ChemPhysChem

Cover image for Vol. 5 Issue 3

March 19, 2004

Volume 5, Issue 3

Pages 293–426

    1. Cover Picture: Activation of Integrin Function by Nanopatterned Adhesive Interfaces (ChemPhysChem 3/2004) (page 293)

      Marco Arnold, Elisabetta Ada Cavalcanti-Adam, Roman Glass, Jacques Blümmel, Wolfgang Eck, Martin Kantlehner, Horst Kessler and Joachim P. Spatz

      Article first published online: 10 MAR 2004 | DOI: 10.1002/cphc.200490013

      The cover picture shows the first demonstration of cell adhesion activation through a nanoadhesive pattern with single integrin resolution. Scanning electron microscopy images nanoscopic 6-nm large Au particles as white dots, which are functionalized with cell ligands and organized in a square pattern. The free glass substrate area between the Au is covered with a biologically inert polymer, thereby avoiding protein or cell interactions with the glass. A few cell lamellipodia experience this environment and adhere entirely to the Au–nanoparticle pattern squares. The substrate forms a well-defined, rigid adhesion pattern where Au particles control integrin–integrin interactions in focal adhesions by their separation distance. A separation between single intergrins of ≥73 nm results in limited cell attachment and spreading, and dramatically reduces the formation of focal adhesion and actin stress fibers. The range of 58–73 nm is found to be a universal length scale for integrin clustering and activation, since these properties are shared by a variety of cultured cells. Find out more in the Communication by Spatz et al. on page 383.

    2. Graphical Abstract: ChemPhysChem 3/2004 (pages 295–301)

      Article first published online: 10 MAR 2004 | DOI: 10.1002/cphc.200490014

    3. Issues in the Synthesis of Crystalline Molecular Sieves: Towards the Crystallization of Low Framework-Density Structures (pages 304–313)

      Avelino Corma and Mark E. Davis

      Article first published online: 10 MAR 2004 | DOI: 10.1002/cphc.200300997

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      Designer sieves: The authors present a comprehensive review on the manipulation of the bulk properties of crystalline, microporous molecular sieves by controlling their atomic structure. The synthesis mechanisms and the parameters that can direct the crystal assembly pathway, and thus the ultimate end-product, are discussed and rationalized. The picture shows the empty volume present in one such zeolite.

    4. Designing Systems for a Multiple Use of Light Signals (pages 315–320)

      Giacomo Bergamini, Paola Ceroni, Vincenzo Balzani, Fritz Vögtle and Sang-Kyu Lee

      Article first published online: 10 MAR 2004 | DOI: 10.1002/cphc.200301076

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      An eclectic dendrimer: A dendrimer consisting of a benzophenone core and branches that contain dimethoxybenzene units shows a very rich and interesting ensemble of photochemical and photophysical processes (see picture). These results demonstrate the great potential of suitably designed dendrimers for a multiple use of light signals.

    5. Infrared Cavity Ringdown Spectroscopy of Jet-Cooled Polycyclic Aromatic Hydrocarbons (pages 321–326)

      Alex J. Huneycutt, Raphael N. Casaes, Benjamin J. McCall, Chao-Yu Chung, Yuan-Pern Lee and Richard J. Saykally

      Article first published online: 10 MAR 2004 | DOI: 10.1002/cphc.200300776

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      Gas-phase spectra calibrate argon matrix perturbations: Using cavity ringdown spectroscopy, low temperature gas-phase infrared spectra have been recorded for polycyclic aromatic hydrocarbons such as pyrene and compared with Ar matrix spectra (see picture) to quantify vibrational mode perturbations in Ar matrices.

    6. Supported Membranes with Well-Defined Polymer Tethers—Incorporation of Cell Receptors (pages 327–335)

      Oliver Purrucker, Anton Förtig, Rainer Jordan and Motomu Tanaka

      Article first published online: 10 MAR 2004 | DOI: 10.1002/cphc.200300863

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      Polymer-tethered lipid bilayer membranes: Stable, homogeneous and fluid lipid bilayer membranes were prepared in a two-step method (Langmuir–Blodgett transfer and vesicle fusion). The planar membranes are attached to solids via tailored flexible lipopolymer tethers. Such polymer-tethered biomimetic membranes can be used for the incorporation of large transmembrane proteins such as cell receptors (integrin; see picture).

    7. Tunnelling Motion of HF Between the Two Oxygen Lone Pairs in the Dimethyl Ether–Hydrogen Fluoride Complex: A Pure Rotational Study (pages 336–341)

      Paolo Ottaviani, Walther Caminati, Biagio Velino, Susana Blanco, Alberto Lesarri, Juan C. López and José L. Alonso

      Article first published online: 10 MAR 2004 | DOI: 10.1002/cphc.200300954

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      The rotational spectrum of Me2O⋅⋅⋅HF was assigned by millimetre-wave free-jet absorption spectroscopy. Fine details of the spectrum were resolved by FT microwave molecular-beam spectroscopy. The HF group acts as a proton donor and tunnels at a rate of 44178.2(7) MHz between the two oxygen lone pairs (see schematic picture), which corresponds to an inversion barrier of 0.17(1) kcal mol−1. The barrier to internal rotation of the two methyl groups is about 25 % lower than in the isolated ether.

