bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aggregation of Octahedral Thiolato Complexes by Forming Sulfur-Bridged Structures with Transition Metal Ions
Authors: Konno Takumi 
Published: April 2004

Abstract
The main developments in rational construction of chiral metallo-aggregates based on octahedral metal complexes with 2-aminoethanethiolate (aet) or l-cysteinate (l-cys), as well as their functionality as an S-donating chiral metalloligand, are reviewed in this paper. The reactions of the tris(thiolato)-type fac(S)-[M(aet or l-cys-N,S)3]0 or 3− (M = CoIII, RhIII, IrIII) with transition metal ions gave a variety of S-bridged metallo-aggregates, the structures and chiral properties of which are highly dependent on the nature of the reacting metal ions. The aggregation of the bis(thiolato)-type cis(S)-[Co(aet)2(en)]2+ was also performed through the replacement of a NiII ion in [Ni{Co(aet)2(en)}2]4+ by other transition metal ions. While aggregation of these tris(thiolato)- and bis(thiolato)-types of octahedral units commonly produced discrete S-bridged polynuclear structures, one-dimensional and two-dimensional extended polymeric structures, besides a discrete trinuclear structure, were constructed by the reactions of the mono(thiolato)-type [Co(aet or l-cys-N,S)(en)2]2+ or + with silver(I) ion, because of the adoption of μ3-thiolato bridging mode and/or the coordination ability of the free carboxylate group.
Magnetic Resonance Energy and Aromaticity of Polycyclic Aromatic Hydrocarbon Dianions/Dications
Authors: Aihara Jun-ichi 
Published: April 2004

Abstract
Molecular dianions/dications of many polycyclic aromatic hydrocarbons (PAHs) have long been regarded as antiaromatics because of their global paratropic π-electron current. However, many of them are supposed to be aromatic due to their positive topological resonance energies (TREs). In order to reconcile such energetic and magnetic criteria of aromaticity, we derived a new TRE-like energetic quantity from the magnetic response of the π-system and called it a magnetic resonance energy (MRE). MRE was found to be highly correlative with TRE for a variety of PAHs and their molecular dianions/dications. We can now discuss energetic and magnetic criteria of aromaticity unambiguously on this theoretical basis. Many PAH dianions/dications indeed turned out to be aromatic with positive MREs even if they exhibit paratropic currents along the periphery of the π-system.
Comparative Studies on the Stability of a Chelate-Ring Unit in Dynamic Aspects. Chelate-Rings of the Cu(II) Complexes Composed of [N-(Glycyl)], [N-(β-Alanyl)], and [N-(2-Aminoethyl)] Moieties
Authors: Hanaki Akira , Ozawa Toshihiko , Funahashi Yasuhiro , Odani Akira 
Published: April 2004

Abstract
The kinetic stability of a chelate-ring unit in Cu(H−1GlyGly), Cu(H−1β-AlaGly), and Cu(EDMA) complexes has been inspected by stopped-flow spectroscopy. Those three Cu(II) complexes reacted with cysteine (CysH) or penicillamine (PesH) to form primarily ternary complexes, formulated as Cu(H−1L)(Rs−); L = GlyGly and β-AlaGly, and Cu(EDMA)(Rs−); where Rs− represents the aminothiolates. The chelate-ring units composed of [N-(Gly)]-, [N-(β-Ala)]-, and [N-(2-aminoethyl)]-moieties in Cu(H−1GlyGly), Cu(H−1β-AlaGly), and Cu(EDMA) were conserved, respectively, in the corresponding ternary complexes. The rate of the ternary complex formation was very rapid, so much so that the rate constants, k1+, could not be determined by the conventional stopped-flow techniques. The ternary complexes upon forming reacted with the RsH to produce the binary Cu(Rs−)2 species. Thus, the observables were limited to the rate constants, k2+, for the transformation from Cu(H−1L)(Rs−) to Cu(Rs−)2. The kinetic stabilities of those chelate-ring units were compared based on the rate constant, k2+, and equilibrium constant, K2. The stability was arranged as follows: [N-(Gly)]- &gt; [N-(2-aminoethyl)]- &gt; [N-(β-Ala)]-unit. Though Cu(EDMA) was kinetically stable, the Cu(II) in Cu(EDMA)(Rs−) was rapidly delivered by a nucleophilic attack of RsH to form Cu(Rs−)2. On the contrary, Cu(H−1GlyGly) was kinetically less stable than Cu(EDMA), but delivery of the Cu(II) from Cu(H−1L)(Rs−), by the proton-assisted mechanism, was comparatively slow.
Tetranuclear NiII and Dinuclear MnIII Complexes Derived from a New Macrocyclic Ligand with Four Endogenous Phenolic Groups
Authors: Ikeda Kazuhide , Matsufuji Kanako , Ohba Masaaki , Kodera Masahito , Okawa Hisashi 
Published: April 2004

