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  • 1.
    Afifi, Hala
    et al.
    King’s College London, Institute of Pharmaceutical Science, U.K..
    Karlsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Heenan, Richard K
    ISIS-CCLRC, Rutherford Appleton Laboratory, U.K..
    Dreiss, Cécile A
    King’s College London, Institute of Pharmaceutical Science, U.K..
    Solubilization of Oils or Addition of Monoglycerides Drives the Formation of Wormlike Micelles with an Elliptical Cross-Section in Cholesterol-Based Surfactants: A Study by Rheology, SANS, and Cryo-TEM2011In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 12, p. 7480-7492Article in journal (Refereed)
    Abstract [en]

    We report the formation of wormlike micelles (WLM) in poly(oxyethylene) cholesteryl ether (ChEO(10)) aqueous solutions by the addition of lipophilic monoglycerides at room temperature (monolaurin (ML), monocaprin (MC), and monocaprylin (MCL)) bearing 12-, 10-, and 8-carbon alkyl chains, respectively. A combination of rheology, small-angle neutron scattering (SANS), and cryo-TEM was used to study their viscoelastic properties and structure. With the successive addition of cosurfactant, a significant increase in viscosity and a clear solidlike behavior is obtained, suggesting the formation of a viscoelastic network of wormlike micelles. Only for MCL is typical Maxwellian behavior obtained. The onset of micellar growth, as detected by the occurrence of solidlike behavior and a significant increase in viscosity, is obtained for 0.30 (1 wt %), 0.34 (1 wt %), and 0.60 (1.5 wt %) cosurfactant/ChEO(10) molar ratios with ML, MC, and MCL, respectively. With ML and MC, extremely long relaxation times (exceeding 20 s) compared to those of MCL are obtained, and zero-shear viscosity values are more than 1 order of magnitude higher than with MCL. These results show that cosurfactants with longer alkyl chain lengths (ML and MC) induce the formation of longer wormlike micelles and do so at lower concentrations. SANS measurements on dilute solutions confirm that the viscoelastic behavior correlates with an increase in contour length and reveals an elliptical cross-section with an axial ratio of around 2. Cryo-TEM images provide visual evidence of the wormlike micelles and confirm the elliptical shape of the cross-section. The addition of small amounts of aliphatic oils (ethyl butyrate, EB, and ethyl caprylate, EC) and cyclic oils (peppermint, PP, and tea tree, TT, oils) to ChEO(10) solutions induces wormlike micelle formation at a lower cosurfactant concentration or even in its absence (for PP, TT, and EC) because of their probable localization in the palisade layer. The viscosity peak and height of the plateau modulus occur at increasing monoglyceride concentration following the order PP ≈ TT > EC > EB > no oil.

  • 2.
    Agmo Hernandez, Victor
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hermes, Michael
    Milchev, Alexander
    Scholz, Fritz
    The overall adhesion-spreading process of liposomes on a mercury electrode is controlled by a mixed diffusion and reaction kinetics mechanism2009In: Journal of Solid State Electrochemistry, ISSN 1432-8488, E-ISSN 1433-0768, Vol. 13, no 4, p. 639-649Article in journal (Refereed)
    Abstract [en]

    Using high-resolution chronoamperometric measurements, with sampling each 1.333 micro s, the initial step of the adhesion-spreading of liposomes on a mercury electrode was studied. These measurements allow getting a deeper insight into the first interaction of the liposomes with the mercury electrode, and they show that the overall adhesion-spreading process at different potentials is partially controlled by a fast but weak interaction equilibrium resulting in a mixed diffusion- and reaction-kinetics-controlled mechanism of the overall reaction.

  • 3.
    Agmo Hernández, Víctor
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Karlsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Intrinsic Heterogeneity in Liposome Suspensions Caused by the Dynamic Spontaneous Formation of Hydrophobic Active Sites in Lipid Membranes2011In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 8, p. 4873-4883Article in journal (Refereed)
    Abstract [en]

    The spontaneous, dynamic formation of hydrophobic active sites in lipid bilayer membranes is studied and characterized. It is shown that the rates of formation and consumption of these active sites control at least two important properties of liposomes: their affinity for hydrophobic surfaces and the rate by which they spontaneously release encapsulated molecules. The adhesion and spreading of liposomes onto hydrophobic polystyrene nanoparticles and the spontaneous leakage of an encapsulated fluorescent dye were monitored for different liposome compositions employing Cryo-TEM, DLS, and fluorescence measurements. It was observed that an apparently homogeneous, monodisperse liposome suspension behaves as if composed by two different populations: a fast leaking population that presents affinity for the hydrophobic substrate employed, and a slow leaking population that does not attach immediately to it. The results reported here suggest that the proportion of liposomes in each population changes over time until a dynamic equilibrium is reached. It is shown that this phenomenom can lead to irreproducibility in, for example, spontaneous leakage experiments, as extruded liposomes leak much faster just after preparation than 24 h afterward. Our findings account for discrepancies in several experimental results reported in the literature. To our knowledge, this is the first systematic study addressing the issue of an existing intrinsic heterogeneity of liposome suspensions.

  • 4.
    Agrios, Alexander G.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Low-temperature TiO2 Films for Dye-sensitized Solar Cells: Factors Affecting Energy Conversion Efficiency2008In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, no 27, p. 10021-10026Article in journal (Refereed)
    Abstract [en]

    Semiconductor films prepd. by electrostatic layer-by-layer deposition can be used to fabricate dye-sensitized solar cells after low-temp. treatment (150 DegC). However, the resulting photocurrent is much less than when the film is sintered at 500 DegC. The difference in short-circuit current is a factor of 2.2 with the Ru-based dye N719 and is 3.5 with the org. dye D5. The photocurrent at a given wavelength is proportional to the light-harvesting efficiency, charge injection effciency, and charge collection efficiency. Sintered films take up more than 60% more of either dye than unsintered films and therefore absorb more photons. Electron injection is hindered in unsintered films due to a conduction band edge potential 100 mV more neg. than in a sintered electrode. Addnl. injection effects could be due to adsorption of the dye to polymer rather than to TiO2 in unsintered films, although our measurements were inconclusive on this point. Kinetic studies show electron transport times (ttr) an order of magnitude faster then electron lifetimes (te) in both sintered and unsintered electrodes. Furthermore, a Li+ insertion expt. shows that both films have good elec. connectivity between TiO2 nanoparticles. Unsintered films thus exhibit efficient charge transport despite the presence of polymer and the lack of heat treatment to induce necking.

  • 5. Al-Manasir, Nodar
    et al.
    Zhu, Kaizheng
    Kjøniksen, Anna-Lena
    Knudsen, Kenneth D.
    Karlsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Nyström, Bo
    Oslo University.
    Effects of Temperature and pH on the Contraction and Aggregation of Microgels in Aqueous Suspensions2009In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 113, no 32, p. 11115-11123Article in journal (Refereed)
    Abstract [en]

    Chemically cross-linked poly(N-isopropylacrylamide) (PNIPAM) microgels   and PNIPAM with different amounts of acrylic acid groups   (PNIPAM-co-PAA) were synthesized and the temperature-induced   aggregation behaviors of aqueous suspensions of these microgels were   investigated mainly with the aid of dynamic light scattering (DLS) and   turbidimetry. The DLS results show that the particles at all conditions   shrink at temperatures up to approximately the lower critical solution temperature (LCST), but the relative contraction effect is larger for   the microgels without acid groups or for microgels with added anionic   surfactant (SDS). A significant depression of the cloud point is found   in suspensions of PNIPAM with very low concentrations of SDS. The   compression of the microgels cannot be traced from the turbidity   results, but rather the values of the turbidity increase in this   temperature interval. This phenomenon is discussed in the framework of   a theoretical model. At temperatures above LCST, the size of the   microgels without attached charged groups in a very dilute suspension   is unaffected by temperature, while the charged particles (pH 7 and 11)   continue to collapse with increasing temperature over the entire   domain. In this temperature range, low-charged particles of higher   concentration and particles containing acrylic acid groups at low pH   (pH 2) aggregate, and macroscopic phase separation is approached at   higher temperatures. This study demonstrates how the stabilization of   microgels can be affected by factors such as polymer concentration,   addition of ionic surfactant to particles without charged acid groups, amount of charged groups in the polymer, and pH.

