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  • 1. Aaldering, L. J.
    et al.
    Poongavanam, V.
    Langkjær, N.
    Natarajan Arul, Murugan
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Jørgensen, P. T.
    Wengel, J.
    Veedu, R. N.
    Development of an Efficient G-Quadruplex-Stabilised Thrombin-Binding Aptamer Containing a Three-Carbon Spacer Molecule2017In: ChemBioChem (Print), ISSN 1439-4227, E-ISSN 1439-7633, Vol. 18, no 8, 755-763 p.Article in journal (Refereed)
    Abstract [en]

    The thrombin-binding aptamer (TBA), which shows anticoagulant properties, is one of the most studied G-quadruplex-forming aptamers. In this study, we investigated the impact of different chemical modifications such as a three-carbon spacer (spacer-C3), unlocked nucleic acid (UNA) and 3′-amino-modified UNA (amino-UNA) on the structural dynamics and stability of TBA. All three modifications were incorporated at three different loop positions (T3, T7, T12) of the TBA G-quadruplex structure to result in a series of TBA variants and their stability was studied by thermal denaturation; folding was studied by circular dichroism spectroscopy and thrombin clotting time. The results showed that spacer-C3 introduction at the T7 loop position (TBA-SP7) significantly improved stability and thrombin clotting time while maintaining a similar binding affinity as TBA to thrombin. Detailed molecular modelling experiments provided novel insights into the experimental observations, further supporting the efficacy of TBA-SP7. The results of this study could provide valuable information for future designs of TBA analogues with superior thrombin inhibition properties. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  • 2. Abdel-Khalek, Ahmed A.
    et al.
    Ali, M. M.
    Ashour, Radwa
    Abdel-Magied, A. F.
    Chemical Studies on Uranium Extraction from Concentrated Phosphoric Acid by Using PC88A and DBBP Mixture.2011In: Journal of Radioanalytical and Nuclear Chemistry, ISSN 0236-5731, E-ISSN 1588-2780, Vol. 290, 353-359 p.Article in journal (Refereed)
    Abstract [en]

    Liquid–liquid extraction of U (VI) from concentrated phosphoric acid by using (2-ethyl hexyl) phosphonic acid, mono (2-ethyl hexyl) ester (PC88A) and di-butyl butyl phosphonate (DBBP) has been investigated. The effect of different factors affecting the extraction process (PC88A concentration, DBBP concentration, shaking time, aqueous/organic phase ratio, phosphoric acid concentration and effect of diluents) have been investigated. The obtained data of temperature on the extraction showed that the enthalpy change is −17.15 kJ mol−1. Uranium was extracted from the strip liquor by using di (2-ethylhexyl) phosphoric acid and tri-octyl phosphine oxide mixture and finally converted to a high purity UO3 product using precipitation with hydrogen peroxide and heat treatment at 365 °C.

  • 3. Abdellah, Mohamed
    et al.
    Zhang, Shihuai
    Wang, Mei
    Hammarstrom, Leif
    Competitive Hole Transfer from CdSe Quantum Dots to Thiol Ligands in CdSe-Cobaloxime Sensitized NiO Films Used as Photocathodes for H-2 Evolution2017In: ACS ENERGY LETTERS, ISSN 2380-8195, Vol. 2, no 11, 2576-2580 p.Article in journal (Refereed)
    Abstract [en]

    Quantum dot (QD) sensitized NiO photocathodes rely on efficient photoinduced hole injection into the NiO valence band. A system of a mesoporous NiO film co-sensitized with CdSe QDs and a molecular proton reduction catalyst was studied. While successful electron transfer from the excited QDs to the catalyst is observed, most of the photogenerated holes are instead quenched very rapidly (ps) by hole trapping at the surface thiols of the capping agent used as linker molecules. We confirmed our conclusion by first using a thiol free capping agent and second varying the thiol concentration on the QD's surface. The later resulted in faster hole trapping as the thiol concentration increased. We suggest that this hole trapping by the linker limits the H-2 yield for this photocathode in a device.

  • 4.
    Abdi, Adel Hirmand
    KTH, School of Architecture and the Built Environment (ABE), Transportvetenskap, Väg- och banteknik.
    Key aspects in winter highway operation and maintenance2010Report (Other academic)
  • 5.
    Abili Nejad, Maryam
    KTH, Superseded Departments, Chemistry.
    Kinetics for oxidation of CRUD model compounds2004Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The formation of CRUD (Chalk River Unidentified Deposit) inwater-cooled nuclear reactors constitute a severe problem. Thestability of CRUD under reactor conditions (high flux ofionizing radition, high temperature and pressure) must be knownin order to minimize the problem. The kinetics for CRUDoxidation by H2O2 and the two more potent oxidants IrCl62-and MnO4- has been studied using aqueous suspensions ofthree metal oxide powders, Fe3O4, Fe2CoO4 and Fe2NiO4. The metal oxides were used as model compounds forCRUD. The latter two oxidants were employed to study therelationship between kinetics and the reduction potential ofthe oxidant. In addition, the activation energies for thereaction between H2O2and the three metal oxides of CRUD model weredetermined. The mechanism of the reaction is discussedindicating that the final solid product in all three cases isFe2O3. Our experimental results show that the reactivityof the metal oxides towards oxidants is in the order Fe2CoO4>Fe3O4>Fe2NiO4. The relative reactivities of Fe2CoO4 and Fe3O4are in contrast with that expected from the studyof the ionization potentials of the divalent metals in theoxides. In addition to the experimental studies, thetheoretical grounds for kinetics of reactions in particlesolutions are discussed. The theoretical discussion is alsoused to explain the somewhat unexpected trends in reactivityobserved experimentally. The same reaction trend is alsoobserved in the reaction of the metal oxides with IrCl62-and MnO4-.

    We found experimentally that the logarithm of second orderrate constants of the reaction of metal oxides with oxidantsagainst the one electron potential of the oxidants follows aparabolic behavior in agreement with the Marcus theory forelectron transfer reactions. This work constitutes a good basisfor the design of further model studies aiming at resolving thestability of CRUD under reactor conditions.

    Keywords:Reactor Chemistry, Radiolysis, Oxidation,Kinetics, CRUD, Metal oxide

  • 6.
    Abraham, Mark J
    Computational Proteomics Group, John Curtin School of Medical Research, Australian National University, Australia.
    Performance enhancements for GROMACS nonbonded interactions on BlueGene.2011In: Journal of Computational Chemistry, ISSN 0192-8651, E-ISSN 1096-987X, Vol. 32, no 9Article in journal (Refereed)
    Abstract [en]

    Several improvements to the previously optimized GROMACS BlueGene inner loops that evaluate nonbonded interactions in molecular dynamics simulations are presented. The new improvements yielded an 11% decrease in running time for both PME and other kinds of GROMACS simulations that use nonbonded table look-ups. Some other GROMACS simulations will show a small gain.

