bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel Supramolecular Frameworks Self‐Assembled from a Two‐Dimensional Polymeric Network: Synthesis and Crystal Structure of a Macrocyclic Organotin(IV) Complex
Authors: Ma Chunlin , Han Yinfeng , Zhang Rufen , Wang Daqi 
Published: April 2005

AbstractThe two‐dimensional polymer [nBu2Sn(O2CC6H4)]4 has been synthesized by the self‐assembly of di‐n‐butyltin oxide and 4‐carboxyphenylboronic acid. The X‐ray crystal structure shows that the metal ions display a trigonal bipyramidal coordination geometry to bind the endocyclic oxygen atom. Intermolecular π–π stacking interactions between adjacent phenyl groups of the ligand cause the self‐assembly into a 1D chain. In this chain one oxygen atom of the carboxylate group binds to one [nBu2Sn(O2CC6H4)]4 unit to give rise to a 2D architecture. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Stereoisomerism in Pentaerythritol‐Bridged Cyclotriphosphazene Tri‐Spiranes: Spiro and Ansa 1,3‐Propanediyldioxy Disubstituted Derivatives
Authors: Uslu Aylin , Coles Simon J. , Davies David B. , Eaton Robert J. , Hursthouse Michael B. , Kılıç Adem , Shaw Robert A. 
Published: April 2005

AbstractIn each spirane structure in Figure 1 on p. 1043 of the original article[1] the spiro atom of the left‐hand cyclophosphazene ring should be phosphorus rather than nitrogen; the correct Figure 1 is shown below.
Synthesis and Characterisation of New Iridium Complexes with the (4S)‐2‐[2‐(Diphenylphosphanyl)phenyl]‐4‐isopropyl‐1,3‐oxazoline Ligand That Catalyse Asymmetric Michael Reactions (Eur. J. Inorg. Chem. 9/2005)
Authors: Carmona Daniel , Ferrer Joaquina , Lorenzo Mónica , Lahoz Fernando J. , Dobrinovitch Isabel T. , Oro Luis A. 
Published: April 2005

AbstractThe cover picture shows the structure of a new chiral iridium(I) complex with the (4S)‐2‐[2‐(diphenylphosphanyl)phenyl]‐4‐isopropyl‐1,3‐oxazoline ligand [(S)‐PN] that catalyses the asymmetric Michael addition of keto or cyano esters to α,β‐unsaturated carbonyl compounds. The hydrido(enolato) species, [IrH(NCCHCO2R2){(S)‐PN}2]Cl, postulated as catalytic intermediates, have also been isolated and spectroscopically characterised. Details are discussed in the article by D. Carmona et al. on p. 1657 ff.
Variable selection and interpretation in correlation principal components
Authors: Al‐Kandari Noriah M. , Jolliffe Ian T. 
Published: April 2005

AbstractPrincipal component analysis (PCA) is a dimension‐reducing tool that replaces the variables in a multivariate data set by a smaller number of derived variables. Dimension reduction is often undertaken to help in interpreting the data set but, as each principal component usually involves all the original variables, interpretation of a PCA can still be difficult. One way to overcome this difficulty is to select a subset of the original variables and use this subset to approximate the principal components. This article reviews a number of techniques for choosing subsets of the variables and examines their merits in terms of preserving the information in the PCA, and in aiding interpretation of the main sources of variation in the data. Copyright © 2005 John Wiley & Sons, Ltd.
Unnatural landscapes in ecology: generating the spatial distribution of brine spills
Authors: Jager Henriette I. , Efroymson Rebecca A. , Sublette Kerry L. , Ashwood Tom L. 
Published: April 2005