  • 6.
    Almgren, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Stomatosomes: perforated bilayer structures2010In: Soft Matter, ISSN 1744-683X, Vol. 6, no 7, p. 1383-1390Article, review/survey (Refereed)
    Abstract [en]

    Stomatosomes and related structures formed by perforated fluid bilayer have been identified in a number of systems comprising surfactants and/or lipids. The types of system show a strong variation, but at the same time the conditions allowing such structures to evolve seem rather restrictive. Small changes in the nature of the surfactant can make the perforated bilayers disappear, and also give a major change of the phase behavior. This behavior is exemplified with phase diagrams for systems with CxTAC (alkyltrimethylammonium chloride, x is number of carbons in the alkyl chain; x = 12,14,16) and lipids in brine. On an increase of the spontaneous curvature the perforated bilayers can be found between lamellar bilayers (or smooth vesicles in dilute samples) and cylindrical micelles. The formation of perforations may be understood as a cooperative process starting at a critical concentration of a surfactant in the bilayer. The surfactant promotes the formation of toroidal holes rimmed by hemi cylindrical micelles. With increasing surfactant concentration the surfactant-rich edges increase in length and finally results in bands or cylindrical micelles. Some theoretical calculations on these types of structures are discussed briefly. Observations and theoretical calculations suggest that usually different structures may give similar free-energies, resulting in coexistence of structures and sensitivity to minor effects.

  • 7.
    Almgren, Mats
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry. Avdelningen för fysikalisk kemi.
    Rangelov, Stanislav
    Polymorph dispersed particles from the bicontinuous cubic phase of glycerol monooleate stabilized by PEG-copolymers with lipid-mimetic hydrophobic anchors2006In: Journal of Dispersion Science and Technology, Vol. 27, no 3, p. 599-609Article in journal (Refereed)
  • 8. Andersen, Felicie F.
    et al.
    Knudsen, Bjarne
    Oliveira, Cristiano Luis Pinto
    Frøhlich, Rikke F.
    Krüger, Dinna
    Bungert, Jörg
    Agbandje-McKenna, Mavis
    McKenna, Robert
    Juul, Sissel
    Veigaard, Christopher
    Koch, Jørn
    Rubinstein, John L.
    Guldbrandtsen, Bernt
    Hede, Marianne S.
    Karlsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Andersen, Anni H.
    Pedersen, Jan Skov
    Knudsen, Birgitta R.
    Assembly and structural analysis of a covalently closed nano-scale DNA cage2008In: Nucleic Acids Research, ISSN 0305-1048, E-ISSN 1362-4962, Vol. 36, no 4, p. 1113-1119Article in journal (Refereed)
    Abstract [en]

    The inherent properties of DNA as a stable polymer with unique affinity for partner mols. detd. by the specific Watson-Crick base pairing makes it an ideal component in self-assembling structures. This has been exploited for decades in the design of a variety of artificial substrates for investigations of DNA-interacting enzymes. More recently, strategies for synthesis of more complex two-dimensional (2D) and 3D DNA structures have emerged. However, the building of such structures is still in progress and more experiences from different research groups and different fields of expertise are necessary before complex DNA structures can be routinely designed for the use in basal science and/or biotechnol. Here we present the design, construction and structural anal. of a covalently closed and stable 3D DNA structure with the connectivity of an octahedron, as defined by the double-stranded DNA helixes that assembles from eight oligonucleotides with a yield of .apprx.30%. As demonstrated by Small Angle X-ray Scattering and cryo-Transmission Electron Microscopy analyses the eight-stranded DNA structure has a central cavity larger than the apertures in the surrounding DNA lattice and can be described as a nano-scale DNA cage, Hence, in theory it could hold proteins or other bio-mols. to enable their investigation in certain harmful environments or even allow their organization into higher order structures.

  • 9. Angelov, Borislav
    et al.
    Angelova, Angelina
    Filippov, Sergey K.
    Karlsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Terrill, Nick
    Lesieur, Sylviane
    Stepanek, Petr
    Topology and internal structure of PEGylated lipid nanocarriers for neuronal transfection: synchrotron radiation SAXS and cryo-TEM studies2011In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 7, no 20, p. 9714-9720Article in journal (Refereed)
    Abstract [en]

    Towards potential treatment of neurodegenerative disorders by nanomedicine gene therapy, a nonviral gene delivery system is created by complexation of novel PEGylated cationic lipid assemblies and a plasmid DNA encoding for the protein brain-derived neurotrophic factor (BDNF). The generated monoolein-based liquid crystalline nanocarriers for BDNF gene transfer are characterized by means of small-angle X-ray scattering (SAXS) and cryogenic transmission electron microscopy (cryo-TEM) techniques. The complexation of the BDNF plasmids (pBDNF) to the positively charged lipid nanocarriers, is directly detected by turbidity measurements. Morphologically variable populations of sterically stabilized, PEGylated multicompartment nanoobjects, with confined supercoiled DNA, are established by cryo-TEM imaging. Synchrotron radiation SAXS measurements, performed with diluted nanoparticulate dispersions, evidence the inner multilamelar structure of pear-type vesicles and flexible onion-like objects functionalized by pBDNF. The experimental SAXS intensity curves are fitted with a scattering model for multilamellar vesicles involving five lamellas. As the monoolein-based multicompartment nanocarriers can strongly affect the organization of targeted membranes, the obtained structural data are of fundamental interest for improvement of brain-targeted gene delivery and understanding of cellular internalization mechanisms of nanocarriers in neuronal transfection studies.

  • 10.
    Arteca, Gustavo A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Rank, Jean Pierre
    Tapia, Orlando
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Generalized electronic diabatic approach to structural similarity in two-dimensional potential energy surfaces of various topologies2008In: International Journal of Quantum Chemistry, ISSN 0020-7608, E-ISSN 1097-461X, Vol. 108, no 4, p. 651-666Article in journal (Refereed)
    Abstract [en]

    Active site properties in some proteins can be affected by conformational fluctuations of neighbor residues, even when the latter are not involved directly in the binding process. A local environment thus appears to alter the relevant potential energy surface and its reaction paths. Here, some aspects of this phenomenon are simulated within a generalized electronic diabatic (GED) scheme to study the geometry and structural similarity for a class of two-dimensional (2D) energy surfaces. The electronic quantum state is a linear superposition of diabatic basis functions, each of which is taken to represent a single (pure) electronic state for the isolated material system. Here, we describe a model reaction of isomerization by shifts in amplitudes for three diabatic species (reactant, product, and an open-shell transition state) coupled in an external field. The "effective" 2D energy surface in the field is characterized in terms of critical points, and the amplitudes along the main reaction paths. A new feature is the introduction of a phase diagram where all possible potential-energy-surface topologies (consistent with three-state systems in two linear coordinates) are matched with actual model parameters. By varying the coupling strengths between diabatic states, we classify regions of this phase diagram in terms of electronic and structural similarities; some regions comprise models whose reaction paths have geometries that belong to the catchment region of the reactant, yet are electronically akin to the diabatic transition state or product.