  • 7.
    Abraham, Mark J
    et al.
    Australian National University, Australia.
    Gready, Jill E
    Australian National University.
    Ensuring Mixing Efficiency of Replica-Exchange Molecular Dynamics Simulations2008In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 4, no 7Article in journal (Refereed)
    Abstract [en]

    We address the question of constructing a protocol for replica-exchange molecular dynamics (REMD) simulations that make efficient use of the replica space, assess whether published applications are achieving such "mixing" efficiency, and provide a how-to guide to assist users to plan efficient REMD simulations. To address our first question, we introduce and discuss three metrics for assessing the number of replica-exchange attempts required to justify the use of a replica scheme and define a "transit number" as the lower bound for the length of an efficient simulation. Our literature survey of applications of REMD simulations of peptides in explicit solvent indicated that authors are not routinely reporting sufficient details of their simulation protocols to allow readers to make independent assessments of the impact of the method on their results, particularly whether mixing efficiency has been achieved. Necessary details include the expected or observed replica-exchange probability, together with the total number of exchange attempts, the exchange period, and estimates of the autocorrelation time of the potential energy. Our analysis of cases where the necessary information was reported suggests that in many of these simulations there are insufficient exchanges attempted or an insufficiently long period between them to provide confidence that the simulation length justifies the size of the replica scheme. We suggest guidelines for designing REMD simulation protocols to ensure mixing efficiency. Two key recommendations are that the exchange period should in general be larger than 1 ps and the number of exchange attempts should be chosen to significantly exceed the transit number for the replica scheme.

  • 8.
    Abraham, Mark J
    et al.
    Australian National University, Australia.
    Gready, Jill E
    Optimization of parameters for molecular dynamics simulation using smooth particle-mesh Ewald in GROMACS 4.52011In: Journal of Computational Chemistry, ISSN 0192-8651, E-ISSN 1096-987X, Vol. 32, no 9Article in journal (Refereed)
    Abstract [en]

    Based on our critique of requirements for performing an efficient molecular dynamics simulation with the particle-mesh Ewald (PME) implementation in GROMACS 4.5, we present a computational tool to enable the discovery of parameters that produce a given accuracy in the PME approximation of the full electrostatics. Calculations on two parallel computers with different processor and communication structures showed that a given accuracy can be attained over a range of parameter space, and that the attributes of the hardware and simulation system control which parameter sets are optimal. This information can be used to find the fastest available PME parameter sets that achieve a given accuracy. We hope that this tool will stimulate future work to assess the impact of the quality of the PME approximation on simulation outcomes, particularly with regard to the trade-off between cost and scientific reliability in biomolecular applications.

  • 9. Abrahamsson, Christoffer
    et al.
    Nordstierna, Lars
    Nordin, Matias
    Dvinskikh, Sergey V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. St. Petersburg State University, Russian Federation.
    Nyden, Magnus
    Magnetic orientation of nontronite clay in aqueous dispersions and its effect on water diffusion2015In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 437, 205-210 p.Article in journal (Refereed)
    Abstract [en]

    The diffusion rate of water in dilute clay dispersions depends on particle concentration, size, shape, aggregation and water-particle interactions. As nontronite clay particles magnetically align parallel to the magnetic field, directional self-diffusion anisotropy can be created within such dispersion. Here we study water diffusion in exfoliated nontronite clay dispersions by diffusion NMR and time-dependant 1H-NMR-imaging profiles. The dispersion clay concentration was varied between 0.3 and 0.7 vol%. After magnetic alignment of the clay particles in these dispersions a maximum difference of 20% was measured between the parallel and perpendicular self-diffusion coefficients in the dispersion with 0.7 vol% clay. A method was developed to measure water diffusion within the dispersion in the absence of a magnetic field (random clay orientation) as this is not possible with standard diffusion NMR. However, no significant difference in self-diffusion coefficient between random and aligned dispersions could be observed.

  • 10. Acciaro, Roberta
    et al.
    Aulin, Christian
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Lindström, Tom
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Varga, Imre
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Investigation of the formation, structure and release characteristics of self-assembled composite films of cellulose nanofibrils and temperature responsive microgels2011In: Soft Matter, ISSN 1744-683X, Vol. 7, no 4, 1369-1377 p.Article in journal (Refereed)
    Abstract [en]

    The possibility of forming self-organized films using charge-stabilized dispersions of cellulose I nanofibrils and microgel beads of poly-(N-isopropylacrylamide-co-acrylic acid) copolymer is presented. The build-up behavior and the properties of the layer-by-layer (LbL)-constructed films were studied using quartz crystal microbalance with dissipation (QCM-D) and ellipsometry. The morphology of the formed films was also characterized using atomic force microscopy (AFM) imaging. The applied methods clearly demonstrated the successful LbL-assembly of the monodisperse microgels and nanofibrils. The in situ QCM-D measurements also revealed that contrary to the polyelectrolyte bound microgel particles, the nanofibrils-bound gel beads preserve their highly swollen state and do not suffer a partial collapse due to the lack of interdigitation of the oppositely charged components. To probe the accessibility of the gel beads in the formed films, the room temperature (similar to 25 degrees C) loading and release of a fluorescent dye (FITC) was also investigated. The incorporation of the cellulose nanofibrils into the multilayer resulted in an open structure that was found easily penetrable for the dye molecules even at constant room temperature, which is in sharp contrast with previously reported systems based on synthetic polyelectrolytes. The amount of dye released from the multilayer films could be fine-tuned with the number of bilayers. Finally, the thermoresponsivity of the films was also shown by triggering the burst release of the loaded dye when the film was collapsed.

  • 11. Adamus, Grazyna
    et al.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Höglund, Anders
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Kowalczuk, Marek
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    MALDI-TOF MS Reveals the Molecular Level Structures of Different Hydrophilic-Hydrophobic Polyether-esters2009In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 10, no 6, 1540-1546 p.Article in journal (Refereed)
    Abstract [en]

    Multi- and triblock copolymers based on 1,5-dioxepan-2-one/epsilon-caprolactone (DXO/CL) were investigated by MALDI-TOF MS to determine the influence of copolymer composition and architecture on the molecular structures at the individual chain level. The copolymer compositions, average block lengths, and molecular weights were determined by H-1 and C-13 NMR and by SEC, respectively. The structures of polyether-ester oligomers (linear, cyclic) as well as the chemical structures of their end groups were established on the basis of their MALDI-TOF mass spectra. The mass spectrum of PDXO homopolymer was relatively simple, however, complex mass spectra were obtained in the case of multi- and triblock copolymers and the mass spectra clearly discerned the molecular level effect of copolymer composition and copolymer type.

