Angewandte Chemie International Edition

Cover image for Vol. 44 Issue 18

April 29, 2005

Volume 44, Issue 18

Pages 2613–2813

    1. Cover Picture: Branching Out of Single-Molecule Fluorescence Spectroscopy: Challenges for Chemistry and Influence on Biology (Angew. Chem. Int. Ed. 18/2005) (page 2613)

      Philip Tinnefeld and Markus Sauer

      Article first published online: 25 APR 2005 | DOI: 10.1002/anie.200590060

      Single-molecule fluorescence spectroscopy allows the direct observation of single receptor molecules in membranes and the identification of mRNA molecules in the nuclei of living cells. The cover picture shows the transcription centers (bright points) in a cell nucleus. The method can give information on the composition of the transcription centers, on the activity of polymerase, and on the synthesis of single-copy genes by the hybridization of a short dye-labeled oligonucleotide (green strand). M. Sauer and P. Tinnefeld describe the method and its uses in their Review on page 2642 ff.

    2. New Developments in the Asymmetric Stetter Reaction (pages 2632–2634)

      Mathias Christmann

      Article first published online: 25 APR 2005 | DOI: 10.1002/anie.200500761

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      Highly active carbene catalysts have revitalized the interest in the asymmetric Stetter reaction as a method for the construction of 1,4-dicarbonyl compounds. With the latest generation of a catalyst developed by Rovis and co-workers (1, for example), products with quaternary stereocenters such as 2 can be generated in 85 % yield and 99 % ee.

    3. Beyond Oil and Gas: The Methanol Economy (pages 2636–2639)

      George A. Olah

      Article first published online: 31 MAR 2005 | DOI: 10.1002/anie.200462121

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      Methanol, a convenient liquid fuel and raw material for synthetic hydrocarbons, offers an alternative to depleting sources of fossil fuels and can be produced, for example, by reacting H2 with CO2 from industrial effluents or the atmosphere—good news with regards to global-warming concerns. This Essay discusses various aspects of current and alternative energy sources, with a particular focus on the “methanol economy” (see scheme).

    4. Branching Out of Single-Molecule Fluorescence Spectroscopy: Challenges for Chemistry and Influence on Biology (pages 2642–2671)

      Philip Tinnefeld and Markus Sauer

      Article first published online: 25 APR 2005 | DOI: 10.1002/anie.200300647

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      One at a time, please: Advanced optical single-molecule techniques enable the monitoring of infectious pathways, the diffusion of single receptor molecules in membranes, and the detection and identification of single mRNA molecules in the nucleus of living cells (see picture). The article reviews recent progress in single-molecule fluorescence spectroscopy (SMFS) and outlines its future potential in combination with smart fluorescence-labeling strategies for successful applications in molecular and structural biology.

    5. Supercritical Water as a Solvent (pages 2672–2692)

      Hermann Weingärtner and Ernst Ulrich Franck

      Article first published online: 13 APR 2005 | DOI: 10.1002/anie.200462468

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      . ‥ and not a drop to drink. Water is not restricted to moderate temperatures and low pressures, but can exist at up to very high temperatures, far above its critical point (CP). In this supercritical regime water can be gradually compressed from gas-like to liquid-like densities (see picture; S=solid, L=liquid, G=gas, TP=triple point). The resulting dense supercritical states have tunable solvent properties which form the basis for innovative technologies.

    6. Molecular Recognition by Glycoside Pseudo Base Pairs and Triples in an Apramycin–RNA Complex (pages 2694–2700)

      Qing Han, Qiang Zhao, Sarah Fish, Klaus B. Simonsen, Dionisios Vourloumis, Jamie M. Froelich, Daniel Wall and Thomas Hermann

      Article first published online: 25 APR 2005 | DOI: 10.1002/anie.200500028

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      In the groove: The crystal structure of the bacterial decoding-site RNA in a complex with the antibiotic apramycin reveals how glycoside scaffolds participate in RNA recognition by natural products through the formation of pseudo base pairs and triples. The structure suggests that the inhibitory action of apramycin is based on interaction of the antibiotic with ribosomal protein S12 (see structural model), a control element of ribosome translocation.

    7. Effect of the Metal-Assisted Assembling Mode on the Redox States of Hexaazatriphenylene Hexacarbonitrile (pages 2700–2704)

      Shuhei Furukawa, Takashi Okubo, Shigeyuki Masaoka, Daisuke Tanaka, Ho-Chol Chang and Susumu Kitagawa

      Article first published online: 6 APR 2005 | DOI: 10.1002/anie.200462962

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      If the hat fits: The size of the ferrocene coligands used during the self-asssembly of hexaazatriphenylene hexacarbonitrile (hat-(CN)6) with CuI ions determines the coordination mode of the hat-(CN)6 ligand (bipyridine chelation or monodentate CN, see picture). The mode of coordination directly affects the oxidation state and the reduction potentials of the hat-(CN)6 ligand.

    8. Terphenyl-Based Helical Mimetics That Disrupt the p53/HDM2 Interaction (pages 2704–2707)

      Hang Yin, Gui-in Lee, Hyung Soon Park, Gregory A. Payne, Johanna M. Rodriguez, Said M. Sebti and Andrew D. Hamilton

      Article first published online: 14 MAR 2005 | DOI: 10.1002/anie.200462316

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      HDM2 regulates p53 by binding to its transactivation domain and promoting its ubiquitin-dependent degradation. Crystallographic analysis of the HDM2/p53 complex revealed that three hydrophobic residues (F19, W23, L26) along one face of the p53 helical peptide are essential for binding (see picture). Terphenyl-based antagonists mimic the α-helical region of p53 and disrupt HDM2/p53 complexation.

    9. Ultra-rapid Synthesis of 15O-Labeled 2-Deoxy-D-glucose for Positron Emission Tomography (PET) (pages 2708–2711)

      Hideki Yorimitsu, Yoshihiro Murakami, Hiroyuki Takamatsu, Shintaro Nishimura and Eiichi Nakamura

      Article first published online: 12 APR 2005 | DOI: 10.1002/anie.200500044

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      Make it quick! The oxygen isotope 15O has a half-life of only 2 min, and was incorporated into a sugar through an ultra-rapid radical hydroxylation of 2,6-dideoxy-6-iodo-D-glucose with labeled molecular oxygen to provide 6-[15O]-2-deoxy-D-glucose (see scheme). The product accumulates in metabolically active organs of rats similarly to a 18F-based tracer in common use, and represents a promising alternative for medical imaging.

    10. Symmetry and Topology Determine the MoV–CN–MnII Exchange Interactions in High-Spin Molecules (pages 2711–2715)

      Eliseo Ruiz, Gopalan Rajaraman, Santiago Alvarez, Béatrice Gillon, John Stride, Rodolphe Clérac, Joulia Larionova and Silvio Decurtins

      Article first published online: 12 APR 2005 | DOI: 10.1002/anie.200500129

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      Ferromagnetic or antiferromagnetic coupling? A theoretical study of complexes containing MoV–CN–MnII bridges reveals that a combination of local symmetry and molecular pseudosymmetry leads to a fascinating electronic structure that imposes antiferromagnetic interactions and results in a ferrimagnetic arrangement. The picture shows the spin density of the Mn9Mo6 complex studied.

    11. An Exceptionally Selective Lead(II)-Regulatory Protein from Ralstonia Metallidurans: Development of a Fluorescent Lead(II) Probe (pages 2715–2719)

      Peng Chen, Bill Greenberg, Safiyh Taghavi, Christine Romano, Daniel van der Lelie and Chuan He

      Article first published online: 31 MAR 2005 | DOI: 10.1002/anie.200462443

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      Lighting up lead: A Pb2+-regulatory protein from Ralstonia metallidurans has been converted into a highly sensitive fluorescent Pb2+ probe (PbR691, turquoise circles in scheme). This fluorescent system reveals that the protein exhibits a surprisingly high binding selectivity towards Pb2+ ions over other metal ions.

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      Proton Sandwiches: Nonclassical Carbocations with Tetracoordinate Protons (pages 2719–2723)

      Pradeep Gutta and Dean J. Tantillo

      Article first published online: 8 APR 2005 | DOI: 10.1002/anie.200461915

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      Exotic species: A number of unusual carbocations in which formally tetracoordinate protons are seemingly suspended between two C[DOUBLE BOND]C bonds were studied computationally. An example, the “proton sandwich” derived from 1,5-cyclooctadiene, is shown in the picture (C black, H white).

    13. Direct Detection of Inter-residue Hydrogen Bonds in Polysaccharides by Single-Molecule Force Spectroscopy (pages 2723–2727)

      Qingmin Zhang, Justyna Jaroniec, Gwangrog Lee and Piotr E. Marszalek

      Article first published online: 22 MAR 2005 | DOI: 10.1002/anie.200462067

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      The elasticity of single amylose chains in solvents that promote or inhibit the formation of inter-residue hydrogen bonds was examined by AFM (see picture). Hydrogen bonds were found to rigidify the amylose chain in solvents of low dielectric constant, and the strength of inter-residue hydrogen bonds in sugars can be measured.

    14. Quantitative Dynamic Interconversion between AgI-Mediated Capsule and Cage Complexes Accompanying Guest Encapsulation/Release (pages 2727–2731)

      Shuichi Hiraoka, Koji Harano, Motoo Shiro and Mitsuhiko Shionoya

      Article first published online: 30 MAR 2005 | DOI: 10.1002/anie.200462394

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      An accommodating host: Capsule- and cage-shaped complexes are formed from AgI and disk-shaped trismonodentate ligands in 1:1 and 1.5:1 concentration ratios, respectively; their interconversion is reversible. The capsule complex can entrap a small neutral molecule such as adamantane in the inner space, but the guest is released when the cage structure is adopted.

    15. Total Synthesis of Antascomicin B (pages 2732–2737)

      Dominic E. A. Brittain, Charlotte M. Griffiths-Jones, Michael R. Linder, Martin D. Smith, Catherine McCusker, Jaqueline S. Barlow, Ryo Akiyama, Kosuke Yasuda and Steven V. Ley

      Article first published online: 1 APR 2005 | DOI: 10.1002/anie.200500174

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      The structurally enticing antascomicin B (1), which exhibits potent immunosuppressant-antagonizing properties, has a complex polyketide structure. Key steps in its enantioselective total synthesis include a transannular catechol-templated Dieckmann reaction to assemble the challenging tricarbonyl functionality and a butanediacetal-directed allylation.

    16. Uniform, Axial-Orientation Alignment of One-Dimensional Single-Crystal Silicon Nanostructure Arrays (pages 2737–2742)

      Kuiqing Peng, Yin Wu, Hui Fang, Xiaoyan Zhong, Ying Xu and Jing Zhu

      Article first published online: 6 APR 2005 | DOI: 10.1002/anie.200462995

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      Neatly scratching the surface: A facile etching technique assisted by a silver-nanoparticle network to produce large-area 1D silicon nanostructure arrays with desired orientation and doping characteristics is demonstrated (see picture). A mechanism for the highly selective etching is proposed on the basis of experimental evidence.

    17. Molecular Basis of Perhydrolase Activity in Serine Hydrolases (pages 2742–2746)

      Peter Bernhardt, Karl Hult and Romas J. Kazlauskas

      Article first published online: 31 MAR 2005 | DOI: 10.1002/anie.200463006

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      Changing substrates: A mutation that forms a cis-proline–peptide bond in a loop structure close to the active site of an aryl esterase from Pseudomonas fluorescens converts the enzyme into a perhydrolase (see picture). The switch in activity is explained by a new hydrogen bond formed between a backbone carbonyl oxygen atom and the peroxy deacylation intermediate.

    18. Strong Means Slow: Dynamic Contributions to the Bulk Mechanical Properties of Supramolecular Networks (pages 2746–2748)

      Wayne C. Yount, David M. Loveless and Stephen L. Craig

      Article first published online: 1 APR 2005 | DOI: 10.1002/anie.200500026

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      Hold on tight: The dynamics, rather than thermodynamics, of reversible cross-links are the primary determinants of bulk viscosities in a family of supramolecular networks. This result comes from a study in which a series of structurally similar pincer complexes (see picture, OTf=CF3SO3) that have different ligand-exchange dynamics is used to cross-link poly(4-vinylpyridine).

    19. Preventing Crystallization of Phospholipids in Monolayers: A New Approach to Lung-Surfactant Therapy (pages 2749–2752)

      Frédéric Gerber, Marie Pierre Krafft, Thierry F. Vandamme, Michel Goldmann and Philippe Fontaine

      Article first published online: 25 APR 2005 | DOI: 10.1002/anie.200462978

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      Control of phospholipid monolayer fluidity: A fluorocarbon gas (gFC) has a highly effective fluidizing effect on a semicrystalline monolayer of dipalmitoylphosphatidylcholine (DPPC, the main component of native lung surfactant), prevents it from crystallizing, and induces the dissolution of pre-existing liquid-condensed-phase domains (see fluorescence micrographs; left: without gFC, right: with gFC). The biocompatible FC may, therefore, prove useful in lung-surfactant therapy.

    20. Copper-Catalyzed Enantioselective Conjugate Addition of Grignard Reagents to α,β-Unsaturated Esters (pages 2752–2756)

      Fernando López, Syuzanna R. Harutyunyan, Auke Meetsma, Adriaan J. Minnaard and Ben L. Feringa

      Article first published online: 11 APR 2005 | DOI: 10.1002/anie.200500317

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      Stable dinuclear Cu complexes have been used to catalyze the conjugate addition of inexpensive and readily available Grignard reagents to acyclic α,β-unsaturated esters. The method provides the corresponding β-substituted optically active esters in high yields and with excellent enantioselectivities (see scheme). R3=cyclohexyl, R4=Ph or R3=Ph, R4=cyclohexyl.

    21. Total Synthesis of (−)-Laulimalide: Pd-Catalyzed Stereospecific Ring Construction of the Substituted 3,6-Dihydro[2H]pyran Units (pages 2756–2760)

      Jun'ichi Uenishi and Masashi Ohmi

      Article first published online: 30 MAR 2005 | DOI: 10.1002/anie.200500029

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      The potent anticancer agent (−)-laulimalide (1) was prepared through a versatile method that should allow access to other marine natural products. Key steps included a Pd-catalyzed 1,3 chirality transfer of an allylic alcohol. The syn-SN2′-like processes occur stereospecifically in either 6-endo-trig or 6-exo-trig fashion to give the desired 3,6-dihydro[2H]pyran rings (see scheme).

    22. Genetically Selected Cyclic-Peptide Inhibitors of AICAR Transformylase Homodimerization (pages 2760–2763)

      Ali Tavassoli and Stephen J. Benkovic

      Article first published online: 13 APR 2005 | DOI: 10.1002/anie.200500417

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      Finding the needle in a haystack need not be as troublesome as once thought. By coupling disruption of protein–protein (X–X) interactions to host-cell survival (see figure), inhibitors of ATIC (a key enzyme in the de novo purine biosynthetic pathway) were readily identified from a biosynthesized library of 107 small molecules. The activity and selectivity of nine cyclic peptides selected by this method were demonstrated in vivo and in vitro. AICAR=aminoimidazole-4-carboxamide ribonucleotide.

    23. DNA Detection through Signal Amplification by Using NADH:Flavin Oxidoreductase and Oligonucleotide–Flavin Conjugates as Cofactors (pages 2764–2767)

      Philippe Simon, Cécile Dueymes, Marc Fontecave and Jean-Luc Décout

      Article first published online: 17 MAR 2005 | DOI: 10.1002/anie.200461145

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      Cofactors on the case: DNA detection by using an enzyme and its cofactor attached to an oligonucleotide is described. If the enzyme is functional only when the cofactor–oligonucleotide conjugate is not hybridized, substrate conversion monitored by fluorescence spectroscopy can be used as a reaction probe for hybridization (see scheme). Furthermore, as the enzyme turns over many copies of the substrate, the signal is greatly amplified.

    24. Reversible Binding of Dioxygen by a Non-Transition-Metal Complex (pages 2767–2771)

      Gleb A. Abakumov, Andrey I. Poddel'sky, Ekaterina V. Grunova, Vladimir K. Cherkasov, Georgy K. Fukin, Yury A. Kurskii and Ludmila G. Abakumova

      Article first published online: 31 MAR 2005 | DOI: 10.1002/anie.200462503

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      Dioxygen binds reversibly to the non-transition-metal complex 1 to form the spiroendoperoxide 2 (see scheme). Complexes 1 and 2 were characterized by NMR, IR, and UV/Vis spectroscopies, and their molecular structures were determined by X-ray crystallography.

    25. Redox-Induced Transformation from an Extended to a π-Stacked Conformer in Acyclic Bis(catecholacetal)s of Acetylacetone (pages 2771–2774)

      Rajendra Rathore, Vincent J. Chebny, Erica J. Kopatz and Ilia A. Guzei

      Article first published online: 30 MAR 2005 | DOI: 10.1002/anie.200463103

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      Removal of a single electron induced the extended conformers of bis(catecholacetal)s of acetylacetone to instantaneously fold into cyclophane-like π-stacked structures (shown schematically).

    26. Asymmetric Amplification Using Chiral Cocrystals Formed from Achiral Organic Molecules by Asymmetric Autocatalysis (pages 2774–2777)

      Tsuneomi Kawasaki, Kazumichi Jo, Hirotaka Igarashi, Itaru Sato, Masaki Nagano, Hideko Koshima and Kenso Soai

      Article first published online: 30 MAR 2005 | DOI: 10.1002/anie.200462963

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      Enantioselective addition of diisopropylzinc to a pyrimidine-5-carbaldehyde was induced by chiral cocrystals of achiral two-component molecular crystals of tryptamine/para-chlorobenzoic acid (see scheme) and 3-indolepropionic acid/phenanthridine. This reaction, in conjunction with asymmetric autocatalysis, afforded a pyrimidyl alkanol in high enantiomeric excess.

    27. Chasing a Phantom by Total Synthesis: The Butylcycloheptylprodigiosin Case (pages 2777–2781)

      Alois Fürstner, Karin Radkowski and Hartwig Peters

      Article first published online: 30 MAR 2005 | DOI: 10.1002/anie.200462215

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      The dispute as to whether “butylcycloheptylprodigiosin” is a natural product or solely a misassigned structure lasted for more than a decade. This open question has now been answered by the first total synthesis of this tripyrrole alkaloid (see picture), which makes explicit use of the peculiarities of its highly strained ortho-anellated nine-membered ring.

    28. Monodisperse Magnetic Single-Crystal Ferrite Microspheres (pages 2782–2785)

      Hong Deng, Xiaolin Li, Qing Peng, Xun Wang, Jinping Chen and Yadong Li

      Article first published online: 30 MAR 2005 | DOI: 10.1002/anie.200462551

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      Particularly uniform: Monodisperse ferrite microspheres can be synthesized to have diameters of about 200–800 nm (TEM image, left). High-resolution TEM analysis (image, right and inset) shows that each microsphere is a single crystal. Their hydrophilic and magnetic properties impart to the microparticles many potential uses in electronics and biomedicine.

    29. Scaling the Alignment of Small Organic Molecules in Substituted Polyglutamates by Variable-Angle Sample Spinning (pages 2787–2790)

      Christina M. Thiele

      Article first published online: 30 MAR 2005 | DOI: 10.1002/anie.200461532

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      Residual dipolar couplings provide important information for the stereochemical assignment of moieties in small organic molecules. By spinning the liquid-crystalline sample at an angle Θr to the magnetic field, the anisotropic interactions can be scaled to meet the experimental requirements. This is shown here for strychnine in the liquid-crystalline phases of poly(γ-benzyl-L-glutamate) and poly(γ-ethyl-L-glutamate) in CDCl3.

    30. Active Sites on Oxide Surfaces: ZnO-Catalyzed Synthesis of Methanol from CO and H2 (pages 2790–2794)

      Melanie Kurtz, Jennifer Strunk, Olaf Hinrichsen, Martin Muhler, Karin Fink, Bernd Meyer and Christof Wöll

      Article first published online: 4 APR 2005 | DOI: 10.1002/anie.200462374

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      Is this place taken? A mechanism has been proposed for the formation of methanol from CO and H2 on ZnO surfaces in which CO is adsorbed at oxygen vacancies on the heterogeneous catalyst (see picture: C red, H white, O gray, Zn black). The active sites are blocked when CO2 is added to the gas mixture.

    31. From AgCN Chains to a Fivefold Helix and a Fishnet-Shaped Framework Structure (pages 2794–2797)

      Victoria Urban, Thorsten Pretsch and Hans Hartl

      Article first published online: 13 APR 2005 | DOI: 10.1002/anie.200462793

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      Halides in control: Treating silver cyanide with CsCl, CsBr, or CsI, gives a zeolitic framework {[Cs]equation image[Ag4(CN)4Cl]2[AgCl4]} (1) of cross-linked, ropelike twisted fivefold helices, a layered polymer with a fishnet structure [Cs]equation image[Ag11(CN)16][Ag(CN)2]⋅2 CH3CN, or a simple double salt Cs5[Ag(CN)2]4I. The existence of tetrachloroargentate(I) [AgCl4]3− included into the channels of 1 is shown by a single-crystal structure for the first time (see picture).

    32. Gold Catalysis: Proof of Arene Oxides as Intermediates in the Phenol Synthesis (pages 2798–2801)

      A. Stephen K. Hashmi, Matthias Rudolph, Jan P. Weyrauch, Michael Wölfle, Wolfgang Frey and Jan W. Bats

      Article first published online: 1 APR 2005 | DOI: 10.1002/anie.200462672

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      An elusive intermediate in the gold-catalyzed phenol synthesis was elucidated by modifying the energy profile of this process. Thus, the use of a ligand based on 2-hydroxymethylpyridine enabled the first observation of the intermediate arene oxide, which can be enriched to account for up to 80 % of the material in the reaction mixture at room temperature (see scheme).

    33. Discotic Liquid Crystals with an Inverted Structure (pages 2801–2805)

      Sigurd Höger, Xiao Hong Cheng, Anne-Désirée Ramminger, Volker Enkelmann, Almut Rapp, Mihail Mondeshki and Ingo Schnell

      Article first published online: 30 MAR 2005 | DOI: 10.1002/anie.200462319

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      What is the design principle of a discotic liquid crystal? Up to now, such systems have involved a more or less rigid core surrounded by flexible side groups that point outward. Herein, shape-persistent macrocycles are introduced with flexible side chains that have intraannular positions (see picture).

    34. Wound Closure in the Invasive Green Alga Caulerpa taxifolia by Enzymatic Activation of a Protein Cross-Linker (pages 2806–2808)

      Sven Adolph, Verena Jung, Janine Rattke and Georg Pohnert

      Article first published online: 30 MAR 2005 | DOI: 10.1002/anie.200462276

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      Rapid polymer formation under physiological conditions is triggered upon wounding of the unicellular macroalga C. taxifolia. This process is initiated by esterase-mediated deacetylation of caulerpenyne (1). The resulting 1,4-dialdehyde oxytoxin 2 (2) instantaneously reacts with nucleophilic groups from proteins to form a cross-linked biopolymer.

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      Preview: Angew. Chem. Int. Ed. 18/2005 (page 2813)

      Article first published online: 25 APR 2005 | DOI: 10.1002/anie.200590062

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