bluuebunny/crossref_metadata_2025 huggingface dataset:
Aberrant Gating of Photic Input to the Suprachiasmatic Circadian Pacemaker of Mice Lacking the VPAC2Receptor
Authors: Hughes Alun T. , Fahey Briana , Cutler David J. , Coogan Andrew N. , Piggins Hugh D.
Published: April 2004

VIP acting via the VPAC2receptor is implicated as a key signaling pathway in the maintenance and resetting of the hypothalamic suprachiasmatic nuclei (SCN) circadian pacemaker; circadian rhythms in SCN clock gene expression and wheel-running behavior are abolished in mice lacking the VPAC2receptor (Vipr2–/–). Here, using immunohistochemical detection of pERK (phosphorylated extracellular signal-regulated kinases 1/2) and c-FOS, we tested whether the gating of photic input to the SCN is maintained in these apparently arrhythmicVipr2–/–mice. Under light/dark and constant darkness, spontaneous expression of pERK and c-FOS in the wild-type mouse SCN was significantly elevated during subjective day compared with subjective night; no diurnal or circadian variation in pERK or c-FOS was detected in the SCN ofVipr2–/–mice. In constant darkness, light pulses given during the subjective night but not the subjective day significantly increased expression of pERK and c-FOS in the wild-type SCN. In contrast, light pulses given during both subjective day and subjective night robustly increased expression of pERK and c-FOS in theVipr2–/–mouse SCN. Although photic stimuli activate intracellular pathways within the SCN ofVipr2–/–mice, they do not engage the core clock mechanisms. The absence of photic gating, together with the general lack of overt rhythms in circadian output, strongly suggests that the SCN circadian pacemaker is completely dysfunctional in theVipr2–/–mouse.
Reduction of Single-Neuron Firing Uncertainty by Cortical Ensembles during Motor Skill Learning
Authors: Cohen Dana , Nicolelis Miguel A. L.
Published: April 2004

Motor skill learning is usually characterized by shortening of response time and performance of faster, more stereotypical movements. However, little is known about the changes in neural activity that underlie these behavioral changes. Here we used chronically implanted electrode arrays to record neuronal activity in the rat primary motor cortex (MI) as animals learned to execute movements in two directions. Strong modulation of MI single-neuron activity was observed while movement duration of the animal decreased. Despite many learning-induced changes, the precision with which single neurons fire did not improve with learning. Hence, prediction of movement direction from single neurons was bounded. In contrast, prediction of movement direction using neuronal ensembles improved significantly with learning, suggesting that, with practice, neuronal ensembles learn to overcome the uncertainty introduced by single-neuron stochastic activity.
Hypocretin/Orexin Innervation and Excitation of Identified Septohippocampal Cholinergic Neurons
Authors: Wu Min , Zaborszky Laszlo , Hajszan Tibor , van den Pol Anthony N. , Alreja Meenakshi
Published: April 2004

Hypothalamic fibers containing the wake-promoting peptides, hypocretins (Hcrts) or orexins, provide a dense innervation to the medial septum–diagonal band of Broca (MSDB), a sleep-associated brain region that has been suggested to show intense axonal degeneration in canine narcoleptics. The MSDB, via its cholinergic and GABAergic projections to the hippocampus, controls the hippocampal theta rhythm and associated learning and memory functions. Neurons of the MSDB express very high levels of the Hcrt receptor 2, which is mutated in canine narcoleptics. In the present study, we investigated the electrophysiological effects of Hcrt peptides on septohippocampal cholinergic neurons that were identified in living brain slices of the MSDB using a selective fluorescent marker. Hcrt activation of septohippocampal cholinergic neurons was reversible, reproducible, and concentration dependent and mediated via a direct postsynaptic mechanism. Both Hcrt1 and Hcrt2 activated septohippocampal cholinergic neurons with similar EC50values. The Hcrt effect was dependent on external Na+, reduced by external Ba2+, and also reduced in recordings with CsCl-containing electrodes, suggesting a dual underlying ionic mechanism that involved inhibition of a K+current, presumably an inward rectifier, and a Na+-dependent component. The Na+component was dependent on internal Ca2+, blocked by replacing external Na+with Li+, and also blocked by bath-applied Ni2+and KB-R7943, suggesting involvement of the Na+–Ca2+exchanger. Using double-immunolabeling studies at light and ultrastructural levels, we also provide definitive evidence for a hypocretin innervation of cholinergic neurons. Thus Hcrt effects within the septum should increase hippocampal acetylcholine release and thereby promote hippocampal arousal.
Ca2+Ion Permeability and Single-Channel Properties of the Metabotropic Slow EPSC of Rat Purkinje Neurons
Authors: Canepari Marco , Auger Céline , Ogden David
Published: April 2004

The slow EPSC (sEPSC) of cerebellar parallel fiber → Purkinje neuron synapses is mediated by metabotropic glutamate receptor type 1 (mGluR1) activation of nonselective cation channels. Here, the channel properties were studied with uniform calibrated photorelease ofl-glutamate with ionotropic receptors blocked, allowing isolation of postsynaptic processes, or with parallel fiber stimulation or mGluR1 agonist application. Evoked current and fluorescence from Ca2+indicators were recorded. Noise analysis of the mGluR1 current gave a single-channel conductance of 0.6 pS and showed low open probability at maximal mGluR1 activation. Similar small single-channel conductances were obtained with the mGluR1 agonist (S)-dihydroxyphenylglycine, with parallel fiber or climbing fiber stimulation. The mGluR1 current fluctuations were unaffected by potassium channel blockers. Photoreleasedl-glutamate triggered a Ca2+concentration increase in the distal dendrites with a time course similar to that of the mGluR1 current. The proximal dendritic and somatic Ca2+changes were delayed with respect to the current. Ca2+channel blockers and the phospholipase Cδ inhibitor 1-[6-[((17δ)-3-methoxyestra-1,3,5[10]-trien-17-yl)amino]hexyl]-1H-pyrrole-2,5-dione, which inhibits mGluR1-activated intracellular Ca2+release, did not prevent the dendritic Ca2+concentration increase. Polyamine naphthylacetyl spermine and cationic adamantanes that block the pore of the channel were used to vary the mGluR1 current over a wide range in each cell but still at maximal mGluR1 activation. The Ca2+influx was inhibited in parallel with the current. The results show that the mGluR1-activated current and the sEPSC are attributable to small-conductance, low-open probability Ca2+-permeable cation channels that will mediate spine-specific Ca2+influx during the parallel fiber sEPSP.
The Derivation of Direction Selectivity in the Striate Cortex
Authors: Peterson Matthew R. , Li Baowang , Freeman Ralph D.
Published: April 2004

