteins. Structural genomics groups have been established worldwide, with the objective of determining protein structures on a genome-wide scale. New methods for protein production and structural determination have become necessary.

    Two methods for high throughput analysis of proteins are presented in the first part of this thesis. The first method is the thermofluor method, which presents a fast way to identify stabilizing conditions for a particular protein. It was shown that the addition of a stabilizing additive, identified with the thermofluor method, significantly increased the likelihood of growing protein crystals. The second method presented in this thesis provides a fast and robust way to detect metal containing proteins.

    The second part of this thesis describes the crystal structures of two RNA modifying enzymes, the pseudouridine synthase TruD and the RNA m5C methyltransferase YebU. The catalytic domain of TruD was shown to bear remarkable structural similarity to the other pseudouridine families despite a lack of sequence similarity. In addition to the catalytic domain, the structure of TruD also contained an insertion domain with a novel fold.

    YebU was also found have two structurally distinct domains. The N-terminal catalytic domain has a high structural similarity to other RNA m5C methyltransferases. The C-terminal domain was revealed to be a so-called PUA domain, which had not been predicted by previous sequence alignments.

  • 5. Ferro, Roberto
    et al.
    Rennig, Maja
    Hernandez-Rollan, Cristina
    Daley, Daniel O.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. CloneOpt AB, Sweden.
    Nørholm, Morten H. H.
    A synbio approach for selection of highly expressed gene variants in Gram-positive bacteria2018In: Microbial Cell Factories, ISSN 1475-2859, E-ISSN 1475-2859, Vol. 17, article id 37Article in journal (Refereed)
    Abstract [en]

    Background: The market for recombinant proteins is on the rise, and Gram-positive strains are widely exploited for this purpose. Bacillus subtilis is a profitable host for protein production thanks to its ability to secrete large amounts of proteins, and Lactococcus lactis is an attractive production organism with a long history in food fermentation. Results: We have developed a synbio approach for increasing gene expression in two Gram-positive bacteria. First of all, the gene of interest was coupled to an antibiotic resistance gene to create a growth-based selection system. We then randomised the translation initiation region (TIR) preceding the gene of interest and selected clones that produced high protein titres, as judged by their ability to survive on high concentrations of antibiotic. Using this approach, we were able to significantly increase production of two industrially relevant proteins; sialidase in B. subtilis and tyrosine ammonia lyase in L. lactis. Conclusion: Gram-positive bacteria are widely used to produce industrial enzymes. High titres are necessary to make the production economically feasible. The synbio approach presented here is a simple and inexpensive way to increase protein titres, which can be carried out in any laboratory within a few days. It could also be implemented as a tool for applications beyond TIR libraries, such as screening of synthetic, homologous or domain-shuffled genes.

  • 6. Hussein, Kamal Hany
    et al.
    Abdelhamid, Hani Nasser
    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).
    Woo, Heung-Myong
    Ultrasonicated graphene oxide enhances bone and skin wound regeneration2019In: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 94, p. 484-492Article in journal (Refereed)
    Abstract [en]

    In the present study, we investigated the applications of ultrasonicated graphene oxide (UGO) for bone regeneration and skin wound healing. Ultrasonication of a GO suspension increased the dispersion and stability (by increasing the zeta potential) of the GO suspension. UGO has fewer oxygen-containing groups but still displays excellent water dispersion. The UGO supension showed high biocompatibility for human fetal osteoblast (hFOB cells), human endothelial cells (EA.hy 926 cells), and mouse embryonic fibroblasts. Importantly, UGO could support cell attachment and proliferation, in addition to promoting the osteogenesis of seeded cells and the promotion of new bone formation. In addition, a 1% UGO supension enhanced cell migration in an in vitro skin scratch assay and promoted wound closure in an in vivo rat excisional skin defect model. These results showed that UGO offers a good environment for cells involved in bone and skin healing, suggesting its potential application in tissue regeneration.