  • 11.
    Arteca, Gustavo A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Rank, Jean Pierre
    Tapia, Orlando
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Topological study of reactive potential-energy surfaces from model diabatic states coupled to surrounding media2007In: Journal of Theoretical and Computational Chemistry, ISSN 0219-6336, E-ISSN 1793-6888, Vol. 6, no 4, p. 869-883Article in journal (Refereed)
    Abstract [en]

    Reaction paths are studied with the help of diabatic potential-energy surfaces coupled in a generic external field. We show that all putative geometrical and topological features of two-dimensional (2D) potential-energy surfaces for an isomerization can be generated with a model consisting of strictly diabatic harmonic 2D wells coupled in a static (yet uniform) external field. For a large class of three-state models, we provide a phase diagram of possible topologies in the relevant parameter space for three-state models. By following the shift in diabatic electronic amplitudes (denoted by {vertical bar c(k)vertical bar(2)}) in coherent quantum states produced in the field, we assess whether the models within each phase can produce reaction paths visiting regions of configurational space that are structurally similar to the diabatic transition state.

  • 12. Arteca, Gustavo A.
    et al.
    Tapia, Orlando
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Quantum states for quantum processes: A toy model for ammonia inversion spectra2011In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 84, no 1, p. 012115-Article in journal (Refereed)
    Abstract [en]

    Chemical transformations are viewed here as quantum processes modulated by external fields, that is, as shifts in reactant to product amplitudes within a quantum state represented by a linear (coherent) superposition of electronuclear basis functions; their electronic quantum numbers identify the "chemical species." This basis set can be mapped from attractors built from a unique electronic configurational space that is invariant with respect to the nuclear geometry. In turn, the quantum numbers that label these basis functions and the semiclassical potentials for the electronic attractors may be used to derive reaction coordinates to monitor progress as a function of the applied field. A generalization of Feynman's three-state model for the ammonia inversion process illustrates the scheme; to enforce symmetry for the entire inversion process model and ensure invariance with respect to nuclear configurations, the three attractors and their basis functions are computed with a grid of fixed floating Gaussian functions. The external-field modulation of the effective inversion barrier is discussed within this conceptual approach. This analysis brings the descriptions of chemical processes near modern technologies that employ molecules to encode information by means of confinement and external fields.

  • 13.
    Arteca, Gustavo
    et al.
    Département de Chimie et Biochimie and Biomolecular Sciences Programme, Laurentian University.
    Rank, Jean Pierre
    Département de Chimie et Biochimie and Biomolecular Sciences Programme, Laurentian University.
    Tapia, Orlando
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Simulating trends in reaction path geometry as a function of external fields: A generalized electronic diabatic model for two-dimensional energy surfaces2008In: International Journal of Quantum Chemistry, ISSN 0020-7608, E-ISSN 1097-461X, Vol. 108, no 10, p. 1810-1820Article in journal (Refereed)
    Abstract [en]

    We introduce a protocol to represent quantum states as a linear superposition of model electronic diabatic basis states coupled in an external (static) elec. field. By considering an entire family of these models, we uncover trends in reaction-path geometry and the topol. of potential-energy surfaces, including all those that can be realized in a two-dimensional configurational space. Our approach can be used as a tool to model the key parameters (e.g., diabatic basis states, external field intensity) that yield desired geometrical characteristics in an actual potential energy surface. In this work, external agents such as laser fields, or a group of neighboring charges, are regarded as essential requirements to prompt, or trigger, the occurrence of a chem. process. In these cases, reaction path geometry can be modulated externally so as to yield processes that would appear to occur far from gas-phase geometries. This phenomenol. is intrinsically nonadiabatic. Our present approach accounts for the possibility of such features, i.e., the occurrence of quantum states whose electronic structures resemble products, while at geometries that are more similar to those of reactants.

  • 14.
    Bergstrand, Nill
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Arfvidsson, Maria C.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Kim, Jong-Mok
    Thompson, David H.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Interactions between pH-sensitive liposomes and model membranes2003In: Biophysical Chemistry, ISSN 0301-4622, E-ISSN 1873-4200, Vol. 104, no 1, p. 361-379Article in journal (Refereed)
    Abstract [en]

    The structure and dynamics of two different pH-sensitive liposome systems were investigated by means of cryo-transmission electron microscopy and different photophysical techniques. Both systems consisted of dioleoylphosphatidylethanolamine (DOPE) and contained either oleic acid (OA) or a novel acid-labile polyethylene glycol-conjugated lipid (DHCho-MPEG5000) as stabiliser. Proton induced leakage, lipid mixing and structural changes were studied in the absence and presence of EPC liposomes, as well as in the presence of liposomes designed to model the endosome membrane. Neither DHCho-MPEG5000- nor OA-stabilised liposomes showed any tendency for fusion with pure EPC liposomes or endosome-like liposomes composed of EPC/DOPE/SM/Cho (40/20/6/34 mol.%). Our investigations showed, however, that incorporation of lipids from the pH-sensitive liposomes into the endosome membrane may lead to increased permeability and formation of non-lamellar structures. Taken together the results suggest that the observed ability of DOPE-containing liposomes to mediate cytoplasmic delivery of hydrophilic molecules cannot be explained by a mechanism based on a direct, and non-leaky, fusion between the liposome and endosome membranes. A mechanism involving destabilisation of the endosome membrane due to incorporation of DOPE, seems more plausible.

  • 15.
    Bergstrand, Nill
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Arfvidsson, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Kim, Jon-mok
    Thompson, David H
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Interaction between pH-sensitive liposomes and model membranes2003In: Biophysical Chemistry, ISSN 0301-4622, E-ISSN 1873-4200, Vol. 104, no 1, p. 361-379Article in journal (Refereed)
    Abstract [en]

    The structure and dynamics of two different pH-sensitive liposome systems were investigated by means of cryo-transmission electron microscopy and different photophysical techniques. Both systems consisted of dioleoylphosphatidylethanolamine (DOPE) and contained either oleic acid (OA) or a novel acid-labile polyethylene glycol-conjugated lipid (DHCho-MPEG5000) as stabiliser. Proton induced leakage, lipid mixing and structural changes were studied in the absence and presence of EPC liposomes, as well as in the presence of liposomes designed to model the endosome membrane. Neither DHCho-MPEG5000- nor OA-stabilised liposomes showed any tendency for fusion with pure EPC liposomes or endosome-like liposomes composed of EPC/DOPE/SM/Cho (40/20/6/34 mol.%). Our investigations showed, however, that incorporation of lipids from the pH-sensitive liposomes into the endosome membrane may lead to increased permeability and formation of non-lamellar structures. Taken together the results suggest that the observed ability of DOPE-containing liposomes to mediate cytoplasmic delivery of hydrophilic molecules cannot be explained by a mechanism based on a direct, and non-leaky, fusion between the liposome and endosome membranes. A mechanism involving destabilisation of the endosome membrane due to incorporation of DOPE, seems more plausible.