  • 12. Adekunle, Kayode
    et al.
    Cho, Sung-Woo
    Patzelt, Christian
    Blomfeldt, Thomas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Skrifvars, Mikael
    Impact and flexural properties of flax fabrics and Lyocell fiber-reinforced bio-based thermoset2011In: Journal of reinforced plastics and composites (Print), ISSN 0731-6844, E-ISSN 1530-7964, Vol. 30, no 8, 685-697 p.Article in journal (Refereed)
    Abstract [en]

    A bio-based thermoset resin was reinforced with flax fabrics and Lyocell fiber. The effect of different weave architectures was studied with four flax fabrics with different architectures: plain, twill (two different types), and dobby. The effect of the outer ply thickness was studied and characterized with flexural and impact testing. Composites manufactured with plain weave reinforcement had the best mechanical properties. The tensile strength, tensile modulus, flexural strength, flexural modulus, and impact strength were 280MPa, 32GPa, 250MPa, 25GPa, and 75 kJ/m (2), respectively. Reinforcements with twill-weave architecture did not impart appreciable flexural strength or flexural modulus even when the outer thickness was increased. Plain- and dobby (basket woven style)-weave architectures gave better reinforcing effects and the flexural properties increased with an increase in outer thickness. Water absorption properties of the composites were studied and it was observed that the hybridization with Lyocell fiber reduced the water uptake. Field-emission scanning electron microscopy was used to study the micro-structural properties of the composites.

  • 13.
    Adhikari, Arindam
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Pani, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Deidinaitei, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Electrochemical behavior and anticorrosion properties of modified polyaniline dispersed in polyvinylacetate coating on carbon steel2008In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, no 12, 4239-4247 p.Article in journal (Refereed)
    Abstract [en]

    Conducting polyaniline (Pani) was prepared in the presence of methane sulfonic acid (MeSA) as dopant by chemical oxidative polymerization. The Pani-MeSA polymer was characterized by FT-IR, UV-vis, X-ray diffraction (XRD) and impedance spectroscopy. The polyrner was dispersed in polyvinylacetate and coated oil carbon steel samples by a dipping method. The electrochemical behavior and anticorrosion properties of the coating, oil carbon steel in 3% NaCl were investigated using Open-circuit Potential (OCP) versus time of exposure, and electrochemical techniques including electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and cyclic voltammetry (CV). During initial exposure, the OCP dropped about 0.35 V and the interfacial resistance increased several times, indicating I certain reduction of the polymer and oxidation of the steel surface. Later the OCP shifted to the noble direction and remained at a stable value during the exposure up to 60 days. The EIS monitoring also revealed the initial change and later stabilization of the coating. The stable high OCP and low coating impedance Suggest that the conducting polymer maintains its oxidative state and provides corrosion protection for carbon steel through out the investigated period. The polarization curves and CV show that the conducting polymer coating induces a passive-like behavior and greatly reduces the corrosion of carbon steel.

  • 14.
    Adhikari, Arindam
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Radhakrishnan, S.
    Patil, Rahul
    Influence of dopant ions on properties of conducting polypyrrole and its electrocatalytic activity towards methanol oxidation2009In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 159, no 15-16, 1682-1688 p.Article in journal (Refereed)
    Abstract [en]

    The polypyrrole (PPy) films were deposited on vacuum metallized substrates by electro-oxidation of pyrrole monomer. These electrodes were then modified with a range of metal halides having different electronegativities. The modified polypyrrole electrodes were employed to investigate electrocatalytic activity towards methanol electrochemical oxidation by means of cyclic voltammetry in 0.1 M HClO4 as supporting electrolyte. It was found that the electronegativity of the dopant ion incorporated in the PPy film governs the electrocatalytic activity towards methanol oxidation. Among different dopant anions used in the present work, the PPy doped with zirconium chloride gave the highest anodic current of 10 mA cm(-2) at the oxidation potential of methanol. Electrical property and the charge created due to doping in the polymers were measured using X-ray photoelectron spectroscopy (XPS) and Electron spin resonance spectroscopy (ESR). Electrocatalytic activity of the modified electrodes was correlated with various factors obtained from different polymer characterization experiments. The results were explained on the basis of the charge-transfer efficiency at the electrode I electrolyte interface, which was associated with the acceptor state created by the dopant in the semi-conducting polymer.

  • 15. Adia, Madina Mohamed
    et al.
    Emami, Seyedeh Noushin
    Byamukama, Robert
    Faye, Ingrid
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Antiplasmodial activity and phytochemical analysis of extracts from selected Ugandan medicinal plants2016In: Journal of Ethnopharmacology, ISSN 0378-8741, E-ISSN 1872-7573, Vol. 186, 14-19 p.Article in journal (Refereed)
    Abstract [en]

    Ethnopharmacological relevance: Resistance of the parasites to known antimalarial drugs has provided the necessity to find new drugs from natural products against malaria. The aim of the study was to evaluate the in vitro antiplasmodial activity of some plants used by Traditional Medical Practitioners (TMPs) of Prometra and Rukararwe in malaria treatment in Uganda to provide scientific proof of the efficacies claimed by these Herbalists. Materials and methods: The air dried samples of Clerodendrum rotundifolium (leaves), Microglossa pyrifolia (leaves), Momordica foetida (leaves) and Zanthoxylum chalybeum (stem bark) used for malaria treatment by TMPs were successively extracted with ethyl acetate, methanol and water to yield twelve extracts. The extracts were tested against the chloroquine-sensitive (NF54) and chloroquine-resistant (FCR3) Plasmodium falciparum strains in vitro using the micro Mark III test which is based on assessing the inhibition of schizont maturation. A compound A was extracted and purified from the stem bark of Z. chalybeum and its structure was identified and confirmed by spectroscopic methods. Results: Most of the extracts tested (92%) showed an antiplasmodial activity with IC50 < 50 mu g/mL. In spite of successive extractions with different solvents, potent anti-plasmodial activity (IC50 < 5 mu g/mL) was observed in the ethyl acetate, methanol and aqueous extracts of M. pyrifolia and C. rotundifolium. Preferential enrichments of activity into water (IC50 < 15 mu g/mL) and Ethyl acetate (IC50 < 5 mu g/mL) were seen in the case of M. foetida and Z chalybeum respectively. The most active extracts were from C rotundifolium and M. pyrifolia with IC50 values less than 2 mu g/mL. Phytochemical analysis of the extracts revealed the presence of saponins, tannins, flavonoids, alkaloids and cardiac glycocides. Fagaramide isolated from Z chalybeum had a higher activity (IC50 2.85 mu g/mL) against the chloroquine-resistant strain than against the chloroquine-senstive (IC50 16.6 mu g/mL) strain used in the study. Conclusion: The plant extracts analysed in this study presented an average antiplasmodial activity (58%). This study revealed for the first time the antiplasmodial activity of the plant C. rotundofolium. It's the first time the compound fagaramide (N-isobutyl-3-(3,4-methylene dioxyphenyl) - 2E-propenamide) has been isolated from Z. chalybeum as one of the compounds that contribute to the activity of this plant against P. falciparum.

