Angewandte Chemie International Edition

Cover image for Vol. 44 Issue 32

August 12, 2005

Volume 44, Issue 32

Pages 4989–5149

    1. Cover Picture: Nanoparticle PCR: Nanogold-Assisted PCR with Enhanced Specificity (Angew. Chem. Int. Ed. 32/2005) (page 4989)

      Haikuo Li, Jiehuan Huang, Junhong Lv, Hongjie An, Xiaodong Zhang, Zhizhou Zhang, Chunhai Fan and Jun Hu

      Article first published online: 8 AUG 2005 | DOI: 10.1002/anie.200590108

      Favorable binding of gold nanoparticles to single-stranded DNA decreases the likelihood of mispair formation during annealing and clearly increases the specificity and yield of PCR, one of the most important standard methods of molecular biology. In their Communication on pp. 5100 ff., Z. Zhang, C. Fan, J. Hu, and co-workers report on this promising field of biotechnology. (Xiaobin Wang assisted in the production of this image.)

    2. Cellular Profiling of Small-Molecule Bioactivities: an Alternative Tool for Chemical Biology (pages 5008–5011)

      Thorsten Berg

      Article first published online: 23 JUN 2005 | DOI: 10.1002/anie.200500721

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      Are they a good match? Target identification is critical to the success of chemical genetics projects that start with phenotypic screens. The method highlighted herein is a novel way to decrease the number of potential biological targets of compounds identified in phenotypic screens by comparison of their cellular activity profiles with those obtained with reference compounds. Activity profiles for hypothetical compounds A and B are shown.

    3. Oxidative Addition of NH3 to a Transition-Metal Complex: A Key Step for the Metal-Mediated Derivatization of Ammonia? (pages 5012–5014)

      Thomas Braun

      Article first published online: 12 JUL 2005 | DOI: 10.1002/anie.200501505

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      Bond cleavage with model character? The oxidative addition of ammonia to a transition-metal complex to yield a terminal amido complex was achieved for the first time recently (see scheme). This model reaction might provide new pathways to use ammonia as a feedstock in catalytic reactions.

    4. Borinium, Borenium, and Boronium Ions: Synthesis, Reactivity, and Applications (pages 5016–5036)

      Warren E. Piers, Sara C. Bourke and Korey D. Conroy

      Article first published online: 8 AUG 2005 | DOI: 10.1002/anie.200500402

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      Any old ion? The title boron cations (see scheme) are elusive and have largely been regarded as chemical curiosities. However, as potent electrophiles the enormous potential of these species is beginning to be recognized. Advances in mass spectrometry have made a systematic investigation of the gas-phase chemistry of these ions possible and have facilitated predictions of practical relevance to their reactivity in the condensed phase.

    5. Stimuli-Responsive Controlled-Release Delivery System Based on Mesoporous Silica Nanorods Capped with Magnetic Nanoparticles (pages 5038–5044)

      Supratim Giri, Brian G. Trewyn, Michael P. Stellmaker and Victor S.-Y. Lin

      Article first published online: 22 JUL 2005 | DOI: 10.1002/anie.200501819

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      Stand and deliver! The release of pore-encapsulated fluorescein molecules from a core/shell mesoporous silica nanorod/superparamagnetic iron oxide nanoparticle carrier in the presence of an external magnetic field and only in response to cell-produced antioxidants indicates promise for such systems in controlled-release drug delivery.

    6. Phosphonate Ligands Stabilize Mixed-Valent {MnIII20−xMnIIx} Clusters with Large Spin and Coercivity (pages 5044–5048)

      Shanmugam Maheswaran, Guillaume Chastanet, Simon J. Teat, Talal Mallah, Roberta Sessoli, Wolfgang Wernsdorfer and Richard E. P. Winpenny

      Article first published online: 20 JUL 2005 | DOI: 10.1002/anie.200501265

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      In a spin: The mixed-valent {MnIII20−xMnIIx} cage complexes (x=2–6) have structures corresponding to a fragment of a cubic close-packed lattice (see picture, Mn large sphere, O small sphere). Magnetic studies show for the cage with x=2 that the ground state has a spin (S) of 19±1 in low field, which increases to about S=30 at higher fields. The cage is a “single molecule magnet” with a high energy barrier (43 K) to reorientation of the magnetization.

    7. Multiple Addressing in a Hybrid Biphotochromic System (pages 5048–5052)

      Michel Frigoli and Georg H. Mehl

      Article first published online: 20 JUL 2005 | DOI: 10.1002/anie.200462575

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      Affairs of state: Investigation of the photochromic properties of a combined naphthopyran and diarylethene biphotochromic system (1) has revealed that four different states with entirely different absorption behaviors are formed. Opening of the naphthopyran ring leads to conjugation and electronic connection of both photochromes, while closure of the open diarylethene system extends the π-electron system over the whole molecule.

    8. Multivalent Peptide and Protein Dendrimers Using Native Chemical Ligation (pages 5052–5057)

      Ingrid van Baal, Hinke Malda, Silvia A. Synowsky, Joost L. J. van Dongen, Tilman M. Hackeng, Maarten Merkx and E. W. Meijer

      Article first published online: 11 JUL 2005 | DOI: 10.1002/anie.200500635

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      A wide variety of well-defined multivalent peptides and proteins can be made by conjugating synthetic peptides and recombinantly expressed proteins to cysteine-functionalized dendrimers using native chemical ligation (see picture). This modular approach provides access to dendrimers that are attractive both for understanding fundamental issues of multivalency in biological interactions as well as for biomedical applications.

    9. Oxidation of Guanine and 8-oxo-7,8-Dihydroguanine by Carbonate Radical Anions: Insight from Oxygen-18 Labeling Experiments (pages 5057–5060)

      Conor Crean, Nicholas E. Geacintov and Vladimir Shafirovich

      Article first published online: 13 JUL 2005 | DOI: 10.1002/anie.200500991

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      Under oxidative stress: The oxidation of guanine and 8-oxo-7,8-dihydroguanine has been monitored by 18O-labeling methods. The combination of nucleobase radicals 1 with the carbonate radical anion 2 results in the net transfer of O from CO3.− to the end products (see scheme).

    10. Fluorinated TRISPHAT Anions: Spectroscopic Probes for Detailed Asymmetric Ion Pairing Studies (pages 5060–5064)

      Richard Frantz, André Pinto, Samuel Constant, Gérald Bernardinelli and Jérôme Lacour

      Article first published online: 12 JUL 2005 | DOI: 10.1002/anie.200500862

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      Placing fluorine atoms at selected positions allows enantiopure hexacoordinate phosphate anions to behave as effective chiral solvating and resolving agents for RuII complexes (the structure of one of the anions is shown: F: yellow; O: red; Cl: green; P: purple). The structural features of the asymmetric ion pairing can be determined by NMR spectroscopy owing to the presence of the fluorine atoms.

    11. Sacrificial Biological Templates for the Formation of Nanostructured Metallic Microshells (pages 5064–5067)

      Emma Kathryn Payne, Nathaniel L. Rosi, Can Xue and Chad A. Mirkin

      Article first published online: 15 JUL 2005 | DOI: 10.1002/anie.200500988

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      Biological templates: Diatom cell walls were coated with metallic films and then subsequently dissolved to yield nanostructured metallic microshells that exhibit the structural characteristics of the diatom templates. The unique nanostructural details of the microshells (see image) make them useful as substrates for surface-enhanced Raman scattering.

    12. A Pyrene-Labeled G-Quadruplex Oligonucleotide as a Fluorescent Probe for Potassium Ion Detection in Biological Applications (pages 5067–5070)

      Satoru Nagatoishi, Takahiko Nojima, Bernard Juskowiak and Shigeori Takenaka

      Article first published online: 20 JUL 2005 | DOI: 10.1002/anie.200501506

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      Ion probes: A potassium-sensing oligonucleotide with terminal pyrene moieties can be used as a fluorescent probe for the real-time monitoring of the extracellular concentration of K+ ions under physiological conditions. The excimer emission intensity (b) of the chair-type quadruplex structure formed depends on the K+ ion concentration (0–200 mm), and differs significantly from that in the absence of potassium (a).

    13. Supramolecular Stereomutation in Kinetic and Thermodynamic Self-Assembly of Helical Merocyanine Dye Nanorods (pages 5071–5074)

      Andreas Lohr, Marina Lysetska and Frank Würthner

      Article first published online: 13 JUL 2005 | DOI: 10.1002/anie.200500640

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      An inversion of the exciton chirality and structural changes upon transformation from kinetic to thermodynamic assembly are features of helical bis(merocyanine) dye nanorods (see picture), as elucidated by time-dependent circular dichroism (CD) spectroscopy and atomic force microscopy.

    14. Shape-Persistent Chiral Alleno-Acetylenic Macrocycles and Cyclophanes by Acetylenic Scaffolding with 1,3-Diethynylallenes (pages 5074–5078)

      Severin Odermatt, J. Lorenzo Alonso-Gómez, Paul Seiler, M. Magdalena Cid and François Diederich

      Article first published online: 20 JUL 2005 | DOI: 10.1002/anie.200501621

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      Rings on her fingers: The chiral alleno-acetylenic macrocycle 1 and the related cyclophane 2 with intriguing three-dimensional shapes were prepared and isolated in diastereoisomerically pure form. The symmetries and structures of these novel unsaturated hydrocarbons were elucidated by 1H NMR spectroscopy and X-ray crystallography. The isolated stereoisomeric cyclophanes undergo photoisomerization; presumably the anthracene moieties serve as intramolecular sensitizers.

    15. Synthesis and Structure Determination of Tellurium Tetracyanide Solvates: Pseudopolymorphism of Te(CN)4 and TeF4 (pages 5079–5082)

      Dieter Lentz and Małgorzata Szwak

      Article first published online: 20 JUL 2005 | DOI: 10.1002/anie.200500168

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      The pseudopolymorphic solvates [{Te(CN)4(CH3CN)2}n] and [{Te(CN)4(thf)3}n] form coordination polymers in the solid state in which Te(CN)3 units are connected by CN groups in cis position to form infinite chains. The picture shows a section of [{Te(CN)4(thf)3}n]. In contrast, the tellurium tetrafluoride solvate [TeF4(thf)2] contains monomeric ψ-trigonal-bipyramidal TeF4 units.

    16. Stimuli-Responsive Controlled Drug Release from a Hollow Mesoporous Silica Sphere/Polyelectrolyte Multilayer Core–Shell Structure (pages 5083–5087)

      Yufang Zhu, Jianlin Shi, Weihua Shen, Xiaoping Dong, Jingwei Feng, Meilin Ruan and Yongsheng Li

      Article first published online: 14 JUL 2005 | DOI: 10.1002/anie.200501500

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      Keeping drugs under control: Hydrothermally stable, hollow mesoporous silica spheres have a high drug storage capacity, and polyelectrolyte multilayers coated on the spheres act as a switch for drug release which is controlled by the pH or ionic strength of the release medium. The picture shows the release of ibuprofen (IBU) from spheres with and without coatings of sodium polystyrene sulfonate (PSS) and poly(allylamine hydrochloride) (PAH).

    17. Orbital-Overlap Control of the Reactivity of a Bicyclic 1-Hydroxy-1,4-Biradical (pages 5087–5089)

      Chao Yang, Wujiong Xia, John R. Scheffer, Mark Botoshansky and Menahem Kaftory

      Article first published online: 20 JUL 2005 | DOI: 10.1002/anie.200500983

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      Radical reform: Cleavage of the enantiotopic C2[BOND]C3 or C2[BOND]C3′ bonds in bicyclic 1-hydroxy-1,4-biradicals (see structure) leads to enantiomeric products. Absolute configuration correlations demonstrate that, in the crystalline state, cleavage occurs mainly in one direction and is controlled by the orientation of the cleaving bonds with respect to the p orbital at the C1 position.

    18. A Stable Aluminacyclopropene LAl(η2-C2H2) and Its End-On Azide Insertion to an Aluminaazacyclobutene (pages 5090–5093)

      Hongping Zhu, Jianfang Chai, Hongjun Fan, Herbert W. Roesky, Cheng He, Vojtech Jancik, Hans-Georg Schmidt, Mathias Noltemeyer, William A. Merrill and Philip P. Power

      Article first published online: 14 JUL 2005 | DOI: 10.1002/anie.200500899

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      Not all down-to-Earth: A stable aluminacyclopropene LAl(η2-C2H2) 1 was isolated from the reaction of LAl with C2H2. Further reaction of 1 with C2H2 results in terminal C[TRIPLE BOND]CH and CH[DOUBLE BOND]CH2 groups at the Al center. The end-on insertion of an azide into one Al[BOND]C bond in 1 leads to the first aluminaazacyclobutene 2. These reactions can be considered prebiotic, as AlI species and acetylene are found in outer space.

    19. Pd-Catalyzed Stereospecific Azide Substitution of α,β-Unsaturated γ,δ-Epoxy Esters with Double Inversion of Configuration (pages 5094–5097)

      Masaaki Miyashita, Taiku Mizutani, Genta Tadano, Yasuhiro Iwata, Masahiro Miyazawa and Keiji Tanino

      Article first published online: 15 JUL 2005 | DOI: 10.1002/anie.200500838

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      Acyclic, cyclic, and optically active unsaturated γ,δ-epoxy esters are employed in a highly stereoselective synthesis of functionalized amino alcohols, amino acids, and α,α-disubstituted amino acids. The key step of the reaction sequence is a double inversion of configuration (see scheme).

    20. Control of Differential Inclusion Complexation in the Solid State by Seed Crystals (pages 5097–5100)

      Kazuhiro Yoshizawa, Shinji Toyota, Fumio Toda, Spyros Chatziefthimiou, Petros Giastas, Irene M. Mavridis and Masako Kato

      Article first published online: 11 JUL 2005 | DOI: 10.1002/anie.200501364

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      Sowing the seeds: Complexation of rac-1 in the solid state with a guest such as Et2O in the gas phase proceeds in the presence of a seed crystal of the inclusion complex (see scheme). For example, passing Et2O over a mixture of 1 and a seed of 1⋅(Et2O)3 gives rise to exclusive formation of the 1:3 complex.

    21. Nanoparticle PCR: Nanogold-Assisted PCR with Enhanced Specificity (pages 5100–5103)

      Haikuo Li, Jiehuan Huang, Junhong Lv, Hongjie An, Xiaodong Zhang, Zhizhou Zhang, Chunhai Fan and Jun Hu

      Article first published online: 8 JUN 2005 | DOI: 10.1002/anie.200500403

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      Nanogold may not glitter, but its presence significantly improves the specificity and yield of PCR reactions owing to the greater affinity of gold nanoparticles to single-stranded DNA than to double-stranded DNA which helps to reduce mispairing. Indeed, gel electrophoresis shows a single predominant band for the target DNA obtained by this method, in contrast to streaking bands for products obtained by conventional PCR (lanes 1 and 2; see image).

    22. Palladium-Catalyzed Tandem Cyclization of Bromoenynes through Aromatic C[BOND]H Bond Functionalization (pages 5103–5106)

      Hiroaki Ohno, Mio Yamamoto, Mutsumi Iuchi and Tetsuaki Tanaka

      Article first published online: 13 JUL 2005 | DOI: 10.1002/anie.200500159

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      The direct approach: Tandem cyclization of 1-aryl-4-aza-2-bromo-1-alken-6-ynes with catalytic Pd(OAc)2 and cesium carbonate in EtOH led to direct construction of tri- or tetracyclic heterocycles, through intramolecular carbopalladation and aromatic C[BOND]H bond functionalization (see scheme). This route in which two C[BOND]C bonds are formed enables the construction of complex heterocyclic skeletons directly from readily prepared enynes.

    23. Correlations between Molecular Numbers and Molecular Masses in an Evanescent Field and Their Applications in Probing Molecular Interactions (pages 5107–5110)

      Hongwei Gai, Qi Wang, Yinfa Ma and Bingcheng Lin

      Article first published online: 12 JUL 2005 | DOI: 10.1002/anie.200500461

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      Complex numbers: The number of molecules detected in the evanescent field during single-molecule fluorescence imaging decreases with increasing molecular weight in free solution (see graphic; FITC=fluorescein isothiocyanate). This technique could be useful for screening undefined molecular interactions at extremely low concentrations without separation.

    24. C2-Symmetrical Thiodigalactoside Bis-Benzamido Derivatives as High-Affinity Inhibitors of Galectin-3: Efficient Lectin Inhibition through Double Arginine–Arene Interactions (pages 5110–5112)

      Ian Cumpstey, Anders Sundin, Hakon Leffler and Ulf J. Nilsson

      Article first published online: 11 JUL 2005 | DOI: 10.1002/anie.200500627

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      Inhibitors of galectin-3, which has been implicated in cancer- and immunity-related processes, can be synthesized from thiodigalactoside derivatives with aromatic amide substituents at both C3 positions (see structure). Dissociation constant (Kd) values as low as 33 nM have been obtained. Computer modeling suggests that such high affinity stems from double arginine–arene stacking interactions.

    25. Thermal Intramolecular [2+2] Cycloaddition of Allenenes and Allenynes: Diastereoselective Access to Bicyclic Nitrogen Heterocycles (pages 5113–5115)

      Hiroaki Ohno, Tsuyoshi Mizutani, Yoichi Kadoh, Kumiko Miyamura and Tetsuaki Tanaka

      Article first published online: 20 JUL 2005 | DOI: 10.1002/anie.200501413

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      Squaring the circle: A route to bicyclo[4.2.0]octane derivatives has been developed by the [2+2] cycloaddition of allenenes or allenynes. The thermal intramolecular [2+2] cycloaddition of simple allenes 1 with an additional multiple bond leads to direct and regioselective formation of the distal adducts 2 in good to excellent yields.

    26. The Fabrication and Switchable Superhydrophobicity of TiO2 Nanorod Films (pages 5115–5118)

      Xinjian Feng, Jin Zhai and Lei Jiang

      Article first published online: 15 JUL 2005 | DOI: 10.1002/anie.200501337

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      Wet and dry: Titanium dioxide nanorod films with micro- and nanoscale hierarchical surface structures have been successfully prepared (left). The nanorod films, which show superhydrophobicity (middle), reversibly become superhydrophilic (right) when exposed to UV light. The mechanism involves the cooperation of the special surface structures, the orientation of crystal planes, and the surface photosensitivity.

    27. A Tiny Excited-State Barrier Can Induce a Multiexponential Decay of the Retinal Chromophore: A Quantum Dynamics Investigation (pages 5118–5121)

      Massimo Olivucci, Alessandro Lami and Fabrizio Santoro

      Article first published online: 20 JUL 2005 | DOI: 10.1002/anie.200501236

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      Excitement over something small: The protonated Schiff base of retinal photoisomerizes on an excited-state hypersurface (S1) that connects the Franck–Condon (FC) point via a flat valley centered on a planar structure (SP) to a conical intersection (CI; see picture). Wave-packet (gray hat) quantum dynamics shows that the depletion of the S1 population switches from mono- to biexponential when a small ridge (dotted line) between SP and CI is present.

    28. Nanotrench Arrays Reveal Insight into Graphite Electrochemistry (pages 5121–5126)

      Trevor J. Davies, Michael E. Hyde and Richard G. Compton

      Article first published online: 15 JUL 2005 | DOI: 10.1002/anie.200462750

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      Watch your step! Decoupling the individual contributions of edge-plane steps (A) and basal-plane terraces (B) to the voltammetry of graphite electrodes can provide information of fundamental importance. This was done by selectively blocking the basal-plane terraces with insulating material to form nanotrench arrays of edge-plane graphite.

    29. Alternate Isotope-Coded Derivatization Assay: An Isotope Dilution Method Applied to the Quantification of Zearalenone in Maize Flour (pages 5126–5130)

      Stefano Sforza, Chiara Dall'Asta, Alessandra Moseriti, Gianni Galaverna, Arnaldo Dossena and Rosangela Marchelli

      Article first published online: 13 JUL 2005 | DOI: 10.1002/anie.200500148

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      Low-cost isotope dilution made easy: An alternate reaction of an analyte in a matrix and in a standard solution with isotope-labeled or unlabeled derivatizing reagents allows quantification of zearalenone in maize flour without the need for a calibration curve. This is possible by direct calculation of the relative response factor for the analyte/internal standard ratio of the sample (see picture).

    30. Approach to the Blues: A Highly Flexible Route to the Azulenes (pages 5130–5133)

      Sébastien Carret, Aurélien Blanc, Yoann Coquerel, Mikaël Berthod, Andrew E. Greene and Jean-Pierre Deprés

      Article first published online: 13 JUL 2005 | DOI: 10.1002/anie.200501276

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      A palette of blues: Chlorobicyclo[5.3.0]decatrienones are readily prepared from cycloheptatrienes by cycloaddition of dichloroketene, ring expansion with a diazoalkane, and dehydrochlorination in dimethylformamide. These compounds are used as intermediates in the regiocontrolled synthesis of a wide variety of natural and nonnatural azulenes (see scheme).

    31. Through-Space (Cofacial) π-Delocalization among Multiple Aromatic Centers: Toroidal Conjugation in Hexaphenylbenzene-like Radical Cations (pages 5133–5136)

      Duoli Sun, Sergiy V. Rosokha and Jay K. Kochi

      Article first published online: 12 JUL 2005 | DOI: 10.1002/anie.200501005

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      Pi and doughnuts: Highly effective through-space conjugation among cofacial (aromatic) redox centers is established in stable hexaanilinylbenzene radical cations (1.+; π conjugation shown by toroid). The radical cations show unusual intervalence absorption bands and are quantitatively analyzed by Mulliken–Hush formulation.

    32. Polyoxovanadometalate-Catalyzed Selective Epoxidation of Alkenes with Hydrogen Peroxide (pages 5136–5141)

      Yoshinao Nakagawa, Keigo Kamata, Miyuki Kotani, Kazuya Yamaguchi and Noritaka Mizuno

      Article first published online: 11 JUL 2005 | DOI: 10.1002/anie.200500491

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      The bis(μ-hydroxo)-bridged dioxovanadium site in [γ-1,2-H2SiV2W10O40]4− catalyzes the epoxidation of alkenes in the presence of only one equivalent of H2O2 with a high yield of epoxide, high efficiency of H2O2 utilization, unusual regioselectivity, and unprecedented diastereoselectivity (see picture).

    33. Mapping Protein–Protein Interfaces on the Basis of Proton Density Difference (pages 5141–5144)

      Xiaogang Sui, Yingqi Xu, Janel L. Giovannelli, Nancy T. Ho, Chien Ho and Daiwen Yang

      Article first published online: 20 JUL 2005 | DOI: 10.1002/anie.200501209

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      Making contact: A protein–protein interface (see structure) can be identified unambiguously from the dependence of amide-proton relaxation on proton density, as demonstrated by the identification of subunit contacts in hemoglobin. The information on upper limits for effective distances thus obtained allows the protein complex structure to be modeled more accurately with docking techniques.

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