  • 16.
    Bohl Kullberg, E
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology.
    Carlsson, Jörgen
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology, Biomedical Radiation Sciences.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Capala, J
    Sjöberg, S
    Gedda, Lars
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Radiology, Oncology and Radiation Science, Biomedical Radiation Sciences.
    Introductory experiments on ligand liposomes as delivery agents for boronneutron capture therapy2003In: International Journal of Oncology, ISSN 1019-6439, Vol. 23, no 2, p. 461-467Article in journal (Refereed)
    Abstract [en]

    Liposomes are, when coupled to receptor ligands, candidates for receptor mediated delivery of boron for tumour therapy since they have capacity to deliver large amounts of boron per receptor interaction. With EGF-liposomes we present a pegylated ligand liposome delivery vehicle, containing water soluble boronated phenanthridine, WSP1, or water soluble boronated acridine, WSA1, for EGFR targeting. In the case of WSA1 a ligand dependent uptake was obtained and the boron uptake was as good as if free WSA1 was given. No ligand dependent boron uptake was seen for WSP1 containing liposomes. Thus, WSA1 is a candidate for further studies. Approximately 10(5) boron atoms were in each liposome. A critical assessment indicates that after optimization up to 10(6) boron atoms can be loaded. Since it is known that, for therapeutic effect, approximately 10(8)-10(9) boron atoms are needed in a single tumour cell it is realized that 10(2)-10(3) receptor interactions are needed to meet the demand. Tests applying cultured glioma cells indicate, without optimization of the delivery conditions, a boron uptake in the ppm range, which is necessary for successful BNCT. Thus, it seems possible to kill micro-invasive tumour cells with targeted liposomes if the delivery conditions are optimal.

  • 17. Bonini, Massimo
    et al.
    Rossi, Simona
    Karlsson, Göran
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry. Avdelningen för fysikalisk kemi.
    Almgren, Mats
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry. Avdelningen för fysikalisk kemi.
    Lo Nostro, Pierandrea
    Baglioni, Piero
    Self-assembly of beta-cyclodextrin in water. Part 1: Cryo-TEM and dynamic and2006In: Langmuir, ISSN 0743-7463, Vol. 22, no 4, p. 1478-84Article in journal (Refereed)
  • 18.
    Boschloo, Gerrit
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Gibson, Elizabeth A.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Photomodulated Voltammetry of Iodide/Triiodide Redox Electrolytes and Its Relevance to Dye-Sensitized Solar Cells2011In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 2, no 24, p. 3016-3020Article in journal (Refereed)
    Abstract [en]

    Photomodulated voltammetry was used to determine the redox potentials of the diiodide radical (I(2)(-center dot)) in water, acetonitrile, and 3-methoxypropionitrile. Iodide/triiodide redox electrolytes were exposed to modulated blue light, resulting in I(2)(-center dot) generation. Using transparent fluorine-doped tinoxide (FTO) electrodes, two modulated photocurrent waves could be discerned in the voltammogram, from which the formal potentials for oxidation and reduction reactions of the diiodide radical were determined. E(0)'(I(2)(-center dot)/I(-)) was found to be +0.79 and +1.04 V versus NHE in acetonitrile and water, respectively. These values give guidelines for E(0)'(D(+)/D) required for efficient regeneration of dyes used in dye-sensitized solar cells.

  • 19.
    Boschloo, Gerrit
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Characteristics of the Iodide/Triiodide Redox Mediator in Dye-Sensitized Solar Cells2009In: Accounts of Chemical Research, ISSN 0001-4842, E-ISSN 1520-4898, Vol. 42, no 11, p. 1819-1826Article, review/survey (Refereed)
    Abstract [en]

    Dye-sensitized solar cells (DSCs) have gained widespread interest because of their potential for low-cost solar energy conversion. Currently, the certified record efficiency of these solar cells is 11.1%, and measurements of their durability and stability suggest lifetimes exceeding 10 years under operational conditions, The DSC is a photoelectrochemical system: a monolayer of sensitizing dye is adsorbed onto a mesoporous TiO2 electrode, and the electrode is sandwiched together with a counter electrode. An electrolyte containing a redox couple fills the gap between the electrodes.

    The redox couple is a key component of the DSC. The reduced part of the couple regenerates the photo-oxidized dye. The formed oxidized species diffuses to the counter electrode, where it is reduced. The photovoltage of the device depends on the redox couple because it sets the electrochemical potential at the counter electrode. The redox couple also affects the electrochemical potential of the TiO2 electrode through the recombination kinetics between electrons in TiO2 and oxidized redox species.

    This Account focuses on the special properties of the iodide/triiodide (I-/I-3(-)) redox couple in dye-sensitized solar cells. It has been the preferred redox couple since the beginning of DSC development and still yields the most stable and efficient DSCs. Overall, the iodide/triiodide couple has good solubility, does not absorb too much light, has a suitable redox potential, and provides rapid dye regeneration. But what distinguishes I-/I-3(-) from most redox mediators is the very slow recombination kinetics between electrons in TiO2 and the oxidized part of the redox couple, triiodide. Certain dyes adsorbed at TiO2 catalyze this recombination reaction, presumably by binding iodine or triiodide.

    The standard potential of the iodide/triiodide redox couple is 0.35 V (versus the normal hydrogen electrode, NHE), and the oxidation potential of the standard DSC-sensitizer (Ru(dcbpy)(2)(NCS)(2)) is 1.1 V. The driving force for reduction of oxidized dye is therefore as large as 0.75 V. This process leads to the largest internal potential loss in DSC devices. We expect that overall efficiencies above 15% might be achieved if half of this internal potential loss could be gained.

    The regeneration of oxidized dye with iodide leads to the formation of the diiodide radical (I-2(-center dot)). The redox potential of the I-2(-center dot)/I- couple must therefore be considered when determining the actual driving force for dye regeneration. The formed I-2(-center dot) disproportionates to I-3(-) and I-, which leads to a large loss in potential energy.

  • 20.
    Bramer, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Paulsson, Mattias
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Edsman, Katarina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Catanionic drug-surfactant mixtures: Phase behavior and sustained release from gels2003In: Pharmaceutical research, ISSN 0724-8741, E-ISSN 1573-904X, Vol. 20, no 10, p. 1661-1667Article in journal (Refereed)
    Abstract [en]

    PURPOSE: To study mixtures of SDS and the drugs diphenhydramine, tetracaine, and amitriptyline to compile phase diagrams and to investigate the use of interesting phases for sustained release from gels. METHODS: Phase diagrams were composed by studying large numbers of different compositions of negatively charged SDS and positively charged drug compounds visually, rheologically, and by cryotransmission electron microscopy. Drug release from Carbopol 940 and agar gels containing interesting phases, e.g., vesicle and branched micelle phases, was measured in vitro by the USP paddle method. RESULTS: Vesicles and elongated and branched micelles were formed on the SDS-rich side in all three systems examined. The tetracaine system differed from the other two in that it showed a vesicle area in the drug-rich side. Release of diphenhydramine from Carbopol 940 gels was slowed by at least a factor of 10 when in the form of vesicles or branched micelles. The same delay was found for both drug-rich and SDS-rich tetracaine vesicles. CONCLUSIONS: Mixtures of SDS and positively charged drugs form the same interesting phases as traditional catanionic mixtures. This may prove useful in obtaining functional controlled-release systems when using gels as drug carriers.

  • 21. Bruder, Ingmar
    et al.
    Karlsson, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Eickenmeyer, Felix
    Hwang, Jaehyung
    Erk, Peter
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Weis, Jürgen
    Pschirer, Neil
    Efficient organic tandem cell combining a solid state dye-sensitized and a vacuum deposited bulk heterojunction solar cell2009In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 93, no 10, p. 1896-1899Article in journal (Refereed)
    Abstract [en]

    In this letter, we report on an efficient organic tandem solar cell combining a solid state dye-sensitized with a ZnPc/C60-based, vacuum deposited bulk heterojunction solar cell. Due to an effective serial connection of both subcells and to the complementary absorption of the dyes used, a power conversion efficiency of ηp=(6.0±0.1)% was achieved under simulated AM 1.5 illumination. The device parameters are , and FF=(54±1)%.