  • 16. Adler, Belinda
    et al.
    Boström, Tove
    KTH, School of Biotechnology (BIO), Proteomics.
    Ekström, Simon
    Hober, Sophia
    KTH, School of Biotechnology (BIO), Proteomics.
    Laurell, Thomas
    Miniaturized and Automated High-Throughput Verification of Proteins in the ISET Platform with MALDI MS2012In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 84, no 20, 8663-8669 p.Article in journal (Refereed)
    Abstract [en]

    A major bottleneck in high-throughput protein production is the validation step, which is why parallel and automated sample processing methods are highly desirable. Also, a miniaturized sample preparation format is preferred, as the reduction of reagent volumes significantly decreases the analysis cost per sample. We have developed an automated and miniaturized protein sequence verification protocol for recombinant proteins utilizing peptide mass fingerprinting and MS/MS analysis. The integrated selective enrichment target (ISET) platform, previously developed in our group, with its dual functionality, being both a sample preparation platform and a MALDI target plate, is employed. All steps including immobilized metal ion affinity chromatography of protein on cobalt-loaded beads, tryptic digestion, and MALDI MS analysis are performed in an array format, without any sample transfers, on the same ISET chip. The automated configuration reduced the sample preparation time significantly. Starting with crude lysate, a full plate of 48 purified, digested samples prepared for MALDI-MS can be generated in 4 h, with only 30 min of operator involvement. This paper demonstrates the utility of the method by parallel analysis of 45 His-tagged human recombinant proteins.

  • 17.
    Adolfsson, Karin H.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hassanzadeh, Salman
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Valorization of cellulose and waste paper to graphene oxide quantum dots2015In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 5, no 34, 26550-26558 p.Article in journal (Refereed)
    Abstract [en]

    Biobased graphene oxide quantum dots (GOQD) were derived from cellulose via carbon nanospheres (CN) as intermediate products. Solid CN were synthesized from cellulose through microwave-assisted hydrothermal degradation of alpha-cellulose with H2SO4 as a catalyst at 160 degrees C. The obtained CN were further utilized for the synthesis of GOQD by a two-step reaction including 30 minutes of sonication followed by heating at 90 degrees C under O-rich acidic conditions (HNO3). This process broke down the 3D CN to 2D GOQD. The size of the synthesized GOQD was controlled by the heating time, reaching a dot diameter of 3.3 nm and 1.2 nm after 30 and 60 minutes of heating, respectively. The synthesis process and products were characterized by multiple analytical techniques including FTIR, TGA, SEM, TEM, XPS, XRD, BET, DLS and AFM. Interesting optical properties in aqueous solutions were demonstrated by UV/Vis and fluorescence spectroscopy. Finally we demonstrated that corresponding GOQD can be synthesized from waste paper. This production route thus uses renewable and cheap starting materials and relatively mild synthesis procedures leads to instant nanometric production of 2D dots. In addition it enables recycling of low quality waste to value-added products.

  • 18. Afonso, Damien
    et al.
    Valetti, Sabrina
    Fraix, Aurore
    Bascetta, Claudia
    Petralia, Salvatore
    Conoci, Sabrina
    Feiler, Adam
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Sortino, Salvatore
    Multivalent mesoporous silica nanoparticles photo-delivering nitric oxide with carbon dots as fluorescence reporters2017In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 9, no 36, 13404-13408 p.Article in journal (Refereed)
    Abstract [en]

    Amino-terminated mesoporous silica nanoparticles embedding carbon dots (MSCD) formed by calcination were functionalized with a nitric oxide (NO) photodonor (1) to give a robust MSCD-1 conjugate. The intense fluorescence of MSCDs was strongly quenched in MSCD-1 by effective energy transfer. Visible light excitation of MSCD-1 liberates NO, suppresses the energy transfer mechanism and leads to concomitant fluorescence restoration of the MSCD scaffold, which acts as an optical reporter for the released NO. The MSCD-1 hybrid is also able to encapsulate the highly hydrophobic photosensitizer temoporfin, preserving the fluorescence reporting function.

  • 19.
    Afrasiabi, Roodabeh
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Jokilaakso, Nima
    KTH, School of Biotechnology (BIO), Protein Technology.
    Schmidt, Torsten
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Björk, P.
    Eriksson Karlström, Amelie
    KTH, School of Biotechnology (BIO), Protein Technology.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Effect of microwave-assisted silanization on sensing properties of silicon nanoribbon FETs2015In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 209, 586-595 p.Article in journal (Refereed)
    Abstract [en]

    An important concern with using silicon nanoribbon field-effect transistors (SiNR FET) for ion-sensing is the pH-response of the gate oxide surface. Depending on the application of the FET sensor, this response has to be chemically manipulated. Thus in silicon oxide-gated pH-sensors with integrated sensor and reference FETS, a surface with high pH-sensitivity, compared to the bare gate oxide, is required in the sensor FETs (SEFET), whereas in the reference FETs (REFET) the surface has to be relatively pH-insensitive. In order to control the sensitivity and chemistry of the oxide surface of the nanoribbons, a silanization reagent with a functional group is often self-assembled on the SiNR surface. Choice of a silanization reaction that results in a self-assembled layer on a silicon oxide surface has been studied extensively over the past decades. However, the effect of various self-assembled layers such as monolayers or mixed layers on the electrical response of SiNR FETs in aqueous solution needs to be exploited further, especially for future integrated SEFET/REFET systems. In this work, we have performed a comprehensive study on 3-aminopropyltriethoxysilane (APTES) silanization of silicon oxide surfaces using microwave (MW) heating as a new biocompatible route to conventional methods. A set of complementary surface characterization techniques (ellipsometry, AFM and ATR-FTIR) was used to analyze the properties of the APTES layer deposited on the silicon surface. We have found that a uniform monolayer can be achieved within 10 min by heating the silanization solution to 75 degrees C using MW heating. Furthermore, electrical measurements suggest that little change in device performance is observed after exposure to MW irradiation. Real-time pH measurements indicate that a uniform APTES monolayer not only reduces the pH sensitivity of SiNR FET by passivating the surface silanol groups, but also makes the device less sensitive to cation concentration in the background electrolyte. Our silanization route proves promising for future chemical surface modification of on-chip REFETs.

