uu.seUppsala universitets publikationer
Ändra sökning
Avgränsa sökresultatet
182183184185186187188 9201 - 9250 av 9479
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 9201. Zadin, Vahur
    et al.
    Brandell, Daniel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Electrochemical simulations of 3D-battery architectures2015Ingår i: SolidState Battery Handbook / [ed] Nancy J. Dudney, William C West, Jagjit Nanda, Singapore: World Scientific , 2015, 2, s. 731-777Kapitel i bok, del av antologi (Refereegranskat)
  • 9202. Zadin, Vahur
    et al.
    Brandell, Daniel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi, Strukturkemi.
    Modelling polymer electrolytes for 3D-microbatteries using finite element analysis2011Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 57, s. 237-243Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Comparisons between a LiPF(6)center dot PEO(20) polymer electrolyte and a 1.5 M LiPF(6) liquid electrolyte in a 3D-microbattery of coated interdigitated current collector pillars is presented here, using Finite Element Analysis (FEA). Ionic transport in the electrolyte is modeled by the Nernst-Planck equation and electrode potentials by Ohm's law. Simulations were carried out in steady state. The height of the electrode pillars and the distance between them were systematically varied in the simulations to evaluate the effects on ionic transport in terms of concentration, concentration gradient and the minimum concentration in the electrolyte. The studies showed that the polarization in the electrolyte can be decreased by increasing the electrode pillar length, while increasing electrode distances led to a nonuniformity of the electrochemical activity. Indications of an optimum pillar length were also observed. Comparisons of the electrolytes showed that the polymer electrolyte was able to deliver a more uniform electrochemical activity for these cell designs, but not able to sustain as high currents as the liquid electrolytes. At the current density used (10 A/m(2)), concentration polarization in the polymer electrolyte led to concentration deviations from the mean value of up to 60%.

  • 9203.
    Zadin, Vahur
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi, Strukturkemi.
    Brandell, Daniel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi, Strukturkemi.
    Kasemaegi, Heiki
    Aabloo, Alvo
    Thomas, John O.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi, Strukturkemi.
    Finite element modelling of ion transport in the electrolyte of a 3D-microbattery2011Ingår i: Solid State Ionics, ISSN 0167-2738, E-ISSN 1872-7689, Vol. 192, nr 1, s. 279-283Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A mathematical model describing ionic transport in a 3D-microbattery (3D-MB) electrolyte is developed here using finite element methodology. The model is then exploited to study a 3D-MB based on an interdigitated plate ("trench") architecture for a 10 pm-thick electrolyte layer separating 10 mu m-thick graphite anode and LiCoO(2) cathode plates. The effect of varying plate length, end-shape and electronic conductivity is also modelled. It is shown that the 3D-MB architecture gives rise to qualitatively non-uniform current densities, leading to sub-optimal surface utilization. This can, in turn, be optimized by varying electrode geometries and/or material properties.

  • 9204. Zadin, Vahur
    et al.
    Brandell, Daniel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Kasemaegi, Heiki
    Lellep, Jaan
    Aabloo, Alvo
    Designing the 3D-microbattery geometry using the level-set method2013Ingår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 244, s. 417-428Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Strategies for automatic design of power-optimized 3D-microbattery geometries are here investigated by utilization of the level-set method with structure topology optimization. The methodology is extended from solid mechanics to electrochemical systems, where battery operation is simulated using the Nernst-Planck equation. The calculations are carried out for the 3D-"trench" geometry with LiCoO2 and LiC6 as electrodes, separated with a LiPF6 center dot PEO20 Polyethylene oxide polymer electrolyte. With the goal to achieve a maximum uniform electrochemical activity over the electrode surface area, an optimized electrode design is produced by coating the current collectors non-uniformly with active material. This is shown to be an effect of the 3D design of the cell. Evaluation of the resulting optimized cell by simulations of the discharge process demonstrates uniform electrode material utilization and almost uniform current density distribution over the entire electrode-electrolyte interface. Comparisons between optimized and non-optimized geometries showed that the geometry optimization increased the cell performance up to 2.25 times. This effect is mainly achieved by minimizing the internal energy losses caused by non-uniformities in the ionic transport in the battery.

  • 9205. Zadin, Vahur
    et al.
    Danilov, Dmitry
    Brandell, Daniel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Notten, Peter H. L.
    Aabloo, Alvo
    Finite element simulations of 3D ionic transportation properties in Li-ion electrolytes2012Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 65, s. 165-173Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In current work, the ionic transport limitations in the Li-ion battery liquid electrolyte with separator are studied by a finite element method. This theoretical approach is based on the Nernst-Planck equation. It is shown that instead of solving coupled PDE system for concentration and potential, it is sufficient to calculate only the concentration profile in a three-dimensional (3D) structure to obtain a full description of the diffusion-migration ionic transport in the electrolyte in the steady-state. Subsequently, the overpotential and electric field can be calculated by using the provided equations. It was found that diffusion and migration overpotentials are equal in the steady-state. Consequently, two algorithms exploiting electrolyte simulations are proposed and successfully used to calculate the limiting current for the simulated battery system. In the present study a single perforated layer of the separator is inserted into the electrolyte and the simulations are carried out by increasing the complexity of the membrane holes. The ionic transportation dependence on the pore shape was found to be local and limited by the spatial area around the perforated separator.

  • 9206. Zadin, Vahur
    et al.
    Kasemägi, Heiki
    Aabloo, Alvo
    Brandell, Daniel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi, Strukturkemi.
    Modelling electrode material utilization in the trench model 3D-microbattery by finite element analysis2010Ingår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 195, nr 18, s. 6218-6224Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A mathematical model for ionic transport in 3D-microbattery (3D-MB) using finite element analysis is presented here, based on concentrated solution theory, ionic and atomic diffusion and the Butler-Volmer equation. The model is used to study electrochemical processes taking place in the electrodes and electrolyte of a 3D-MB in the trench architecture, with a 10 mu m thick electrolyte layer separating 10 mu m thick graphite anode and LiCoO2 cathode plates. The effect of changing conductivity of the positive electrode and the electrode plate height is also studied. Qualitative and quantitative data describing battery performance in terms of concentration gradient development and discharge curves points out the range for the most favourable electronic conductivity values of the electrodes: the values should not differ by more than order of magnitude. Furthermore, it is shown that also with optimal electrode conductivity values for electrodes, the Li ion diffusion in the electrodes during discharge is limiting the performance of the battery due to inhomogeneous lithiation and delithiation. Changing electrode height can be used to fine tune surface area usage, but has a limited effect on the overall battery performance.

  • 9207.
    Zaharieva, Ivelina
    et al.
    Free Univ Berlin, Dept Phys, D-14195 Berlin, Germany..
    Chernev, Petko
    Free Univ Berlin, Dept Phys, D-14195 Berlin, Germany..
    Berggren, Gustav
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Anderlund, Magnus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Styring, Stenbjörn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik.
    Dau, Holger
    Free Univ Berlin, Dept Phys, D-14195 Berlin, Germany..
    Haumann, Michael
    Free Univ Berlin, Dept Phys, D-14195 Berlin, Germany..
    Room-Temperature Energy-Sampling K beta X-ray Emission Spectroscopy of the Mn4Ca Complex of Photosynthesis Reveals Three Manganese-Centered Oxidation Steps and Suggests a Coordination Change Prior to O-2 Formation2016Ingår i: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 55, nr 30, s. 4197-4211Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In oxygenic photosynthesis, water is oxidized and dioxygen is produced at a Mn4Ca complex bound to the proteins of photosystem II (PSII). Valence and coordination changes in its catalytic S-state cycle are of great interest. In room-temperature (in situ) experiments, time-resolved energy-sampling X-ray emission spectroscopy of the Mn K beta(1,3) line after laser-flash excitation of PSII membrane particles was applied to characterize the redox transitions in the S-state cycle. The K beta(1,3) line energies suggest a high-valence configuration of the Mn4Ca complex with Mn(III)(3)Mn(IV) in S-0, Mn(III)(2)Mn(IV)(2) in S-1, Mn(III)Mn(IV)(3) in S-2, and Mn(IV)(4) in S-3 and, thus, manganese oxidation in each of the three accessible oxidizing transitions of the water-oxidizing complex There are no indications of formation of a ligand radical, thus rendering partial water oxidation before reaching the S-4 state unlikely. The difference spectra of both manganese K beta(1,3) emission and K-edge X-ray absorption display different shapes for Mn(III) oxidation in the S-2 -> S-3 transition when compared to Mn(III) oxidation in the S-1 -> S-2 transition. Comparison to spectra of manganese compounds with known structures and oxidation states and varying metal coordination environments suggests a change in the manganese ligand environment in the S-2 -> S-3 transition, which could be oxidation of five-coordinated Mn(III) to six-coordinated Mn(IV). Conceivable options for the rearrangement of (substrate) water species and metal ligand bonding patterns at the Mn4Ca complex in the S-2 -> S-3 transition are discussed.