  • 22.
    Cappel, Ute
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Characterisation of Organic Dyes for Solid State Dye-Sensitized Solar Cells2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Energy from the sun can be converted to low cost electricity using dye-sensitized solar cells (DSCs). Dye molecules adsorbed to the surface of mesoporous TiO2 absorb light and inject electrons into the semiconductor. They are then regenerated by the reduced redox species from an electrolyte, typically consisting of the iodide/tri-iodide redox couple in an organic solvent. In a solid state version of the DSC, the liquid electrolyte is replaced by an organic hole conductor. Solid state DSCs using 2,2'7,7'-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9'-spirobifluorene (spiro-MeOTAD) have reached conversion efficiencies of up to 6 %, which is about half of the efficiency of the best iodide/tri-iodide cells.

     

    Measurement techniques, such as spectroelectrochemistry and photo-induced absorption spectroscopy (PIA), were developed and applied to study the working mechanism of organic dyes in solid state DSCs under solar cell operating conditions. The energy alignment of the different solar cell components was studied by spectroelectrochemistry and the results were compared to photoelectron spectroscopy. PIA was used to study the injection and regeneration processes. For the first time, it was shown here that the results of PIA are influenced by an electric field due to the electrons injected into the TiO2. This electric field causes a shift in the absorption spectrum of dye molecules adsorbed to the TiO2 surface due to the Stark effect.

     

    Taking the Stark effect into consideration during the data analysis, mechanistic differences between solid state and conventional DSCs were found. A perylene dye, ID176, was only able to efficiently inject electrons into the TiO2 in presence of lithium ions and in absence of a solvent. As a result, the sensitiser worked surprisingly well in solid state DSCs but not in liquid electrolyte ones. Regeneration of oxidised dye molecules by spiro-MeOTAD was found to be fast and efficient and spiro-MeOTAD could even reduce excited dye molecules.

    List of papers
    1. Dye regeneration by spiro-MeOTAD in solid state dye-sensitized solar cells studied by photoinduced absorption spectroscopy and spectroelectrochemistry.
    Open this publication in new window or tab >>Dye regeneration by spiro-MeOTAD in solid state dye-sensitized solar cells studied by photoinduced absorption spectroscopy and spectroelectrochemistry.
    2009 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 15, p. 6275-6281Article in journal (Refereed) Published
    Abstract [en]

    Photoinduced absorption (PIA) spectroscopy is presented as a tool for the systematic study of dye regeneration and pore filling in solid state dye-sensitized solar cells (DSC). Oxidn. potentials and extinction coeffs. for oxidized species of the perylene dye, ID28, on TiO2 and of the hole conductor, 2,2'7,7'-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9'-spirobifluorene (spiro-MeOTAD), were detd. by spectroelectrochem. The onset of oxidn. of a solid film of spiro-MeOTAD was found to be 0.15 V vs. Fc/Fc+ and extinction coeffs. of spiro-MeOTAD+ were found to be 33 000 M-1 cm-1 at 507 nm and 8500 M-1 cm-1 at 690 nm. Electrons in TiO2 films were shown to alter the ground-state absorption spectra of ID28 attached to TiO2. PIA measurements indicated a good contact between ID28 and spiro-MeOTAD for different spiro-MeOTAD concns. for both 2- and 6-micro m thick TiO2 films. We discuss the possibility of estg. the quality of pore filling from the positions of absorption peaks. Results suggested that with a spiro-MeOTAD concn. of 300 mg mL-1 in chlorobenzene, a uniform distribution of spiro-MeOTAD in the pores of the 6-micro m thick TiO2 film could be achieved.

    National Category
    Chemical Sciences
    Research subject
    Physical Chemistry
    Identifiers
    urn:nbn:se:uu:diva-100979 (URN)10.1021/jp811196h (DOI)000265030200058 ()
    Available from: 2009-04-15 Created: 2009-04-15 Last updated: 2017-12-13Bibliographically approved
    2. The influence of local electric fields on photoinduced absorption in dye-sensitized solar cells.
    Open this publication in new window or tab >>The influence of local electric fields on photoinduced absorption in dye-sensitized solar cells.
    Show others...
    2010 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 132, no 26, p. 9096-9101Article in journal (Refereed) Published
    Abstract [en]

    The dye-sensitized solar cell (DSC) challenges conventional photovoltaics with its potential for low-cost production and its flexibility in terms of color and design Transient absorption spectroscopy is widely used to unravel the working mechanism of DSCs A surprising, unexplained feature observed in these studies is an apparent bleach of the ground-state absorption of the dye, under conditions where the dye is in the ground state. Here, we demonstrate that this feature can be attributed to a change of the local electric field affecting the absorption spectrum of the dye, an effect related to the Stark effect first reported in 1913 We present a method for measuring the effect of an externally applied electric field on the absorption of dye monolayers adsorbed on flat TiO2 substrates. The measured signal has the shape of the first derivative of the absorption spectra of the dyes and reverses sign along with the reversion of the direction of the change in dipole moment upon excitation relative to the TiO2 surface A very similar signal is observed in photoinduced absorption spectra of dye-sensitized TiO2 electrodes under solar cell conditions, demonstrating that the electric field across the dye molecules changes upon illumination This result has important implications for the analysis of transient absorption spectra of DSCs and other molecular optoelectronic devices and challenges the interpretation of many previously published results.

    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-135810 (URN)10.1021/ja102334h (DOI)000279561200067 ()20552960 (PubMedID)
    Available from: 2010-12-09 Created: 2010-12-08 Last updated: 2017-12-11Bibliographically approved
    3. A broadly absorbing perylene dye for solid-state dye-sensitized solar cells.
    Open this publication in new window or tab >>A broadly absorbing perylene dye for solid-state dye-sensitized solar cells.
    Show others...
    2009 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 33, p. 14595-14597Article in journal (Refereed) Published
    Abstract [en]

    We present a new perylene sensitizer, ID 176, for dye-sensitized solar cells (DSCs). The dye has the capability for very high photocurrents due to strong absorption from 400 to over 700 rim. Photocurrents Of LIP to 9 mA cm(-2) were achieved in solid-state DSCs employing the hole conductor 2,2'7,7'-tetrakis-(NN-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-MeOTAD), with a conversion efficiency of 3.2%. In contrast, the sensitizer did not perform well in conjunction with liquid iodide/tri-iodide electrolytes, suggesting a difference in the injection and regeneration mechanisms in these two types of dye-sensitized solar cells.

    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-128305 (URN)10.1021/jp906409q (DOI)000268907500004 ()
    Available from: 2010-07-21 Created: 2010-07-20 Last updated: 2017-12-12Bibliographically approved
    4. Characterization of the Interface Properties and Processes in Solid State Dye-Sensitized Solar Cells Employing a Perylene Sensitizer
    Open this publication in new window or tab >>Characterization of the Interface Properties and Processes in Solid State Dye-Sensitized Solar Cells Employing a Perylene Sensitizer
    Show others...
    2011 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 10, p. 4345-4358Article in journal (Refereed) Published
    Abstract [en]

    We recently reported on a perylene sensitizer, ID176, which performs much better in solid state dye-sensitized solar cells than in those using liquid electrolytes with iodide/tri-iodide as the redox couple (J. Phys. Chem. C2009, 113, 14595-14597). Here, we present a characterization of the sensitizer and of the TiO2/dye interface by UV-visible absorption and fluorescence spectroscopy, spectroelectrochemistry, photoelectron spectroscopy, electroabsorption spectroscopy, photoinduced absorption spectroscopy, and femtosecond transient absorption measurements. We report that the absorption spectrum of the sensitizer is red-shifted by addition of lithium ions to the surface due to a downward shift of the excited state level of the sensitizer, which is of the same order of magnitude as the downward shift of the titanium dioxide conduction band edge. Results from photoelectron spectroscopy and electrochemistry suggest that the excited state is largely located below the conduction band edge of TiO2 but that there are states in the band gap of TiO2 which might be available for photoinduced electron injection. The sensitizer was able to efficiently inject into TiO2, when a lithium salt was present on the surface, while injection was much less effective in the absence of lithium ions or in the presence of solvent. In the presence of the hole conductor 2,2-,7,7-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9-spirobifluorene (spiro-MeOTAD) and LiTFSI, charge separation was monitored by the emergence of a Stark shift of the dye in transient absorption spectra, and both injection and regeneration appear to be completed within 1 ps. Regeneration by spiro-MeOTAD is therefore several orders of magnitude faster than regeneration by iodide, and ID176 can even be photoreduced by spiro-MeOTAD.