  • 7. Ishikawa, Mai
    et al.
    Oaki, Yuya
    Tanaka, Yoshihisa
    Kakisawa, Hideki
    Salazar-Alvarez, German
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Royal Institute of Technology, Sweden.
    Imai, Hiroaki
    Fabrication of nanocellulose-hydroxyapatite composites and their application as water-resistant transparent coatings2015In: Journal of materials chemistry. B, ISSN 2050-750X, E-ISSN 2050-7518, Vol. 3, no 28, p. 5858-5863Article in journal (Refereed)
    Abstract [en]

    Nanosized composite rods similar to 300 nm in length and similar to 20 nm in width were produced by deposition of 22-77 wt% of a c-axis-oriented hydroxyapatite (HA) on cellulose nanocrystals (CNCs). The CNCs functionalized with sulphonic groups were covered with the HA nanocrystals through controlled nucleation and growth under a moderately supersaturated condition in a solution system based on a simulated body fluid. Water-resistant transparent coatings 2-4 mm thick were obtained via evaporation-induced assembly of CNC-HA nanocomposites by casting their suspension on a glass substrate and the subsequent growth of HA nanocrystals by vapour hydrothermal treatment. The composite coatings exhibited improved mechanical strength compared to that of crustacean exoskeletons, and potential for bone regeneration.

  • 8.
    Lehto, Tõnis
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Guidelines for developing safe and efficient acylated cell-penetrating peptides for nanoparticle mediated non-covalent nucleic acid delivery in vivoManuscript (preprint) (Other academic)
    Abstract [en]

    We have previously described how the in vitro therapeutic window of cell-penetrating peptides (CPPs) in non-covalent oligonucleotide delivery can be widened by increasing the N-terminal acyl chain length and by reducing the free fraction of peptide in the peptide/nucleic acid complexes. Here we show on the same peptide library how varying the acyl chain length from 2-22 carbons influences the complexation and plasmid delivery both in cell culture and systemically in vivo.

    For that we first show by DLS and electron microscopy that for efficient complexation of plasmid DNA into stable and condensed nanoparticles hydrophobic interactions play the key role. Moreover, these cationic nanoparticles maintain their size in serum containing cell culture media, but not in serum free DMEM. When the transfection ability of these peptide/pDNA complexes was assessed in cell cultures, the more stable analogs (C14-22) showed similar functional activity. On the contrary, when these complexes were intravenously administered to mice, the most hydrophobic analog (C22) showed superior gene induction in liver and lungs over other tested analogs. Moreover, at optimal peptide/pDNA charge ratio (CR2) the complexes with intermediate carbon chain analogs (C8-C14) caused acute death in around 50% of the animals, whereas, with shorter and longer analogs survival was not affected. To emphasize the discrepancies between gene induction in cell culture and in vivo even further, we demonstrate by changing the size of the complexes and centrifugation that in cell culture the transfection efficiency is in part dependent on sedimentation, which can be misleading when translating these formulations to in vivo. Collectively these findings provide guidelines for how to design safe and efficient next generation CPPs for nanoparticle-mediated intravenous nucleic acid delivery.

  • 9. Newman, P.
    et al.
    Lu, Z.
    Roohani-Esfahani, S. I.
    Church, Tamara L.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). The University of Sydney, Australia.
    Biro, M.
    Davies, B.
    King, A.
    Mackenzie, K.
    Minett, A. I.
    Zreiqat, H.
    Porous and strong three-dimensional carbon nanotube coated ceramic scaffolds for tissue engineering2015In: Journal of materials chemistry. B, ISSN 2050-750X, E-ISSN 2050-7518, Vol. 3, no 42, p. 8337-8347Article in journal (Refereed)
    Abstract [en]

    Biomaterials research is investigating increasingly complex materials capable of mirroring the highly organized biochemical and architectural environments of the body. Accordingly, tissue scaffolds with nanoscale properties that mirror the fibrous proteins present in tissue are being developed. Such materials can benefit from the inherent dimensional similarities and nanocomposite nature of the cellular environment, altering nanoscale dimensional and biochemical properties to mimic the regulatory characteristics of natural cellular environments. One nanomaterial which demonstrates potential across a diverse range of biomaterial applications is carbon nanotubes (CNTs). Building on previous reports, a method to coat CNTs throughout 3D porous structures is developed. Through modifications to typical chemical vapour deposition (CVD), a high-quality uniform coating of carbon nanotubes (CNTs) is demonstrated over beta-tricalcium phosphate/hydroxyapatite (or TCP/HA), which is in clinical use; and the high-mechanical-strength multicomponent ceramic Ca2ZnSi2O7-ZnAl2O4, (or Sr-HT-Gah). The resulting materials address deficiencies of previously reported CNT biomaterials by simultaneously presenting properties of high porosity, biocompatibility and a mechanical stability. Together, this unique combination of properties makes these scaffolds versatile materials for tissue engineering in load bearing applications.