  • 20. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Coulometric Calcium Pump for Thin Layer Sample Titrations2015In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 87, no 19, 10125-10130 p.Article in journal (Refereed)
  • 21. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Counter electrode based on an ion-exchanger Donnan exclusion membrane for bioelectroanalysis2014In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 61, 64-69 p.Article in journal (Refereed)
  • 22. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Direct Ion Speciation Analysis with Ion-Selective Membranes Operated in a Sequential Potentiometric/Time Resolved Chronopotentiometric Sensing Mode2012In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 84, no 20, 8813-8821 p.Article in journal (Refereed)
  • 23. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Flow Chronopotentiometry with Ion-Selective Membranes for Cation, Anion, and Polyion Detection2016In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 88, no 7, 3945-3952 p.Article in journal (Refereed)
  • 24. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Bakker, Eric
    Thin-Layer Chemical Modulations by a Combined Selective Proton Pump and pH Probe for Direct Alkalinity Detection2015In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 54, no 28, 8110-8113 p.Article in journal (Refereed)
  • 25. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Dorokhin, Denis
    Neel, Bastien
    Bakker, Eric
    Thin Layer Coulometry of Nitrite with Ion-Selective Membranes2015In: Electroanalysis, ISSN 1040-0397, E-ISSN 1521-4109, Vol. 27, no 3, 609-615 p.Article in journal (Refereed)
  • 26. Afshar, Majid Ghahraman
    et al.
    Crespo, Gaston A.
    Xie, Xiaojiang
    Bakker, Eric
    Direct Alkalinity Detection with Ion-Selective Chronopotentiometry2014In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 86, no 13, 6461-6470 p.Article in journal (Refereed)
  • 27.
    Afzal, Muhammad
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Raza, R.
    Du, S.
    Lima, R.B.d
    Zhu, Bin
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics. Hubei Univ, Fac Phys & Elect Technol, Hubei Collaborat Innovat Ctr Adv Organ Chem Mat, Wuhan 430062, Peoples R China.
    Synthesis of Ba0.3Ca0.7Co0.8Fe0.2O3-δ composite material as novel catalytic cathode for ceria-carbonate electrolyte fuel cells2015In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 178, 385-391 p.Article in journal (Refereed)
    Abstract [en]

    This work reports a new composite BaxCa1-xCoyFe1-yO3-delta (BCCF) cathode material for advanced and low temperature solid oxide fuel cells (SOFCs). The BCCF-based composite material was synthesized by sol gel method and investigated as a catalytic cathode for low temperature (LT) SOFCs. XRD analysis of the as-prepared material revealed the dominating BCCF perovskite structure as the main phase accompanied with cobalt and calcium oxides as the secondary phases resulting into an overall composite structure. Structure and morphology of the sample was observed by Field Emission Scanning Electron Microscope (FE-SEM). In particular, the Ba0.3Ca0.7Co0.8Fe0.2O3-delta (BCCF37) showed a maximum conductivity of 143 S cm(-1) in air at 550 degrees C measured by DC 4 probe method. The BCCF at the optimized composition exhibited much higher electrical conductivities than the commercial Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) perovskite cathode material. A maximum power density of 325 mW cm(-2) at 550 degrees C is achieved for the ceria-carbonate electrolyte fuel cell with BCCF37 as the cathode material.

  • 28.
    Afzal, Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Saleemi, Mohsin
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Wang, Baoyuan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Xia, Chen
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Zhang, Wei
    He, Yunjuan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Jayasuriya, Jeevan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Zhu, Binzhu
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Fabrication of novel electrolyte-layer free fuel cell with semi-ionic conductor (Ba0.5Sr0.5Co0.8Fe0.2O3-delta- Sm0.2Ce0.8O1.9) and Schottky barrier2016In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 328, 136-142 p.Article in journal (Refereed)
    Abstract [en]

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

  • 29.
    Agfors, Gunnar
    et al.
    Ledamot av IVA.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Grenthe, Ingmar
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Ödberg, Lars
    et, al
    KEMI: den gränslösa vetenskapen2011Book (Other (popular science, discussion, etc.))
    Abstract [sv]

    Kemi – handlar inte det bara om farliga ämnen och onödiga tillsatser? Det är kanske bildenmånga har av kemi, men faktum är att utan kemi skulle vi inte ha det höga välstånd vi har i dag.Tack vare kemisk kunskap har vi tillgång till läkemedel som botar sjukdomar och lindrar smärta– med hjälp av syntetiska antibiotika kan infektionssjukdomar som tidigare var dödliga botas,magsår kan behandlas utan dyra och plågsamma operationer och många cancerformer kanframgångsrikt behandlas med syntetiska preparat. Konstgödsel och medel som hindrar skadeinsektergör att skördar kan ökas och svälten i världen därigenom begränsas. Tack vare kemin harvi även tillgång till alla de material vi behöver för att tillverka allt från kläder, rengöringsprodukteroch kosmetika till bilar, TV-apparater och reservdelar till kroppen. Det är genom kemisk syntes vikan framställa dessa och alla de övriga produkter vi behöver för vårt dagliga liv och det är keminsom visar vägen till hållbar produktion som utnyttjar förnybara råvaror och ger minimala mängderavfall. Kemisk kunskap är också oumbärlig för utveckling av nanoteknik och medicinskdiagnostik och andra till kemin angränsande områden. Kemin bidrar alltså till att finna lösningartill många av de komplexa globala problem vi står inför: hälsa, klimat, brist på råvaror, utnyttjandetav nya energikällor och tillgång till livsmedel för att föda jordens ökande befolkning.

    DET ÄR OM ALLT DETTA DEN HÄR BOKEN HANDLAR.