    National Category
    Physical Chemistry
    Research subject
    Physical Chemistry
    Identifiers
    urn:nbn:se:uu:diva-149013 (URN)10.1021/jp111466h (DOI)000288113400064 ()
    Available from: 2011-03-14 Created: 2011-03-14 Last updated: 2017-12-11Bibliographically approved
    5. Energy Alignment and Surface Dipoles of Rylene Dyes adsorbed to TiO2 nanoparticles
    Open this publication in new window or tab >>Energy Alignment and Surface Dipoles of Rylene Dyes adsorbed to TiO2 nanoparticles
    Show others...
    2011 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 32, p. 14767-14774Article in journal (Refereed) Published
    Abstract [en]

    The energy loss in dye-sensitized solar cells calculated from the energy difference between the lowest electronic transition of the dye and the obtained open-circuit voltage is often 1 eV or even more. To minimize this loss, it is important to accurately determine the energy alignment at the TiO2/dye/redox-mediator interface. In this study, we compared the results from electrochemistry and photoelectron spectroscopy for determining the energy alignment of three rylene dyes, two of which absorb relatively far in the red. The trends observed with the methods were different, as in the former, the energy alignment is measured relative to an external reference and includes contributions from solvent reorganization energies, while in the latter, it is measured relative to the energetics of the TiO2 and is lacking such contributions. The influence of the dyes' dipole moments on the energetics of the TiO2 was also measured and explained some of the differences in trends. Finally, we compared the injection efficiencies of the two red-absorbing dyes and found that the differences in injection efficiencies can be better explained using the energy alignment determined from photoelectron spectroscopy. This shows that the method for measuring the energetics of a DSC should be chosen according to what process one intends to study.

    National Category
    Natural Sciences
    Research subject
    Physical Chemistry
    Identifiers
    urn:nbn:se:uu:diva-150046 (URN)10.1039/c1cp20911f (DOI)000293516200058 ()
    Available from: 2011-03-25 Created: 2011-03-25 Last updated: 2017-12-11Bibliographically approved
  • 23.
    Cappel, Ute B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Feldt, Sandra M.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Schoeneboom, Jan
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    The influence of local electric fields on photoinduced absorption in dye-sensitized solar cells.2010In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 132, no 26, p. 9096-9101Article in journal (Refereed)
    Abstract [en]

    The dye-sensitized solar cell (DSC) challenges conventional photovoltaics with its potential for low-cost production and its flexibility in terms of color and design Transient absorption spectroscopy is widely used to unravel the working mechanism of DSCs A surprising, unexplained feature observed in these studies is an apparent bleach of the ground-state absorption of the dye, under conditions where the dye is in the ground state. Here, we demonstrate that this feature can be attributed to a change of the local electric field affecting the absorption spectrum of the dye, an effect related to the Stark effect first reported in 1913 We present a method for measuring the effect of an externally applied electric field on the absorption of dye monolayers adsorbed on flat TiO2 substrates. The measured signal has the shape of the first derivative of the absorption spectra of the dyes and reverses sign along with the reversion of the direction of the change in dipole moment upon excitation relative to the TiO2 surface A very similar signal is observed in photoinduced absorption spectra of dye-sensitized TiO2 electrodes under solar cell conditions, demonstrating that the electric field across the dye molecules changes upon illumination This result has important implications for the analysis of transient absorption spectra of DSCs and other molecular optoelectronic devices and challenges the interpretation of many previously published results.

  • 24.
    Cappel, Ute B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Smeigh, Amanda L.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Plogmaker, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Characterization of the Interface Properties and Processes in Solid State Dye-Sensitized Solar Cells Employing a Perylene Sensitizer2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 10, p. 4345-4358Article in journal (Refereed)
    Abstract [en]

    We recently reported on a perylene sensitizer, ID176, which performs much better in solid state dye-sensitized solar cells than in those using liquid electrolytes with iodide/tri-iodide as the redox couple (J. Phys. Chem. C2009, 113, 14595-14597). Here, we present a characterization of the sensitizer and of the TiO2/dye interface by UV-visible absorption and fluorescence spectroscopy, spectroelectrochemistry, photoelectron spectroscopy, electroabsorption spectroscopy, photoinduced absorption spectroscopy, and femtosecond transient absorption measurements. We report that the absorption spectrum of the sensitizer is red-shifted by addition of lithium ions to the surface due to a downward shift of the excited state level of the sensitizer, which is of the same order of magnitude as the downward shift of the titanium dioxide conduction band edge. Results from photoelectron spectroscopy and electrochemistry suggest that the excited state is largely located below the conduction band edge of TiO2 but that there are states in the band gap of TiO2 which might be available for photoinduced electron injection. The sensitizer was able to efficiently inject into TiO2, when a lithium salt was present on the surface, while injection was much less effective in the absence of lithium ions or in the presence of solvent. In the presence of the hole conductor 2,2-,7,7-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9-spirobifluorene (spiro-MeOTAD) and LiTFSI, charge separation was monitored by the emergence of a Stark shift of the dye in transient absorption spectra, and both injection and regeneration appear to be completed within 1 ps. Regeneration by spiro-MeOTAD is therefore several orders of magnitude faster than regeneration by iodide, and ID176 can even be photoreduced by spiro-MeOTAD.

  • 25.
    Cappel, Ute
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Plogmaker, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Energy Alignment and Surface Dipoles of Rylene Dyes adsorbed to TiO2 nanoparticles2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 32, p. 14767-14774Article in journal (Refereed)
    Abstract [en]

    The energy loss in dye-sensitized solar cells calculated from the energy difference between the lowest electronic transition of the dye and the obtained open-circuit voltage is often 1 eV or even more. To minimize this loss, it is important to accurately determine the energy alignment at the TiO2/dye/redox-mediator interface. In this study, we compared the results from electrochemistry and photoelectron spectroscopy for determining the energy alignment of three rylene dyes, two of which absorb relatively far in the red. The trends observed with the methods were different, as in the former, the energy alignment is measured relative to an external reference and includes contributions from solvent reorganization energies, while in the latter, it is measured relative to the energetics of the TiO2 and is lacking such contributions. The influence of the dyes' dipole moments on the energetics of the TiO2 was also measured and explained some of the differences in trends. Finally, we compared the injection efficiencies of the two red-absorbing dyes and found that the differences in injection efficiencies can be better explained using the energy alignment determined from photoelectron spectroscopy. This shows that the method for measuring the energetics of a DSC should be chosen according to what process one intends to study.

  • 26.
    Carlsson, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Arteca, G. A.
    Sundberg, Jill
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Elvingson, Christer
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Off-equilibrium response of grafted polymer chains subject to a variable rate of compression2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 24, p. 11757-11765Article in journal (Refereed)
    Abstract [en]

    We present Brownian dynamics simulations of single grafted semiflexible chains (i.e., "polymer mushrooms'') with varying persistence lengths, intra-chain interactions, and subject to confinement. The results from different rates of compression are presented in the cases of an approaching infinite plane and a paraboloid tip. We discuss the different behaviour observed for grafted chains with strong and weak self-attraction (i.e., "hard'' and "soft'' polymer mushrooms). In both cases the effect on the size and shape is more pronounced for a slow compression rate, especially for "hard mushrooms''. We have also studied the relaxation of the chain while the compressing plane is maintained, and when it is removed suddenly. We find that the response depends strongly on the time allowed for relaxation in the compressed state. When using instead a paraboloid tip, the overall effects are similar yet less pronounced because the chain can dodge the confining object via an "escape transition.''