In the central visual pathway of binocular animals, the property of directional selectivity (DS) is first exhibited in striate cortex. In this study, we sought to determine the neural circuitry underlying the transformation from non-DS neurons to DS cortical cells. In a well established model, DS receptive fields (RFs) are derived from the sum of two non-DS inputs with 90° (quadrature) spatiotemporal phase differences. We explored possible input sources for this model, which include non-DS simple cells and lateral geniculate nucleus (LGN) neurons, by examination of spatiotemporal RFs of single cells and of pairs of cells. We find that distributions of non-DS simple RFs do not match the temporal predictions of the quadrature model because of a lack of long-latency responses. The long-latency inputs could potentially arise from lagged LGN afferents. However, analysis of cell pairs indicates that DS cells receive cortical input from non-DS simple cells for both short- and long-latency components, with temporal phase differences typically <90°. Furthermore, the distribution of minimum phase differences needed to generate DS cells overlaps that exhibited by non-DS simple cells. Considered together, these results are consistent with a linear model whereby DS simple cells are formed from simple-cell inputs, with temporal phase differences often less than quadrature.
Bidirectional Interactions between H-Channels and Na+–K+Pumps in Mesencephalic Trigeminal Neurons
Authors: Kang Youngnam , Notomi Takuya , Saito Mitsuru , Zhang Wei , Shigemoto Ryuichi
Published: April 2004

The Na+–K+pump current (Ip) and the h-current (Ih) flowing through hyperpolarization-activated channels (h-channels) participate in generating the resting potential. These two currents are thought to be produced independently. We show here bidirectional interactions between Na+–K+pumps and h-channels in mesencephalic trigeminal neurons. Activation ofIhleads to the generation of two types of ouabain-sensitiveIpwith temporal profiles similar to those of instantaneous and slow components ofIh, presumably reflecting Na+transients in a restricted cellular space. Moreover, theIpactivated by instantaneousIhcan facilitate the subsequent activation of slowIh. Such counteractive and cooperative interactions were also disclosed by replacing extracellular Na+with Li+, which is permeant through h-channels but does not stimulate the Na+–K+pump as strongly as Na+ions. These observations indicate that the interactions are bidirectional and mediated by Na+ions. Also after substitution of extracellular Na+with Li+, the tailIhwas reduced markedly despite an enhancement ofIhitself, attributable to a negative shift of the reversal potential forIhpresumably caused by intracellular accumulation of Li+ions. This suggests the presence of a microdomain where the interactions can take place. Thus, the bidirectional interactions between Na+–K+pumps and h-channels are likely to be mediated by Na+microdomain. Consistent with these findings, hyperpolarization-activated and cyclic nucleotide-modulated subunits (HCN1/2) and the Na+–K+pumpα3 isoform were colocalized in plasma membrane of mesencephalic trigeminal neurons having numerous spines.
Simulation of helical flows in microchannels
Authors: Schönfeld Friedhelm , Hardt Steffen
Published: April 2004

Helical flows are investigated in structured microchannels with regard to micromixing by means of computational fluid dynamics (CFD). In the case of bas‐relief structured channels the numerical results are found to be in good agreement with experimental findings. The magnitude of the transverse flow is computed for various Reynolds numbers and for different geometries including channels with bas‐relief structures on two opposite walls. Transverse flows in structured microchannels are compared to secondary flow patterns in curved square channels. The corresponding helical flows are analyzed for Dean numbers ranging from 1 to 900. Special attention is paid to the occurrence of additional vortices close to the center of the outer channel wall. Based on the results a new type of micromixer is proposed that relies on the transition of the secondary flow pattern from two to four vortices. © 2004 American Institute of Chemical Engineers AIChE J, 50: 771–778, 2004
Melt grafting of n‐butyl methacrylate onto poly(vinyl chloride): Synthesis and characterization*
Authors: Maiti Ajit K. , Choudhary Manjeet S.
Published: April 2004

The graft copolymerization of n‐butyl methacrylate monomer onto compounded poly(vinyl chloride) was carried out by melt‐mixing process in a Brabender plasticorder (BPCR) using a free‐radical initiator. The reaction conditions such as initiator and monomer concentration, shear rate (rpm), residence time, and temperature were optimized in the mixing head of BPCR attached to a torque rheometer. The graft copolymers were Soxhlet extracted with cyclohexane and were characterized by intrinsic viscosity, FTIR, and 13C‐NMR spectroscopy. A maximum of 14% grafting was obtained. The graft copolymer showed significant improvement in processibility and both thermal and mechanical properties. Scale‐up studies of the optimized recipe were carried out in a single‐screw extruder for commercial trials/evaluation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2442–2449, 2004
Morphology and thermodynamic analysis of composite polymer particles prepared by soap‐free emulsion polymerization in the presence of poly(methyl methacrylate) and polystyrene as biseeds
Authors: Pang Xingshou , Cheng Guoxiang , Lu Shulai
Published: April 2004

