Cover image for Vol. 5 Issue 2

February 20, 2004

Volume 5, Issue 2

Pages 157–290

    1. Cover Picture: Functional Microdomains of Glycolipids with Partially Fluorinated Membrane Anchors: Impact on Cell Adhesion (ChemPhysChem 2/2004) (page 157)

      Christian Gege, Matthias F. Schneider, Gabriele Schumacher, Laurent Limozin, Ulrich Rothe, Gerd Bendas, Motomu Tanaka and Richard R. Schmidt

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200490006

      The cover picture shows a confocal microscopy image of glycolipid microdomains designed by mixing neoglycolipids with partially fluorinated (F-alkyl) chains. For more information, see the Article by Tanaka et al. on pp. 216–224.

    2. Visualization of Atomic Processes on Ruthenium Dioxide using Scanning Tunneling Microscopy (pages 167–174)

      H. Over, M. Knapp, E. Lundgren, A. P. Seitsonen, M. Schmid and P. Varga

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200300833

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      Watching how a model catalyst works on the atomic scale: With scanning tunneling microscopy (STM) the authors studied the microscopic reaction steps in the complex redox chemistry of RuO2 surfaces oriented along the (110) and (100) directions. Undercoordinated Ru atoms at the surface (see picture) determine the activity of RuO2 towards molecules from the gas phase. Under slightly oxidizing conditions, RuO2 (100) can transform into a catalytically inactive phase.

    3. Molecular Basis of the Dynamic Strength of the Sialyl Lewis X—Selectin Interaction (pages 175–182)

      Xiaohui Zhang, Daniela F. Bogorin and Vincent T. Moy

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200300813

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      Binding blood: The molecular interactions that govern leukocyte rolling in blood vessels are explored using single-molecule dynamic force spectroscopy (set-up shown in graphic). Selectins, calcium-dependent cell-adhesion molecules on the vascular walls, bind to carbohydrate moieties on the leukocytes, initiating the rolling and eventual adhesion. Unbinding measurements on the selectin–sialyl-Lewis-X tetrasaccharide reveal a dissociation potential with two activation energy barriers. These barriers arise from specific interactions between the selectin, the calcium ion, and two distinct residues on the tetrasaccharide.

    4. The Gas-Phase Hydrogen Bond Complexes between Formic Acid with Hydroxyl Radical: A Theoretical Study (pages 183–191)

      Miquel Torrent-Sucarrat and Josep M. Anglada

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200300826

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      Prereactive species in the atmosphere: Seventeen stationary point structures have been found in a systematic theoretical investigation of the gas-phase hydrogen-bond complexes formed between formic acid and OH radical (see picture). The different bonding features have been analyzed with the aid of the atoms in molecules theory and the natural bond orbital partition scheme. The computed red-shifts in the O[BOND]H vibrational stretching modes, originating from the complex formation, are also reported.

    5. Manganese, Iron, Cobalt, and Nickel Oxo-, Peroxo-, and Superoxoclusters: A Density Functional Theory Study (pages 192–201)

      Ellie L. Uzunova, Georgi St. Nikolov and Hans Mikosch

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200300895

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      Angular array: Oxide, peroxide, and superoxide clusters of Mn, Fe, Co, and Ni are examined by DFT to elicit their relative stability, bonding scheme, and electronic states. The dioxides have bent geometry in their ground states, with only CoO2 coming close to a linear structure (see picture). The terminal oxygen atom of the superoxides is more nucleophilic than the M-bonded oxygen atom, which differs from expectations based on charge-distribution analysis.

    6. Two- and Three-Dimensional Molecular Organization of Schiff-Base Derivatives (pages 202–208)

      Zhong-Cheng Mu, Jian-Fei Kong, Yue Wang, Ling Ye, Guang-Di Yang and Xi Zhang

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200300931

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      Bulk matters: The structural features of a series of Schiff-base derivatives in 2D and 3D states were studied by combining scanning tunneling microscopy and X-ray diffraction experiments. The STM images (one of which is shown) indicate that the introduction of two methoxy groups into the molecule can change the structure of these 2D assemblies as a result of the increased steric hindrances.

    7. Improper Hydrogen C[BOND]H⋅⋅⋅O Bonds Cause Self-Association of α,β-Enaminoketones Containing Fluorosubstituted Alkyl Groups (pages 209–215)

      Jacek Wójcik, Krystyna Kamienska-Trela, Magdalena Pecul, Elzbieta Bartoszak-Adamska, Siergiej I. Vdovienko and Igor I. Gerus

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200300937

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      Fluorinated enaminoketones dimerize reversibly in nonpolar solvents with formation of the antiparallel “closed” dimer with a network of intermolecular C[BOND]H⋅⋅⋅O hydrogen bonds. Evidence for these bonds was provided by IR and NMR spectroscopy, dipole moment measurements and X-ray structure analysis, and confirmed by ab initio calculations. The crystal structure of 4-N,N-dimethylamino-1,1,1-trifluoro-3-buten-2-one (see picture) revealed the presence of four hydrogen-bonding interactions (dotted lines).