  • 27.
    Carlsson, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Kamerlin, N.
    Arteca, G. A.
    Elvingson, Christer
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Brownian dynamics of a compressed polymer brush model: Off-equilibrium response as a function of surface coverage and compression rate2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 35, p. 16084-16094Article in journal (Refereed)
    Abstract [en]

    We study the compressive behaviour of a polymer-covered surface (i.e., a "polymer brush'') using Brownian dynamics simulations. The model consists of grafted chains with variable flexibility, variable intra-and inter-chain interactions, as well as different surface coverage. We discuss the polymer brush response to confinement by considering variable rates of compression under a hard plane. Our results show a small degree of inter-chain entanglement, regardless of whether the interaction is attractive or merely excluded volume. We observe that the molecular shape depends strongly on the surface coverage. Dense brushes exhibit a limited degree of lateral deformation under compression; instead, chains undergo a transition that produces a local patch with near-solid packing. This effect due to surface density can be undone partially by increasing the attractive nature of the chain interaction, by modulating the rate of compression, or by allowing "soft anchoring'', i.e., the possible Brownian drift of the grafting bead on the surface. We have also studied the polymer brush relaxation while maintaining the compressing plane, as well as after its sudden removal. We find evidence that also the relaxation depends on surface density; dense brushes appear to be configurationally frustrated at high compression and are unable to undergo swelling, regardless of the pressure applied.

  • 28.
    Czapla, Luke
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Siretskiy, Alexey
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Grime, John
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Khan, Malek
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Free Energy Monte Carlo Simulations on a Distributed Network2012In: Applied Parallel and Scientific Computing: 10th International Conference, PARA 2010, Reykjavík, Iceland, June 6-9, 2010, Revised Selected Papers, Part II, 2012, Vol. 7134, p. 1-2Conference paper (Refereed)
    Abstract [en]

    While the use of enhanced sampling techniques and parallel computing to determine potentials of mean force is in widespread use in modern Molecular Dynamics and Monte Carlo simulation studies, there have been few methods that efficiently combine heterogeneous computer resources of varying quality and speeds in realizing a single simulation result on a distributed network. Here, we apply an algorithm based on the Monte Carlo method of Wang and Landau within a client-server framework, in which individual computing nodes report a histogram of regions of phase space visited and corresponding updates to a centralized server at regular intervals entirely asynchronously. The server combines the data and reports the sum to all nodes so that the overall free energy determination scales linearly with the total amount of resources allocated. We discuss our development of this technique and present results for molecular simulations of DNA.

  • 29.
    Dew, Noel
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Eriksson, Jonny
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Edsman, Katarina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Björk, Erik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Gel formulations containing catanionic vesicles composed of alprenolol and SDS: effects of drug release and skin penetration on aggregate structure2012In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 89, p. 53-60Article in journal (Refereed)
    Abstract [en]

    To fully utilize the extended contact time of gel formulations a novel formulation with drug containing catanionic aggregates offering prolonged drug release and skin penetration were investigated. This study aimed to further explore the drug release process from catanionic vesicles in gels. Catanionic vesicles were formed from alprenolol and sodium dodecyl sulphate. Physical gels composed of catanionic vesicles and a SoftCAT polymer were used as well as covalent Carbopol gels. Drug release was measured in vitro using a modified USP paddle method and the skin penetration was studied using dermatomized pig ear skin mounted in horizontal Ussing chambers. The aggregate structure was visualized with cryo-TEM during the drug release and skin penetration process. The study results show that catanionic vesicles are present in the formulations throughout the drug release process and during the clinically relevant skin application time. Hence, the decreased skin penetration rate stems from the prolonged release of drug substance from the gels. The rheological investigation shows that the gel structure of the physically cross-linked gels is maintained even as the drug substance is released and the gel volume is decreased.These findings indicate that the applicability of formulations like these is a future possibility.

  • 30. Dos Santos, Nancy
    et al.
    Allen, Christine
    Doppen, Anne-Marie
    Anantha, Malathi
    Cox, Kelly A K
    Gallagher, Ryan C
    Karlsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Kenner, Gail
    Samuels, Lacey
    Webb, Murray S
    Bally, Marcel B
    Influence of poly(ethylene glycol) grafting density and polymer length on liposomes: Relating plasma circulation lifetimes to protein binding2007In: Biochimica et Biophysica Acta - Biomembranes, ISSN 0005-2736, E-ISSN 1879-2642, Vol. 1768, no 6, p. 1367-1377Article in journal (Refereed)
    Abstract [en]

    The incorporation of poly(ethylene glycol) (PEG)-conjugated lipids in lipid-based carriers substantially prolongs the circulation lifetime of liposomes. However, the mechanism(s) by which PEG-lipids achieve this have not been fully elucidated. It is believed that PEG-lipids mediate steric stabilization, ultimately reducing surface-surface interactions including the aggregation of liposomes and/or adsorption of plasma proteins. The purpose of the studies described here was to compare the effects of PEG-lipid incorporation in liposomes on protein binding, liposome-liposome aggregation and pharmacokinetics in mice. Cholesterol-free liposomes were chosen because of their increasing importance as liposomal delivery systems and their marked sensitivity to protein binding and aggregation. Specifically, liposomes containing various molecular weight PEG-lipids at a variety of molar proportions were analyzed for in vivo clearance, aggregation state (size exclusion chromatography, quasi-elastic light scattering, cryo-transmission and freeze fracture electron microscopy) as well as in vitro and in vivo protein binding. The results indicated that as little as 0.5 mol% of 1,2-distearoyl-sn-glycero-3-phosphatidylethanolamine (DSPE) modified with PEG having a mean molecular weight of 2000 (DSPE-PEG(2000)) substantially increased plasma circulation longevity of liposomes prepared of 1,2-distearoyl-sn-glycero-3-phosphatidylcholine (DSPC). Optimal plasma circulation lifetimes could be achieved with 2 mol% DSPE-PEG(2000). At this proportion of DSPE-PEG(2000), the aggregation of DSPC-based liposomes was completely precluded. However, the total protein adsorption and the protein profile was not influenced by the level of DSPE-PEG(2000) in the membrane. These studies suggest that PEG-lipids reduce the in vivo clearance of cholesterol-free liposomal formulations primarily by inhibition of surface interactions, particularly liposome-liposome aggregation.

  • 31.
    Dunn, Halina K.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Westin, Per-Oskar
    Staff, Daniel R.
    Peter, Laurence M.
    Waker, Alison B.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Determination of the Electron Diffusion Length in Dye-Sensitized Solar Cells by Substrate Contact Patterning2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 28, p. 13932-13937Article in journal (Refereed)
    Abstract [en]

    A new method to estimate the electron diffusion length in dye-sensitized solar cells (DSCs) is presented. DSCs were fabricated on conducting glass substrates that were patterned by laser ablation of the fluorine-doped tin oxide coating to form parallel contact strips separated by uncontacted strips of the same width. The relative collection efficiency was measured as a function of the gap between the contact strips, which determines the lateral distance traveled by electrons to reach the contacts. To avoid complications arising from non-linear recombination kinetics, current measurements were performed using small amplitude perturbations of the electron density close to open circuit and the maximum power point to minimize electron density gradients in the film. One and two-dimensional solutions of the continuity equation for electron transport and back reaction predict that the relative collection efficiency should fall as spacing between the contact strips exceeds the electron diffusion length and electrons are lost by back electron transfer during transit to the contacts. Measurements of the relative collection efficiency were fitted to the predicted dependence of the collection efficiency on the spacing between the contact strips to obtain the value of the electron diffusion length. The diffusion length is found to increase with voltage both at open circuit and at the maximum power point.