Biseeds emulsion polymerization was investigated with poly(methyl methacrylate) (PMMA) and polystyrene (PSt) as biseeds and styrene (St) as second‐stage monomer, as well as with thermodynamic analysis; namely, the principle of minimum interfacial free‐energy change was utilized to explain the competitiveness of different seeds for second‐stage monomer and the final equilibrium morphology of composite polymer particles. The experimental results indicated the polymeric particles prepared had bimodal size distribution and the PMMA seed particles showed a higher chance of obtaining St than that of the PSt seed particles, which was in agreement with the computational outcome by the principle of minimum interfacial free‐energy change. Owing to the kinetic factors, the equilibrium morphology could not be reached in the experiments. However, the results demonstrated that double or multiple seeds emulsion polymerization could be used as a model experiment to study the morphology of polymer particle and the morphological prediction. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2675–2680, 2004
The central region of NGC 3077: ground‐based photometry and age of bright ‘starlike’ objects
Authors: Notni P. , Karachentsev I.D. , Makarova L.N.
Published: April 2004

We present UBVIC photometry of starlike objects in the central region of NGC 3077. The colour‐colour and colour‐magnitude diagrams of the objects are discussed. Many of the objects under consideration, starlike from the ground, are probably dense young star clusters (super star clusters, SSC). Ages spreading over ∼4 to ∼150 Myr are estimated for most of these objects. Sakai and Madore (2001) found enhanced star formation ∼30–125 Myr ago also in the halo of this galaxy; thus, high star forming activity has occurred within the entire galaxy (centre and halo) since ∼130…150 Myr. Having ended in the outer regions about 30 Myr ago, it is going on near the centre with full vigour. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ferricytochrome c encapsulated in silica nanoparticles: Structural stability and functional properties
Authors: Fiandaca Gianluca , Vitrano Eugenio , Cupane Antonio
Published: April 2004

Using a modified sol–gel technique, we have succeeded in encapsulating ferric cytochrome c in silica nanoparticles obtained from hydrolysis and polycondensation of tetramethylorthosilicate. Particles dimensions have been determined with dynamic light scattering; this technique yields an hydrodynamic radius of about 100 nm, each nanoparticle containing about 102–103 proteins. If stored in the cold at low ionic strength, nanoparticles are stable for more than one week, even if a slow radius increase with time is observed. CD measurements show that encapsulated proteins exhibit substantially increased stability against guanidinium hydrochloride induced denaturation. Reduction kinetics of encapsulated ferric cytochrome c by sodium dithionite, measured with standard stopped flow techniques, are slower by a factor of ten with respect to those measured in solution. Analogous experiments with myoglobin suggest that this slowing down is due to the diffusion time of dithionite within the silica matrix. Indeed, if a smaller ligand like CO is used, the intrinsic kinetic properties of encapsulated proteins are found to be unaltered even in the millisecond time range. The reported data show that our nanoparticles are extremely useful both for basic research, to study the stability and functions of encapsulated proteins, and for their potential biotechnological applications. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004
Fourier transform infrared spectroscopic study on the conformational reorganization in Escherichia coli complex I due to redox‐driven proton translocation
Authors: Hellwig Petra , Stolpe Stefan , Friedrich Thorsten
Published: April 2004

The proton‐pumping NADH:ubiquinone oxidoreductase (complex I) couples the transfer of electrons from NADH to ubiquinone with the translocation of protons across the membrane. Electron transfer is accomplished by flavin mononucleotide (FMN) and a series of iron–sulfur (Fe/S) clusters. A novel mechanism has been proposed wherein the electron transfer reaction induces conformational changes that subsequently lead to the translocation of protons. Redox‐induced Fourier transform infrared difference spectra have been obtained, showing strong conformational changes in the amide I region. The amplitude of the signal is pH dependent, as expected for an energy coupling step in the enzymes reaction. Furthermore, pH‐dependent protonation events and quinone binding were detected. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004
Resonance Raman spectroscopy of xanthophylls in pigment mutant thylakoid membranes of pea
Authors: Andreeva Atanaska , Stoitchkova Katerina , Busheva Mira , Apostolova Emilia , Várkonyi Zsuzsanna , Garab Gyözö
Published: April 2004

Low‐temperature resonance Raman spectroscopy was used to study the changes in the molecular structure and configuration of the major xanthophylls in thylakoid membranes isolated from mutants of pea with modified pigment content and altered structural organization of their pigment–protein complexes. The Raman spectra contained four known groups of bands, ν1–ν4, which could be assigned to originate mainly from the long wavelength absorbing lutein and neoxanthin upon 514.5 nm and at 488 nm excitations, respectively. The overall configuration of these bound xanthophyll molecules in the mutants appeared to be similar to the wild type, and the configuration in the wild type was almost identical with that in the isolated main chlorophyll a/b light harvesting protein complex of photosystem II (LHCII). Significant differences were found mainly in the region of ν4 (around 960 cm−1), which suggest that the macroorganization of PS II–LHCII supercomplexes and/or of the LHCII‐only domains are modified in the mutants compared to the wild type. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004
Delayed fluorescence from the photosynthetic reaction center measured by electronic gating of the photomultiplier
Authors: Filus Z. , Laczkó G. , Wraight C. A. , Maróti P.
Published: April 2004

The decay of the delayed fluorescence (920 nm) of reaction centers from the photosynthetic bacterium Rhodobacter sphaeroides R26 in the P+QA‐ charge‐separated state (P and QA are the primary donor and quinone, respectively) has been monitored in a wide (100 ns to 100 ms) time range. The photomultiplier (Hamamatsu R3310–03) was protected from the intense prompt fluorescence by application of gating potential pulses (‐280 V) to the first, third, and fifth dynodes during the laser pulse. The gain of the photomultiplier dropped transiently by a factor of 1 × 106. The delayed fluorescence showed a smooth but nonexponential decay from 100 ns to 1 ms that was explained by the relaxation of the average free energy between P* and P+QA‐ changing from ‐580 to ‐910 meV. This relaxation is due to the slow protein response to charge separation and can be described by a Kohlrausch relaxation function with time constant of 65 μs and a stretching exponent of α = 0.45. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004
In situ Raman investigation of single lipid droplets in the water‐conducting xylem of four woody plant species
Authors: Rösch P. , Schneider H. , Zimmermann U. , Kiefer W. , Popp J.
Published: April 2004