Abstract
A tetranucleating macrocyclic ligand with four endogenous phenolic groups is obtained by the condensation of 3-aminomethyl-5-methylsalicylaldehyde in the presence of metal ion as two tetranuclear NiII complexes, [Ni4(L)(OH)(H2O)4](ClO4)3 (1) and [Ni4(L)(O)(dmf)4](ClO4)2 (2), and a dinuclear MnIII complex, [Mn2(H2L)(OH)(AcO)2(H2O)]Br (3). X-ray crystallographic studies for [Ni4(L)(OH)(H2O)8](ClO4)3·7H2O (1′) indicate that the macrocyclic ligand accommodates four NiII ions, producing a square Ni4 core with μ4-hydroxo group at the center of the core. Water molecules occupy the axial sites of each Ni affording a nearly octahedral geometry about the metal. Complex 2 has a similar tetranuclear Ni4-core possessing a μ4-oxo group at the center of the core. In complex 3, the di-protonated ligand (H2L)2− accommodates two MnIII ions, affording a (μ-hydroxo)(μ-acetato)dimanganese(III) core. Magnetic studies for 1 and 2 indicate a ferromagnetic interaction between the adjacent NiII centers and an antiferromagnetic interaction between the diagonal NiII centers. Complex 3 shows a weak antiferromagnetic interaction between the two MnIII ions.
Pyrolysis of High-Molecular-Weight Complex Organics Synthesized from a Simulated Interstellar Gas Mixture Irradiated with 3 MeV Proton Beam
Authors: Takano Yoshinori , Tsuboi Taiki , Kaneko Takeo , Kobayashi Kensei , Marumo Katsumi 
Published: April 2004

Abstract
High-molecular-weight organic matter synthesized from mixtures of carbon monoxide, ammonia, and water gases similar to those found in the interstellar medium were irradiated with a 3 MeV proton beam and analyzed by Curie-point pyrolysis with detection by a gas chromatograph and a mass spectrometer (Pyr–GC–MS). A wide variety of organic compounds, not only a number of amide compounds, but also heterocyclic and polycyclic aromatic hydrocarbons (PAHs), were detected among the products of the pyrolysis. Detection of biologically interesting compounds, such as glycolamide (HOCH2CONH2), is also cosmochemically interesting. The present data show that primary and primitive organic matter serving as “precursors” to bioorganic compounds, such as amino acids, nucleic acid bases, and sugar, might have been formed in a gaseous mixture of similar composition to that of the interstellar dust environment. Consequently, the matrix of extraterrestrial organic compounds delivered by comets and meteorites may have played an important role in the early stages of chemical evolution on the primitive Earth.
Self-Assembly of Synthetic Bacteriochlorophyll-f Analogues Having C8-Formyl Group
Authors: Sasaki Shin-ichi , Tamiaki Hitoshi 
Published: April 2004