    8. Cuii in Liquid Ammonia: An Approach by Hybrid Quantum-Mechanical/Molecular-Mechanical Molecular Dynamics Simulation (pages 342–348)

      Christian F. Schwenk and Bernd M. Rode

      Article first published online: 10 MAR 2004 | DOI: 10.1002/cphc.200300972

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      Simulations of the solvation structure of CuII in liquid ammonia (at HF and B3 LYP levels) indicate a preferred [2+4] configuration with four elongated Cu[BOND]N bonds (in contrast to hydrated CuII), which leads to a strong increase of the dynamics of the CuII solvate. The picture is a snapshot of the solvated CuII ion, obtained by a quantum mechanical/molecular mechanical MD simulation, showing the “inverse” ([2+4]) Jahn–Teller distortion with four elongated Cu[BOND]N bonds (small spheres).

    9. Can One Assess the π Character of a C–C Bond with the Help of the NMR Spin–Spin Coupling Constants? (pages 349–366)

      Dieter Cremer, Elfi Kraka, Anan Wu and Wolfgang Lüttke

      Article first published online: 10 MAR 2004 | DOI: 10.1002/cphc.200300987

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      Testing the π character of a C–C bond: NMR spin–spin coupling constants are sensitive to the π character of a bond through their noncontact terms. It is shown that the magnitude of the noncontact terms is related to the π character of the C–C bond via a quadratic function. Data points cluster in typical regions for single, double, triple, and aromatic C–C bonds (for example, see graphic), which can be used in a qualitative or semiquantitative way for describing C–C bonds, with the help of NMR spin–spin coupling constants.

    10. Microarray-Based in vitro Evaluation of DNA Oligomer Libraries Designed in silico (pages 367–372)

      Udo Feldkamp, Ron Wacker, Hendrik Schroeder, Wolfgang Banzhaf and Christof M. Niemeyer

      Article first published online: 10 MAR 2004 | DOI: 10.1002/cphc.200300978

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      From computers to real life: A library of DNA oligomer sequences designed for efficient and specific hybridization with a software tool in silico was experimentally evaluated in vitro by employing DNA microarray technology (see graphic). This approach can be used in a wide variety of applications, including DNA-based nanotechnology and DNA computing.

    11. Computer Simulation of Long Side-Chain Substituted Poly(phenylene vinylene) Polymers (pages 373–381)

      Hsiao-Ching Yang, Chih-Yu Hua, Ming-Yu Kuo, Qiang Huang and Cheng-Lung Chen

      Article first published online: 10 MAR 2004 | DOI: 10.1002/cphc.200300996

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      Between the backbones: A molecular dynamics simulation was employed to investigate structural features and segment orientation of four poly(phenylene vinylene) (PPV) derivatives with long, flexible side chains at room temperature. In the simulations, the main chains of the polymers were found to be semirigid and to exhibit a tendency to coil into helices or form zigzag conformations. The figure shows the system of polymers between two hypothetical electrodes.

    12. Activation of Integrin Function by Nanopatterned Adhesive Interfaces (pages 383–388)

      Marco Arnold, Elisabetta Ada Cavalcanti-Adam, Roman Glass, Jacques Blümmel, Wolfgang Eck, Martin Kantlehner, Horst Kessler and Joachim P. Spatz

      Article first published online: 10 MAR 2004 | DOI: 10.1002/cphc.200301014

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      Sticky dots: To study the function behind the molecular arrangement of single integrins in cell adhesion, the authors designed a hexagonally close-packed rigid template of cell adhesive gold nanodots by means of micellar diblock copolymer lithography. A critical separation length of ≥73 nm between the adhesive dots dramatically reduces cell functions due to restricted integrin clustering (see picture). The range between 58–73 nm is proposed to be a universal length scale for integrin clustering and activation, since these properties are shared by a variety of cultured cells lines.

    13. Polymer Functionalized AFM tips for Long-Term Measurements in Single-Molecule Force Spectroscopy (pages 388–393)

      Claudia Friedsam, Aránzazu Del Campo Bécares, Ulrich Jonas, Hermann E. Gaub and Markus Seitz

      Article first published online: 10 MAR 2004 | DOI: 10.1002/cphc.200300797

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      Tips for long life: A long-term stable polymer coating of AFM tips (see graphic) can be achieved by the use of a mixed self-assembled monolayer of alkanethiols. More than 10 000 force–extension curves under various environmental conditions, for example, different substrates, can be recorded without any hint of degradation. Thus the results can be better compared, as deviations arising from different sample preparations are ruled out.

    14. Temperature-Induced Composition Changes in a Critical Polymer Blend (pages 393–395)

      Wolfgang Enge and Werner Köhler

      Article first published online: 10 MAR 2004 | DOI: 10.1002/cphc.200301028

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      Approaching critical: Coherent periodic temperature and concentration fluctuations have been excited in a critical polymer blend by means of laser-induced transient gratings (see graphic for results). On the approach to the critical point, the amplitude of the concentration modulation diverges with a mean-field critical exponent far above and Ising-like critical exponent close to the critical temperature. Interestingly, microscopic friction effects cancel out in the Soret coefficient.

    15. Cobalt(II)-tris-2,2′-bipyridine as a Spin-Crossover Complex: Evidence for Cooperative Effects in Three-Dimensional Oxalate Networks (pages 395–399)

      Mohamed Zerara and Andreas Hauser

      Article first published online: 10 MAR 2004 | DOI: 10.1002/cphc.200301044

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      In a spin: In the three-dimensional oxalate network structures of composition [CoxMII1-x(bpy)3][MICr(ox)3], the spin state of the [Cox(bpy)3]2+ complex can be tuned by means of chemical pressure. With MI=Na it is a classic high-spin complex. Substitution of Na by Li stabilises the complex and it becomes a spin-crossover complex. Dilution with MII=Fe reinforces this effect, and MII=Zn reverses it (see picture).

    16. Steady-State and Time-Resolved Studies on Photoinduced Disulfide Bond Cleavage Using Aniline as an Electron Donor (pages 399–402)

      Changyuan Lu, Götz Bucher and Wolfram Sander

      Article first published online: 10 MAR 2004 | DOI: 10.1002/cphc.200300759

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      Crucial radicals: The aniline-mediated photochemical disulfide bond cleavage of linear or cyclic disulfide compounds (RSSR; see scheme) is shown to initiate by a photoinduced electron transfer from the excited state of aniline as well as by reduction with solvated electrons produced by the direct photoionization of aniline. The crucial intermediates in the disulfide cleavage are the disulfide radical anions.

    17. Formation of Light-Emitting Ag2 and Ag3 Species in the Course of Condensation of Ag Atoms with Ar (pages 403–407)

      Wilfried Schulze, Irene Rabin and Gerhard Ertl

      Article first published online: 10 MAR 2004 | DOI: 10.1002/cphc.200300939

      Fluorescent clusters: The agglomeration of Ag clusters resulting from the codeposition of Ag and Ar atoms onto a cold substrate is accompanied by light emission from deexcitation of intermediately formed electronically excited Ag2* and Ag3* species. The yield of chemiluminescence was investigated as a function of the deposition rates of Ag and Ar. The relative concentrations of Ag, Ag2, Ag3, and Ag8 species were monitored by means of their fluorescence spectra, and it is concluded that the light-emitting species are created by aggregation of Agn clusters with n>8.

    18. Optimal System Size for Mesoscopic Chemical Oscillation (pages 407–410)

      Zhonghuai Hou and Houwen Xin

      Article first published online: 10 MAR 2004 | DOI: 10.1002/cphc.200300969

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      Size does matter: Stochastic simulations and chemical Langevin equations were used to investigate the effects of system size on the oscillatory behavior of the Brusselator model. In the region close to the deterministic oscillatory dynamics, stochastic oscillations are observed. Interestingly, an optimal system size exists for such stochastic oscillations, characterized by a clear maximum in the signal-to-noise ratio (SNR) as a function of system size V (see picture). This result may have interesting implications for biological rhythms and signaling processes.

    19. Rovibrational Corrections to Transition Metal NMR Shielding Constants (pages 410–414)

      Michael Bühl, Petra Imhof and Michal Repisky

      Article first published online: 10 MAR 2004 | DOI: 10.1002/cphc.200300979

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      Beyond static molecules: The effect of zero-point motion on NMR parameters of transition-metal complexes (for example, see graphic), as assessed by a perturbational approach, can be sizeable; for example, for the metal nucleus in iron pentacarbonyl, a deshielding of about 100 ppm relative to the equilibrium geometry is predicted.

    20. Challenges in Direct-Space Structure Determination from Powder Diffraction Data: A Molecular Material with Four Independent Molecules in the Asymmetric Unit (pages 414–418)

      David Albesa-Jové, Benson M. Kariuki, Simon J. Kitchin, Leanne Grice, Eugene Y. Cheung and Kenneth D. M. Harris

      Article first published online: 10 MAR 2004 | DOI: 10.1002/cphc.200301078

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      Complex structure from powder diffraction: The direct-space strategy for carrying out structure solution directly from powder X-ray diffraction data has been applied successfully in the challenging case of a molecular cocrystal (see graphic) containing four independent molecules in the asymmetric unit.

    21. Nanopatterns and Nanostructures at Interfaces, Mulhouse, 12–15 October 2003 (pages 419–420)

      Graham J. Leggett

      Article first published online: 10 MAR 2004 | DOI: 10.1002/cphc.200301203

      Getting down to nano. This conference on nanotechnology was attended by eminent physical chemists and state-of-the-art work was presented on topics such as self-assembly, supramolecular chemistry, surface organisation, surface patterning, optical techniques and lithography. Although a real nanotechnology may still be a long way off, there are many exciting developments across a broad spectrum of interfacial physical chemistry and many opportunities to push forward the boundaries of science.

    22. You have free access to this content
      Preview: ChemPhysChem 3/2004 (page 426)

      Article first published online: 10 MAR 2004 | DOI: 10.1002/cphc.200490018

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