  • 10.
    Nordlund, Gustav
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Ng, Jovice Boon Sing
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Brzezinski, Peter
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    A Membrane-reconstituted Multisubunit Functional Proton Pump on Mesoporous Silica Particles2009In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 3, no 9, p. 2639-2646Article in journal (Refereed)
    Abstract [en]

    We have investigated formation of a proteolipid membrane surrounding mesoporous silica particles with a diameter of 550 nm and pore sizes of 3.0 nm. A multisubunit redox-driven proton pump, cytochrome c oxidase, was incorporated into the membrane and we show that the enzyme is fully functional, both with respect to catalysis of O2 reduction to water, and charge separation across the membrane. The orientation of cytochrome c oxidase in the membrane was found to be the same (~70/30 %) in the lipid vesicles and in the silica-particle supported lipid membrane, which provides information on the mechanism by which the vesicles adsorb to the surface. Furthermore, cytochrome c oxidase could maintain a proton electrochemical gradient across the supported proteomembrane, i.e. the membrane system was proton tight, defining an interior particle compartment that is separated from the surrounding aqueous media. Such a biofunctional cellular interface, supported onto a colloid that has a connected interior cytoskeleton-like pore structure, provides a basis for functional studies of membrane-bound transport proteins, and also for applications within pharmaceutical drug delivery.

  • 11.
    Qian, Bin
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Saeidi, Kamran
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kvetková, L.
    Lofaj, F.
    Xiao, Changhong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Defects-tolerant Co-Cr-Mo dental alloys prepared by selective laser melting2015In: Dental Materials, ISSN 0109-5641, E-ISSN 1879-0097, Vol. 31, no 12, p. 1435-1444Article in journal (Refereed)
    Abstract [en]

    Objectives. CrCoMo alloy specimens were successfully fabricated using selective laser melting (SLM). The aim of this study was to carefully investigate microstructure of the SLM specimens in order to understand the influence of their structural features inter-grown on different length scales ranging from nano-to macro-levels on their mechanical properties.

    Methods. Two different sets of processing parameters developed for building the inner part( core) and the surface (skin) of dental prostheses were tested. Microstructures were characterized by SEM, EBSD and XRD analysis. The elemental distribution was assessed by EDS line profile analysis under TEM. The mechanical properties of the specimens were measured.

    Results. The microstructures of both specimens were characterized showing formation of grains comprised of columnar sub-grains with Mo-enrichment at the sub-grain boundaries. Clusters of columnar sub-grains grew coherently along one common crystallographic direction forming much larger single crystal grains which are intercrossing in different directions forming an overall dendrite-like microstructure. Three types of microstructural defects were occasionally observed; small voids (<10 mu m), fine cracks at grain boundaries (<10 mu m) and cracks at weld line boundaries (>10 mu m). Despite the presence of these defects, the yield and the ultimate tensile strength (UTS) were 870 and 430 MPa and 1300 MPa and 1160 MPa, respectively, for the skin and core specimens which are higher than casted dental alloy.

    Significance. Although the formation of microstructural defects is hard to be avoided during the SLM process, the SLM CoCrMo alloys can achieve improved mechanical properties than their casted counterparts, implying they are defect-tolerant.

  • 12.
    Ray, Arjun
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Lindahl, Erik
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Wallner, Björn
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Model quality assessment for membrane proteins2010In: Bioinformatics, ISSN 1367-4803, E-ISSN 1367-4811, Vol. 26, no 24, p. 3067-3074Article in journal (Refereed)
    Abstract [en]

    Motivation: Learning-based model quality assessment programs have been quite successful at discriminating between high-and low-quality protein structures. Here, we show that it is possible to improve this performance significantly by restricting the learning space to a specific context, in this case membrane proteins. Since these are among the most important structures from a pharmaceutical point-of-view, it is particularly interesting to resolve local model quality for regions corresponding, e. g. to binding sites. Results: Our new ProQM method uses a support vector machine with a combination of general and membrane protein-specific features. For the transmembrane region, ProQM clearly outperforms all methods developed for generic proteins, and it does so while maintaining performance for extra-membrane domains; in this region it is only matched by ProQres. The predictor is shown to accurately predict quality both on the global and local level when applied to GPCR models, and clearly outperforms consensus-based scoring. Finally, the combination of ProQM and the Rosetta low-resolution energy function achieve a 7-fold enrichment in selection of near-native structural models, at very limited computational cost.

  • 13. Ruiz-Hitzky, Eduardo
    et al.
    Fernandes, Francisco M.
    Wicklein, Bernd
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Aranda, Pilar
    Clay-Based Bionanocomposite Foams2016In: Biofoams: science and applications of bio-based cellular and porous materials / [ed] Salvatore Iannace, Chul B. Park, Boca Raton: Taylor & Francis, 2016, p. 251-265Chapter in book (Refereed)
  • 14.
    Salih, Tagrid
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Ahlford, Annika
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Nilsson, Mats
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Plichta, Zdenek
    Horak, Daniel
    Streptavidin-modified monodispersed magnetic poly(2-hydroxyethyl methacrylate) microspheres as solid support in DNA-based molecular protocols2016In: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 61, p. 362-367Article in journal (Refereed)
    Abstract [en]

    Molecular diagnostics may provide tailored and cost efficient treatment for infectious disease and cancer. Rolling circle amplification (RCA) of padlock probes guarantees high specificity to identify nucleic acid targets down to single nucleotide resolution in a multiplex fashion. This makes the assay suitable for molecular analysis of various diseases, and interesting to integrate into automated devices for point-of-care analysis. A critical prerequisite for many molecular assays is (i) target-specific isolation from complex clinical samples and (ii) removal of reagents, inhibitors and contaminants between reaction steps. Efficient solid supports are therefore essential to enable multi-step, multi-analyte protocols. Superparamagnetic micro- and nanoparticles, with large surface area and rapid liquid-phase kinetics, are attractive for multi-step protocols. Recently, streptavidin-modified magnetic monodispersed poly(2-hydroxyethyl methacrylate) (STV-mag.PHEMA) microspheres were developed by multiple swelling polymerization. They are easily separated by a magnet and exhibit low non-specific protein sorption. In this study, the performance and the binding efficiency of STV-mag.PHEMA was addressed by circle-to-circle amplification (C2CA). A lower number of RCA products were detected as compared to the gold standard Dynabeads. Nevertheless, this study was the first to successfully adapt STV-mag.PHEMA microspheres as solid support in a DNA-based protocol, which is an important finding. The STV-mag.PHEMA microspheres were larger with about 16 times less surface area as compared to the Dynabeads, which might partly explain the lower rolling circle product (RCP) count obtained. Further research is currently ongoing comparing particles of similar sizes and optimizing reaction conditions to establish their full utility in the field. Ultimately, low cost and versatile particles are a great resource to facilitate future clinical molecular diagnostics.

  • 15.
    Sandström, Anders G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Highly Combinatorial Reshaping of the Candida antarctica lipase A Substrate Pocket Using an Extremely Condensed LibraryManuscript (preprint) (Other academic)
    Abstract [en]

    A highly combinatorial structure based protein engineering method is demonstrated resulting in a thorough modification of the binding pocket of Candida antarctica lipase A (CALA). Nine amino acid sites surrounding the entire pocket were simultaneously mutated, contributing to a sculpting of the substrate pocket toward a sterically demanding substrate, an ibuprofen ester. The best variant was highly active and displayed remarkable increase in enantioselectivity toward the substrate, with an E-value of 101, compared to the wild type CALA that poor activity and possesses an E-value of 3.4. The potential mutations introduced were a highly reduced set of amino acids, containing only the wild type residue and an alternative residue, preferably a smaller one with similar properties. These minimal ‘binary’ sets allow for extremely condensed protein libraries. The choice of amino acid sites were based on a computer model, with the substrate forcibly bound in the active site. This highly combinatorial method can be used to obtain tailor-made enzymes that are active toward substrates that are not normally accepted by the enzyme. When multiple sites are altered simultaneously, there is a higher possibility of obtaining positive synergistic effects, and the protein fitness landscape is explored efficiently.

  • 16.
    Sandström, Anders G.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Protein Engineering of Candida antarctica Lipase A: Enhancing Enzyme Properties by Evolutionary and Semi-Rational Methods2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Enzymes are gaining increasing importance as catalysts for selective transformations in organic synthetic chemistry. The engineering and design of enzymes is a developing, growing research field that is employed in biocatalysis. In the present thesis, combinatorial protein engineering methods are applied for the development of Candida antarctica lipase A (CALA) variants with broader substrate scope and increased enantioselectivity. Initially, the structure of CALA was deduced by manual modelling and later the structure was established by X-ray crystallography. The elucidation of the structure of CALA revealed several biocatalytically interesting features. With the knowledge derived from the enzyme structure, enzyme variants were produced via iterative saturation mutagenesis (ISM), a powerful protein engineering approach. Several of these variants were highly active and enantioselective towards bulky esters. Furthermore, an extensively combinatorial protein engineering approach was developed and investigated. A CALA variant with a spacious substrate binding pocket that can accommodate an unusually bulky substrate, an ester derivate of the non-steroidal anti-inflammatory drug (S)-ibuprofen, was obtained with this approach.

  • 17.
    Skiöld, Sara
    et al.
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Naslund, Ingemar
    Brehwens, Karl
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Andersson, Arja
    Wersall, Peter
    Lidbrink, Elisabet
    Harms-Ringdahl, Mats
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Wojcik, Andrzej
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Haghdoost, Siamak
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Radiation-induced stress response in peripheral blood of breast cancer patients differs between patients with severe acute skin reactions and patients with no side effects to radiotherapy2013In: Mutation research. Genetic toxicology and environmental mutagenesis, ISSN 1383-5718, E-ISSN 1879-3592, Vol. 756, no 1-2, p. 152-157Article in journal (Refereed)
    Abstract [en]

    The aim of the study was to compare the radiation-induced oxidative stress response in blood samples from breast cancer patients that developed severe acute skin reactions during the radiotherapy, with the response in blood samples from patients with no side effects. Peripheral blood was collected from 12 breast cancer patients showing no early skin reactions after radiotherapy (RTOG grade 0) and from 14 breast cancer patients who developed acute severe skin reactions (RTOG grade 3-4). Whole blood was irradiated with 0, 5 and 2000 mGy gamma-radiation and serum was isolated. The biomarker for oxidative stress, 8-oxo-dG, was analyzed in the serum by a modified ELISA. While a significant radiation-induced increase of serum 8-oxo-dG levels was observed in serum of the RTOG 0 patients, no increase was seen in serum of the RTOG 3-4 patients. The radiation induced increase in serum 8-oxo-dG levels after 5 mGy did not differ significantly from the increase observed for 2000 mGy in the RTOG 3-4 cohort, thus no dose response relation was observed. A receiver operating characteristic (ROC) value of 0.97 was obtained from the radiation-induced increase in 8-oxo-dG indicating that the assay could be used to identify patients with severe acute adverse reactions to radiotherapy. The results show that samples of whole blood from patients, classified as highly radiosensitive (RTOG 3-4) based on their skin reactions to radiotherapy, differ significantly in their oxidative stress response to ionizing radiation compared to samples of whole blood from patients with no skin reactions (RTOG 0). Extracellular 8-oxo-dG is primarily a biomarker of nucleotide damage and the results indicate that the patients with severe acute skin reactions differ in their cellular response to ionizing radiation at the level of induction of oxidative stress or at the level of repair or both.

  • 18. Style, Robert W.
    et al.
    Che, Yonglu
    Park, Su Ji
    Weon, Byung Mook
    Je, Jung Ho
    Hyland, Callen
    German, Guy K.
    Power, Michael P.
    Wilen, Larry A.
    Wettlaufer, John S.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Yale Univversity, USA.
    Dufresne, Eric R.
    Patterning droplets with durotaxis2013In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 110, no 31, p. 12541-12544Article in journal (Refereed)
    Abstract [en]

    Numerous cell types have shown a remarkable ability to detect and move along gradients in stiffness of an underlying substrate-a process known as durotaxis. The mechanisms underlying durotaxis are still unresolved, but generally believed to involve active sensing and locomotion. Here, we show that simple liquid droplets also undergo durotaxis. By modulating substrate stiffness, we obtain fine control of droplet position on soft, flat substrates. Unlike other control mechanisms, droplet durotaxis works without imposing chemical, thermal, electrical, or topographical gradients. We show that droplet durotaxis can be used to create large-scale droplet patterns and is potentially useful for many applications, such as microfluidics, thermal control, and microfabrication.

  • 19.
    Sörensen, Malin
    et al.
    YKI, Institute for Surface Chemistry.
    Ng, Jovice Boon Sing
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Alberius, Peter
    YKI, Institute for Surface Chemistry.
    Improved enzymatic activity of Thermomyces lanuginosus lipase immobilized in a hydrophobic particulate2010In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 343, no 1, p. 359-365Article in journal (Refereed)
    Abstract [en]

    Lipase from Thermomyces lanuginosus has been immobilized within particulate mesoporous silica carriers, with either hydrophilic or hydrophobic supporting surfaces, produced by the newly developed emulsion and solvent evaporation (ESE) method.  The Michaelis-Menten model was used to calculate the parameters related to the enzymatic activity of lipase i.e. the turnover number, kcat, and the specific activity. The specific activity was improved by immobilization of lipase onto the hydrophobic support, compared to lipase immobilized onto the hydrophilic support and lipase free in solution. The enhanced enzymatic activity of lipase onto a hydrophobic support was attributed to interfacial activation of the Thermomyces lanuginosus lipase when it is attached to a hydrophobic surface and a reduced denaturation. Confocal scanning laser microscopy (CLSM) studies, of fluorescently tagged lipase, showed that leakage of the lipase from the mesoporous particles was limited to an initial period of only a few hours. Both the rate and the amount of lipase leached were reduced when the lipase was immobilized onto the hydrophobic support.

  • 20.
    Walldén, Karin
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Structural Studies of Human 5'-Nucleotidases2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    5’-Nucleotidases (5’NTs) are catabolic enzymes of the nucleotide metabolism. They catalyze dephosphorylation of deoxyribo- and ribonucleoside monophosphates and constitute an important control point in the regulation of intracellular nucleotide pools for the maintenance of correct DNA and RNA synthesis.

    By removing the alfa-phosphate group from a nucleotide, the 5’NTs release the nucleoside to pass the plasma membrane by facilitated diffusion. Depending on the cellular need for nucleotides, the nucleosides can either exit the cell for reuse elsewhere or be imported and subsequently phosphorylated by nucleoside and nucleotide kinases.

    The knowledge of how nucleotides are metabolized has been used for rational design of nucleoside analogues that are used in treatment of cancer and viral diseases. These drugs are phosphorylated within the cell to become active. Their dephosphorylation by 5’NTs might be one of the mechanisms behind the resistance experienced by patients towards such drugs.

    This thesis describes structure-function studies on four of the seven known human 5’-NTs. The focus of the work is on the substrate specificity and regulation of these enzymes. Inactive variants of the mitochondrial and cytosolic deoxynucleotidases and the cytosolic 5’-nucleotidase II were used to characterize the structural basis for their substrate specificity in high detail.

    Based on structures of the apoprotein and activator/activator+substrate complexes of cytosolic 5’-nucleotidase II, a mechanism for the allosteric activation of this enzyme was presented. In this mechanism, the activator induces a conformational change that involves conserved residues of the active site. The conformational change drastically increases the enzyme affinity for the phosphate moiety of the substrate.

  • 21. Zhang, Ranran
    et al.
    Elkhooly, Tarek A.
    Huang, Qianli
    Liu, Xujie
    Yang, Xing
    Yan, Hao
    Xiong, Zhiyuan
    Ma, Jing
    Feng, Qingling
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Tsinghua University, China.
    A dual-layer macro/mesoporous structured TiO2 surface improves the initial adhesion of osteoblast-like cells2017In: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 78, p. 443-451Article in journal (Refereed)
    Abstract [en]

    A dual-layer TiO2 surface with hierarchical macro and mesoporous structure was prepared by a combinational approach of micro-arc oxidation followed by evaporation-induced self-assembly of nano-crystallites. The mesoporous layer contains pores with an average size of <10 nm and consists of anatase TiO2 nanocrystallites. The dual-layer hierarchical macro/mesoporous structured TiO2 surface improves the hydrophilicity and fibronectin adsorption ability in comparison with the sole macroporous or smooth TiO2 surface. With the formation of an additional mesoporous layer on macroporous TiO2 surface, the attached number of human osteogenic sarcoma cells (SaOS-2) increases in the initial incubation of 4 h but it does not show significant difference after 24 h compared to that attached on the macroporous or smooth surfaces. Whereas, it was noticed that SaOS-2 cells have larger spread area and more stress fibers on the macro/mesoporous structured surface than those on the other surfaces. To understand the intracellular mechanism of the initial cell adhesion on the macro/mesoporous surface, the Rho/ROCK pathway was investigated to reveal the topography-induced biological functions by introducing the ROCK inhibitor Y-27632 during cell culture. In the presence of Y-27632, cells on the macroporous surface and macro/mesoporous surface both show stellate appearance, with poor assembly stress fibers and long cell membrane protrusions. Cells on the smooth surface have larger spread areas compared to the former two surfaces. And the attached cells significantly reduced but there are no differences among the three surfaces. It reveals that the ROCK inhibitor invalidates the promotion of initial cell adhesion on the macro/mesoporous structure. This study may shed light on the mechanism behind the enhancement effect of macro/mesoporous structure for initial cell adhesion.

  • 22. Zhang, Ranran
    et al.
    Elkhooly, Tarek A.
    Huang, Qianli
    Liu, Xujie
    Yang, Xing
    Yan, Hao
    Xiong, Zhiyuan
    Ma, Jing
    Feng, Qingling
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Tsinghua University, China.
    Effects of the hierarchical macro/mesoporous structure on the osteoblast-like cell response2018In: Journal of Biomedical Materials Research. Part A, ISSN 1549-3296, E-ISSN 1552-4965, Vol. 106, no 7, p. 1896-1902Article in journal (Refereed)
    Abstract [en]

    To improve the success of medical devices, implants with strong surface bioactivity are urgently required. Coatings with a macroporous structure produced by micro-arc oxidation possess advantages, such as strong adhesion to substrate and excellent resistance to wear and corrosion. Mesoporous structures contain pores with sizes of 2-50 nm, which can endow the biomaterials with the ability to enhance osteogenesis and to be loaded with diverse drugs. Thus, in this study, we aimed to evaluate the effects of both macroporous and mesoporous structures using a hierarchical macro/mesoporous structure to modify the titanium implant surface. The behaviors of SaOS-2 human osteosarcoma cells on the macro/mesoporous structure, including initial adhesion, proliferation, alkaline phosphatase (ALP) activity, and collagen secretion, were investigated. Cells that attached on the macro/mesoporous surface showed the highest cell numbers and greatest spreading area after incubation for 1, 2, and 4 h compared with the polished smooth substrate and macroporous surface in the presence of fetal bovine serum (FBS). However, in the absence of FBS, cell adhesion on the polished substrate, macroporous structure, and macro/mesoporous structure did not differ significantly. Cell proliferation on the macroporous and macro/mesoporous surfaces increased compared with that on the smooth substrate surface. Furthermore, ALP activity and collagen secretion were enhanced on the macro/mesoporous structure. Our findings provided important insights into the cellular responses to macro/mesoporous structures in the field of implant surface modification.

  • 23. Zirk, Katrin
    et al.
    Langel, Ülo
    Stockholm University, Faculty of Science, Department of Neurochemistry. University of Tartu, Estonia.
    Vectorization of splice-correcting oligonucleotides with cell-penetrating peptides2013In: Chimica oggi, ISSN 0392-839X, E-ISSN 1973-8250, Vol. 31, no 2, p. 12-15Article in journal (Refereed)
    Abstract [en]

    Personalized medicine approaches based on different gene therapy settings have gained much attention lately. In order to enforce successful gene therapy, genetic material needs to be delivered into cells. Nucleic acids and their analogues are unable to do so and thus require assistance to reach their site of action residing in the cytoplasm or nucleus. Here we give a short review on recent advancements in cell-penetrating peptide mediated delivery of splice-correcting oligonucleotides. We report on different cell-penetrating peptides applied for vectorization of splice-correcting oligonucleotides using both covalent conjugation and non-covalent nanoparticle formation approach. While covalent conjugation has gained extensive interest, there have also been great advances in non-covalent complex formation.

1 - 23 of 23
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