A micro‐Raman spectroscopy approach was used for the direct in situ characterization of lipid bodies in the water‐conducting branch xylem of an African resurrection plant and three deciduous European tree species. Because of average diameters of at least 1 μm, the lipid bodies of all investigated species proved to be easily accessible by this technique. All vesicle‐forming xylem lipids were identified as fatty acid esters, which may correspond to phospholipids. Whereas in the resurrection plant saturated lipids were dominant, the lipid bodies of the European trees consisted of highly unsaturated fatty acids. A comparison of the spectra of lipid droplets of lime obtained in situ and from isloated xylem sap revealed slightly different signatures. This finding suggests that micro‐Raman spectroscopy may be used to detect modifications of the chemical composition of biological substances as a result of the extraction mode. © 2004 Wiley Periodicals, Inc. Biopolymers 74: 00–000, 2004
Effects of hydraulic retention time and sulfide toxicity on ethanol and acetate oxidation in sulfate‐reducing metal‐precipitating fluidized‐bed reactor
Authors: Kaksonen Anna H. , Franzmann Peter D. , Puhakka Jaakko A.
Published: April 2004

The effects of hydraulic retention time (HRT) and sulfide toxicity on ethanol and acetate utilization were studied in a sulfate‐reducing fluidized‐bed reactor (FBR) treating acidic metal‐containing wastewater. The effects of HRT were determined with continuous flow FBR experiments. The percentage of ethanol oxidation was 99.9% even at a HRT of 6.5 h (loading of 2.6 g ethanol L−1 d−1), while acetate accumulated in the FBR with HRTs below 12 h (loading of 1.4 g ethanol L−1 d−1). Partial acetate utilization was accompanied by decreased concentrations of dissolved sulfide (DS) and alkalinity in the effluent, and eventually resulted in process failure when HRT was decreased to 6.1 h (loading of 2.7 g ethanol L−1 d−1). Zinc and iron precipitation rates increased to over 600 mg L−1 d−1 and 300 mg L−1 d−1, respectively, with decreasing HRT. At HRT of 6.5 h, percent metal precipitation was over 99.9%, and effluent metal concentrations remained below 0.08 mg L−1. Under these conditions, the alkalinity produced by substrate utilization increased the wastewater pH from 3 to 7.9–8.0. The percentage of electron flow from ethanol to sulfate reduction averaged 76 ± 10% and was not affected by the HRT. The lowest HRT did not result in significant biomass washout from the FBR. The effect of sulfide toxicity on the sulfate‐reducing culture was studied with batch kinetic experiments in the FBR. Noncompetitive inhibition model described well the sulfide inhibition of the sulfate‐reducing culture. (DS) inhibition constants (Ki) for ethanol and acetate oxidation were 248 mg S L−1 and 356 mg S L−1, respectively, and the corresponding Ki values for H2S were 84 mg S L−1 and 124 mg S L−1. In conclusion, ethanol oxidation was more inhibited by sulfide toxicity than the acetate oxidation. © 2004 Wiley Periodicals, Inc.
Solanaceae — a model for linking genomics with biodiversity
Authors: Knapp Sandra , Bohs Lynn , Nee Michael , Spooner David M.
Published: April 2004

Recent progress in understanding the phylogeny of the economically important plant family Solanaceae makes this an ideal time to develop models for linking the new data on plant genomics with the huge diversity of naturally occurring species in the family. Phylogenetics provides the framework with which to investigate these linkages but, critically, good species‐level descriptive resources for the Solanaceae community are currently missing. Phylogeny in the family as a whole is briefly reviewed, and the new NSF Planetary Biodiversity Inventories project ‘PBI: Solanum—a worldwide treatment’ is described. The aims of this project are to provide species‐level information across the global scope of the genus Solanum and to make this available over the Internet. The project is in its infancy, but will make available nomenclatural information, descriptions, keys and illustrative material for all of the approximately 1500 species of Solanum. With this project, the opportunity of linking valid, up‐to‐date taxonomic information about wild species of Solanum with the genomic information being generated about the economically important species of the genus (potato, tomato and eggplant) can be realized. The phylogenetic framework in which the PBI project is set is also of enormous potential benefit to other workers on Solanum. The community of biologists working with Solanaceae has a unique opportunity to effectively link genomics and taxonomy for better understanding of this important family, taking plant biology to a new level for the next century. Copyright © 2004 John Wiley & Sons, Ltd.
On the tetraploid origin of the maize genome
Authors: Swigonova Zuzana , Lai Jinsheng , Ma Jianxin , Ramakrishna Wusirika , Llaca Victor , Bennetzen Jeffrey L. , Messing Joachim
Published: April 2004

Data from cytological and genetic mapping studies suggest that maize arose as a tetraploid. Two previous studies investigating the most likely mode of maize origin arrived at different conclusions. Gaut and Doebley proposed a segmental allotetraploid origin of the maize genome and estimated that the two maize progenitors diverged at 20.5 million years ago (mya). In a similar study, using larger data set, Brendel and colleagues (quoted in) suggested a single genome duplication at 16 mya. One of the key components of such analyses is to examine sequence divergence among strictly orthologous genes. In order to identify such genes, Lai and colleagues sequenced five duplicated chromosomal regions from the maize genome and the orthologous counterparts from the sorghum genome. They also identified the orthologous regions in rice. Using positional information of genetic components, they identified 11 orthologous genes across the two duplicated regions of maize, and the sorghum and rice regions. Swigonova et al. analyzed the 11 orthologues, and showed that all five maize chromosomal regions duplicated at the same time, supporting a tetraploid origin of maize, and that the two maize progenitors diverged from each other at about the same time as each of them diverged from sorghum, about 11.9 mya. Copyright © 2004 John Wiley & Sons, Ltd.
MAGIC Database and interfaces: an integrated package for gene discovery and expression
Authors: Cordonnier‐Pratt Marie‐Michèle , Liang Chun , Wang Haiming , Kolychev Dmitri S. , Sun Feng , Freeman Robert , Sullivan Robert , Pratt Lee H.
Published: April 2004