  • 30.
    Agrios, Alexander George
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630). KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Cesar, I.
    Comte, P.
    Nazeeruddin, M. K.
    Grätzel, M.
    Nanostructured composite films for dye-sensitized solar cells by electrostatic layer-by-layer deposition2006In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 18, no 23, 5395-5397 p.Article in journal (Refereed)
    Abstract [en]

    The possibilities for making nanocomposite semiconductor films for DSC using the ELBL method was investigated. Coated slides were cut in half vertically giving two strips that can be subjected to different treatments for comparison. The electrode was heated to 450 °C for 30 min and then Cooled to 80 °C. Scanning electron microscopy of a sintered film with 5 cycles of TiO2 nanoparticles shows that the particles are well distributed and completely cover the transparent conducting oxide substrate. Spectroscopic measurements of a dye-coated film in acetonitrile found a dye concentration within the film of 0.15 mM based on an extinction coefficient. The solar cell including a scattering layer had more than double the current of the transparent layer-only cell. It was observed that ELBL method can produce TiO2 films for DSC with high efficiencies at low thickness.

  • 31. Aguirre, Miren
    et al.
    Johansson Salazar-Sandoval, Eric
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. SP Technical Research Institute of Sweden, Sweden.
    Johansson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Ahniyaz, Anwar
    Paulis, Maria
    Ramon Leiza, Jose
    Hybrid acrylic/CeO2 nanocomposites using hydrophilic, spherical and high aspect ratio CeO2 nanoparticles2014In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 2, no 47, 20280-20287 p.Article in journal (Refereed)
    Abstract [en]

    A dispersion of CeO2 nanoparticles and nanorods stabilized with nitrilotriacetic acid (NTA) and a 4,4'-azobis(4-cyanovaleric acid) (V-501) initiator has been used to initiate the emulsion polymerization of acrylic monomers, yielding stable hybrid CeO2 nanoparticle-nanorod/polyacrylate latexes for the first time. Films cast from these hybrid latexes are transparent due to the very homogenous distribution of the polymer compatibilized CeO2. Furthermore, it has been proven that the UV-Vis absorption capacity of the hybrid latexes is enhanced with the incorporation of the nanorods.

  • 32. Ahlberg, P.
    et al.
    Karlsson, A.
    Goeppert, A.
    Lill, S. O. N.
    Dinér, Peter
    Sommer, J.
    Solvated CH5+ in liquid superacid2001In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 7, no 12, 2501-2510 p.Article in journal (Refereed)
  • 33.
    Ahlquist, Mårten
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Fabrizi, G
    Cacchi, S
    Norrby, Per-Ola
    Technical University of Denmark.
    Palladium(0) alkyne complexes as active species: a DFT investigation2005In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, no 33, 4196-4198 p.Article in journal (Refereed)
    Abstract [en]

    Alkynes have been found to be excellent ligands for Pd(0); the stability of a range of alkyne-Pd(0) complexes, and their reactivity in oxidative addition, have been investigated by DFT methods.

  • 34.
    Ahlquist, Mårten
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Fabrizi, Giancarlo
    Cacchi, Sandro
    Norrby, Per-Ola
    Technical Univeristy of Denmark.
    The mechanism of the phosphine-free palladium-catalyzed hydroarylation of alkynes2006In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 128, no 39, 12785-12793 p.Article in journal (Refereed)
    Abstract [en]

    The mechanism of the Pd-catalyzed hydroarylation and hydrovinylation reaction of alkynes has been studied by a combination of experimental and theoretical methods (B3LYP), with an emphasis on the phosphine-free version. The regioselectivity of the hydroarylation and hydrovinylation shows unexpected differences, which could be attributed mainly to the higher steric demand of the cyclohexenyl group as compared to the phenyl group. Hydroarylation of alpha,beta-acetylenic carbonyl substrates yields a very unusual anti-Michael selectivity, which is shown to result from reaction of the nonconjugated double bond, leaving the conjugation intact. In all cases were the regioselectivities reproduced by the calculations.

  • 35.
    Ahlquist, Mårten
    et al.
    Scripps Research Insititute.
    Fokin, Valery V.
    Enhanced reactivity of dinuclear Copper(I) acetylides in dipolar cycloadditions2007In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 26, no 18, 4389-4391 p.Article in journal (Refereed)
    Abstract [en]

    Dinuclear alkynyl copper(I) complexes exhibit superior reactivity toward organic azides compared to their monomeric analogues. DFT studies indicate that the second copper center facilitates the formation of the cupracycle in the rate-determining step and stabilizes the metallacycle intermediate itself. These findings support the experimentally determined rate law and shed light on the origin of high reactivity of the in situ generated copper acetylides.

  • 36.
    Ahlquist, Mårten
    et al.
    Technical University of Denmark.
    Fristrup, P
    Tanner, David
    Technical University of Denmark.
    Norrby, Per-Ola
    Technical Univeristy of Denmark.
    Theoretical evidence for low-ligated palladium(0): [Pd-L] as the active species in oxidative addition reactions2006In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 25, no 8, 2066-2073 p.Article in journal (Refereed)
    Abstract [en]

    The oxidative addition of PhI to Pd-O has been studied by DFT with a continuum representation of the solvent. It is shown that the preferred number of ligands on palladium is lower than would be expected from "conventional wisdom" and the 18-electron rule. The most favored oxidative addition is obtained when Pd is coordinated by only the aryl iodide and one additional ligand in a linear arrangement. The calculations indicate that p-orbitals on the central metal are not involved in bonding in any of the complexes described herein, in good agreement with classic ligand field theory and also with a recent bonding analysis by Weinhold and Landis, but in apparent violation of the 18-electron rule.

  • 37.
    Ahlquist, Mårten
    et al.
    Lund University.
    Gustafsson, Mikaela
    Karlsson, Magnus
    Thaning, Mikkel
    Axelsson, Oskar
    Wendt, Ola F.
    Rhodium(I) hydrogenation in water: Kinetic studies and the detection of an intermediate using C-13{H-1} PHIPNMR spectroscopy2007In: Inorganica Chimica Acta, ISSN 0020-1693, E-ISSN 1873-3255, Vol. 360, no 5, 1621-1627 p.Article in journal (Refereed)
    Abstract [en]

    The mechanism for hydrogenation of dimethylmaleate in water using cationic rhodium complexes with water-soluble bi-dentate phosphines has been investigated using kinetics and a novel method for the indirect detection of intermediates in catalytic hydrogenation reactions, whereby a late intermediate was detected. A mechanism is proposed involving fast, irreversible substrate binding followed by a rate-determining reaction with dihydrogen.