AbstractQuantitative tools are needed to evaluate the ecological effects of increasing petroleum production. In this article, we describe two stochastic models for simulating the spatial distribution of brine spills on a landscape. One model uses general assumptions about the spatial arrangement of spills and their sizes; the second model distributes spills by siting rectangular well complexes and conditioning spill probabilities on the configuration of pipes. We present maps of landscapes with spills produced by the two methods and compare the ability of the models to reproduce a specified spill area. A strength of the models presented here is their ability to extrapolate from the existing landscape to simulate landscapes with a higher (or lower) density of oil wells. Published in 2005 by John Wiley & Sons, Ltd.
Possibilities of Mass Spectrometry and Tandem‐Mass Spectrometry in the Analysis of Cellulose Ethers
Authors: Mischnick Petra , Niedner Wulff , Adden Roland 
Published: April 2005

AbstractThe investigation of the substituent pattern of cellulose and starch ethers and esters on various structural levels as in the glucosyl unit, along the polymer chain, and over the polymer molecules, still is a very challenging task.By means of mass spectrometric methods as ESI‐MS or MALDI‐TOF‐MS the composition of oligosaccharide mixtures which represent the substituent distribution in the original polymer can principally be determined. However, to obtain reliable quantitative data mass spectra must be recorded under appropriate instrumental conditions and after special sample preparation While O‐methyl/O‐methyl‐d3‐oligosaccharides give representative data with the mentioned MS techniques and FAB‐MS as well, hydroxyalkyl ethers require labelling with a quaternary ammonium tag and MALDI‐TOF‐MS to prevent discrimination of lower substituted oligosaccharides. In this way, information on the neighbourhood of glucosyl units in the polymer chain is available which – together with the monomer composition – is a valuable parameter to describe a random or a heterogeneous pattern with regions of local higher densities of substituents compared to the random model, a regular distribution, or a block‐like substituent pattern, i.e. a more clustered localisation of substiuents in the polymer chain. In addition, tandem‐mass spectrometry (ESI‐MSn) allows to gain further insight in the composition of isomeric oligosaccharide derivatives of the same m/z ratio and to calculate the complete monomer composition of methyl celluloses.
Structure Determination of Cellulose Esters via Subsequent Functionalization and NMR Spectroscopy
Authors: Liebert Tim , Hussain Muhammad A. , Heinze Thomas 
Published: April 2005

AbstractNew paths for the fast and reliable analysis of cellulose esters (CE) via subsequent functionalization and 1H NMR spectroscopy were studied. Perpropionylation of the CE is an inexpensive and efficient method. For cellulose diacetates used as representative ester well resolved 1H NMR spectra were obtained, which can be used for the calculation of the over all degree of substitution (DS) and the partial DS values at position 2, 3, and 6. No transesterification occurs during the subsequent acylation and a standard deviation of S2 = 1.32 x 10−4 was found for a series of experiments. In case of more complex ester structures especially with extended aliphatic moieties per‐4‐nitrobenzoylation need to be applied prior to NMR measurements. The spectra obtained can be completely assigned and applied for the calculation of DS values.
Endoglucanase Degradation and Enzyme‐Aided Characterization of Cellulose Acetates
Authors: Saake Bodo , Altaner Clemens , Lee Soo‐Jung , Puls Jürgen 
Published: April 2005

AbstractEndoglucanases were used as a selective tool to determine the substituent distribution along the chains of partially substituted cellulose acetates. Unsubstituted segments are intensively fragmented while highly substituted segments are only slightly degraded or not affected at all. Two different procedures were developed to perform a preparative separation of the fragments by size exclusion chromatography. One system is based on a direct separation of the fragmentation products using pyridine : water (9 : 1) as an eluent. The isolated fragments can be analysed regarding to their DS values by ATR/FTIR spectroscopy or by hydrolysis and HPLC. The second system is based on deutero‐acetylation of endoglucanase fragmented samples. The complete acetylation of all OH groups enables a chromatographic separation in chloroform. Afterwards the isolated fragments can be analysed regarding to their partial DS values by 1H‐NMR spectroscopy.
NMR investigation of hydrogen bonding and 1,3‐tautomerism in 2‐(2‐hydroxy‐5‐substituted‐aryl) benzimidazoles
Authors: Sridharan V. , Saravanan S. , Muthusubramanian S. , Sivasubramanian S. 
Published: April 2005