Abstract
31-Epimerically pure C8-formyl analogues Zn–3R/S of zinc methyl bacteriopheophorbide-f (Zn–MBPhe-f) were synthesized. Their spectroscopic and self-aggregation properties were compared to those of Zn–MBPhe-f possessing the C7-formyl group (Zn–2R/S) as a model compound of bacteriochlorophyll-f. Movement of a formyl group from the 7- to 8-position as in Zn–2 → Zn–3 caused large spectral changes in both monomeric and oligomeric forms. Monomeric Zn–3R/S in THF showed a more red-shifted Qy peak (650 nm) than Zn–2R/S (628 nm), but both afforded the same Soret maximum at 448 nm. Self-aggregates of Zn–3R/S in 6% (v/v) THF–H2O gave a more red-shifted Qy peak accompanied by a large diastereomeric control in the oligomeric Qy peaks.
Control Crystallization of Calcium Carbonate in Aqueous Solution with In-Situ Radical Polymerization of Sodium Acrylate as a Latent Inductor for Crystal Nucleation and Growth
Authors: Naka Kensuke , Keum Dong-Ki , Tanaka Yasuyuki , Chujo Yoshiki 
Published: April 2004

Abstract
Crystallization of CaCO3 with in-situ radical polymerization of sodium acrylate in aqueous solution was carried out by a double jet method to prevent heterogeneous nucleation at glass walls. The concentration of sodium acrylate was 1.71 mM and the feed ratio of sodium acrylate to calcium ions was 0.62. After addition of the calcium reactants into the aqueous solution of sodium acrylate was completed, an aqueous solution of potassium peroxodisulfate as a water-soluble radical initiator was added to the reaction mixture after incubation at 30 °C for several minutes (1, 3, or 20 min). Three different crystal polymorphs of CaCO3 (aragonite, vaterite, and calcite) were selectively induced by changing the time for adding the radical initiator to a calcium carbonate solution with sodium acrylate. Formation of crystalline CaCO3 in the presence of sodium acrylate with the radical initiator at different feed ratio of sodium acrylate to calcium ions was also studied. The higher concentration of sodium acrylate increased sizes of vaterite spherical particles. The present results indicate that the final crystalline phases are highly sensitive to the presence of the active additives at the very initial nucleation stage (within several minutes).
DDI‐μFIA—A Readily Configurable Microarray‐Fluorescence Immunoassay Based on DNA‐Directed Immobilization of Proteins
Authors: Wacker Ron , Niemeyer Christof M. 
Published: April 2004

AbstractWe describe a chip‐based immunoassay for multiplex antigen detection, based on the self‐assembly of semi‐synthetic DNA–protein conjugates to generate an easily configurable protein microarray. The general principle of this microarray‐fluorescence immunoassay (μFIA) is similar to that of a two‐sided (sandwich) immunoassay. However, covalent single‐stranded DNA–streptavidin conjugates are employed for the efficient immobilization of biotinylated capture antibodies through hybridization to complementary surface‐bound DNA oligomers. In a model system, we use the DNA‐directed immobilization (DDI) of antibodies to generate an antibody microarray for the parallel detection of the tumor marker human carcinoembryonic antigen (CEA), recombinant mistletoe lectin rViscumin (rVis), ceruloplasmin (CEP), and complement‐1‐inactivator (C1 A) in human blood serum samples. Detection limits down to 400 pg mL−1 are reached. In addition, we describe a method for the internal standardization of protein microarray analyses, based on the simultaneous measurement of constant amounts of the blood proteins CEP and C1 A, intrinsically present in human serum, to compensate for interexperimental variations usually occurring in microarray analyses. The standardization leads to a significantly higher data reliability and reproducibility in intra‐ and interassay measurements. We further demonstrate that the DDI‐μFIA can also be carried out in a single step by tagging of the analyte simultaneously with both capture and detection antibody and subsequent immobilization of the immunocomplex formed, on the DNA microarray capture matrix. This protocol significantly reduces handling time and costs of analysis.
Immunological Optimization of a Generic Hydrophobic Pocket for High Affinity Hapten Binding and Diels–Alder Activity
Authors: Piatesi Andrea , Hilvert Donald 
Published: April 2004