  • 32.
    Edvinsson, Tomas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Pschirer, Niel
    Schöneboom, Jan
    Eickemeyer, Felix
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Photoinduced electron transfer from a terrylene dye to TiO2: Quantification of band edge shift effects2009In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 357, no 1-3, p. 124-131Article in journal (Refereed)
    Abstract [en]

    A terrylene chromophore exhibiting a high extinction coefficient has been developed as a sensitizer for photovoltaic applications. The photophysical and photochemical properties of the dye were analyzed both experimentally and theoretically. Terrylene-sensitized nanocrystalline TiO2 solar cells yielded good photocurrents providing more than 60% in external quantum efficiency. The photoinduced electron transfer from the dye to TiO2 was found to be very sensitive to conduction band edge shifts in TiO2 induced, either by changes in the composition of the redox electrolyte or by UV-illumination. This sensitivity was observed in quantum efficiencies for photocurrent generation of terrylene-sensitized solar cells and in photoinduced absorption experiments. The conduction band shifts were quantified using charge extraction methods. The observed sensitivity of the injection efficiency suggests that photoinduced electron transfer occurs from the relaxed excited state, possibly due to poor electronic coupling between TMIMA excited states and TiO2 conduction band states.

  • 33.
    Elmgren, Maja
    Uppsala University, University Administration. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Att gå från ord till handling: Bologna som språngbräda för pedagogisk utveckling genom samverkan med pedagogiska ledare2007Conference paper (Refereed)
  • 34.
    Eriksson, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Malmström, David
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Agmo Hernández, Víctor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Optimized Protocol for On-Target Phosphopeptide Enrichment Prior to Matrix-Assisted Laser Desorption-Ionization Mass Spectrometry Using Mesoporous Titanium Dioxide2010In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 82, no 11, p. 4577-4583Article in journal (Refereed)
    Abstract [en]

    A novel on-target phosphopeptide enrichment method is presented that allows specific enrichment and direct analysis by matrix assisted laser desorption-ionization mass spectrometry (MALDI-MS) of phosphorylated peptides. Spots consisting of a thin film of anatase titanium dioxide are sintered onto a conductive glass surface. Enrichment and analysis can be performed on the modified target with minimal sample handling. The protocol leads to an enrichment efficiency that is superior to what has been reported before for similar methods. The method was tested using beta-casein as a model phosphorylated protein as well as with a custom peptide mixed with its phosphorylated form. A very low detection limit, a significantly improved phosphoprofiling capability, and a simple experimental approach provide a powerful tool for the enrichment, detection, and analysis of phosphopeptides.

  • 35.
    Eriksson, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Malmström, David
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Hernandez, Victor Agmo
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Mesoporous TiO2-Based Experimental Layout for On-Target Enrichment and Separation of Multi- and Monophosphorylated Peptides Prior to Analysis with Matrix-Assisted Laser Desorption-Ionization Mass Spectrometry2011In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 83, no 3, p. 761-766Article in journal (Refereed)
    Abstract [en]

    A simple method for on-target enrichment and subsequent separation and analysis of phosphorylated peptides is presented. The tryptic digest of a phosphorylated protein, in this case beta-casein, is loaded onto a spot on a thin stripe made of mesoporous TiO2 sintered onto a conductive glass surface. After washing with a salicylic buffer in order to remove the nonphosphorylated peptides, the stripe is placed in an elution chamber containing a phosphate solution. In a way analogous to thin layer chromatography (TLC), the phosphate solution acts as an eluent, clearly separating multi- and monophosphorylated peptides. By performing matrix-assisted laser desorption-ionization mass spectrometry (MALDI-MS) along the stripe, the detection of all phosphorylated peptides present in the digest is facilitated, as they are isolated from each other. The method was also tested on commercial drinking milk, achieving successful separation between multi- and monophosphorylated peptides, as well as a detection limit in the femtomole range. As the enrichment, separation, and analysis take place in the same substrate, sample handling and risk of contamination and sample loss is minimized. The results obtained suggest that the method, once optimized, may successfully provide a complete phosphoproteome.

  • 36. Eriksson, Hanna M.
    et al.
    Wessman, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Ge, Changrong
    Edwards, Katarina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Wieslander, Åke
    Massive Formation of Intracellular Membrane Vesicles in Escherichia coli by a Monotopic Membrane-bound Lipid Glycosyltransferase2009In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 284, no 49, p. 33904-33914Article in journal (Refereed)
    Abstract [en]

    The morphology and curvature of biological bilayers are determined by the packing shapes and interactions of their participant molecules. Bacteria, except photosynthetic groups, usually lack intracellular membrane organelles. Strong overexpression in Escherichia coli of a foreign monotopic glycosyltransferase (named monoglycosyldiacylglycerol synthase), synthesizing a nonbilayer-prone glucolipid, induced massive formation of membrane vesicles in the cytoplasm. Vesicle assemblies were visualized in cytoplasmic zones by fluorescence microscopy. These have a very low buoyant density, substantially different from inner membranes, with a lipid content of ≥60% (w/w). Cryo-transmission electron microscopy revealed cells to be filled with membrane vesicles of various sizes and shapes, which when released were mostly spherical (diameter ≈100 nm). The protein repertoire was similar in vesicle and inner membranes and dominated by the glycosyltransferase. Membrane polar lipid composition was similar too, including the foreign glucolipid. A related glycosyltransferase and an inactive monoglycosyldiacylglycerol synthase mutant also yielded membrane vesicles, but without glucolipid synthesis, strongly indicating that vesiculation is induced by the protein itself. The high capacity for membrane vesicle formation seems inherent in the glycosyltransferase structure, and it depends on the following: (i) lateral expansion of the inner monolayer by interface binding of many molecules; (ii) membrane expansion through stimulation of phospholipid synthesis, by electrostatic binding and sequestration of anionic lipids; (iii) bilayer bending by the packing shape of excess nonbilayer-prone phospholipid or glucolipid; and (iv) potentially also the shape or penetration profile of the glycosyltransferase binding surface. These features seem to apply to several other proteins able to achieve an analogous membrane expansion.

  • 37. Eriksson, Sven B.
    et al.
    Ågren, Per Olof
    Henriksson, Ann-Sofie
    Uppsala University, University Administration.
    Elmgren, Maja
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry. Uppsala University, University Administration.
    Supporting Pedagogical Leaders2010Conference paper (Refereed)
  • 38. Feitosa, Eloi
    et al.
    Karlsson, Göran
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry. Avdelningen för fysikalisk kemi.
    Dioctadecyldimethylammonium bromide vesicles prepared by the surfactant removal method.2006In: J Colloid Interface Sci, ISSN 0021-9797, Vol. 298, no 2, p. 1000-1Article in journal (Refereed)
  • 39. Feitosa, Eloi
    et al.
    Karlsson, Göran
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry. Avdelningen för fysikalisk kemi.
    Edwards, Katarina
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry. Avdelningen för fysikalisk kemi.
    Unilamellar vesicles obtained by simply mixing dioctadecyldimethylammonium chloride and bromide with water.2006In: Chem Phys Lipids, ISSN 0009-3084, Vol. 140, no 1-2, p. 66-74Article in journal (Refereed)
  • 40.