  • 9208.
    Zakaria, Nadia
    et al.
    Antwerp Univ Hosp, Ophthalmol CCRG, Antwerp, Belgium;Univ Antwerp, Antwerp, Belgium.
    Haagdorens, Michel
    Univ Antwerp, Antwerp, Belgium.
    Liszka, Aneta
    Linkoping Univ, Linkoping, Sweden.
    Ulcinas, Arturas
    Ferentis, Vilnius, Lithuania.
    Cepla, Vytautas
    CPST, Vilnius, Lithuania.
    Valiokas, Ramunas
    Ferentis, Vilnius, Lithuania.
    Ljunggren, Monika Kozak
    Linkoping Univ, Linkoping, Sweden.
    Samanta, Ayan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Polymerkemi.
    Tassignon, Marie-Jose B. R.
    Antwerp Univ Hosp, Ophthalmol CCRG, Antwerp, Belgium.
    Tal, Yeheil
    Collplant, 3 Sapir St,Weizmann Sci Park,POB 4132, IL-74140 Ness Ziona, Israel.
    Orr, Nadav
    Collplant, 3 Sapir St,Weizmann Sci Park,POB 4132, IL-74140 Ness Ziona, Israel.
    Shoseyov, Oded
    Collplant, 3 Sapir St,Weizmann Sci Park,POB 4132, IL-74140 Ness Ziona, Israel.
    Pintelon, Isabel
    Univ Antwerp, Antwerp, Belgium.
    Griffith, May
    10 Univ Montreal, Montreal, PQ, Canada;Maisonneuve Rosemont Hosp Res Ctr, Montreal, PQ, Canada.
    Recombinant human collagen type I hydrogels as superior cell carriers for corneal epithelial stem cells2018Ingår i: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 59, nr 9Artikel i tidskrift (Övrigt vetenskapligt)
  • 9209.
    Zand, Zahra
    et al.
    IASBS, Dept Chem, Zanjan 4513766731, Iran.
    Salimi, Payam
    IASBS, Dept Chem, Zanjan 4513766731, Iran.
    Mohammadi, Mohammad Reza
    Free Univ Berlin, Dept Phys, Arnimallee 14, D-14195 Berlin, Germany;Univ Sistan & Baluchestan, Dept Phys, Zahedan 9816745845, Iran.
    Bagheri, Robabeh
    Chinese Acad Sci, Key Lab Marine Mat & Related Technol, Zhejiang Key Lab Marine Mat & Protect Technol, Ningbo Inst Mat Technol & Engn, Ningbo 315201, Zhejiang, Peoples R China;Soochow Univ, Soochow Inst Energy & Mat Innovat, Sch Phys Sci & Technol, Coll Energy, Suzhou 215006, Peoples R China;Soochow Univ, Key Lab Adv Carbon Mat & Wearable Energy Technol, Suzhou 215006, Peoples R China.
    Chernev, Petko
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik. Free Univ Berlin, Dept Phys, Arnimallee 14, D-14195 Berlin, Germany.
    Song, Zhenlun
    Chinese Acad Sci, Key Lab Marine Mat & Related Technol, Zhejiang Key Lab Marine Mat & Protect Technol, Ningbo Inst Mat Technol & Engn, Ningbo 315201, Zhejiang, Peoples R China.
    Dau, Holger
    Free Univ Berlin, Dept Phys, Arnimallee 14, D-14195 Berlin, Germany.
    Görlin, Mikaela
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Najafpour, Mohammad Mahdi
    IASBS, Dept Chem, Zanjan 4513766731, Iran;IASBS, Ctr Climate Change & Global Warming, Zanjan 4513766731, Iran;IASBS, Res Ctr Basic Sci & Modern Technol RBST, Zanjan 4513766731, Iran.
    Nickel-Vanadium Layered Double Hydroxide under Water-Oxidation Reaction: New Findings and Challenges2019Ingår i: ACS SUSTAINABLE CHEMISTRY & ENGINEERING, ISSN 2168-0485, Vol. 7, nr 20, s. 17252-17262Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nickel-vanadium layered double hydroxide has recently been considered as a highly active, low-cost electrocatalyst and as a benchmark non-noble metal-based electrocatalyst for water oxidation. The material showed a current density of 27 mA/cm(2) at an overpotential of 350 mV, which is comparable to the best-performing nickel-iron-layered double hydroxides for water oxidation in alkaline media. The enhanced conductivity and facile electron transfer were suggested among important factors for the high activity of nickel-vanadium layered double hydroxide. In the present study, the stability of an Ni-V catalyst was investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and electrochemical characterization methods. These methods show that the initial Ni-V catalyst during water oxidation in alkaline conditions is converted from an initial alpha-Ni(OH)(2) phase to a partially oxidized alpha-Ni(OH)(2/)NiOOH phase and VO(4)(3-)ions. We carefully evaluate the stability of the catalysts and analyze the compositional changes during prolonged water-oxidation conditions using inductively coupled plasma-optical emission spectroscopy (ICP-OES). The experiments using both Fe-free electrolyte and Fe-free nickel-vanadium layered double hydroxide reveal that vanadium do not affect the water-oxidizing activity of alpha-Ni(OH)(2).

  • 9210.
    Zanni, Giulia
    et al.
    Karolinska Univ Hosp, Karolinska Inst, Dept Womens & Childrens Hlth, Stockholm, Sweden.;Univ Gothenburg, Sahlgrenska Acad, Ctr Brain Repair & Rehabil, Inst Neurosci & Physiol, Gothenburg, Sweden..
    Michno, Wojciech
    Univ Gothenburg, Sahlgrenska Acad, Inst Neurosci & Physiol, Dept Psychiat & Neurochem, Molndal, Sweden.;Sahlgrens Univ Hosp, Clin Neurochem Lab, Molndal, Sweden..
    Di Martino, Elena
    Karolinska Univ Hosp, Karolinska Inst, Dept Womens & Childrens Hlth, Stockholm, Sweden..
    Tjärnlund-Wolf, Anna
    Univ Gothenburg, Sahlgrenska Acad, Ctr Brain Repair & Rehabil, Inst Neurosci & Physiol, Gothenburg, Sweden..
    Pettersson, Jean
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Mason, Charlotte Elizabeth
    Karolinska Univ Hosp, Karolinska Inst, Dept Womens & Childrens Hlth, Stockholm, Sweden..
    Hellspong, Gustaf
    Karolinska Univ Hosp, Karolinska Inst, Dept Womens & Childrens Hlth, Stockholm, Sweden..
    Blomgren, Klas
    Karolinska Univ Hosp, Karolinska Inst, Dept Womens & Childrens Hlth, Stockholm, Sweden.;Karolinska Univ Hosp, Dept Pediat Oncol, Stockholm, Sweden..
    Hanrieder, Jorg
    Univ Gothenburg, Sahlgrenska Acad, Inst Neurosci & Physiol, Dept Psychiat & Neurochem, Molndal, Sweden.;Sahlgrens Univ Hosp, Clin Neurochem Lab, Molndal, Sweden.;Chalmers, Dept Chem & Chem Engn, Gothenburg, Sweden.;UCL, Inst Neurol, Dept Mol Neurosci, London WC1E 6BT, England..
    Lithium Accumulates in Neurogenic Brain Regions as Revealed by High Resolution Ion Imaging2017Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, artikel-id 40726Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Lithium (Li) is a potent mood stabilizer and displays neuroprotective and neurogenic properties. Despite extensive investigations, the mechanisms of action have not been fully elucidated, especially in the juvenile, developing brain. Here we characterized lithium distribution in the juvenile mouse brain during 28 days of continuous treatment that result in clinically relevant serum concentrations. By using Time-of-Flight Secondary Ion Mass Spectrometry-(ToF-SIMS) based imaging we were able to delineate temporospatial lithium profile throughout the brain and concurrent distribution of endogenous lipids with high chemical specificity and spatial resolution. We found that Li accumulated in neurogenic regions and investigated the effects on hippocampal neurogenesis. Lithium increased proliferation, as judged by Ki67-immunoreactivity, but did not alter the number of doublecortin-positive neuroblasts at the end of the treatment period. Moreover, ToF-SIMS revealed a steady depletion of sphingomyelin in white matter regions during 28d Li-treatment, particularly in the olfactory bulb. In contrast, cortical levels of cholesterol and choline increased over time in Li-treated mice. This is the first study describing ToF-SIMS imaging for probing the brain-wide accumulation of supplemented Li in situ. The findings demonstrate that this technique is a powerful approach for investigating the distribution and effects of neuroprotective agents in the brain.

