Angewandte Chemie International Edition

Cover image for Vol. 45 Issue 19

May 5, 2006

Volume 45, Issue 19

Pages 2985–3185

    1. Cover Picture: Proteolytic Actuation of Nanoparticle Self-Assembly (Angew. Chem. Int. Ed. 19/2006) (page 2985)

      Todd J. Harris, Geoffrey von Maltzahn, Austin M. Derfus, Erkki Ruoslahti and Sangeeta N. Bhatia

      Version of Record online: 27 APR 2006 | DOI: 10.1002/anie.200690067

      Sterically shielded …… nanoparticles diffuse freely in solution and biological fluids until proteases expressed by cancer cells trigger them to self-assemble. In their Communication on page 3161ff., S. N. Bhatia and co-workers show that complimentary Fe3O4 nanoparticle binding is inhibited by the attachment of protease-cleavable polymers. Cleavage of these polymers triggers “latent” nanoparticles to form multimeric assemblies with emergent properties.

    2. To Boldly Pass the Metal–Metal Quadruple Bond (pages 3006–3010)

      Udo Radius and Frank Breher

      Version of Record online: 27 APR 2006 | DOI: 10.1002/anie.200504322

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      The metal–metal quintuple bond: Minimizing the number of sterically demanding ligands increases the number of valence orbitals available to form metal–metal bonds. Following this concept, Power et al. have recently synthesized and structurally characterized a dinuclear chromium–chromium-bonded complex with one ligand per metal atom (see picture) featuring a metal–metal quintuple bond. Driving this concept to an extreme, even larger bond orders than five should be feasible.

    3. How High the Spin? Allowed and Forbidden Spin States in Transition-Metal Chemistry (pages 3012–3020)

      Santiago Alvarez and Jordi Cirera

      Version of Record online: 10 APR 2006 | DOI: 10.1002/anie.200503492

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      Howhighis high and howlowis low? With respect to transition-metal complexes of different coordination numbers and stereochemistry, high-, low-, and intermediate-spin states may mean different things. The hybridization of the d orbitals, similar to the deformation of a balloon subjected to pressure (see picture), provides a rationale for the splitting of the d manifold and, hence, for the allowed spin states in a given complex.

    4. Why Are Proteins Charged? Networks of Charge–Charge Interactions in Proteins Measured by Charge Ladders and Capillary Electrophoresis (pages 3022–3060)

      Irina Gitlin, Jeffrey D. Carbeck and George M. Whitesides

      Version of Record online: 18 APR 2006 | DOI: 10.1002/anie.200502530

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      Electrostatic effects in proteins are complicated: The charged groups form a network of interactions in which the members can influence each other at long distances. Sets of derivatives in which variable numbers of charges are removed or added by chemical reactions (protein charge ladders) together with capillary electrophoresis comprise a tool with which to examine the character of this network.

    5. Droplet-Based DNA Purification in a Magnetic Lab-on-a-Chip (pages 3062–3067)

      Ulrike Lehmann, Caroline Vandevyver, Virendra K. Parashar and Martin A. M. Gijs

      Version of Record online: 23 MAR 2006 | DOI: 10.1002/anie.200503624

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      Merge, mix, split, and transport are the main manipulation steps used for on-chip droplet-based DNA purification (see figure). The system is able to extract genomic material from dilute raw cell samples by using the actuation of magnetic microparticles within the droplets through a matrix of coils.

    6. Lydiamycins A–D: Cyclodepsipetides with Antimycobacterial Properties (pages 3067–3072)

      Xueshi Huang, Ernst Roemer, Isabel Sattler, Ute Moellmann, Arnulf Christner and Susanne Grabley

      Version of Record online: 18 APR 2006 | DOI: 10.1002/anie.200503381

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      Out of the brew! Four new antibiotics were isolated from a fermentation broth of Steptomyces lydicus (strain HKI0343). The 13-membered-ring peptides (see formula, X[BOND]Y: CH2[BOND]NH, CH[DOUBLE BOND]NH; R1, R2: H, OH) are cyclized through a lactone function at serine and also contain the nonproteinogenic amino acid piperazic acid (or a derivative thereof). The peptides show promising activity against various mycobacteria without being cytotoxic.

    7. Regio- and Stereoselective Rhodium-Catalyzed Allylic Alkylations of Chelated Enolates (pages 3072–3075)

      Uli Kazmaier and Daniel Stolz

      Version of Record online: 5 APR 2006 | DOI: 10.1002/anie.200600100

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      Rehabilitated: The rhodium-catalyzed allylic alkylation is indeed a viable alternative to the better-known palladium-catalyzed version. Rhodium complexes show a different regioselectivity and have a low tendency for isomerization. The allylations proceed with excellent chirality transfer for both branched and linear products (see scheme; Tfa=trifluoroacetyl).

    8. Intramolecular Concerted Insertion of Vinyl Cations into C[BOND]H Bonds: Hydroalkylating Cyclization of Alkynes with Alkyl Chloroformates To Give Cyclopentanes (pages 3076–3079)

      Ursula Biermann, Rainer Koch and Jürgen O. Metzger

      Version of Record online: 5 APR 2006 | DOI: 10.1002/anie.200504288

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      Tying the knot: In analogy to singlet carbenes, vinyl cations insert into C[BOND]H bonds in a concerted intramolecular reaction, as shown by experimental investigations and quantum mechanical calculations. This reaction is useful for the synthesis of cyclopentane derivatives.

    9. Functional-Group Chemistry of Organolithium Compounds: Photochemical [2+2] Cycloaddition of Alkenyl-Substituted Lithium Cyclopentadienides (pages 3079–3082)

      Jan Paradies, Gerhard Erker and Roland Fröhlich

      Version of Record online: 29 MAR 2006 | DOI: 10.1002/anie.200503726

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      Li and light: Alkenyl-substituted lithium cyclopentadienides, which are in equilibrium with the substituted lithocene anion structure 1, undergo a photochemical [2+2] cycloaddition to yield selectively the carbon–carbon coupling product 2. This is a rare case of organic functional-group chemistry for a reactive organolithium compound.

    10. A PH-Functionalized Polyphosphazene: A Macromolecule with a Highly Flexible Backbone (pages 3083–3086)

      Michael Raab, Gerold Schick, Rebecca Fondermann, Michael Dolg, Wolfram Henze, Ulrike Weynand, Ruth M. Gschwind, Karl Fischer, Manfred Schmidt and Edgar Niecke

      Version of Record online: 3 APR 2006 | DOI: 10.1002/anie.200504208

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      The simplest side group: The first example of a completely H-substituted polyphosphazene I is obtained by the polycondensation of (Me2N)2PNH2 in solution at low temperature. NMR investigations and light-scattering experiments substantiate the constitution of the polymer. The conformation and a reaction pathway to I are proposed on the basis of ab initio calculations.

    11. A Reaction–Diffusion Memory Device (pages 3087–3089)

      Akiko Kaminaga, Vladimir K. Vanag and Irving R. Epstein

      Version of Record online: 29 MAR 2006 | DOI: 10.1002/anie.200600400

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      A face to remember: A photoimprinted image in a reactive microemulsion persisted for more than an hour. Such localized patterns in reaction–diffusion systems could find application in memory-storage devices. The picture shows the image of a face immediately following illumination (a) and after 1 h (b). The area at the right shows the evolution of a spontaneous Turing pattern.

    12. Catalytic Properties of Hierarchical Mesoporous Zeolites Templated with a Mixture of Small Organic Ammonium Salts and Mesoscale Cationic Polymers (pages 3090–3093)

      Feng-Shou Xiao, Lifeng Wang, Chengyang Yin, Kaifeng Lin, Yan Di, Jixue Li, Ruren Xu, Dang Sheng Su, Robert Schlögl, Toshiyuki Yokoi and Takashi Tatsumi

      Version of Record online: 30 MAR 2006 | DOI: 10.1002/anie.200600241

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      Holey zeolites! Hierarchical mesoporous zeolites (see SEM image) were prepared by a one-step hydrothermal reaction using both a small organic ammonium salt and a mesoscale cationic polymer as templates. The zeolites thus obtained reveal excellent catalytic properties relative to conventional zeolites, indicating the importance of their mesoporous structure for industrial catalysis.

    13. Functionalized Chiral Ionic Liquids as Highly Efficient Asymmetric Organocatalysts for Michael Addition to Nitroolefins (pages 3093–3097)

      Sanzhong Luo, Xueling Mi, Long Zhang, Song Liu, Hui Xu and Jin-Pei Cheng

      Version of Record online: 4 APR 2006 | DOI: 10.1002/anie.200600048

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      Catalytic combination: By combining the advantages of organocatalysts and ionic liquids, a functionalized chiral ionic liquid such as 1 can act as a highly efficient and reusable organocatalyst for the asymmetric Michael addition reaction of ketones and aldehydes with nitroalkenes.

    14. A Bimetallic, Coordinated-Ketene Complex Formed from a Bimetallic Lithium–Carbon Spirocycle by Lithium-Mediated Insertion of CO into a Rhodium–Carbon Bond (pages 3097–3101)

      Min Fang, Nathan D. Jones, Robert Lukowski, Jim Tjathas, Michael J. Ferguson and Ronald G. Cavell

      Version of Record online: 30 MAR 2006 | DOI: 10.1002/anie.200503814

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      Metals helping metals: The bimetallic spirocyclic bridged-carbene complex 1 reacts almost quantitatively with CO by formal “insertion” into the Rh[BOND]C(Li) bond to form the dimeric complex 2, the first example of a μ22-(O,C) lithium–rhodium ketene complex (see scheme). Complex 2 reacts with water to transform the ketene ligand into a methine group by CO elimination.

    15. Spatially Encoded Single-Bead Biginelli Synthesis in a Microstructured Silicon Array (pages 3102–3106)

      G. Alexander Groß, Günther Mayer, Jens Albert, Daniel Riester, Jens Osterodt, Hanns Wurziger and Andreas Schober

      Version of Record online: 30 MAR 2006 | DOI: 10.1002/anie.200503041

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      Miniature labs: A microstructured silicon wafer was used as a microreactor array for single-bead synthesis on a nanovolume scale. Products were prepared by combinatorial synthesis and spatially encoded by their position in the array. Three-component Biginelli condensations were carried out at 100 °C for 14 h and therefore required the development of a specially sealed reactor device.

    16. Catalytic Carbon Oxidation Over Ruthenium-Based Catalysts (pages 3106–3109)

      Kenneth Villani, Christine E. A. Kirschhock, Duoduo Liang, Gustaaf Van Tendeloo and Johan A. Martens

      Version of Record online: 30 MAR 2006 | DOI: 10.1002/anie.200503799

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      Exceptional activity in carbon oxidation is displayed by a zeolite-supported ruthenium catalyst (see diagram; Y=carbon weight loss) that unlike platinum catalysts does not require the presence of NOx in the gas stream. This catalyst opens up a new route for catalytic soot oxidation in diesel engine exhaust filters.

    17. Asymmetric Allylic Alkylation of Cyclic Vinylogous Esters and Thioesters by Pd-Catalyzed Decarboxylation of Enol Carbonate and β-Ketoester Substrates (pages 3109–3112)

      Barry M. Trost, Robert N. Bream and Jiayi Xu

      Version of Record online: 5 APR 2006 | DOI: 10.1002/anie.200504421

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      Excellent yields and enantioselectivities were achieved for the palladium-catalyzed asymmetric allylic alkylation of vinylogous thioesters. The close-to-neutral reaction conditions ensure that this reaction can tolerate a wide range of functionalities. Furthermore, this approach provides a convenient protocol for the synthesis of synthetically important α,α- and γ,γ-disubstituted cycloalkenones.

    18. Confined Synthesis of a cis-Isotactic Ladder Polysilsesquioxane by Using a π-Stacking and H-Bonding Superstructure (pages 3112–3116)

      Xiaojing Zhang, Ping Xie, Zhongrong Shen, Jinqiang Jiang, Chuanfeng Zhu, Huihui Li, Taoyi Zhang, Charles C. Han, Lijun Wan, Shouke Yan and Rongben Zhang

      Version of Record online: 4 APR 2006 | DOI: 10.1002/anie.200504474

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      On the rung way: Concerted self-organization of an α,ω-bis(triphenylenetetrahydroxy)disiloxane through π–π-stacking and H-bonding interactions generates a supramolecular channel in which silanol groups are entrapped between two hydrophobic columns. Ordered polycondensation leads to a high-molecular-weight, soluble, ladder cis-isotactic polysilsesquioxane (see picture).

    19. Highly Diastereoselective Synthesis of Bicyclo[3.2.1]octenones through Phosphine-Mediated Condensations of 1,4-Dien-3-ones (pages 3117–3119)

      Nolan T. McDougal and Scott E. Schaus

      Version of Record online: 5 APR 2006 | DOI: 10.1002/anie.200600126

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      Making rings: A highly diastereoselective synthesis of bicyclo[3.2.1]octenones from 1,4-dien-3-ones occurs through a domino phosphine-mediated formal [4+2] cycloaddition followed by an intramolecular Wittig olefination.

    20. A Direct CO Polymer Electrolyte Membrane Fuel Cell (pages 3120–3122)

      Shin-ichi Yamazaki, Tsutomu Ioroi, Yusuke Yamada, Kazuaki Yasuda and Tetsuhiko Kobayashi

      Version of Record online: 29 MAR 2006 | DOI: 10.1002/anie.200504379

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      A good source of energy: The reformation of hydrocarbons generates CO as well as H2. Despite its high reducing activity, CO is not suitable as a fuel in polymer electrolyte membrane fuel cells (PEMFCs) because it is a strong poison for the Pt catalyst used as the anode. A new fuel cell has now been developed with a rhodium octaethylporphyrin ([Rh(oep)]) anode catalyst that uses neat CO as a fuel, and delivers high performance (see graph).

    21. Allosterically Coupled Double Induced Fit for 1+1+1+1 Self-Assembly of a Calix[6]trisamine, a Calix[6]trisacid, and Their Guests (pages 3123–3126)

      Stéphane Le Gac, Jérôme Marrot, Olivia Reinaud and Ivan Jabin

      Version of Record online: 3 APR 2006 | DOI: 10.1002/anie.200503906

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      Special guests: A cooperative double induced-fit process leads to the 1+1+1+1 self-assembly of quaternary complexes comprising two complementary calix[6]arene-based hosts and their specific guests (see picture). The guests direct self-assembly by shaping their hosts. Such allosteric control involves multiple recognition levels reminiscent of those in biology.

    22. Rationally Designed Chemical Modulators Convert a Bacterial Channel Protein into a pH-Sensory Valve (pages 3126–3130)

      Armaǧan Koçer, Martin Walko, Erna Bulten, Erik Halza, Ben L. Feringa and Wim Meijberg

      Version of Record online: 4 APR 2006 | DOI: 10.1002/anie.200503403

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      Open channels: Chemical modulators are developed to convert a naturally occurring channel protein into a pH-actuated nanovalve. The pH interval, sensitivity, and activation of the valve by channel opening are tunable through the design of the modulators. The valve is useful for releasing or mixing the contents of liposomes at a desired location, time, and dosage, for example, in micro/nanosensory and delivery devices (see picture).

    23. Formation of a Methyleneimine Moiety by Reaction of a RuII-Coordinated Azide Ion with Methyl Iodide (pages 3131–3133)

      Hirotaka Nagao, Takehiro Kikuchi, Minako Inukai, Akihiro Ueda, Takao Oi, Noriyuki Suzuki and Mikio Yamasaki

      Version of Record online: 3 APR 2006 | DOI: 10.1002/anie.200504157

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      A rare methyleneimine complex of ruthenium(II), cis-[Ru(NH[DOUBLE BOND]CH2)(NCCH3)(bpy)2]2+ (see structure), was obtained from the reaction of cis-[Ru(N3)2(bpy)2]⋅H2O (bpy=2,2′-bipyridine) with CH3I in CH3CN at room temperature in the dark. The reaction of such azido complexes will be useful in the synthesis of nitrogen-containing ligands.

    24. Experimental Evidence from H/D Exchange Studies for the Failure of Direct C[BOND]C Coupling Mechanisms in the Methanol-to-Olefin Process Catalyzed by HSAPO-34 (pages 3133–3136)

      David M. Marcus, Kelly A. McLachlan, Mark A. Wildman, Justin O. Ehresmann, Philip W. Kletnieks and James F. Haw

      Version of Record online: 29 MAR 2006 | DOI: 10.1002/anie.200504372

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      Pool view preferred: In agreement with recent theoretical work, a new line of experimental evidence was obtained in support of the controversial claim that direct mechanisms do not couple methanol to ethylene in the catalyzed methanol-to-olefin process. The results preclude carbene routes and oxonium ylide mechanisms, among others (see picture), in favor of the hydrocarbon pool mechanism.

    25. Intracellular Inducible Alkylation System That Exhibits Antisense Effects with Greater Potency and Selectivity than the Natural Oligonucleotide (pages 3136–3140)

      Md. Monsur Ali, Motoi Oishi, Fumi Nagatsugi, Kenya Mori, Yukio Nagasaki, Kazunori Kataoka and Shigeki Sasaki

      Version of Record online: 30 MAR 2006 | DOI: 10.1002/anie.200504441

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      One mismatch is discriminated in a target mRNA sequence by an inducible alkylation system based on sulfide precursors to the nucleoside 2-amino-6-vinylpurine (see scheme). The reactive oligonucleotides were delivered into the cell as poly(ethylene glycol) (PEG) conjugates in polyion-complex (PIC) micelles and showed antisense activity of high selectivity and greater potency than that of the natural antisense oligonucleotide.

    26. Direct Intramolecular Arylation of Aldehydes Promoted by Reaction with IPy2BF4/HBF4: Synthesis of Benzocyclic Ketones (pages 3140–3143)

      José Barluenga, Mónica Trincado, Eduardo Rubio and José M. González

      Version of Record online: 30 MAR 2006 | DOI: 10.1002/anie.200504448

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      Iodine helps: Aldehydes acylate arenes upon treatment at low temperature with IPy2BF4 and HBF4. This reaction is exploited in a novel intramolecular approach to the preparation of benzocyclic ketones (see scheme). A plausible mechanistic rational is also given.

    27. TiO2-Based Light-Driven XOR/INH Logic Gates (pages 3143–3146)

      Luis F. O. Furtado, Anamaria D. P. Alexiou, Léia Gonçalves, Henrique E. Toma and Koiti Araki

      Version of Record online: 30 MAR 2006 | DOI: 10.1002/anie.200600076

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      Logical progression: Optoelectronic XOR and INH logic gates based on two light inputs and an electrical output were demonstrated using a nanocrystalline TiO2 dye-sensitized solar cell. The Grätzel-type cell was generated using a ruthenium complex as dye, with reverse injection of electrons at the semiconductor/dye interface (see picture).

    28. Trichloromethyl Ketones as Synthetically Versatile Donors: Application in Direct Catalytic Mannich-Type Reactions and the Stereoselective Synthesis of Azetidines (pages 3146–3150)

      Hiroyuki Morimoto, Sean H. Wiedemann, Akitake Yamaguchi, Shinji Harada, Zhihua Chen, Shigeki Matsunaga and Masakatsu Shibasaki

      Version of Record online: 5 APR 2006 | DOI: 10.1002/anie.200600227

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      Chemical transformers! Catalytic nucleophilic activation of trichloromethyl ketones allows applications in intermolecular carbon–carbon bond-forming reactions. Mannich adducts such as azetidines can be obtained from the primary products in high yield and syn selectivity. PG=protecting group.

    29. A Near-Infrared-Fluorescent Chemodosimeter for Mercuric Ion Based on an Expanded Porphyrin (pages 3150–3154)

      Xun-Jin Zhu, Shi-Tao Fu, Wai-Kwok Wong, Jian-Ping Guo and Wai-Yeung Wong

      Version of Record online: 3 APR 2006 | DOI: 10.1002/anie.200600248

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      Running rings around mercuric ions: A [26]hexaphyrin(, comprising an α,α′-bipyrrole unit and four pyrrolic and five pentafluorophenyl rings, was prepared and characterized by X-ray crystallography (see picture; N blue, F green, C black). The expanded porphyrin displays near-infrared luminescence above 900 nm and may serve as a highly sensitive and selective chemodosimeter for Hg2+ ions.

    30. Practical Synthesis of Amides from In Situ Generated Copper(I) Acetylides and Sulfonyl Azides (pages 3154–3157)

      Michael P. Cassidy, Jessica Raushel and Valery V. Fokin

      Version of Record online: 29 MAR 2006 | DOI: 10.1002/anie.200503805

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      A direct, simple, and efficient route from terminal alkynes to amides is achieved by their copper(I)-catalyzed reaction with sulfonyl azides (see scheme). The reaction proceeds with the in situ generation of copper(I) acetylides and represents a one-step formal oxidative hydration of a triple bond.

    31. Copper-Catalyzed Reaction Cascade: Direct Conversion of Alkynes into N-Sulfonylazetidin-2-imines (pages 3157–3161)

      Matthew Whiting and Valery V. Fokin

      Version of Record online: 29 MAR 2006 | DOI: 10.1002/anie.200503936

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      Selective conversion, take three: Densely functionalized azetidine derivatives are formed in an experimentally simple three-component catalytic procedure through the highly selective reaction of readily available terminal alkynes under mild conditions (see scheme). The azetidinimine products are remarkably stable to a wide range of reaction conditions and readily undergo further functionalization.

    32. Proteolytic Actuation of Nanoparticle Self-Assembly (pages 3161–3165)

      Todd J. Harris, Geoffrey von Maltzahn, Austin M. Derfus, Erkki Ruoslahti and Sangeeta N. Bhatia

      Version of Record online: 27 APR 2006 | DOI: 10.1002/anie.200600259

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      Sleeping giant: Inorganic nanoparticles are synthesized to exist in a latent form until proteolytic activation drives them to self-assemble into nanostructures with amplified magnetic properties. Binding of complimentary Fe3O4 nanoparticles is blocked by the attachment of inhibitory polymers that may be removed by proteases involved in cancer-cell invasion and metastasis.

    33. Light-Regulated Release of DNA and Its Delivery to Nuclei by Means of Photolabile Gold Nanoparticles (pages 3165–3169)

      Gang Han, Chang-Cheng You, Byoung-jin Kim, Rosemary S. Turingan, Neil S. Forbes, Craig T. Martin and Vincent M. Rotello

      Version of Record online: 30 MAR 2006 | DOI: 10.1002/anie.200600214

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      Light and life: A photolabile gold nanoparticle has been constructed to serve as a DNA carrier. UV irradiation causes the reversal of the nanoparticle surface charge, resulting in effective DNA release and reactivation of suppressed DNA transcription in vitro. This effect was also observed in living cells, together with efficient internalization of DNA into the nucleus.

    34. Intramolecular B–N Coordination as a Scaffold for Electron-Transporting Materials: Synthesis and Properties of Boryl-Substituted Thienylthiazoles (pages 3170–3173)

      Atsushi Wakamiya, Takuhiro Taniguchi and Shigehiro Yamaguchi

      Version of Record online: 29 MAR 2006 | DOI: 10.1002/anie.200504391

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      Stacking the deck: Incorporation of boryl groups into the thienylthiazole system fixes the π-conjugated framework in a planar fashion by intramolecular B–N coordination. The dimer of boryl-substituted thienylthiazole forms a unique packing structure with offset face-to-face π stacking (see picture; B orange, N blue, S yellow, C turquoise) and films of it show high electron mobility.

    35. Broadband Femtosecond Fluorescence Spectroscopy of [Ru(bpy)3]2+ (pages 3174–3176)

      Andrea Cannizzo, Frank van Mourik, Wojciech Gawelda, Goran Zgrablic, Christian Bressler and Majed Chergui

      Version of Record online: 4 APR 2006 | DOI: 10.1002/anie.200600125

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      It's sizzling! Femtosecond fluorescence-upconversion studies of aqueous [Ru(bpy)3]2+ show a short-lived vibrationally hot emission of the singlet metal-to-ligand charge-transfer state, with an ultrafast intersystem crossing (≈10 fs) to the triplet state at constant energy (the colors indicate the luminescence intensity).

    36. Precise Facial Control in Threading Guests into a Molecular Cage and the Formation of a Turtlelike Supramolecular Complex (pages 3176–3181)

      Chi-Feng Lin, Yi-Hung Liu, Chien-Chen Lai, Shie-Ming Peng and Sheng-Hsien Chiu

      Version of Record online: 29 MAR 2006 | DOI: 10.1002/anie.200600336

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      Caught in a cage: Two different thread components and a molecular cage generate different [2]pseudorotaxane-like complexes, which represent a new type of molecular machinery. An unprecedented type of molecular motion is generated by the addition of K+ ions and [2,2,2]cryptand units to this mixture and their removal from it, in which the rodlike components penetrate the molecular cage alternately through its different faces.

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