AbstractAntibody 1E9, which binds a tetrachloronorbornene derivative with subnanomolar affinity and catalyzes the Diels–Alder reaction between tetrachlorothiophene dioxide and N‐ethylmaleimide with high efficiency, arose from a family of highly restricted germ‐line immunoglobulins that bind diverse hydrophobic ligands. Two somatic mutations, one at position L89 in the light chain (SerL89Phe) and another at position H47 in the heavy chain (TrpH47Leu), have been postulated to be responsible for the unusually high degree of shape and chemical complementarity observed in the crystal structure of 1E9 complexed with its hapten. To test this hypothesis, the germ‐line sequence at these two positions was restored by site‐directed mutagenesis. The ensuing 160 to 3900‐fold decrease in hapten affinity and the complete loss of catalytic activity support the hypothesis that these somatic mutations substantially remodel the antibody binding pocket. Mutation of the highly conserved hydrogen‐bond donor AsnH35, which sits at the bottom of the active site and is a hallmark of this family of antibodies, is also catastrophic with respect to hapten binding and catalysis. In contrast, residues in the CDR H3 loop, which contributes a significant fraction of the hapten‐contacting protein surface, have a more subtle influence on the properties of 1E9. Interestingly, while most changes in this loop have neutral or modestly deleterious effects, replacement of MetH100b at the floor of the pocket with phenylalanine leads to a significant sevenfold increase in catalytic activity. The latter result is surprising given the unusually close fit of the parent antibody to the transition‐state analogue. Further fine‐tuning of the interactions between 1E9 and its ligands by introducing mutations outside the active site could conceivably yield substantially more active catalysts.
Membrane Protein–Lipid Interactions in Mixed Micelles Studied by NMR Spectroscopy with the Use of Paramagnetic Reagents
Authors: Hilty Christian , Wider Gerhard , Fernández César , Wüthrich Kurt 
Published: April 2004

AbstractFor solution NMR studies of the structure and function of membrane proteins, these macromolecules have to be reconstituted and solubilized in detergent micelles. Detailed characterization of the mixed detergent/protein micelles is then of key importance to validate the results from such studies, and to evaluate how faithfully the natural environment of the protein in the biological membrane is mimicked by the micelle. In this paper, a selection of paramagnetic probes with different physicochemical properties are used to characterize the 60 kDa mixed micelles consisting of about 90 molecules of the detergent dihexanoylphosphatidylcholine (DHPC) and one molecule of the Escherichia coli outer‐membrane protein X (OmpX), which had previously been extensively studied by solution NMR techniques. The observation of highly selective relaxation effects on the NMR spectra of OmpX and DHPC from a water‐soluble relaxation agent and from nitroxide spin labels attached to lipophilic molecules, confirmed data obtained previously with more complex NMR studies of the diamagnetic OmpX/DHPC system, and yielded additional novel insights into the protein–detergent interactions in the mixed micelles. The application of paramagnetic probes to the well‐characterized OmpX/DHPC system indicates that such probes should be widely applicable as an efficient support of NMR studies of the topology of mixed membrane protein–detergent micelles.
Isolation and developmental expression of Mitf in Xenopus laevis
Authors: Kumasaka Mayuko , Sato Hiraku , Sato Shigeru , Yajima Ichiro , Yamamoto Hiroaki 
Published: April 2004

AbstractMitf (gene for microphthalmia‐associated transcription factor) encodes a transcription factor of the basic/helix‐loop‐helix/leucine‐zipper family and is a key regulator during the development of two different types of melanin‐producing cell lineages, namely neural crest‐derived melanocytes/melanophores, and the retinal pigment epithelium (RPE) differentiated from the outer layer of the eye cup. Mitf‐deficient mice show a lack of melanocytes and small eyes caused by abnormal RPE development. An interesting feature of Mitf is the existence of multiple isoforms with different amino termini and their functions in the development of these melanin‐producing pigment cells. In this study, we isolated two Mitf homologues (XlMitfα and XlMitfβ) and their isoforms from Xenopus laevis. Alignment analysis of the amino acid sequences of the N‐termini suggests that these isoforms are homologues of mouse Mitf‐M (expressed specifically in the melanocyte lineage) and Mitf‐A (strongly expressed in the RPE, although this expression is ubiquitous). In Xenopus, XlMitfα is strongly expressed in the melanophore lineage (especially in premigratory melanoblasts) and the presumptive RPE and the epiphysis, in which melanin‐producing cells differentiate in some vertebrates. Conservation of the Mitf isoforms expected to possess specific functions in the development of melanin‐producing cells and of the expressions in such cell types in Xenopus suggest that XlMitf plays a central role in the development of melanin‐producing cell lineages, and that, as in mice and humans, most of the signaling molecules or transcription factors implicated genetically in the development of melanin‐producing cell lineages affect either Mitf expression or its function (Goding [2000] Genes Dev. 14:1712–1728). Developmental Dynamics 230:107–113, 2004. © 2004 Wiley‐Liss, Inc.
Different molecular mechanisms underlie placental overgrowth phenotypes caused by interspecies hybridization, cloning, and Esx1 mutation
Authors: Singh Umashankar , Fohn Laurel E. , Wakayama Teruhiko , Ohgane Jun , Steinhoff Christine , Lipkowitz Bettina , Schulz Ralph , Orth Annie , Ropers H. Hilger , Behringer Richard R. , Tanaka Satoshi , Shiota Kunio , Yanagimachi Ryuzo , Nuber Ulrike A. , Fundele Reinald 
Published: April 2004

AbstractTo obtain a deeper insight into the genes and gene networks involved in the development of placentopathies, we have assessed global gene expression in three different models of placental hyperplasia caused by interspecies hybridization (IHPD), cloning by nuclear transfer, and mutation of the Esx1 gene, respectively. Comparison of gene expression profiles of approximately 13,000 expressed sequence tags (ESTs) identified specific subsets of genes with changed expression levels in IHPD, cloned, and Esx1 mutant placentas. Of interest, only one gene of known function and one EST of unknown function were found common to all three placentopathies; however, a significant number of ESTs were common to IHPD and cloned placentas. In contrast, only one gene was shared between IHPD and Esx1 mutant, and cloned and Esx1 mutant placentas, respectively. These genes common to different abnormal placental growth genotypes are likely to be important in the occurrence of placentopathy. Developmental Dynamics 230:149–164, 2004. © 2004 Wiley‐Liss, Inc.
Synthesis, Structures and Luminescent Properties of σ‐Alkynyl Complexes of Orthomercuriated Schiff Bases
Authors: Wong Wai‐Yeung , Lu Guo‐Liang , Liu Li , Shi Jian‐Xin , Lin Zhenyang 
Published: April 2004

AbstractA novel series of σ‐alkynyl complexes of orthomercuriated Schiff bases of substituted benzylideneanilines and anthracenylmethyleneanilines were synthesised in good yields by alkynylation of the mercuric chlorides of the appropriate Schiff bases with terminal alkynes RC≡CH (R = Ph, ferrocenyl, p‐ferrocenylphenyl) at room temperature in a basic medium. All the new compounds generally displayed good solubility in polar organic solvents and their identities were completely elucidated by various spectroscopic methods. The X‐ray crystal structures of these acetylide‐functionalised compounds represent the first structurally characterised examples of such alkynylmercury(II) complexes and confirmed that the alkynylmercury(II) moiety is directed to the ortho position of the N‐phenyl ring of the Schiff bases. In one instance, the crystal structure reveals that a loose 1D polymeric aggregate is formed for the first time through a combination of weak intermolecular Hg···Hg and Hg···η2‐C≡C interactions to afford an infinite zigzag chain of Hg atoms supported by acetylide linkages. All the complexes in this study were found to exhibit rich luminescence and solution redox behaviour and correlation of these data with the theoretical calculations by the density functional theory was made. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Synthesis and Characterisation of Two Supramolecular Polymers [CuAg4(CN)6(tacn)]n and [CuAu2(CN)4(tacn)]n Containing Metal−Metal Interactions
Authors: Han Wei , Yi Long , Liu Zhan‐Quan , Gu Wen , Yan Shi‐Ping , Cheng Peng , Liao Dai‐Zheng , Jiang Zong‐Hui 
Published: April 2004

AbstractTwo novel heterobimetallic supramolecular polymers, [CuAg4(CN)6(tacn)]n (1) and [CuAu2(CN)4(tacn)]n (2) (tacn = 1,4,7‐triazacyclononane), have been synthesised from the building block [Cu(tacn)]2+, together with [Ag(CN)2]− (for 1) and [Au(CN)2]− (for 2). The large difference in structural type between 1 and 2 is probably due to the fact that the AgI centre is three‐coordinate and trigonal whereas the AuI centre is linear. Metal−metal interactions play an important role in the formation of the supramolecular framework of 1 and the novel topology of 2. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Optically Active Phospholanes as Substituents on Ferrocene and Chromium‐Arene Complexes
Authors: Braun Wolfgang , Calmuschi Beatrice , Haberland Jürgen , Hummel Werner , Liese Andreas , Nickel Thomas , Stelzer Othmar , Salzer Albrecht 
Published: April 2004

AbstractAn improved synthesis of (R,R)‐ and (S,S)‐hexane‐2,5‐diol is presented. The (S,S)‐derivative was converted into a cyclic sulfate, which on treatment with NaPH2 in liquid ammonia ultimately gave the secondary (R,R)‐2,5‐dimethylphospholane. This phospholane can be introduced into the side chain of chiral tricarbonylchromium and ferrocene derivatives to give new bidentate ligands of the Josiphos and Daniphos type. Both the ferrocene‐ and tricarbonylchromium‐based diphosphanes have been characterized by X‐ray diffraction analysis. A discussion of their structural features is included. The new ligands were successfully applied to the enantioselective hydrogenation of itaconic acid esters. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Five‐ and Six‐Coordinate Ruthenium(II) Complexes Containing the Bidentate Phosphane (−)‐N,N‐Bis(diphenylphosphanyl)‐(S)‐1‐phenylethylamine [(S)‐peap]: X‐ray Crystal Structure of the First 16‐Electron Ruthenium Complex Bearing a Four‐Membered Ring [RuCl{κ2‐P,P‐(S)‐peap}2][SbF6]·C2H4Cl2
Authors: Díez Josefina , Gamasa M. Pilar , Gimeno José , Rodríguez Yolanda , García‐Granda Santiago 
Published: April 2004

AbstractThe complex trans‐[RuCl2{κ2‐P,P‐(S)‐peap}2] (1) has been stereoselectively prepared by the treatment of a stoichiometric mixture of complex [RuCl2(DMSO)4] (DMSO = dimethyl sulfoxide) and (S)‐peap [(S)‐peap = (−)‐N,N‐bis(diphenylphosphanyl)‐(S)‐1‐phenylethylamine] in refluxing toluene. Irradiation of a dichloromethane solution of 1 with a UV lamp (400 W) at −15 °C affords the complex cis‐[RuCl2{κ2‐P,P‐(S)‐peap}2] (2). The thermodynamically stable trans isomer 1 has also been obtained by heating complex 2 in toluene. The reaction of 1 with AgSbF6 in dichloromethane yields the complex [RuCl{κ2‐P,P‐(S)‐peap}2][SbF6] (3), the first 16‐electron cationic ruthenium complex bearing a four‐membered chelate diphosphane ligand which has been fully characterized including its X‐ray crystal structure. The reaction of unsaturated derivative 3 with CO gives the six‐coordinate complex cis‐[RuCl(CO){κ2‐P,P‐(S)‐peap}2][SbF6] (4) in a stereoselective manner, which slowly transforms into trans‐[RuCl(CO){κ2‐P,P‐(S)‐peap}2][SbF6] (5) in a dichloromethane solution. The reaction of [RuCl{κ2‐P,P‐(S)‐peap}2][BF4] with 1‐phenyl‐2‐propyn‐1‐ol in 1,2‐dichloroethane (60 °C) affords the allenylidene derivative trans‐[RuCl(=C=C=CHPh){κ2‐P,P‐(S)‐peap}2][BF4] (6). The cis‐[Ru(acac){κ2‐P,P‐(S)‐peap}2][SbF6] (7) is prepared by reaction of 3 and Na[acac]. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)