The rapidly increasing rate at which biological data is being produced requires a corresponding growth in relational databases and associated tools that can help laboratories contend with that data. With this need in mind, we describe here a Modular Approach to a Genomic, Integrated and Comprehensive (MAGIC) Database. This Oracle 9i database derives from an initial focus in our laboratory on gene discovery via production and analysis of expressed sequence tags (ESTs), and subsequently on gene expression as assessed by both EST clustering and microarrays. The MAGIC Gene Discovery portion of the database focuses on information derived from DNA sequences and on its biological relevance. In addition to MAGIC SEQ‐LIMS, which is designed to support activities in the laboratory, it contains several additional subschemas. The latter include MAGIC Admin for database administration, MAGIC Sequence for sequence processing as well as sequence and clone attributes, MAGIC Cluster for the results of EST clustering, MAGIC Polymorphism in support of microsatellite and single‐nucleotide‐polymorphism discovery, and MAGIC Annotation for electronic annotation by BLAST and BLAT. The MAGIC Microarray portion is a MIAME‐compliant database with two components at present. These are MAGIC Array‐LIMS, which makes possible remote entry of all information into the database, and MAGIC Array Analysis, which provides data mining and visualization. Because all aspects of interaction with the MAGIC Database are via a web browser, it is ideally suited not only for individual research laboratories but also for core facilities that serve clients at any distance. Copyright © 2004 John Wiley & Sons, Ltd.
Photosensitized Degradation of Dyes in Polyoxometalate Solutions Versus TiO2 Dispersions under Visible‐Light Irradiation: Mechanistic Implications
Authors: Chen Chuncheng , Zhao Wei , Lei Pengxiang , Zhao Jincai , Serpone Nick
Published: April 2004

This article examines the photoxidation of a dye (rhodamine‐B, RhB) by visible‐light irradiation in the presence of a polyoxometalate (12‐tungstosilicic acid, H4SiW12O40), and compares it with the analogous process in the presence of TiO2. The photoreaction processes were examined by UV‐visible spectroscopy, fluorescence spectroscopy, high‐performance liquid chromatography (HPLC), liquid chromatography/mass spectral techniques (LC‐MS), and total organic carbon (TOC) assays in order to identify the intermediates produced. Formation of oxygen species, such as H2O2 and O2.−, was also investigated to clarify the details of the reaction pathway. With the use of SiW12O404− ions as the photocatalyst, the photoreaction leads mainly to N‐dealkylation of the chromophore skeleton. In contrast, cleavage of the whole conjugated chromophore structure predominates in the presence of TiO2. Strong O2.−/HO2.− ESR signals were detected in the TiO2 dispersions, whereas only weak ESR signals for the O2.− radical ion were seen in the SiW12O404− solutions during the irradiation period. Experimental results imply that reduction of O2 occurs by different pathways in the two photocatalytic systems.
Towards Surface‐Supported Supramolecular Architectures: Tailored Coordination Assembly of 1,4‐Benzenedicarboxylate and Fe on Cu(100)
Authors: Lingenfelder Magalí A. , Spillmann Hannes , Dmitriev Alexandre , Stepanow Sebastian , Lin Nian , Barth Johannes V. , Kern Klaus
Published: April 2004

We present a comprehensive investigation of the modular assembly of surface‐supported metal–organic coordination systems with specific topologies and high structural stability formed by vapor deposition of 1,4‐benzenedicarboxylic acid molecules and iron atoms on a Cu(100) surface under ultra‐high vacuum conditions. By making use of the two carboxylate moieties available for lateral linkage to Fe atoms, we succeeded in the fabrication of distinct Fe–carboxylate coordination architectures at the surface by carefully adjusting the ligand and metal concentration ratio and the temperature of the post‐deposition annealing treatment. The mononuclear, 1D‐polymeric and fully 2D‐reticulated metallosupramolecular arrangements obtained were characterized in situ at the single‐molecule level by scanning tunneling microscopy.
Synthesis, Nuclear, and Magnetic Structures and Magnetic Properties of [Mn3(OH)2(SO4)2(H2O)2]
Authors: Ben Salah Mohsen , Vilminot Serge , André Gilles , Richard‐Plouet Mireille , Bourée‐Vigneron Françoise , Mhiri Tahar , Kurmoo Mohamedally
Published: April 2004

[Mn3(OH)2(SO4)2(H2O)2] and its deuterated anlaogue were synthesized by a hydrothermal technique and characterized by differential thermal analysis, thermogravimetric analysis, and IR spectroscopy. Its nuclear structure, determined by single‐crystal X‐ray analysis and Rietveld analysis of neutron powder‐diffraction data, consists of a 3D network of chains of edge‐sharing Mn(1)O6, running along the c axis, connected by the apices of Mn(2)O6 and SO4 units. It is isostructural to the nickel analogue. Determination of the magnetic structure and measurements of magnetization and heat capacity indicate the coexistence of both magnetic long‐range ordering (LRO) and short‐range ordering (SRO) below a Néel temperature of 26 K, while the SRO is retained at higher temperatures. The moments of the two independent Mn atoms lie in the bc plane, and that of Mn(1) rotates continuously by 54° towards the c axis on decreasing the temperature from 25 to 1.4 K. While the SRO may be associated with frustration of the moments within a Mn3 trimer, the LRO is achieved by antiparallel alignment of the four symmetry‐related trimers within the magnetic unit cell. A spin‐flop field, measured by dc and ac magnetization on a SQUID, is observed at 15 kOe.
The Direct Catalytic Asymmetric Cross‐Mannich Reaction: A Highly Enantioselective Route to 3‐Amino Alcohols and α‐Amino Acid Derivatives
Authors: Córdova Armando
Published: April 2004