AbstractThe 1,3‐tautomerism associated with 2‐(2‐hydroxy‐5‐substituted‐aryl)benzimidazoles was studied in different solvents. The effect of hydrogen bonding involving the hydroxyl group of the 2‐aryl ring on the tautomerism was investigated using NMR spectroscopy. The influence of the solvent concentration on 2‐(2‐hydroxy‐5‐chloroaryl)benzimidazole was studied in acetone‐d6 and DMSO‐d6. Copyright © 2005 John Wiley & Sons, Ltd.
1H and 13C NMR identification of unexpected 3,4‐dihydroquinoxalines in the syntheses of 1,5‐benzodiazepine derivatives
Authors: Tjiou E. M. , Lhoussaine E. G. , Virieux D. , Fruchier A. 
Published: April 2005

AbstractThe reaction between o‐phenylenediamines, dehydroacetic acid and aromatic aldehydes is shown to give not only the expected 1,5‐benzodiazepine derivative but also a 3,4‐dihydroquinoxaline, the structure of which was determined by its 1H and 13C 1D and 2D NMR spectra. Copyright © 2005 John Wiley & Sons, Ltd.
A concave‐cost production planning problem with remanufacturing options
Authors: Yang Jian , Golany Boaz , Yu Gang 
Published: April 2005

AbstractWe focus on the concave‐cost version of a production planning problem where a manufacturer can meet demand by either producing new items or by remanufacturing used items. Unprocessed used items are disposed. We show the NP‐hardness of the problem even when all the costs are stationary. Utilizing the special structure of the extreme‐point optimal solutions for the minimum concave‐cost problem with a network flow type feasible region, we develop a polynomial‐time heuristic for the problem. Our computational study indicates that the heuristic is a very efficient way to solve the problem as far as solution speed and quality are concerned. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2005
Matchings in 3‐vertex‐critical graphs: The even case
Authors: Ananchuen Nawarat , Plummer Michael D. 
Published: April 2005

AbstractA subset of vertices D of a graph G is a dominating set for G if every vertex of G not in D is adjacent to one in D. The cardinality of any smallest dominating set in G is denoted by γ(G)and called the domination number of G. Graph G is said to be γ‐vertex‐critical if γ(G − v) < γ(G), for every v vertex in G. Comparatively little is known to date about the structure of γ‐vertex‐critical graphs, even in the case when γ = 3. In the present article, we begin the study of matchings in 3‐vertex‐critical graphs. In particular, we show that any 3‐vertex‐critical graph on an even number of vertices, which has no induced subgraph isomorphic to the bipartite graph K1,5 much have a perfect matching, whereas 3‐vertex‐critical even graphs in general need not contain such a matching. We close with a conjecture. © 2005 Wiley Periodicals, Inc. NETWORKS, Vol. 45(4), 210–213 2005
Preparation and characterization of rigid poly (vinyl chloride)/MMT nanocomposites
Authors: Chen Cheng‐Ho , Teng Chih‐Chun , Yang Chien‐Hsin 
Published: April 2005

AbstractIn this article, a Haake torque rheometer equipped with an internal mixer is used to study the influence of the amount of sodium montmorillonite (Na+‐MMT) and organically modified MMT (O‐MMT) on the characteristics of rigid poly (vinyl chloride) (PVC)/Na+‐MMT and PVC/O‐MMT nanocomposites, respectively. It is observed that the fusion time and temperature of the rigid PVC/Na+‐MMT nanocomposites are decreased with increasing the amount of Na+‐MMT. On the contrast, the fusion time and temperature of the rigid PVC/O‐MMT nanocomposites are increased with increasing the amount of O‐MMT. Results of X‐ray diffraction (XRD) and transmission electron microscope (TEM) indicate that MMT is partially encapsulated and intercalated in the rigid PVC/Na+‐MMT nanocomposites. However, results of XRD and TEM show MMT is partially intercalated and exfoliated in the rigid PVC/O‐MMT nanocomposites. Tensile strength, yield strength, and elongation at break of the rigid PVC/MMT (including PVC/Na+‐MMT and PVC/O‐MMT) nanocomposites were improved simultaneously with adding 1–3 wt % Na+‐MMT or O‐MMT with respect to those of pristine PVC. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1465–1474, 2005
Reversal of some viral IL‐6 electrostatic properties compared to IL‐6 contributes to a loss of alpha receptor component recruitment
Authors: Perret David , Rousseau François , Tran Vinh , Gascan Hugues 
Published: April 2005