    8. Functional Microdomains of Glycolipids with Partially Fluorinated Membrane Anchors: Impact on Cell Adhesion (pages 216–224)

      Christian Gege, Matthias F. Schneider, Gabriele Schumacher, Laurent Limozin, Ulrich Rothe, Gerd Bendas, Motomu Tanaka and Richard R. Schmidt

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200300947

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      Giant vesicles and monolayers containing functional microdomains formed by self-assembly of clusters of partially fluorinated glycolipids with sialyl Lewis X head groups in unfluorinated matrix lipids were studied. The size and distribution of the domains is controlled by demixing of fluoroalkyl and alkyl membrane anchors. In the picture the confocal microscopy image of such a giant vesicle is shown.

    9. Kinetics and Mechanisms for the Reactions of Phenyl Radical with Ketene and its Deuterated Isotopomer: An Experimental and Theoretical Study (pages 225–232)

      Y. M. Choi and M. C. Lin

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200300919

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      Addition to Cβof ketene is the primary channel in its reaction with phenyl radical, according to measurements by cavity ring-down spectroscopy and calculations at the the G2MS//B3LYP/6-31G(d) level of theory. The first step of this process is formation of the long-lived intermediate C6H5CH2CO via transition state TS1, which eliminates CO via TS2 (see picture). In the less favorable Cα addition pathway the adduct eliminates an H atom via higher lying TS3 (not shown) to give C6H5CHCO, and the absence of a kinetic isotope effect for CD2CO indicates that direct H abstraction is insignificant.

    10. 18O Isotope Substitution, Vibrational Coupling and Protein Structure: A Theoretical Approach (pages 233–235)

      Thorsten Koslowski and Andreas Labahn

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200300902

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      Site-specific 18O substitution of two amino acids that are in a close spatial vicinity, but far apart in the primary sequence, exhibits characteristic IR fingerprints; the corresponding spectral shifts of the absorption bands are shown color-coded in the figure. This approach can be used to obtain detailed structural information, for example, about membrane proteins which are difficult to crystallize.

    11. Supramolecular Architectures of Electrostatic Self-Assembled Glucose Oxidase Enzyme Electrodes (pages 235–239)

      Ernesto J. Calvo and Alejandro Wolosiuk

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200300930

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      Get wired! The layer-by-layer electrostatic self-assembly of a redox enzyme as glucose oxidase (GOx) and a redox polymer mediator allowed different spatial organizations of both components to be explored. These organized systems (see picture) can work efficiently in molecular recognition, redox mediation, and generation of an electrical signal. Moreover, differences in GOx electrical wiring efficiency have been detected with the different assembling strategies.

    12. Energy Transfer from Dye–Zeolite L Antenna Crystals to Bulk Silicon (pages 239–242)

      Stefan Huber and Gion Calzaferri

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200301002

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      Artificial antenna systems: Zeolite L crystals loaded with a fluorescing donor dye and modified at the external surface with an acceptor dye are studied on a semiconductor surface (see picture). Radiationless excitation energy transfer from the donor dye to the acceptor dye and further through a thin insulating layer to the semiconductor is observed.

    13. Molecular Insight, through IR Spectroscopy, on Solvating Phenomena Occurring in CO2-Expanded Solutions (pages 243–245)

      Santiago Sala, Thierry Tassaing, Nora Ventosa, Yann Danten, Marcel Besnard and Jaume Veciana

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200300921

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      Solvation power of CO2-expanded solvents: Mid-IR spectroscopy is used in CO2-expanded solvents (see graphic) to investigate the molecular interaction between solute and solvent functional groups responsible for the differential solubility behaviour of acetaminophen, an analgesic drug, in “CO2-expanded ethanol” and “CO2-expanded acetone”.

    14. Modelling of the Adsorption of C60 on the Au(110) Surface (pages 245–248)

      Richard J. Baxter, Petra Rudolf, Gilberto Teobaldi and Francesco Zerbetto

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200300936

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      Glued to gold: A simple approach based on i) the “glue” model for gold, ii) an empirical force field for C60, and iii) the charge equilibration plus the Born–Mayer potential for their interaction shows that the two experimentally detected structures for C60 on Au(110) are competitive from 100 K. The model (see picture) further shows the different nature of the Au–Au and Au–C60 interactions inside the two unit cells, which should make one structure prevail over the other as a function of the experimental conditions.

    15. Potential Energy Landscape for Conformationally Gated Secondary Ubiquinone Binding in the Photosynthetic Reaction Center of Rhodobacter Sphaeroides (pages 249–252)

      Asif Rahaman and Ralph A. Wheeler

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200300961

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      Migration of the secondary ubiquinone, UQB, to a site proximal to His-L190 was proposed to be rate-determining for electron transfer in bacterial photosynthetic reaction centers (shown). This study shows that 1) the proximal binding site is the global minimum on the potential energy landscape, 2) multiple minima exist, in qualitative agreement with various binding sites observed in X-ray diffraction studies, and 3) the energy barrier for direct migration of UQB and migration gated by a protein conformational change both agree with the activation energy measured for electron transfer.

    16. Mechanical Properties of Microtubules Explored Using the Finite Elements Method (pages 252–257)

      Sandor Kasas, András Kis, Beat Michel Riederer, Lászlo Forró, Giovanni Dietler and Stefan Catsicas

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200300799

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      Model railways: Microtubules (MTs) are filamentous proteins involved in several physiological processes such cell division, neurotransmitter-filled-vesicle transport, or cell migration (see picture). The shear and Young's modulus of these filamentous structures have recently been measured by atomic force microscopy. Their values were used to build a finite element model of MT and to explore its behaviour under load.

    17. A Strategy for the Measurement of the Vibrations of a Muoniated Radical Centre: Experimental Evidence (pages 257–261)

      Upali A. Jayasooriya, Francis L. Pratt, Georgina M. Aston, Susan Hall, Penny L. Hubbard and Martin McCoustra

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200300832

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      Measuring muons: The longitudinal field μSR spectrum of a single crystal of benzophenone (see picture) shows significant sensitivity to simultaneous irradiation with NIR radiation of wavelengths >850 nm. The possible use of this phenomenon in a strategy to measure the vibrational modes of a muoniated centre is discussed.

    18. Synthesis of a Surface Photovoltage Sensor Using Self-Ordered Tin-Modified MCM-41 Films: Enhanced NO2 Gas Sensing (pages 261–265)

      Brian Yuliarto, HaoShen Zhou, Takeo Yamada, Itaru Honma and Keisuke Asai

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200300884

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      High sensitivity at room temperature. A surface photovoltage (SPV) NO2 gas sensor was fabricated, with a self-ordered tin-modified MCM-41 film, based on a metal–insulator–semiconductor (MIS) structure (see picture). A high sensitivity of the tin-modified mesoporous MCM-41 sensor was obtained at an NO2 gas concentration of only 1 ppm at room temperature.

    19. Epitaxial Growth of Pentacene Films on Metal Surfaces (pages 266–270)

      Simon Lukas, Sandra Söhnchen, Gregor Witte and Christof Wöll

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200300892

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      The right temperature for growth: High quality, epitaxial pentacene thin films were grown on Cu(110) by applying a two-step growth procedure, which involves the formation (using organic molecular beam epitaxy) of a complete monolayer at elevated temperatures followed by multilayer deposition at reduced temperatures. The organic films prepared (see picture) using this approach have their molecular axes orientated perpendicular to the substrate surface and are promising for the fabrication of lateral field effect transistors (FETs).

    20. 4′-Pivaloyl Substituted Thymidine as a Precursor for the Thymyl Radical: An EPR Spectroscopic Study (pages 270–274)

      Olav Schiemann, Emiliano Feresin, Thomas Carl and Bernd Giese

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200300896

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      Electron transfer in thymidine. Electron paramagnetic resonance (EPR) spectroscopy was used to study the light-induced radical formation from a 4′-pivaloyl substituted thymidine. The observation of the thymyl radical (2) suggests that a hydrogen- or proton-coupled electron-transfer step from the first formed carbohydrate radical 1 to the thymine base occurs (see Scheme).

    21. Electrochemical Doping of Double-Walled Carbon Nanotubes: An In Situ Raman Spectroelectrochemical Study (pages 274–277)

      Ladislav Kavan, Martin Kalbáč, Markéta Zukalová, Matthias Krause and Lothar Dunsch

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200300916

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      Nanotubes in electric fields: Electrochemistry of double-walled carbon nanotubes (DWCNTs; see picture) was studied for the first time. The DWCNT was prepared by pyrolysis of fullerene peapods, C60@SWCNTs. Responses to electrochemical doping of outer and inner walls were traced and distinguished by in situ Raman spectroelectrochemistry in the area of radial breathing and tangential displacement modes.

    22. Photophysical and Redox NIR-Sensitivity Enhancement in Photorefractive Polymer Composites (pages 277–284)

      Erwin Mecher, Francisco Gallego-Gómez, Klaus Meerholz, Hartwig Tillmann, Hans-Heinrich Hörhold and Jan C. Hummelen

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200300943

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      Through the gate: The photophysical effect of “gating” (preillumination at a shorter wavelength) dramatically enhances the near-infrared sensitivity of photorefractive polymer composites with generation-limited recording dynamics. Gating with a short, intense pulse yields better results than when using a longer pulse of reduced intensity. Redox doping (providing permanent charges) leads to an additional improvement of the sensitivity by a factor of two. See the picture for an illustration of the gating mechanism.

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      Version of Record online: 16 FEB 2004 | DOI: 10.1002/cphc.200490012