  • 9211. Zatsepin, D.A.
    et al.
    Galakhov, V.R.
    Gizhevskii, B.A.
    Kurmaev, E.Z.
    Fedorenko, V.V.
    Samokhvalov, A.A.
    Berger, Rolf
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Kemiska institutionen. Oorganisk kemi.
    SOFT-X-RAY EMISSION STUDY OF THE INFLUENCE OF LI+ DOPING, IRRADIATION AND PLASTIC DEFORMATION ON CUO1999Ingår i: Phys Rev.B, Vol. 59, nr 1, s. 211-214Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of Li+ doping, shear under pressure, and irradiation with He+ or electrons on the oxygen 2p-band and valence states of copper ions in CuO was studied using soft-X-ray emission spectroscopy. The doping with lithium leads to the appearance of copper ions with formal valency of 3+.

  • 9212. Zatsepin, D.A.
    et al.
    Galakhov, V.R.
    Korotin, M.A.
    Fedorenko, V.V.
    Kurmaev, E.Z.
    Bartkowski, S
    Neumann, M
    Berger, R
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Kemiska institutionen. Oorganisk kemi.
    Valence states of copper ions and electronic structure of LiCu2O21998Ingår i: Phys Rev B, Vol. 57, nr 8, s. 4377-4381Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The electronic structure of LiCu2O2 was studied using x-ray emission and photoelectron spectroscopy (valence band and core levels) as well as band-structure calculations in terms of LSDA and LSDA+U approaches. According to the x-ray emission and photoelectron spectra the valence states of the Cu atoms are found to be mixed, i.e. 2+ and 1+.

  • 9213.
    Zavafer, Alonso
    et al.
    Australian Natl Univ, Coll Sci, Res Sch Biol, GPO Box 4, Canberra, ACT 2601, Australia.
    Iermak, Ievgeniia
    Wageningen Univ, Lab Biophys, POB 8128, NL-6700 ET Wageningen, Netherlands;BioSolar Cells Project Off, POB 98, NL-6700 AB Wageningen, Netherlands;Univ Sao Paulo, Sao Carlos Inst Phys, Sao Carlos, SP, Brazil.
    Cheah, Mun Hon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Molekylär biomimetik. Australian Natl Univ, Coll Sci, Res Sch Biol, GPO Box 4, Canberra, ACT 2601, Australia.
    Chow, Wah Soon
    Australian Natl Univ, Coll Sci, Res Sch Biol, GPO Box 4, Canberra, ACT 2601, Australia.
    Two Quenchers Formed During Photodamage of Phostosystem II and The Role of One Quencher in Preemptive Photoprotection2019Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, artikel-id 17275Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The quenching of chlorophyll fluorescence caused by photodamage of Photosystem II (qI) is a well recognized phenomenon, where the nature and physiological role of which are still debatable. Paradoxically, photodamage to the reaction centre of Photosystem II is supposed to be alleviated by excitation quenching mechanisms which manifest as fluorescence quenchers. Here we investigated the time course of PSII photodamage in vivo and in vitro and that of picosecond time-resolved chlorophyll fluorescence (quencher formation). Two long-lived fluorescence quenching processes during photodamage were observed and were formed at different speeds. The slow-developing quenching process exhibited a time course similar to that of the accumulation of photodamaged PSII, while the fast-developing process took place faster than the light-induced PSII damage. We attribute the slow process to the accumulation of photodamaged PSII and the fast process to an independent quenching mechanism that precedes PSII photodamage and that alleviates the inactivation of the PSII reaction centre.

  • 9214. Zavodnik, Valery E.
    et al.
    Ivanov, Sergey A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi.
    Stash, Adam I.
    alpha-lead tellurite from single-crystal data2008Ingår i: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. 64, s. I16-U10Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The crystal structure of the title compound, alpha-PbTeO3 ( PTO), has been reported previously by Mariolacos [ Anz. Oesterr. Akad. Wiss. Math. Naturwiss. Kl. ( 1969), 106, 128-130], refined on powder data. The current determination at room temperature from data obtained from single crystals grown by the Czochralski method shows a significant improvement in the precision of the geometric parameters when all atoms have been refined anisotropically. The selection of a centrosymmetric (C2/c) structure model was confirmed by the second harmonic generation test. The asymmetric unit contains three formula units. The structure of PTO is built up of three types of distorted [PbOx] polyhedra (x=7 and 9) which share their O atoms with TeO3 pyramidal units. These main anionic polyhedra are responsible for establishing the two types of tunnel required for the stereochemical activity of the lone pairs of the Pb2+ and Te4+ cations.

  • 9215. Zavodnik, Valery E.
    et al.
    Ivanov, Sergey A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi.
    Stash, Adam I.
    On the thermal evolution of the crystal structure of SrTeO3. Part III. The gamma-phase of SrTeO3 at 583 K2007Ingår i: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. 63, nr 7, s. I151-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    As a part of current systematic investigations of strontium tellurite, SrTeO3, with particular emphasis on crystal chemistry and phase transitions, the structure of the gamma phase has been determined at 583 K using a single-crystal analysis. Both structural and nonlinear optical measurements indicate a beta-gamma first-order phase transition temperature that is close to 563 K. The structure of the gamma phase is monoclinic (C2) and does not differ essentially from the alpha phase (C2). Comparison of the alpha and gamma structures shows that the main atomic shifts and tiltings are connected with Te4, Te5 and Te6 pyramids.

  • 9216. Zavodnik, Valery E.
    et al.
    Ivanov, Sergey A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi.
    Stash, Adam I.
    On the thermal evolution of the crystal structure of SrTeO3: the beta-form at 473 K2007Ingår i: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. 63, nr 4, s. I111-I112Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    As part of a programme to study structural phase transitions in strontium tellurite, SrTeO3, (STO), the structure of the beta-form has been determined at 473 K using single-crystal analysis. Both the structural and non-linear optical measurements indicate an alpha-beta first-order phase-transition temperature that is close to 363 K on heating and 308 K on cooling. The structure of the beta-phase is monoclinic (C2/c) and does not differ essentially from the alpha-phase (C2) configuration. During the alpha-beta phase transition there is a slight rearrangement of the cation building blocks [n-vertex SrOn polyhedra (n = 6, 7 or 8) and TeO3 pyramids]; this phase transformation can be described by a displacive mechanism.

  • 9217. Zavodnik, Valery E.
    et al.
    Ivanov, Sergey A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi.
    Stash, Adam I.
    The alpha-phase of SrTeO3 at 295 K2007Ingår i: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. 63, s. i75-i76Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The crystal structure of strontium tellurite (STO), SrTeO3, has been determined at room temperature using X-ray diffraction data obtained from single crystals grown by the Czochralski method. Selection of a non-centrosymmetric (C2) structure model was confirmed by the second harmonic generation test. The structure of STO is built up of three types of distorted [SrOx] polyhedra (x = 6, 7 and 8) which share their oxygen anions with TeO3 pyramidal units. These main anionic polyhedra are responsible for establishing two types of tunnels required for the electron lone pairs of the Te4+ cation.

  • 9218. Zavodnik, Valery E.
    et al.
    Ivanov, Sergey A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi.
    Stash, Adam I.
    The delta-phase of SrTeO3 at 780 K2008Ingår i: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. 64, s. I52-U75Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    As part of a structural investigation of strontium tellurate(IV) (STO), SrTeO3, with particular emphasis on the crystal chemistry and phase transitions, the structure of the delta-phase has been determined at 780 K using a single-crystal analysis. Both structural and non-linear optical measurements indicate that STO undergoes a gamma -> ;delta second-order ferroelectric phase transition at 633 K from the C2 (gamma) to the C2/m (delta) modification. Systematic differences between the similar gamma- and delta-phase structures were determined and it was found that this phase transformation can be described by a displacive mechanism.

  • 9219.
    Zayny, Ahmad
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaceutisk biovetenskap.
    Almokhtar, Mokhtar
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaceutisk biovetenskap.
    Wikvall, Kjell
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaceutisk biovetenskap.
    Ljunggren, Östen
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinska vetenskaper, Endokrinologi och mineralmetabolism.
    Ubhayasekera, Kumari
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Bergquist, Jonas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Kibar, Pinar
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaceutisk biovetenskap.
    Norlin, Maria
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaceutisk biovetenskap.
    Effects of glucocorticoids on vitamin D3-metabolizing 24-hydroxylase (CYP24A1) in Saos-2 cells and primary human osteoblasts2019Ingår i: Molecular and Cellular Endocrinology, ISSN 0303-7207, E-ISSN 1872-8057, Vol. 496, artikel-id 110525Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Vitamin D is essential for bone function and deficiency in active vitamin D hormone can lead to bone disorders. Long-term treatment with glucocorticoids results in osteoporosis and increased risk of fractures. Much remains unclear regarding the effects of these compounds in bone cells. In the current study, human osteosarcoma Saos-2 cells and primary human osteoblasts were found to express mRNA for the vitamin D receptor as well as activating and deactivating enzymes in vitamin D-3 metabolism. These bone cells exhibited CYP24A1-mediated 24-hydroxylation which is essential for deactivation of the active vitamin form. However, bioactivating vitamin D-3 hydroxylase activities could not be detected in either of these cells. Several glucocorticoids, including prednisolone, down regulated CYP24A1 mRNA and CYP24A1-mediated 24-hydroxylase activity in both Saos-2 and primary human osteoblasts. Also, prednisolone significantly suppressed a human CYP24A1 promoter-luciferase reporter gene in Saos-2 cells co-transfected with the glucocorticoid receptor. Thus, the results of the present study show suppression by glucocorticoids on CYP24A1 mRNA, CYP24A1-mediated metabolism and CYP24A1 promoter activity in human osteoblast-like cells. As part of this study we examined if glucocorticoids are formed locally in Saos-2 cells. The experiments indicate formation of 11-deoxycortisol, a steroid with glucocorticoid activity, which can bind the glucocorticoid receptor. Our data showing suppression by glucocorticoids on CYP24A1 expression in human osteoblasts suggest a previously unknown mechanism for effects of glucocorticoids in human bone, where these compounds may interfere with regulation of active vitamin D levels.

  • 9220.
    Zayny, Ahmad
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaceutisk biovetenskap.
    Almokhtar, Mokhtar
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaceutisk biovetenskap.
    Wikvall, Kjell
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaceutisk biovetenskap.
    Ljunggren, Östen
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinska vetenskaper.
    Ubhayasekera, S. J. Kumari A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Bergqvist, Jonas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Norlin, Maria
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaceutisk biovetenskap.
    Effects of glucocorticoids on vitamin D3 24-hydroxylase (CYP24A1) in Saos-2 cells and primary human osteoblastsManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Vitamin D is essential for bone function and deficiency in active vitamin D hormone can lead to rickets, osteomalacia or osteoporosis. Long-term treatment with glucocorticoids is known to result in osteoporosis and a substantially increased risk of fractures. Although the actions of vitamin D and glucocorticoids play important roles for bone function and in the development of osteoporosis, much remains unclear regarding the effects of these compounds in cells of the bone. In the current study, the human osteosarcoma Saos-2 cell line and primary human osteoblast-like cells were found to express mRNA for the vitamin D receptor as well as both activating and deactivating enzymes in vitamin D3 metabolism. These bone cells exhibited the CYP24A1-mediated 24-hydroxylation, involved in deactivation of the active vitamin D3 form. However, bioactivating vitamin D3 hydroxylase activities could not be detected in either of these cells. Several commonly used therapeutic glucocorticoids, including prednisolone, down regulated mRNA expression for the CYP24A1 gene as well as the CYP24A1-mediated 24-hydroxylase activity in both Saos-2 and primary human osteoblast-like cells. Prednisolone had the strongest suppressive effect on CYP24A1 expression. Results from experiments with a human CYP24A1 promoter-luciferase reporter gene in Saos-2 cells, co-transfected with the glucocorticoid receptor, showed that treatment with prednisolone significantly suppresses the CYP24A1 promoter activity. Thus, the results of the present study showed suppression by glucocorticoids on expression of CYP24A1 mRNA, CYP24A1-mediated metabolism and CYP24A1 promoter activity in human osteoblast-like cells. As part of the present investigation we examined if glucocorticoids are formed locally in Saos-2 cells. The experiments indicate formation of 11-deoxycortisol, a steroid that has glucocorticoid activity and is able to bind to the glucocorticoid receptor.

    Our data showing suppression by glucocorticoids on CYP24A1 expression in human osteoblast-like cells suggest a previously unknown mechanism for effects of glucocorticoids in human bone, where these compounds may act by increasing the normal levels of active vitamin D.

  • 9221. Zeiai, S.
    et al.
    Zhao, J.
    Ekblad, A.
    Nordenskjold, A.
    Hilborn, Jöns
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Polymerkemi.
    Gotherstrom, C.
    Fossum, M.
    From bone marrow to an autologous urothelium-PCL-collagen transplant2014Ingår i: Journal of Tissue Engineering and Regenerative Medicine, ISSN 1932-6254, E-ISSN 1932-7005, Vol. 8, s. 294-295Artikel i tidskrift (Övrigt vetenskapligt)
  • 9222.
    Zeleskov, Dianna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC.
    The hunt after a monooxygenase for styrene epoxidation: Extending an artificial synthetic pathway in E. coli2018Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
  • 9223.
    Zendehdel, Mahmoud
    et al.
    Islamic Azad Univ, Najafabad Branch, Dept Chem, Najafabad, Isfahan, Iran.;Kimia Solar Co, KSRI, Esfahan, Iran..
    Nia, Narges Yaghoobi
    Univ Roma Tor Vergata, Dept Elect Engn, CHOSE, Via Politecn 1, I-00133 Rome, Italy..
    Nasr-Esfahani, Mojtaba
    Islamic Azad Univ, Najafabad Branch, Dept Chem, Najafabad, Isfahan, Iran..
    Farahani, Pooria
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Teoretisk kemi. Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, BR-05508000 Sao Paulo, SP, Brazil..
    Karbaschi, Mohamad Reza
    Islamic Azad Univ, Najafabad Branch, Dept Chem, Najafabad, Isfahan, Iran..
    A combined computational and experimental study on the hydrogen bonding with chloride ion in a crab-claw like site of a new chromium Schiff base complex2016Ingår i: Inorganica Chimica Acta, ISSN 0020-1693, E-ISSN 1873-3255, Vol. 447, s. 150-161Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A combined experimental and computational study to understand the nature of the hydrogen bonding in a crab-claw site of a new synthesized chromium Schiff base complex is reported. The fully optimized equilibrium structures of the Cr(III) complex in the presence and absence of chloride ion are obtained at the B3LYP functional in conjunction with LanL2DZ basis set. The crystal structure of the chromium Schiff base complex consists of [CrL2](+) cation, in which L is a tridentate Schiff base ligand with full name of N-(2-(2-hydroxyethylamino)ethyl)5-methoxysalicylideneimine, and a chloride anion, in the asymmetric unit. The chromium(III) cation possesses a distorted octahedral geometry, coordinated with four nitrogen and two phenoxo oxygen atoms derived from two chelate Schiff base ligands. The harmonic vibrational frequencies, infrared intensities and Raman scattering activities of the complexes are also reported. The scaled computational geometry and vibrational wavenumbers are in very good agreement with the experimental values of single crystal X-ray diffraction and FT-IR, respectively. The electronic properties calculations of the complexes are also performed at the TD-B3LYP/LanL2DZ level of theory. The spectroscopic excitation parameters obtained for frontier molecular orbitals of the complexes are reported as well. These findings are in good agreement with the experimental UV-Vis diffuse-reflectance spectroscopy. Parabolic diagrams are derived for the chloride insertion and hydrogen bonding in the crab-claw site with the average optimized H center dot center dot center dot H distances of the effective hydrogen atoms in the crab-claw site as reaction coordinate.

  • 9224.
    Zeng, Cheng-Ming
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för naturvetenskaplig biokemi.
    New approaches in biomembrane chromatomatography and microchromatographic techniques1998Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Development of methods for rendering chromatography more applicable to studies in lifesciences remains an area of active research. In the present work, new methods inbiomembrane chromatography and microchromatographic techniques have been developedand applied successfully to quantitative analysis of biological interactions and separations ofproteins on a micro-scale.

    Biomembranes, specifically: human red cells/ghosts, membrane vesicles and proteoliposomes, were immobilized in gel beds for chromatographic analyses of solutes specificallybound to the glucose transporter Glut1 and the nucleoside transporter of the red cellmembrane. The resultant binding parameters revealed that this system can be a practical toolfor quantitative analysis of biological interactions involving integral membrane proteins andfor monitoring procedures for purification and reconstitution of membrane proteins. Analternative method based on Hummel and Dreyer analysis was introduced and proved usefulin analyses of cytochalasin-B binding to Glut1 in membrane vesicles and proteoliposomes.

    Chromatographic analysis of non-specific partitioning of a drug into lipid bilayers wasperformed on a microcolumn containing liposomes immobilized in the gel bed. The resultsshowed that this method can be utilized for predicting absorption of a drug in vivo.Hydrophobic interaction microchromatography of proteins and a blotting membranetechnique for detection of minute amounts of proteins have been developed on the basis ofcontinuous beds which can be synthesized directly in the microcolumn tubes. Thesedevelopments extend the uses of continuous beds to a broader field in life science.

  • 9225. Zeng, Wen
    et al.
    Ma, Ming-Guo
    Zhu, Jie-Fang
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Cao, Shao-Wen
    Development and Fabrication of Advanced Materials for Energy and Environment Applications2013Ingår i: Journal of Nanomaterials, ISSN 1687-4110, E-ISSN 1687-4129, s. 279309-Artikel i tidskrift (Övrigt vetenskapligt)
  • 9226.
    Zeng X., Thibblin A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Kemiska institutionen.
    Competing base-promoted E2 and E1 reactions of an acidic tertiary substrate2002Ingår i: J. Chem. Soc., Perkin Trans 2, s. 1352-Artikel i tidskrift (Refereegranskat)
  • 9227.
    Zeng, XF
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Kemiska institutionen.
    Thibblin, A
    Competing solvolytic elimination and substitution reactions via very short-lived ion-pair intermediates2001Ingår i: JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2, ISSN 1472-779X, nr 9, s. 1600-1607Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The solvolysis of 9-methyl-9-(2-X-2-propyl)fluorene (X = Cl, Br, or OOCCF3) (1-X) in aqueous acetonitrile or aqueous 1,1,1-trifluoroethanol (TFE) yields the alkene, 9-methyl-9-(propen-2-yl)fluorene (2), and the alcohol, 9-methyl-9-(2-hydroxy-2-propyl)fluo

  • 9228.
    Zeng, Xiaofeng
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Kemiska institutionen, Avdelningen för organisk kemi.
    Mechanisms for Solvolytic Elimination and Substitution Reactions Involving Short-lived Carbocation Intermediates2002Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Solvolysis reactions of a range of tertiary substrates in largely aqueous solvents were studied in such respects as β-deuterium kinetic isotope effects, linear free energy relationships and stereochemistry.

    Solvolysis of the fluorene derivatives 9-methyl–9-(2´-X-2´-propyl)fluorene (1-X, X = Cl, Br, OOCCF3) involves a very short-lived carbocation intermediate. The fraction of alkene is increased by addition of general bases, which can be expressed by a Brφnsted parameter β = 0.07. The kinetic deuterium isotope effects vary with solvent composition in a way which is not consistent with a common carbocation intermediate which has time to choose between dehydronation and addition of a solvent water molecule.

    In the absence of bases, the reaction of 4-chloro-4-(4´-nitrophenyl)pentan-2-one (2-Cl) proceeds through a short-lived carbocation intermediate yielding 4-(4´-nitrophenyl)-2-oxopent-4-ene (2-t-ne)as the main elimination product. Addition of acetate ion and other weak bases results in the base-promoted E2 (or E1cb) reaction to give (E)-4-(4´-nitrophenyl)-2-oxopent-3-ene (2-E-ne) and (Z)-4-(4´-nitrophenyl)-2-oxopent-3-ene(2-Z-ne). There is no evidence for a water-promoted E2 (or E1cb) reaction.

    The stereochemistry studies of elimination from (R,S and S,R)-[1-(3´-fluoro)phenyl-2-methyl]cyclopentyl-p-nitrobenzoate (3-PNB) and its (R,R and S,S)isomer 3´-PNB and (R,S and S,R)-[1´-(3´´-fluoro)phenyl-2´-methylcyclopentyl]-2,2,2-trifluoroacetate(3-OOCCF3) exclude the concerted pericyclic elimination mechanism for formation of the alkene 1-(3´-fluoro)phenyl-2-methylcyclopentene(3-m-ne). The effects of added thiocyanate ion and halide ions on the solvolysis reaction are discussed.

    Mass spectrometry analysis showed complete incorporation of the labeled oxygen from solvent water into the product 2-hydroxy-2-phenyl-3-butene (4-OH), confirming that it is the tertiary carbon-oxygen bond that is broken in the acid-catalyzed solvolysis of 2-methoxy-2-phenyl-3-butene (4-OMe). The mechanism for the dominant formation of the less stable 4-OH is discussed.

  • 9229.
    Zetterberg, Malin M.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Fysikalisk kemi.
    Reijmar, Karin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Fysikalisk kemi.
    Pränting, Maria
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinsk biokemi och mikrobiologi.
    Engström, Åke
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinsk biokemi och mikrobiologi.
    Andersson, Dan I.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinsk biokemi och mikrobiologi.
    Edwards, Katarina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Fysikalisk kemi.
    PEG-stabilized lipid disks as carriers for amphiphilic antimicrobial peptides2011Ingår i: Journal of Controlled Release, ISSN 0168-3659, E-ISSN 1873-4995, Vol. 156, nr 3, s. 323-328Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Antimicrobial peptides hold potential as a possible alternative, or complement, to conventional antibiotics but new, safe and efficient means are needed for formulation and administration of the peptides. In this study we have investigated the utility of a novel type of lipid particles, the polyethylene glycol-stabilized lipid-disks, as carriers for the model peptide melittin. The structural integrity of the carrier particle when loaded with the peptide was investigated using cryo-transmission electron microscopy. Liposome leakage upon addition of the peptide-lipid-disks was monitored as a means to verify the membrane lytic effect of the formulation. The susceptibility of melittin to tryptic digestion was studied and compared in the absence and presence of lipid-disks. Finally, the antibacterial effect of the peptide-lipid-disk formulation was compared to that of free melittin after both single and repeated exposure to Escherichia coli. The results show that melittin can redistribute from the disk into a new host membrane and that formulation in the disks does not compromise melittin's membrane permeabilizing ability. Further, the peptide was found to be fully protected against degradation when bound to the disks. Time-kill experiments revealed that all the antibacterial effect of melittin administered in free form was gone after a single exposure to E. coli. In contrast, the disk formulation showed significant cell-killing effect also upon a second exposure to bacteria, indicating an extended release of peptide from the lipid-disks. These results suggest that the lipid-disks constitute a new class of promising carriers for peptide antibiotics.

  • 9230. Zettersten, C
    et al.
    Bökman, C. F.
    Sjöberg, P. J. R.
    Nyholm, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi, Oorganisk kemi.
    A Novel Set-Up for the Coupling of a Thin Layer Electrochemical Cell to Electrospray Mass Spectrometry2003Ingår i: presented at the 16th International Mass Spectrometry Conference (IMSC), Edinburgh, August 31 - September 5, 2003, 2003Konferensbidrag (Refereegranskat)
  • 9231. Zettersten, C
    et al.
    Sjöberg, P. J. R.
    Nyholm, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi, Oorganisk kemi.
    The Reaction Mechanism of 4-Chloroaniline studied by Cyclic Voltammetry and Electrochemistry coupled to Electrospray Ionisation Mass Spectrometry2008Ingår i: presented at the 18th Analysdagarna (The Analytical Days), Göteborg, 16-18 June, 2008., 2008Konferensbidrag (Refereegranskat)
  • 9232.
    Zettersten, Camilla
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Analytisk kemi.
    On-line Electrochemistry Electrospray Ionisation Mass Spectrometry: Method Development and Applications2009Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis deals with studies of on-line electrochemistry electrospray ionisation mass spectrometry (EC/ESI-MS). It is shown that the use of EC/ESI-MS demands optimal coupling characteristics.

    Pre-concentration and desalting, due to matrix exchange, were demonstrated for the model substance 1-hexanethiol in an EC/ESI-MS setup. The setup was also used for investigations of the oxidation states of the manganese complex [Mn2(bpmp)(µ-OAc)2][ClO4], where bpmp is a 2,6-bis[[N,N-di(2-pyridylmethyl)amino]methyl]-4-methylphenol compound. The manganese complex, which is relevant to artificial photosynthesis, was found to be a good model compound for the EC/ESI-MS studies, thanks to its many oxidation states. For the first time, the presence of the Mn(III,IV) state of the manganese complex was demonstrated in the studies.

    During the experimental work, the importance of the electrode positioning within the electrochemical cell was investigated. Different EC cell configurations were studied using the manganese complex as a model substance. It was clearly shown that the EC cell design influences the distribution between the peaks in the mass spectra - not only for manganese complexes and Olsalazine but also for 4-chloroaniline.

    A previously unknown comproportionation reaction was found for 4-chloroaniline involving the oxidised dimer, 4-[(4-chlorophenyl)imino]-2,5-cyclohexadien-1-imine. This reaction explained the unexpected presence of the signal due to the reduced dimer, 4-amino-4'-chlorodiphenylamine, in the mass spectra.

    Furthermore, it was shown that EC/ESI-MS was successful in conjunction with miniaturised gold wire electrodes in a PDMS chip within which dopamine was oxidised with a conversion efficiency of 30%. The oxidation products of dopamine were detected after 0.6-1.2 seconds for 1.0 and 0.5 µl/min, respectively. The combination of electrochemically controlled solid-phase extraction (EC-SPE) with ESI-MS was found to be less straightforward than detecting anions pre-concentrated on a polypyrrole coated electrode with EC-SPE/ICP-MS.

    The on-line combination of liquid chromatography with EC/ESI-MS/MS for studying antioxidants in yellow onion extracts was shown to be fast and a relatively easy complement to classical antioxidant activity determinations.

    Delarbeten
    1. A Setup for the Coupling of a Thin-Layer Electrochemical Flow Cell to Electrospray Mass Spectrometry
    Öppna denna publikation i ny flik eller fönster >>A Setup for the Coupling of a Thin-Layer Electrochemical Flow Cell to Electrospray Mass Spectrometry
    2004 (Engelska)Ingår i: Analytical Chemistry, Vol. 76, nr 7, s. 2017-2024Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    A novel setup for the coupling of commercially available thin-layer cell to electrospray mass spectrometry (ESI-MS) which allows the elctrochemical reactions at the counter electrode to be straightforwardly separated from the flow into the mass spectrometer has been developed. In this way interferences from reaction products formed at the counter electrode can be minimized. This reduces the risk of changes in the mass spectra as a result of electrochemical reactions in the solution. The described setup also enables the working electrode to be positioned close to the electrospray (ESI) emitter without the need for a grounding point or a long transfer line between the electrochemical cell and the electrospray emitter. By decoupling the electrochemical reactions in the flow cell and those in the electrospray emitter, improved facilities for studies of electrochemical reactions are obtained through a better control of the potential of the working electrode. The setup has been used to study the oxidation of a drug (Olsalazine), which previously has been found to involve chemical follow-up reactions. It is also demonstrated that uncharged thiols can be detected in ESI-MS after spontaneous adsorption on a gold working electrode, followed by oxidative desorption to yield sulfinates or sulfonates. This adsorption and potential-controlled desorption has been used for the preconcentration of micromolar concentrations of 1-hexanethiol as well as for desalting of solutions containing micromolar concentrations of thiols. The results indicate that the present on-line coupling of an electrochemical cell to ESI-MS provides promising possibilities for sample preconcentration, matrix exchange (including desalting), and ionization of neutral compounds, such as thiols.

    Identifikatorer
    urn:nbn:se:uu:diva-70661 (URN)
    Tillgänglig från: 2005-04-26 Skapad: 2005-04-26 Senast uppdaterad: 2011-03-25
    2. Ligand exchange upon oxidation of a dinuclear Mn complex - Detection of structural changes by FT-IR spectroscopy and ESI-MS.
    Öppna denna publikation i ny flik eller fönster >>Ligand exchange upon oxidation of a dinuclear Mn complex - Detection of structural changes by FT-IR spectroscopy and ESI-MS.
    Visa övriga...
    2005 (Engelska)Ingår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, nr 6, s. 1033-1041Artikel i tidskrift (Refereegranskat) Published
    Nationell ämneskategori
    Naturvetenskap
    Identifikatorer
    urn:nbn:se:uu:diva-95874 (URN)
    Tillgänglig från: 2007-05-04 Skapad: 2007-05-04 Senast uppdaterad: 2017-12-14
    3. On-line coupling of a microelectrode array equipped poly(dimethylsiloxane) microchip with an integrated graphite electrospray emitter for electrospray ionisation mass spectrometry
    Öppna denna publikation i ny flik eller fönster >>On-line coupling of a microelectrode array equipped poly(dimethylsiloxane) microchip with an integrated graphite electrospray emitter for electrospray ionisation mass spectrometry
    Visa övriga...
    2005 (Engelska)Ingår i: Lab on a Chip, nr 5, s. 1008-1016Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    A novel method for the manufacturing of microchips for on-chip combinations of electrochemistry (EC) and sheathless electrospray ionisation mass spectrometry (ESI-MS) is described. The technique, which does not require access to clean-room facilities, is based on the incorporation of an array of gold microcoil electrodes into a poly(dimethylsiloxane) (PDMS) microflow channel equipped with an integrated graphite based sheathless ESI emitter. Electrochemical measurements, which were employed to determine the electroactive area of the electrodes and to test the microchips, show that the manufacturing process was reproducible and that the important interelectrode distance in the electrochemical cell could to be adequately controlled. The EC-ESI-MS device was evaluated based on the ESI-MS detection of the oxidation products of dopamine. The results demonstrate that the present on-chip approach enables full potentiostatic control of the electrochemical cell and the attainment of very short transfer times between the electrochemical cell and the electrospray emitter. The transfer times were 0.6 and 1.2 s for flow rates of 1.0 and 0.5 uL min-1, respectively, while the electrochemical conversion efficiency of the electrochemical cell was found to be 30% at a flow rate of 0.5 uL min-1. To decouple the electrochemical cell from the ESI-MS high voltage and to increase the user-friendliness, the on-line electrochemistry-ESI-MS experiments were performed using a wireless Bluetooth battery-powered instrument with the chip floating at the potential induced by the ESI high voltage. The described on-chip EC-ESI-MS device can be used for fundamental electrochemical investigations as well as for applications based on the use of electrochemically controlled sample pretreatment, preconcentration and ionisation steps prior to ESI-MS.

    Nationell ämneskategori
    Oorganisk kemi
    Identifikatorer
    urn:nbn:se:uu:diva-74547 (URN)doi:10.1039/b506289f (DOI)
    Tillgänglig från: 2007-03-28 Skapad: 2007-03-28 Senast uppdaterad: 2011-01-11
    4. On-line electrochemically controlled solid-phase extraction interfaced to electrospray and inductively coupled plasma mass spectrometry
    Öppna denna publikation i ny flik eller fönster >>On-line electrochemically controlled solid-phase extraction interfaced to electrospray and inductively coupled plasma mass spectrometry
    Visa övriga...
    2005 Ingår i: The Analyst, ISSN 0003-2654, Vol. 130, nr 10, s. 1358-1368Artikel i tidskrift (Refereegranskat) Published
    Identifikatorer
    urn:nbn:se:uu:diva-96097 (URN)
    Tillgänglig från: 2007-09-04 Skapad: 2007-09-04Bibliografiskt granskad
    5. The influence of the thin-layer flow cell design on the mass spectra when coupling electrochemistry to electrospray ionisation mass spectrometry
    Öppna denna publikation i ny flik eller fönster >>The influence of the thin-layer flow cell design on the mass spectra when coupling electrochemistry to electrospray ionisation mass spectrometry
    Visa övriga...
    2006 (Engelska)Ingår i: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 590, nr 1, s. 90-99Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The influence of the flow cell configuration on the mass spectra obtained when coupling an electrochemical thin-layer flow cell to electrospray mass spectrometry (ESI-MS) has been investigated. It is shown that interferences due to the electrochemical reaction on the counter electrode and/or the absence of 100% conversion efficiency can alter the mass spectra when conventional thin-layer flow cells are used in conjunction with ESI-MS. The effects, which affect the intensities and distribution of the peaks in the mass spectra, can result in the inability to detect products formed at the working electrode. Comparisons of mass spectra, generated after the electrochemical oxidation of a dinuclear Mn complex (where bpmp = 2,6-bis[bis(2-pyridylmethyl) amino]methyl-4-methylphenol) using two different thin-layer flow cells clearly show that the potential dependence and appearance of the mass spectra depend on the flow cell configuration used. The use of a modified thin-layer flow cell, in which the counter electrode had been separated from the working electrode, gave rise to significantly increased intensities for the oxidised MnIII,IV state of the complex. With the conventional unmodified cell, the corresponding complex was only seen for considerably higher oxidation potentials. The different results can be explained by the reduced risk of redox cycling and interferences due to species generated at the counter electrode with the modified cell. As interferences due to the counter electrode reactions likewise may be expected with many coulometric flow cells, the electrochemical cell design clearly needs to be considered when using electrochemistry coupled to ESI-MS to study electrochemical reactions.

    Nyckelord
    Electrochemistry, Electrospray ionisation mass spectrometry, Thin-layer cells, Flow cell design, Binuclear manganese complexes, Oxidation
    Nationell ämneskategori
    Oorganisk kemi
    Identifikatorer
    urn:nbn:se:uu:diva-82120 (URN)doi:10.1016/j.jelechem.2006.02.028 (DOI)
    Tillgänglig från: 2007-03-06 Skapad: 2007-03-06 Senast uppdaterad: 2017-12-14Bibliografiskt granskad
    6. Oxidation of 4-chloroaniline studied by on-line electrochemistry electrospray ionization mass spectrometry
    Öppna denna publikation i ny flik eller fönster >>Oxidation of 4-chloroaniline studied by on-line electrochemistry electrospray ionization mass spectrometry
    2009 (Engelska)Ingår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 81, nr 13, s. 5180-5187Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The oxidation of 4-chloroaniline (4-CA) has been studied by electrochemistry (EC) coupled on-line with electrospray ionization mass spectrometry (ESI-MS) using two electrochemical flow cells of different design. The experimental results, which generally verify previously suggested oxidation pathways for 4-CA, also indicate the presence of a so far unrecognized comproportionation reaction. The oxidation of 4-CA (m/z 128.2) was found to give rise to the formation of both an oxidized dimer, 4-[(4-chlorophenyl)imino]-2,5-cyclohexadien-1-imine (m/z 217.2) and a reduced dimer, 4-amino-4’-chlorodiphenylamine (m/z 219.2), in addition to a dimer intermediate (m/z 253.2). This unexpected formation of the reduced dimer is shown to stem from a comproportionation reaction involving 4-CA and the oxidized dimer. The presence of the latter reaction was clearly seen by comparing results obtained with two thin-layer flow cells, both with conversion efficiencies of 50% but of different design, with respect to the influence of the counter electrode reaction on the reaction at the working electrode. The experimental results demonstrate that the formation of the reduced dimer is favored by a decrease in the local pH in the flow cell and the influence of the pH on the oxidation of 4-CA was also investigated in the pH range between 2.0 and 6.0 using off-line voltammetry. It is concluded that EC/ESI-MS is a powerful tool for the study of the present type of reactions and that studies on reaction pathways are best carried out with thin-layer flow cells having conversion efficiencies smaller than 100% as this facilitates the detection of reaction intermediates. Comproportionation reactions, similar to the reaction present in the 4-CA system, can also be expected to be present during the formation of conducting polymers such as polyaniline and polypyrrole.

    Nyckelord
    4-chloroaniline, oxidation, electrochemistry, electrospray ionization mass spectrometry, reaction pathway, (p-chlorophenyl)aniline
    Nationell ämneskategori
    Kemi
    Forskningsämne
    Analytisk kemi
    Identifikatorer
    urn:nbn:se:uu:diva-99325 (URN)10.1021/ac802563f (DOI)000267609500013 ()19563209 (PubMedID)
    Tillgänglig från: 2009-03-12 Skapad: 2009-03-12 Senast uppdaterad: 2018-06-26Bibliografiskt granskad
    7. Identification and Characterization of Polyphenolic Antioxidants Using On-Line Liquid Chromatography, Electrochemistry, and Electrospray Ionization Tandem Mass Spectrometry
    Öppna denna publikation i ny flik eller fönster >>Identification and Characterization of Polyphenolic Antioxidants Using On-Line Liquid Chromatography, Electrochemistry, and Electrospray Ionization Tandem Mass Spectrometry
    Visa övriga...
    2009 (Engelska)Ingår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 81, nr 21, s. 8968-8977Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    It is demonstrated that electrochemistry (EC) coupled to liquid chromatography (LC) and electrospray ionization tandem mass spectrometry (LC/EC/ESI-MS/MS) can be used to rapidly obtain information about the antioxidant activity (i.e., oxidation potential) and capacity (i.e., amount) of polyphenolic compounds, including catechin, kaempferol, resveratrol, quercetin, and quercetin glucosides. The described on-line LC/EC/ESI-MS/MS method facilitates the detection and characterization of individual antioxidants based on a combination of the obtained m/z values for the antioxidants and their oxidation products, the potential dependences for the ion intensities, and correlations between the retention times in the LC, EC, and MS chromatograms. As these results provide patterns that can be used in rapid screening for antioxidants in complex samples, the method should be a valuable complement to chemical assays commonly used to determine the total antioxidant capacity of samples. It is shown that the antioxidant capacity for a mixture of polyphenolic compounds depends on the redox potential employed in the evaluation, and this should consequently be taken into account when comparing results from different total antioxidant capacity assays. It is also demonstrated that the inherent antioxidant capacities of phenolic compounds increase with an increasing number of hydroxyl groups and that the potential needed to oxidize the remaining hydroxyl groups increases successively upon oxidation of the compound. Unlike chemical assays, which generally do not provide any information about the identities of the compounds on the molecular level, the present screening method can be used to identify individual antioxidants, rank compounds with respect to their ease of oxidation, and to study the antioxidant capacity at any redox potential of interest.

    Nationell ämneskategori
    Analytisk kemi Oorganisk kemi
    Forskningsämne
    Analytisk kemi; Oorganisk kemi
    Identifikatorer
    urn:nbn:se:uu:diva-99328 (URN)10.1021/ac901397c (DOI)000276191900046 ()
    Tillgänglig från: 2009-03-12 Skapad: 2009-03-12 Senast uppdaterad: 2018-06-26Bibliografiskt granskad
  • 9233.
    Zettersten, Camilla
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi. Analytisk kemi.
    On-line Electrochemistry Electrospray Ionisation Mass Spectrometry: Practical Aspects and Applications2007Licentiatavhandling, monografi (Övrigt vetenskapligt)
  • 9234.
    Zettersten, Camilla
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Analytisk kemi.
    Co, Michelle
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Analytisk kemi.
    Wende, Sandra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Analytisk kemi.
    Turner, Charlotta
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Analytisk kemi.
    Nyholm, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi.
    Sjöberg, Per J. R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Analytisk kemi.
    Identification and Characterization of Polyphenolic Antioxidants Using On-Line Liquid Chromatography, Electrochemistry, and Electrospray Ionization Tandem Mass Spectrometry2009Ingår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 81, nr 21, s. 8968-8977Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It is demonstrated that electrochemistry (EC) coupled to liquid chromatography (LC) and electrospray ionization tandem mass spectrometry (LC/EC/ESI-MS/MS) can be used to rapidly obtain information about the antioxidant activity (i.e., oxidation potential) and capacity (i.e., amount) of polyphenolic compounds, including catechin, kaempferol, resveratrol, quercetin, and quercetin glucosides. The described on-line LC/EC/ESI-MS/MS method facilitates the detection and characterization of individual antioxidants based on a combination of the obtained m/z values for the antioxidants and their oxidation products, the potential dependences for the ion intensities, and correlations between the retention times in the LC, EC, and MS chromatograms. As these results provide patterns that can be used in rapid screening for antioxidants in complex samples, the method should be a valuable complement to chemical assays commonly used to determine the total antioxidant capacity of samples. It is shown that the antioxidant capacity for a mixture of polyphenolic compounds depends on the redox potential employed in the evaluation, and this should consequently be taken into account when comparing results from different total antioxidant capacity assays. It is also demonstrated that the inherent antioxidant capacities of phenolic compounds increase with an increasing number of hydroxyl groups and that the potential needed to oxidize the remaining hydroxyl groups increases successively upon oxidation of the compound. Unlike chemical assays, which generally do not provide any information about the identities of the compounds on the molecular level, the present screening method can be used to identify individual antioxidants, rank compounds with respect to their ease of oxidation, and to study the antioxidant capacity at any redox potential of interest.

  • 9235.
    Zettersten, Camilla
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Kemiska institutionen, Avdelningen för analytisk kemi.
    Lomoth, Reiner
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen.
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen.
    Sjöberg, Per
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Kemiska institutionen, Avdelningen för analytisk kemi.
    Nyholm, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi.
    The influence of the thin-layer flow cell design on the mass spectra when coupling electrochemistry to electrospray ionisation mass spectrometry2006Ingår i: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 590, nr 1, s. 90-99Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of the flow cell configuration on the mass spectra obtained when coupling an electrochemical thin-layer flow cell to electrospray mass spectrometry (ESI-MS) has been investigated. It is shown that interferences due to the electrochemical reaction on the counter electrode and/or the absence of 100% conversion efficiency can alter the mass spectra when conventional thin-layer flow cells are used in conjunction with ESI-MS. The effects, which affect the intensities and distribution of the peaks in the mass spectra, can result in the inability to detect products formed at the working electrode. Comparisons of mass spectra, generated after the electrochemical oxidation of a dinuclear Mn complex (where bpmp = 2,6-bis[bis(2-pyridylmethyl) amino]methyl-4-methylphenol) using two different thin-layer flow cells clearly show that the potential dependence and appearance of the mass spectra depend on the flow cell configuration used. The use of a modified thin-layer flow cell, in which the counter electrode had been separated from the working electrode, gave rise to significantly increased intensities for the oxidised MnIII,IV state of the complex. With the conventional unmodified cell, the corresponding complex was only seen for considerably higher oxidation potentials. The different results can be explained by the reduced risk of redox cycling and interferences due to species generated at the counter electrode with the modified cell. As interferences due to the counter electrode reactions likewise may be expected with many coulometric flow cells, the electrochemical cell design clearly needs to be considered when using electrochemistry coupled to ESI-MS to study electrochemical reactions.

  • 9236.
    Zettersten, Camilla
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi.
    Sjöberg, Per J. R.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi.
    Nyholm, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi.
    Oxidation of 4-chloroaniline studied by on-line electrochemistry electrospray ionization mass spectrometry2009Ingår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 81, nr 13, s. 5180-5187Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The oxidation of 4-chloroaniline (4-CA) has been studied by electrochemistry (EC) coupled on-line with electrospray ionization mass spectrometry (ESI-MS) using two electrochemical flow cells of different design. The experimental results, which generally verify previously suggested oxidation pathways for 4-CA, also indicate the presence of a so far unrecognized comproportionation reaction. The oxidation of 4-CA (m/z 128.2) was found to give rise to the formation of both an oxidized dimer, 4-[(4-chlorophenyl)imino]-2,5-cyclohexadien-1-imine (m/z 217.2) and a reduced dimer, 4-amino-4’-chlorodiphenylamine (m/z 219.2), in addition to a dimer intermediate (m/z 253.2). This unexpected formation of the reduced dimer is shown to stem from a comproportionation reaction involving 4-CA and the oxidized dimer. The presence of the latter reaction was clearly seen by comparing results obtained with two thin-layer flow cells, both with conversion efficiencies of 50% but of different design, with respect to the influence of the counter electrode reaction on the reaction at the working electrode. The experimental results demonstrate that the formation of the reduced dimer is favored by a decrease in the local pH in the flow cell and the influence of the pH on the oxidation of 4-CA was also investigated in the pH range between 2.0 and 6.0 using off-line voltammetry. It is concluded that EC/ESI-MS is a powerful tool for the study of the present type of reactions and that studies on reaction pathways are best carried out with thin-layer flow cells having conversion efficiencies smaller than 100% as this facilitates the detection of reaction intermediates. Comproportionation reactions, similar to the reaction present in the 4-CA system, can also be expected to be present during the formation of conducting polymers such as polyaniline and polypyrrole.

  • 9237.
    Zhan, Shaoqi
    et al.
    KTH Royal Inst Technol, Sch Biotechnol, Div Theoret Chem & Biol, S-10691 Stockholm, Sweden.
    Martensson, Daniel
    KTH Royal Inst Technol, Sch Biotechnol, Div Theoret Chem & Biol, S-10691 Stockholm, Sweden.
    Purg, Miha
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Biokemi.
    Kamerlin, Shina C. Lynn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Biokemi.
    Ahlquist, Marten S. G.
    KTH Royal Inst Technol, Sch Biotechnol, Div Theoret Chem & Biol, S-10691 Stockholm, Sweden.
    Capturing the Role of Explicit Solvent in the Dimerization of Ru-V(bda) Water Oxidation Catalysts2017Ingår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 56, nr 24, s. 6962-6965Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A ground-breaking empirical valence bond study for a soluble transition-metal complex is presented. The full reaction of catalyst monomers approaching and reacting in the Ru-V oxidation state were studied. Analysis of the solvation shell in the reactant and along the reaction coordinate revealed that the oxo itself is hydrophobic, which adds a significant driving force to form the dimer. The effect of the solvent on the reaction between the prereactive dimer and the product was small. The solvent seems to lower the barrier for the isoquinoline (isoq) complex while it is increased for pyridines. By comparing the reaction in the gas phase and solution, the proposed p-stacking interaction of the isoq ligands is found to be entirely driven by the water medium.

  • 9238. Zhang, Biaobiao
    et al.
    Chen, Hong
    Daniel, Quentin
    Philippe, Bertrand
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Yu, Fengshou
    Valvo, Mario
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Li, Yuanyuan
    Ambre, Ram B.
    Zhang, Peili
    Li, Fei
    Rensmo, Håkan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Molekyl- och kondenserade materiens fysik.
    Sun, Licheng
    Defective and “c-Disordered” Hortensia-like Layered MnOx as an Efficient Electrocatalyst for Water Oxidation at Neutral pH2017Ingår i: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 7, nr 9, s. 6311-6322Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The development of a highly active manganese-based water oxidation catalyst in the design of an ideal artificial photosynthetic device operating under neutral pH conditions remains a great challenge, due to the instability of pivotal Mn3+ intermediates. We report here defective and “c-disordered” layered manganese oxides (MnOx-300) formed on a fluorine-doped tin oxide electrode by constant anodic potential deposition and subsequent annealing, with a catalytic onset (0.25 mA/cm2) at an overpotential (η) of 280 mV and a benchmark catalytic current density of 1.0 mA/cm2 at an overpotential (η) of 330 mV under neutral pH (1 M potassium phosphate). Steady current density above 8.2 mA/cm2 was obtained during the electrolysis at 1.4 V versus the normal hydrogen electrode for 20 h. Insightful studies showed that the main contributing factors for the observed high activity of MnOx-300 are (i) a defective and randomly stac