AbstractHuman interleukin‐6 (hIL‐6) is a pleiotropic mediator of activation and proliferation across a large number of different cell types. Human herpesvirus‐8 (HHV‐8) has been associated with classical and AIDS‐related Kaposi's sarcoma (KS). HHV‐8 encodes viral IL‐6 (vIL‐6), a functional homolog of human interleukin‐6, that promotes the growth of KS and of some lymphoma cells. Signaling induced by human IL‐6 requires recruitment of the glycoprotein gp130, which acts as the signal transducing chain, and of IL‐6Rα, which is necessary for cognate recognition and high affinity receptor complex formation. In contrast, the formation of a functional complex between vIL‐6 and gp130 does not require the presence of IL‐6Rα. The physico‐chemical properties of vIL‐6 have been analyzed and compared to those of hIL‐6 and of the receptor chains, gp130 and IL‐6Rα. Interaction sites on vIL‐6 involve more hydrophobic residues than those of hIL‐6. The electrostatic fields induced by vIL‐6 and IL‐6Rα are repulsive and prevent interaction between vIL‐6 and IL‐6Rα, whereas the electrostatic field induced by hIL‐6 steers the complex formation with IL‐6Rα. Subsequently, electrostatic binding free energy in the vIL‐6/IL‐6Rα complex is destabilizing, whereas it is stabilizing in the complex comprising hIL‐6. These properties result from charge reversals between viral and human IL‐6, an unusual phenomenon of amino acid substitutions within a homologous protein family. This suggests a selection pressure for vIL‐6 to by‐pass the IL‐6Rα control of host defense against virus infection. This selection pressure has yielded the reversal of electrostatic properties of vIL‐6 when compared to hIL‐6. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Application of InChI to curate, index, and query 3‐D structures
Authors: Prasanna M.D. , Vondrasek Jiri , Wlodawer Alexander , Bhat T.N. 
Published: April 2005

AbstractThe HIV structural database (HIVSDB) is a comprehensive collection of the structures of HIV protease, both of unliganded enzyme and of its inhibitor complexes. It contains abstracts and crystallographic data such as inhibitor and protein coordinates for 248 data sets, of which only 141 are from the Protein Data Bank (PDB). Efficient annotation, indexing, and querying of the inhibitor data is crucial for their effective use for technological and industrial applications. The application of IUPAC International Chemical Identifier (InChI) to index, curate, and query inhibitor structures HIVSDB is described. Proteins 2005. Published 2005 Wiley‐Liss, Inc.
Recognizing protein folds by cluster distance geometry
Authors: Crippen Gordon M. 
Published: April 2005

AbstractCluster distance geometry is a recent generalization of distance geometry whereby protein structures can be described at even lower levels of detail than one point per residue. With improvements in the clustering technique, protein conformations can be summarized in terms of alternative contact patterns between clusters, where each cluster contains four sequentially adjacent amino acid residues. A very simple potential function involving 210 adjustable parameters can be determined that favors the native contacts of 31 small, monomeric proteins over their respective sets of nonnative contacts. This potential then favors the native contacts for 174 small, monomeric proteins that have low sequence identity with any of the training set. A broader search finds 698 small protein chains from the Protein Data Bank where the native contacts are preferred over all alternatives, even though they have low sequence identity with the training set. This amounts to a highly predictive method for ab initio protein folding at low spatial resolution. Proteins 2005;. © 2005 Wiley‐Liss, Inc.
Tryptophan to phenylalanine substitutions allow differentiation of short‐ and long‐range conformational changes during denaturation of goat α‐lactalbumin
Authors: Vanhooren Ann , Chedad Allel , