Change search
Refine search result
1 - 8 of 8
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1. Karl, Matthias
    et al.
    Leck, Caroline
    Stockholm University, Faculty of Science, Department of Meteorology .
    Mashayekhy Rad, Farshid
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Bäcklund, Are
    Lopez-Aparicio, Susana
    Heintzenberg, Jost
    Sources of the sub-micrometre aerosol at Mt. Zeppelin Observatory (Spitsbergen) in the year 2015: Indication for ice-related marinegelsManuscript (preprint) (Other academic)
  • 2.
    Keshavarzi, Neda
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mashayekhy Rad, Farshid
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Mace, Amber
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ansari, Farhan
    Akhtar, Farid
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Berglund, Lars
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nanocellulose-Zeolite Composite Films for Odor Elimination2015In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 7, no 26, p. 14254-14262Article in journal (Refereed)
    Abstract [en]

    Free standing and strong odor-removing composite films of cellulose nanofibrils (CNF) with a high content of nanoporous zeolite adsorbents have been colloidally processed. Thermogravimetric desorption analysis (TGA) and infrared spectroscopy combined with computational simulations showed that commercially available silicalite-1 and ZSM-5 have a high affinity and uptake of volatile odors like ethanethiol and propanethiol, also in the presence of water. The simulations showed that propanethiol has a higher affinity, up to 16%, to the two zeolites compared with ethanethiol. Highly flexible and strong free-standing zeolite CNF films with an adsorbent loading of 89 w/w% have been produced by Ca-induced gelation and vacuum filtration. The CNF-network controls the strength of the composite films and 100 mu m thick zeolite CNF films with a CNF content of less than 10 vol % displayed a tensile strength approaching 10 MPa. Headspace solid phase microextraction (SPME) coupled to gas chromatography mass spectroscopy (GC/MS) analysis showed that the CNF zeolite films can eliminate the volatile thiol-based odors to concentrations below the detection ability of the human olfactory system. Odor removing zeolite-cellulose nanofibril films could enable improved transport and storage of fruits and vegetables rich in odors, for example, onion and the tasty but foul-smelling South-East Asian Durian fruit.

  • 3.
    Leck, Caroline
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gao, Qiuju
    Stockholm University, Faculty of Science, Department of Meteorology .
    Mashayekhy Rad, Farshid
    Stockholm University, Faculty of Science, Department of Meteorology . Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Size-resolved atmospheric particulate polysaccharides in the high summer Arctic2013In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 13, no 24, p. 12573-12588Article in journal (Refereed)
    Abstract [en]

    Size-resolved aerosol samples for subsequent quantitative determination of polymer sugars (polysaccharides) after hydrolysis to their subunit monomers (monosaccharides) were collected in surface air over the central Arctic Ocean during the biologically most active summer period. The analysis was carried out by novel use of liquid chromatography coupled with highly selective and sensitive tandem mass spectrometry. Polysaccharides were detected in particle sizes ranging from 0.035 to 10 mu m in diameter with distinct features of heteropolysaccharides, enriched in xylose, glucose + mannose as well as a substantial fraction of deoxysugars. Polysaccharides, containing deoxysugar monomers, showed a bimodal size structure with about 70% of their mass found in the Aitken mode over the pack ice area. Pentose (xylose) and hexose (glucose + mannose) had a weaker bimodal character and were largely found with super-micrometer sizes and in addition with a minor sub-micrometer fraction. The concentration of total hydrolysable neutral sugars (THNS) in the samples collected varied over two orders of magnitude (1 to 160 pmol m(-3)) in the supermicrometer size fraction and to a somewhat lesser extent in sub-micrometer particles (4 to 140 pmol m(-3)). Lowest THNS concentrations were observed in air masses that had spent more than five days over the pack ice. Within the pack ice area, about 53% of the mass of hydrolyzed polysaccharides was detected in sub-micrometer particles. The relative abundance of sub-micrometer hydrolyzed polysaccharides could be related to the length of time that the air mass spent over pack ice, with the highest fraction (> 90 %) observed for > 7 days of advection. The aerosol samples collected onboard ship showed similar monosaccharide composition, compared to particles generated experimentally in situ at the expedition's open lead site. This supports the existence of a primary particle source of polysaccharide containing polymer gels from open leads by bubble bursting at the air-sea interface. We speculate that the occurrence of atmospheric surface-active polymer gels with their hydrophilic and hydrophobic segments, promoting cloud droplet activation, could play a potential role as cloud condensation nuclei in the pristine high Arctic.

  • 4.
    Mashayekhy Rad, Farshid
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Analytical methods for biomolecules involved in atmospheric aerosol formation in the Arctic2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the Arctic, increasing ice-free conditions and nutrients freed from the melting ice must strongly influence the marine life. Aerosol emissions from microbiological marine processes may affect the low clouds and fogs over the summer Arctic, which in turn have effects on the melting of sea ice. The radiative properties of the high Arctic low clouds are strongly dependent on the number concentration of airborne water-soluble particles, known as cloud condensation nuclei (CCN). If the effects of CCN on cloud optical properties is to be fully understood it is important to be able to specify the source and concentrations of the Arctic aerosol particles.

    Previous studies in the Arctic have indicated that organic material formed in the uppermost ocean surface is transferred to the atmosphere and plays a potentially very important role in the aerosol-fog/cloud cycle. However, many aspects of this process remain unverified and chemical characterisation of targeted groups of biomolecules is still notably fragmentary or non-existing. Investigation of biomolecules, particularly amino acids, peptides and proteins together with mono- and polysac­charides and fatty acids in the airborne aerosol, and their relative contributions to fog/cloud water, requires development of an array of “cutting edge” analytical techniques and methods.

    In this thesis, electrospray ionization mass spectrometry was used for all applications and target biomolecules. The measurements in the Arctic turned out to be challenging due to the highly complex, salty matrices, combined with very low concentration and high diversity of the target biomolecules, and each step of the analytical chain needed careful consideration. To increase the detectability of the very low levels of polysaccharides and proteins in aerosols, these compounds were hydrolyzed to their subunits, monosaccharides and amino acids. Monosaccharides were separated using hydrophilic interaction chromatography, which was beneficial for their detection in electrospray ionization mass spectrometry. Amino acids were derivatized, yielding improvement in reversed-phase chromatographic separation, ionization efficiency as well as selectivity. For fatty acids in a sea surface sample, a novel fast screening method was developed, utilizing travelling-wave ion mobility separation as an orthogonal technique connected to mass spectrometry. In addition, a method for the detection of wood burning as an anthropogenic source of aerosols was developed, utilizing anhydrous monosaccharides as markers. This method can be used in the upcoming expeditions for source apportionment studies.

    The results from the analyses of the aerosol and fog water samples, collected over the summer pack ice north of 80 °N, show that both total polysaccharides and total proteinaceous compounds (sum of proteins, peptides and amino acids) occurred at the pmol m-3 to nmol m-3 level. Interestingly, the levels were found higher between different years, suggested to be coupled to less ice coverage and thus to a higher biological activity in the ocean surface. The highest concentrations of polysaccharides, as an indication of marine polymer gels, were found during the summer over the pack ice area. In addition, a pilot source apportionment study was carried out combining the measurement of different molecular tracers, used as source markers. This study indicates the seasonality and abundance of marine polymer gels as an important feature of the Arctic Ocean connected to the melting and freezing of sea ice. It should be further studied how the abundance of these gels, which have a high potential for cloud droplet activation, affect the melting and freezing of the perennial sea ice.

    Given the successful development of analytical methods for targeted groups of biomolecules, this thesis has supported the importance of biomolecules as CCN and for cloud formation in the Arctic. Less ice coverage may further increase the number of biomolecular CCN which could change the radiative balance, by the formation of more low-level clouds. Overall, more studies are required to further unravel the complex relationship of biogenic sources, atmospheric chemistry and meteorology to assess the impact of climate change on the Arctic.

  • 5.
    Mashayekhy Rad, Farshid
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Leck, Caroline
    Stockholm University, Faculty of Science, Department of Meteorology .
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Investigation of ultrahigh-performance liquid chromatography/travelling-wave ion mobility/time-of-flight mass spectrometry for fast profiling of fatty acids in the high Arctic sea surface microlayer2018In: Rapid Communications in Mass Spectrometry, ISSN 0951-4198, E-ISSN 1097-0231, Vol. 32, no 12, p. 942-950Article in journal (Refereed)
    Abstract [en]

    Rationale

    Fatty acids are enriched in the ocean surface microlayer (SML) and have as a consequence been detected worldwide in sea spray aerosols. In searching for a relationship between the properties of the atmospheric aerosol and its ability to form cloud condensation nuclei and to promote cloud droplet formation over remote marine areas, the role of surface active fatty acids sourced from the SML is of interest to be investigated. Here is presented a fast method for profiling of major fatty acids in SML samples collected in the high Arctic (89 °N, 1 °W) in the summer of 2001.

    Methods

    UHPLC/travelling‐wave ion mobility spectrometry (TWIMS)/time‐of‐flight (TOF) mass spectrometry (MS) for profiling was evaluated and compared with UHPLC/TOFMS. No sample preparation, except evaporation and centrifugation, was necessary to perform prior to the analysis.

    Results

    TOFMS data on accurate mass, isotopic ratios and fragmentation patterns enabled identification of the fatty acids. The TWIMS dimension added to the selectivity by extensive reduction of the noise level and the entire UHPLC/TWIMS/TOFMS method provided a fast profiling of the acids, ranging from C8 to C24. Hexadecanoic and octadecanoic acids were shown to yield the highest signals among the fatty acids detected in a high Arctic SML sample, followed by the unsaturated octadecenoic and octadecadienoic acids. The predominance of signal from even‐numbered carbon chains indicates a mainly biogenic origin of the detected fatty acids.

    Conclusions

    This study presents a fast alternative method for screening and profiling of fatty acids, which has the advantage of not requiring any complicated sample preparation thus limiting the loss of analytes. Almost no manual handling, together with the very small sample volumes needed, is certainly beneficial for the determination of trace amounts and should open up the field of applications to also include atmospheric aerosol and fog.

  • 6.
    Mashayekhy Rad, Farshid
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Spinicci, Silvia
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Silvergren, Sanna
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Validation of a HILIC/ESI-MS/MS method for the wood burning marker levoglucosan and its isomers in airborne particulate matter2018In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 211, p. 617-623Article in journal (Refereed)
    Abstract [en]

    In the present study, a methodology involving hydrophilic interaction liquid chromatography (HILIC) and electrospray (ESI) tandem mass spectrometry (MS/MS) was developed for measurement of anhydrous monosaccharides as markers for wood burning in atmospheric aerosols, PM10. No extensive sample preparation, other than ultrasound-assisted solvent extraction and evaporation, was applied. A pentahydroxysilica column enabled separation of levoglucosan from mannosan and galactosan within 5 min and the quantitative performance was validated using the standard reference materials (SRM) 1649a and 1649b. The experimentally obtained results for SRMs were in agreement with values previously reported in other studies. Achieved instrumental limits of detection (LODs) were below 10 pg injected on column, corresponding to LODs in air lower than 0.10 ng/m3 for all measured isomers for 2–3 day sampling with 1.0 m−3 h−1 sampling rate.

    The validated method was used for the determination of levoglucosan and its isomers in atmospheric aerosols collected in three different Swedish urban areas during the winter and summer time in 2017. The total measured concentrations for levoglucosan and galactosan + mannosan were determined to be between 78 and 167 ng/m3 in January 2017, which is approximately 10-times higher compared to the levels detected in July, reflecting the higher frequency of wood burning for heating during the cold season. Calculated concentration ratios between levoglucosan and its isomers in the urban area samples indicated mostly mixed softwood/hardwood combustion in winter time; on the other hand, softwood burning was observed as the major emission in summer time.