  • 38.
    Ahlquist, Mårten
    et al.
    Technical University of Denmark.
    Kozuch, S
    Shaik, S
    Tanner, David
    Technical University of Denmark.
    Norrby, Per-Ola
    Technical Univeristy of Denmark.
    On the performance of continuum solvation models for the solvation energy of small anions2006In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 25, no 1, 45-47 p.Article in journal (Refereed)
    Abstract [en]

    The determination of continuum solvation models for the solvation energy of anions, was described. To investigate the reliability of the solvent model, a few explicit THF molecules were incorporated. A set of anions was chosen for which the experimental free energiesof solvation were available for both H 2O and DMSO solutions. A major difference between the water model and the DMSO model is that the latter systematically overestimates the free energy of solvation. The full water model in Jaguar v 4.2, including also nonelectrostatic terms, gives good correlation with experimental values for energy of solvation.

  • 39.
    Ahlquist, Mårten
    et al.
    Technical University of Denmark.
    Nielsen, Robert J.
    Periana, Roy A.
    Goddard, William A., III
    Product Protection, the Key to Developing High Performance Methane Selective Oxidation Catalysts2009In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 131, no 47, 17110-17115 p.Article in journal (Refereed)
    Abstract [en]

    Selective, direct conversion of methane to methanol might seem an impossible task since the C-H bond energy of methane is 105 kcal mol(-1) compared to the C-H bond energy for methanol of 94. We show here that the Catalytica catalyst is successful because the methanol is protected as methyl bisulfate, which is substantially less reactive than methanol toward the catalyst. This analysis suggests a limiting performance for systems that operate by this type of protection that is well above the Catalytica system.

  • 40.
    Ahlquist, Mårten
    et al.
    Technical University of Denmark.
    Nielsen, T E
    Le Quement, S
    Tanner, David
    Technical University of Denmark.
    Norrby, Per-Ola
    Technical Univeristy of Denmark.
    An experimental and theoretical study of the mechanism of stannylcupration of alpha, beta-acetylenic ketones and esters2006In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 12, no 10, 2866-2873 p.Article in journal (Refereed)
    Abstract [en]

    The title reaction has been investigated by experimental and computational (DFT) techniques, and subsequently compared to the corresponding carbocupration reaction, with particular emphasis oil the stereoselectivity. For stannylcupration of an ynone substrate, only the anti-addition product is observed, whereas for the corresponding ynoate substrate, the stereoselectivity can be affected by the reaction conditions: in the presence of methanol as proton donor, the initial syn-addition product can be trapped, whereas a syn/anti mixture is obtained in a non-protic solvent. This is in sharp contrast to the carbocupration of the same ynone substrate with a cyanocuprate (RCu(CN)Li), which is highly selective for syn-addition. The product selectivities can be understood from a detailed computational characterization of the reaction paths, and in particular from the relative stabilities of the vinyl cuprate and allenolate intermediates. It is suggested that the stereodetermining step is protonation of vinyl cuprate intermediates.

  • 41.
    Ahlquist, Mårten
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Norrby, Per-Ola
    Department of Chemistry, University of Gothenburg, Sweden.
    Dispersion and Back-Donation Gives Tetracoordinate [Pd(PPh3)4]2011In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 50, no 49, 11794-11797 p.Article in journal (Refereed)
    Abstract [en]

    18e R.I.P. The apparent compliance of [Pd(PPh3)4] ("tetrakis") with the 18-electron rule is not due to an electronic preference on the central metal. Pd is valence-saturated already by two ligands. Further ligand addition gives a minor energy gain, and is only possible due to strong back-bonding. Dispersion corrections are needed for properly describing the interactions between the ligands.

  • 42.
    Ahlquist, Mårten
    et al.
    Technical University of Denmark.
    Norrby, Per-Ola
    Göteborg University.
    Oxidative addition of aryl chlorides to monoligated palladium(0): A DFT-SCRF study2007In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 26, no 3, 550-553 p.Article in journal (Refereed)
    Abstract [en]

    Oxidative addition of aryl chlorides to palladium has been investigated by hybrid density functional theory methods (B3LYP), including a continuum model describing the solvent implicitly. A series of para-substituted aryl chlorides were studied to see the influence of electronic effects on the reaction. It was found that the experimentally observed higher reactivity of the more electron deficient aryl chlorides is due to their ability to accept back-donation from Pd-0 and form reasonably strong pre-reactive complexes. This effect is less pronounced in the transition state; when it is measured from the pre-reactive complex, the barrier to oxidative addition is actually higher for the electron-deficient aryl chlorides, but the overall reaction barrier is still lower than for the electron-rich aryl chlorides.

  • 43.
    Ahlquist, Mårten
    et al.
    California Institute of Technology.
    Periana, Roy A.
    Goddard, William A., III
    C-H activation in strongly acidic media. The co-catalytic effect of the reaction medium2009In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, no 17, 2373-2375 p.Article in journal (Refereed)
    Abstract [en]

    Quantum mechanical (QM) results are used to establish the role of sulfuric acid solvent in facilitating the reaction between Pt(II)(bpym)Cl(2) (bpym = 2,2'-bipyrimidinyl) and methane; coordination of methane to the platinum catalyst is found to be catalyzed by the acidic medium.

  • 44.
    Ahlquist, Mårten S. G.
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Norrby, Per-Ola
    Department of Chemistry, University of Gothenburg, Sweden.
    Dispersion and back-donation gives tetracoordinate Pd(PPh3)(4)2012In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 243Article in journal (Other academic)
  • 45.
    Ahlquist, Mårten S. G.
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Wang, Ying
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Xue, Liqin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Sanchez-de-Armas, Rocio
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Proton transfers in first row transition metal complexes2013In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 245, 1381-INOR- p.Article in journal (Other academic)
  • 46. Ahlstrand, David A.
    et al.
    Polukeev, Alexey V.
    Marcos, Rocio
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ahlquist, Mårten S. G.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Wendt, Ola F.
    Csp(3)-H Activation without Chelation Assistance in an Iridium Pincer Complex Forming Cyclometallated Products2017In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 23, no 8, 1748-1751 p.Article in journal (Refereed)
    Abstract [en]

    Cyclometallation of 8-methylquinoline and 2-(dimethylamino)-pyridine in an iridium-based pincer complex is described. The C-H activation of 2-(dimethylamino) pyridine is not chelation assisted, which has not been described before for Csp(3)-H bonds in cyclometallation reactions. The mechanism of the cyclometallation of 2-(dimethylamino) pyridine was studied by DFT calculations and kinetic measurements.

  • 47.
    AHMADZADEH, KARAN
    KTH, School of Chemical Science and Engineering (CHE).
    Interaktions potentialla energin mellan ändliga rektangulära disperserade celullosa nanofibriller2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Thermodynamically, native cellulose nano fibrils are more stable in an aggregated state. The aggregated state is however not useful from a material development perspective. Therefore much research has been done to stabilize the dispersal of the fibrils. One method to overcome this instability is by surface substitution of the O6 hydroxyl group with carboxylate groups, to make highly charged fibrils in aqueous solutions. It is therefore of much interest to understand the interaction of highly charged fibrils in aqueous solutions. In this study, we aim to model the interaction potential energy between native and surface modified cellulose nanofibrils in order to understand under what conditions the contribution from the dipole interactions can be neglected. To achieve this we propose to use a continuum electrostatic approach, modeling the electrostatic interactions as a function of the fibrils relative dipole orientation, separation, surface charge as well as ionic strength of the solution, by means of using the Poisson-Boltzmann equation.

  • 48. Ahmed, Towfiq
    et al.
    Haraldsen, Jason T.
    Zhu, Jian-Xin
    Balatsky, Alexander V.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. Institute for Materials Science, Los Alamos National Laboratory, United States.
    Next-Generation Epigenetic Detection Technique: Identifying Methylated Cytosine Using Graphene Nanopore2014In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 5, no 15, 2601-2607 p.Article in journal (Refereed)
    Abstract [en]

    DNA methylation plays a pivotal role in the genetic evolution of both embryonic and adult cells. For adult somatic cells, the location and dynamics of methylation have been very precisely pinned down with the 5-cytosine markers on cytosine-phosphate-guanine (CpG) units. Unusual methylation on CpG islands is identified as one of the prime causes for silencing the tumor suppressant genes. Early detection of methylation changes can diagnose the potentially harmful oncogenic evolution of cells and provide promising guideline for cancer prevention. With this motivation, we propose a cytosine methylation detection technique. Our hypothesis is that electronic signatures of DNA acquired as a molecule translocates through a nanopore would be significantly different for methylated and nonmethylated bases. This difference in electronic fingerprints would allow for reliable real-time differentiation of methylated DNA. We calculate transport currents through a punctured graphene membrane while the cytosine and methylated cytosine translocate through the nanopore. We also calculate the transport properties for uracil and cyanocytosine for comparison. Our calculations of transmission, current, and tunneling conductance show distinct signatures in their spectrum for each molecular type. Thus, in this work, we provide a theoretical analysis that points to a viability of our hypothesis.

  • 49.
    Ahrenstedt, Lage
    University of Cape Town.
    Drug Eluting Hydrogels: Design, Synthesis and Evaluation2012Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Hydrogels have successfully proved themselves useful for drug delivery applications and several delivery routes have been developed over the years. The particular interest in this work was to design, synthesise and evaluate in situ forming drug eluting hydrogels, which have the potential to ameliorate the healing of cardiovascular diseases.

    With this aim the anti-inflammatory and immunosuppressant drugs rapamycin (Ra) and dexamethasone (Dex) were made water soluble by conjugation with polyethylene glycol (PEG). Ra was attached pendant from the terminal of PEGs while Dex was incorporated into dendritic structures grown from PEGs. These conjugates were further crosslinked into hydrogels by either conjugate or thiol-ene addition. The gel degradation was tuned to take between 5 and 27 days by using gel building block combinations that induced either 2 or 4 hydrolytically labile bonds per crosslink or by varying the number of crosslinking sites of the building blocks. The use of thiol-ene addition prolonged the degradation time nearly seven folded compared to conjugate addition as a more stable crosslink was formed.

    Two different formulations for gelling via conjugate addition were used (acrylate-thiol or vinyl sulphone-thiol) to deliver Ra, which was carried by either a 4- or 2-armed PEG. The elution kinetic for the respective gel formulation was of zero order during 15 and 19 days of gel degradation. In addition, Ra was PEGylated via esters, with a distance of either one or two carbons to a nearby thio-ether functionality. The difference in ester conjugation resulted in a slight but significant change in drug-PEG conjugate stability, which was mirrored by the increased time to reach the half amount of total drug elution; from 9.3 to 10.2 days and from 5.1 to 9.7 days for the two gel formulations, respectively. Dexamethasone was incorporated via an ester into dendrons of first and second generation pending from 2- and 4-armed PEGs at loadings of 2, 4 or 6 Dex molecules per carrier molecule. The resulting elution kinetic was of zero order during degradation periods of 5-27 days. Released Dex still possessed biological activity as determined by an in vitro cell assay.

    The novelties in this thesis are: (A) slow release of rapamycin obtained by covalent incorporation into hydrogels, (B) the use of unique PEG-based dendrimers to incorporate dexamethasone into a hydrogel and (C) zero order sustained release of dexamethasone at physiological pH.

  • 50. Ahrén, M.
    et al.
    Selegård, L.
    Söderlind, F.
    Linares, M.
    Kauczor, J.
    Norman, Patrick
    Käll, P. -O
    Uvdal, K.
    A simple polyol-free synthesis route to Gd 2O 3 nanoparticles for MRI applications: An experimental and theoretical study2012In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 14, no 8, 1006Article in journal (Refereed)
    Abstract [en]

    Chelated gadolinium ions, e.g., Gd-DTPA, are today used clinically as contrast agents for magnetic resonance imaging (MRI). An attractive alternative contrast agent is composed of gadolinium oxide nanoparticles as they have shown to provide enhanced contrast and, in principle, more straightforward molecular capping possibilities. In this study, we report a new, simple, and polyol-free way of synthesizing 4-5-nm-sized Gd 2O 3 nanoparticles at room temperature, with high stability and water solubility. The nanoparticles induce high-proton relaxivity compared to Gd-DTPA showing r 1 and r 2 values almost as high as those for free Gd 3+ ions in water. The Gd 2O 3 nanoparticles are capped with acetate and carbonate groups, as shown with infrared spectroscopy, near-edge X-ray absorption spectroscopy, X-ray photoelectron spectroscopy and combined thermogravimetric and mass spectroscopy analysis. Interpretation of infrared spectroscopy data is corroborated by extensive quantum chemical calculations. This nanomaterial is easily prepared and has promising properties to function as a core in a future contrast agent for MRI. © 2012 Springer Science+Business Media B.V.

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