The first proline‐catalyzed direct catalytic asymmetric one‐pot, three‐component cross‐Mannich reaction has been developed. The highly chemoselective reactions between two different unmodified aldehydes and one aromatic amine are new routes to 3‐amino aldehydes with dr>19:1 and up to >99 % ee. The asymmetric cross‐Mannich reactions are highly syn‐selective and in several cases the two new carbon centers are formed with absolute stereocontrol. The reaction does not display nonlinear effects and therefore only one proline molecule is involved in the transition state. The reaction was also catalyzed with good selectivity by other proline derivatives. The Mannich products were converted into 3‐amino alcohols and 2‐aminobutane‐1,4‐diols with up to >99 % ee. The first one‐pot, three‐component, direct catalytic asymmetric cross‐Mannich reactions between unmodified aldehydes, p‐anisidine, and ethyl glyoxylate have been developed. The novel cross‐Mannich reaction furnishes either enantiomer of unnatural α‐amino acid derivatives in high yield and up to >99 % ee. The one‐pot, three‐component, direct catalytic asymmetric reactions were readily scaled up, operationally simple, and conductible in environmentally benign and wet solvents. The mechanism and stereochemistry of the proline‐catalyzed, one‐pot, three‐component, asymmetric cross‐Mannich reaction are also discussed.
Structural Motifs in Secondary Ammonium Halides: Ring‐Stacking and Ring‐Laddering in the Organic Solid State
Authors: Bond Andrew D.
Published: April 2004

The ring‐stacking and ring‐laddering concepts of structural inorganic chemistry may be applied to rationalize motifs observed for secondary ammonium halides R2NH2X (X = Cl, Br) in the organic solid state. General examination of the directional preferences of N+⋅⋅⋅X− contacts in 166 crystal structures confirms that the shortest contacts (3.0–3.2 and 3.2–3.4 Å, X = Cl, Br) are N+H⋅⋅⋅X− hydrogen bonds lying approximately along the directions of the N+H bond vectors. The next shortest N+⋅⋅⋅X− contacts display two preferred directions of approach: i) contacts in the distance range 3.2–3.5 (X = Cl) and 3.2–3.9 Å (X = Br) lie close to the HN+H plane, along the direction of the bisector of the HN+H angle; ii) contacts in the distance range 4.0–4.2 (X = Cl) and 4.0–4.4 Å (X = Br) lie close to the HN+H plane, along the direction of an axis extending to the rear of one of the N+H bonds. Both directions of approach lead frequently to association of R2NH2+X− ion pairs into laddered motifs. Stacking association is also observed, giving rise in one case to discrete cubanes and in several other cases to extended stacked‐cube arrangements. In each case, the distribution of N+⋅⋅⋅X− contacts reflects a balance between the directional properties of the N+H⋅⋅⋅X− hydrogen bonds and (primarily steric) interactions between the R groups of the organic moieties. The ladder and stack motifs of the organic ammonium halides are in many cases directly comparable to those in alkali metal amides, [R2NM]n, and information derived from the extensive organic sample provides insight into the motifs adopted by the inorganic complexes.
A Neutral Organometallic Fluoro Complex Can Be a Good Ligand
Authors: Coue Laurent , Cuesta Luciano , Morales Dolores , Halfen Jason A. , Pérez Julio , Riera Lucía , Riera Víctor , Miguel Daniel , Connelly Neil G. , Boonyuen Supakorn
Published: April 2004

The reaction of the complex [Mo(OTf)(η3‐C3H4‐Me‐2)(CO)2(phen)] (1) (OTf = trifluoromethylsulfonate; phen = 1,10‐phenanthroline) with tetrabutylammonium fluoride trihydrate afforded the fluoride complex [MoF(η3‐C3H4‐Me‐2)(CO)2(phen)] (2). The IR spectrum and the oxidation potential of 2 reflect the fact that its metal center is more electron‐rich than that of the chloro analogue [MoCl(η3‐C3H4‐Me‐2)(CO)2(phen)]. Compound 2 reacted with 1 affording the homobinuclear complex [{Mo(η3‐C3H4‐Me‐2)(CO)2(phen)}2(μ‐F)][OTf] (3), with a fluoride bridge. Compound 2 also reacts with the species generated in situ by triflate abstraction from [M(OTf)(CO)3(′NN′)] (M = Mn, Re; ′NN′ = 2,2′‐bipyridine (bipy), phen) using NaBAr′4 (Ar′ = 3,5‐bis(trifluoromethyl)phenyl), affording the heterobinuclear complexes [{Mo(η3‐C3H4‐Me‐2)(CO)2(phen)}(μ‐F){M(CO)3(′NN′)}][BAr′4] (M = Mn, ′NN′ = bipy (4); M = Re, ′NN′ = phen (5)). All new compounds have been characterized by spectroscopic methods (IR and NMR) and, in the case of 1, 2, 3, and 4, also by means of X‐ray diffraction analysis.
Stable Optically Pure Phosphino(silyl)carbenes: Reagents for Highly Enantioselective Cyclopropanation Reactions
Authors: Krysiak Jerzy , Lyon Céline , Baceiredo Antoine , Gornitzka Heinz , Mikolajczyk Marian , Bertrand Guy
Published: April 2004

The stability of phosphino(trimethylsilyl)carbenes bearing cyclic diamino substituents on phosphorus is strongly dependent on the steric hindrance of the nitrogen substituents. Phosphinocarbenes 3 and 7, derived from the trans‐N,N′‐diisopropylcyclohexane‐1,2‐diamine and N,N′‐diisopropyl‐1,2‐ethanediamine, are not observed; instead the 1,3‐diphosphete 4 and a novel six‐membered heterocycle 8, which results from the dimerization of 3 and the reaction of 7 with its diazo precursor 6, respectively, have been isolated. In contrast, the phosphino(silyl)carbene 14 derived from N,N′‐di‐tert‐butyl‐1,2‐ethanediamine has been isolated in high yield. By using the enantiomerically pure (S,S)‐, and (R,R)‐N,N′‐di‐tert‐butyl‐1,2‐diphenyl‐1,2‐ethanediamines, the first optically pure phosphino(sily)carbenes (S,S)‐17 and (R,R)‐17 have been prepared. They react with methyl acrylate to give the corresponding cyclopropanes (S,S,R,R)‐19 and (R,R,S,S)‐19 with a total syn diastereoselectivity and an excellent enantioselectivity (de>98 %).
Factors Relevant for the Ruthenium–Benzylidene‐Catalyzed Cyclopolymerization of 1,6‐Heptadyines
Authors: Krause Jens O. , Nuyken Oskar , Buchmeiser Michael R.
Published: April 2004

Fourteen metathesis initiators that had been designed for use in the living polymerization of diethyl dipropargylmalonate (DEDPM), including the Hoveyda catalyst [RuCl2(IMesH2)(CH‐2‐(2‐PrO)C6H4)] (1 a), as well as [Ru(CF3COO)2(IMesH2)(CH‐2‐(2‐PrO)C6H4)] (1 b), [Ru(CF3CF2COO)2(IMesH2)(CH‐2‐(2‐PrO)C6H4)] (1 c), [Ru(CF3CF2CF2COO)2(IMesH2)(CH‐2‐(2‐PrO)C6H4)] (1 d), [RuCl2(IMesH2)(CH‐2,4,5‐(MeO)3C6H2)] (2 a), [Ru(CF3COO)2(IMesH2)(CH‐2,4,5‐(MeO)3C6H2)] (2 b), [Ru(CF3CF2COO)2(IMesH2)(CH‐ 2,4,5‐(MeO)3C6H2)] (2 c), [Ru(CF3CF2CF2COO)2(IMesH2)(CH‐2,4,5‐(MeO)3 C6H2)] (2 d), [RuCl2(IMes)(CH‐2‐(2‐PrO)C6H4)] (3 a), [Ru(CF3COO)2(IMes)(CH‐2‐(2‐PrO)C6H4)] (3 b), [RuCl2(IMesH2)(CH‐2‐(2‐PrO)‐5‐NO2C6H3)] (4 a), [Ru(CF3COO)2(IMesH2)(CH‐2‐(2‐PrO)‐5‐NO2C6H3)] (4 b), [Ru(CF3CF2COO)2(IMesH2)(CH‐2‐(2‐PrO)‐5‐NO2C6H3)] (4 c), and [Ru(CF3CF2CF2COO)2(IMesH2)(CH‐2‐(2‐PrO)‐5‐NO2C6H3)] (4 d) (IMes=1,3‐dimesitylimidazol‐2‐ylidene; IMesH2=1,3‐dimesityl‐4,5‐dihydroimidazol‐2‐ylidene) were prepared. Living polymerization systems could be generated with DEDPM by careful tuning of the electronic nature and steric placement of the ligands. Although 1 a, 2 a, 3 a, 3 b, and 4 a were inactive in the cyclopolymerization of DEDPM, and initiators 1 b–d did not allow any control over molecular weight, initiators 2 b–d and 4 b–d offered access to class VI living polymerization systems. In particular, compounds 2 b and 4 d were superior. The livingness of the systems was demonstrated by linear plots of Mn versus the number of equivalents of monomer added (N). For initiators 2 b–d and 4 b–d, values for kp/ki were in the range of 3–7, while 1 b, 1 c, and 1 d showed a kp/ki ratio of >1000, 80, and 40, respectively. The use of non‐degassed solvents did not affect these measurements and underlined the high stability of these initiators. The effective conjugation length (Neff) was calculated from the UV/Vis absorption maximum (λmax). The final ruthenium content in the polymers was determined to be 3 ppm.
Properties of WAu12.
Authors: Autschbach Jochen , Hess Bernd A. , Johansson Mikael P. , Neugebauer Johannes , Patzschke Michael , Pyykkoe Pekka , Reiher Markus , Sundholm Dage
Published: April 2004

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New Binary Alkaline Metal Stannides A52Sn82 (A: K, Cs) with Sn44‐ Zintl and Sn94‐ Cluster Anions.
Authors: Hoch Constantin , Wendorff Marco , Roehr Caroline
Published: April 2004

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Partial Sn‐Atom Ordering in Sm3Ga0.80—2.48Sn4.20—2.52.
Authors: Tokaychuk Yaroslav O. , Filinchuk Yaroslav E. , Fedorchuk Anatoliy O. , Bodak Oksana I.
Published: April 2004

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Synthesis and Characterization of AgBiO3 with the Cubic KSbO3 Structure.
Authors: Sharma Ramesh , Mandal T. K. , Ramesha K. , Gopalakrishnan J.
Published: April 2004

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Direct Decomposition of NO on Cu‐Doped La(Ba)Mn(In)O3 Perovskite Oxide under Coexistence of O2, H2O, and SO2.
Authors: Ishihara Tatsumi , Anami Kazuhiro , Takiishi Keiko , Yamada Hiroshi , Nishiguchi Hiroyasu , Takita Yusaku
Published: April 2004

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Decomposition of A‐Type Sandwiches. Synthesis and Characterization of New Polyoxometalates Incorporating Multiple d‐Electron‐Centered Units.
Authors: Ritorto Michelle D. , Anderson Travis M. , Neiwert Wade A. , Hill Craig L.
Published: April 2004

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Cross‐Couplings of Unactivated Secondary Alkyl Halides: Room‐Temperature Nickel‐Catalyzed Negishi Reactions of Alkyl Bromides and Iodides.
Authors: Zhou Jianrong , Fu Gregory C.
Published: April 2004

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Rapid, Easy Cyanation of Aryl Bromides and Chlorides Using Nickel Salts in Conjunction with Microwave Promotion.
Authors: Arvela Riina K. , Leadbeater Nicholas E.
Published: April 2004

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Aza‐MIRC Reactions of Sulfonyl‐Activated Hydroxycarbamates with α,β‐Difunctionalized Acrylates.
Authors: Fioravanti Stefania , Morreale Alberto , Pellacani Lucio , Tardella Paolo A.
Published: April 2004

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Synthesis of 4,5‐Dihydro‐3‐(1′‐naphthyl)‐2H‐pyrazolino[3,4‐a]carbazoles and 3‐(1′‐Naphthyl)isooxazolo[3,4‐a]carbazoles.
Authors: Vandana T. , Prasad K. J. Rajendra
Published: April 2004

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Synthesis of Pyridopyrrolo[2,1‐a]isoindoles by Palladium‐Catalyzed Annulation.
Authors: Kang Song Su , Yum Eul Kgun , Sung Nack‐Do
Published: April 2004

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Synthesis of 2H‐1,2,3‐triazolo[4,5‐d]pyrimidine‐5,7‐diones from Uracils Using Cyclization Reaction of β‐Azo‐α,β‐unsaturated Sulfilimines.
Authors: Matsumoto Nobuaki , Takahashi Masahiko
Published: April 2004

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Synthesis and Characterization of Cationic Iodonium Macrocycles
Authors: Radhakrishnan Ukkiramapandian , Stang Peter J.
Published: April 2004

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A Novel Sulfonamidoglycosylation of Glycals.
Authors: Colinas Pedro A. , Bravo Rodolfo D.
Published: April 2004

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An Approach to the Generation of Simple Analogues of the Antitumor Agent Spicamycin.
Authors: Mons Stephane , Fleet George W. J.
Published: April 2004

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Recent Developments in the Synthesis of Heterocyclic Derivatives by PdI2‐Catalyzed Oxidative Carbonylation Reactions.
Authors: Gabriele Bartolo , Salerno Giuseppe , Costa Micro , Chiusoli Gian Paolo
Published: April 2004

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Chiral Tertiary Alcohols Made by Catalytic Enantioselective Addition of Unreactive Zinc Reagents to Poorly Electrophilic Ketones?
Authors: Ramon Diego J. , Yus Miguel
Published: April 2004

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Addition to Carbon—Hetero Multiple Bonds
Authors: Grosche Philipp , Rademann Jorg , Jung Gunther
Published: April 2004

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Photochemical Rearrangements of 6/6‐ and 6/5‐Fused Cross‐Conjugated Cyclohexadienones
Authors: Blay Gonzalo
Published: April 2004

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Re‐Engineering the Genetic Code: Combining Molecular Biology and Organic Chemistry.
Authors: van Maarseveen Jan H. , Back Jaap Willem
Published: April 2004

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NMR Spectroscopy Tools for Structure‐Aided Drug Design.
Authors: Homans Steve W.
Published: April 2004

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Theoretical Study of the Reaction Mechanism of BO, B2O2, and BS with H2
Authors: Chin Chih‐Hao , Mebel Alexander M. , Hwang Der‐Yan
Published: April 2004

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Synthesis and Structure of Ca18Li5In25.07: A Novel Intergrowth of Li‐Centered In12 Icosahedral Clusters and Electron‐Precise Zintl Layers.
Authors: Mao Jiang‐Gao , Goodey Joanna , Guloy Arnold M.
Published: April 2004

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A Calcium Uranium Nitride — Ca3UN4 — with Sodium Chloride Structure Type.
Authors: Heckers Uwe , Jacobs Herbert , Kockelmann Winfried
Published: April 2004

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Two Mercury Chloro Thiocyanate Complexes: NH4[HgCl2(SCN)] and NH4[HgCl(SCN)2].
Authors: Gacemi Aissa , Benbertal Djamal , Bagieu‐Beucher Muriel , Lecchi Amelie , Mosset Alain
Published: April 2004

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New Representative of Bi95+‐Containing Phases: Synthesis and Crystal Structure of the NbIV‐Containing Bi10Nb3Cl18 Compound.
Authors: Kuznetsov A. N. , Naumenko P. I. , Popovkin B. A. , Kloo L.
Published: April 2004

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Synthesis and Characterization of Mo6 Chalcobromides and Cyano‐Substituted Compounds Built from a Novel [(Mo6Br6iY2i) L6a]n‐ Discrete Cluster Unit (Yi: S or Se and La: Br or CN).
Authors: Cordier Stephane , Naumov Nikolai G. , Salloum Diala , Paul Frederic , Perrin Christiane
Published: April 2004

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Synthesis and Structure of the First Three‐Legged Low‐Dimensional Iron Phosphate, [H3N(CH2)3NH2 (CH2)2NH2 (CH2)3NH3] [Fe3F6(HPO4)2(PO4)] ×3H2O.
Authors: Mandal Sukhendu , Pati Swapan K. , Green Mark A. , Wang Sue‐Lein , Natarajan Srinivasan
Published: April 2004

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Preparation, Crystal Structure, and Normal Coordinate Analysis of Linkage Isomeric Pentachloroiodoselenocyanatoosmates(IV). Crystal Structure of trans‐(PPh4)2[OsCl4I(NCSe)].
Authors: Dallmann K. , Rehbehn S. , Preetz W.
Published: April 2004

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Designing New α,β‐Unsaturated Thioesters for the Catalytic, Enantioselective Friedel—Crafts Alkylation of Indoles.
Authors: Bandini Marco , Melloni Alfonso , Tommasi Simona , Umani‐Ronchi Achille
Published: April 2004

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Asymmetric Hydrogenation of Ketones with Polymer‐Supported Chiral 1,2‐Diphenylethylenediamine.
Authors: Li Xiaoguang , Chen Weiping , Hems William , King Frank , Xiao Jianliang
Published: April 2004

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Synthesis of β‐Amino and β‐Methoxy Ketones by Lewis Acid Promoted β‐Substitution Reactions of β,γ‐Unsaturated Ketones.
Authors: Lee Adam Shih‐Yuan , Wang Shu‐Huei , Chang Yu‐Ting , Chu Shu‐Fang
Published: April 2004

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3‐Nitrocoumarins as Dienophiles in the Diels—Alder Reaction in Water. An Approach to the Synthesis of Nitrotetrahydrobenzo[c]chromenones and Dihydrodibenzo[b,d]furans.
Authors: Amantini David , Fringuelli Francesco , Piermatti Oriana , Pizzo Ferdinando , Vaccaro Luigi
Published: April 2004

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Highly Chemo‐ and Regioselective Intermolecular Cyclotrimerization of Alkynes Catalyzed by Cationic Rhodium(I)/Modified BINAP Complexes.
Authors: Tanaka Ken , Shirasaka Kaori
Published: April 2004

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