  • 7.
    Mashayekhy Rad, Farshid
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Stockholm University, Faculty of Science, Department of Meteorology .
    Zurita, Javier
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Gilles, Philippe
    Rutgeerts, Laurens A. J.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Leck, Caroline
    Stockholm University, Faculty of Science, Department of Meteorology .
    Measurements of Atmospheric Proteinaceous Aerosol in the Arctic Using a Selective UHPLC/ESI-MS/MS Strategy2018In: Journal of the American Society for Mass Spectrometry, ISSN 1044-0305, E-ISSN 1879-1123Article in journal (Refereed)
    Abstract [en]

    In this article, an analytical methodology to investigate the proteinaceous content in atmospheric size-resolved aerosols collected at the Zeppelin observatory (79 °N, 12 °E) at Ny Ålesund, Svalbard, from September to December 2015, is proposed. Quantitative determination was performed after acidic hydrolysis using ultrahigh-performance liquid chromatography in reversed-phase mode coupled to electrospray ionization tandem mass spectrometry. Chromatographic separation, as well as specificity in the identification, was achieved by derivatization of the amino acids with N-butyl nicotinic acid N-hydroxysuccinimide ester prior to the analysis. The chromatographic run was performed within 11 min and instrumental levels of detection (LODs) were between 0.2 and 8.1 pg injected on the column, except for arginine which exhibited an LOD of 37 pg. Corresponding method LODs were between 0.01 and 1.9 fmol/m3, based on the average air sampling volume of 57 m3. The sum of free amino acids and hydrolyzed polyamino acids was shown to vary within 6–2914 and 0.02–1417 pmol/m3 for particles in sizes < 2 and 2–10 μm in equivalent aerodynamic diameter, respectively. Leucine, alanine, and valine were the most abundant among the amino acids in both aerosol size fractions. In an attempt to elucidate source areas of the collected aerosols, 5- to 10-day 3D backward trajectories reaching the sampling station were calculated. Overall, the method described here provides a first time estimate of the proteinaceous content, that is, the sum of free and polyamino acids, in size-resolved aerosols collected in the Arctic.

  • 8.
    Österlund, Nicklas
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Kulkarni, Yashraj S.
    Misiaszek, Agata D.
    Wallin, Cecilia
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Krüger, Dennis M.
    Liao, Qinghua
    Mashayekhy Rad, Farshid
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Jarvet, Jüri
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Strodel, Birgit
    Wärmländer, Sebastian K. T. S.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Ilag, Leopold L.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Kamerlin, Shina C. L.
    Gräslund, Astrid
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Amyloid-beta Peptide Interactions with Amphiphilic Surfactants: Electrostatic and Hydrophobic Effects2018In: ACS Chemical Neuroscience, ISSN 1948-7193, E-ISSN 1948-7193, Vol. 9, no 7, p. 1680-1692Article in journal (Refereed)
    Abstract [en]

    The amphiphilic nature of the amyloid-beta (A beta) peptide associated with Alzheimer's disease facilitates various interactions with biomolecules such as lipids and proteins, with effects on both structure and toxicity of the peptide. Here, we investigate these peptide-amphiphile interactions by experimental and computational studies of A beta(1-40) in the presence of surfactants with varying physicochemical properties. Our findings indicate that electrostatic peptide-surfactant interactions are required for coclustering and structure induction in the peptide and that the strength of the interaction depends on the surfactant net charge. Both aggregation-prone peptide-rich coclusters and stable surfactant-rich coclusters can form. Only A beta(1-40) monomers, but not oligomers, are inserted into surfactant micelles in this surfactant-rich state. Surfactant headgroup charge is suggested to be important as electrostatic peptide-surfactant interactions on the micellar surface seems to be an initiating step toward insertion. Thus, no peptide insertion or change in peptide secondary structure is observed using a nonionic surfactant. The hydrophobic peptide-surfactant interactions instead stabilize the A beta monomer, possibly by preventing self-interaction between the peptide core and C terminus, thereby effectively inhibiting the peptide aggregation process. These findings give increased understanding regarding the molecular driving forces for A beta aggregation and the peptide interaction with amphiphilic biomolecules.

1 - 8 of 8
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf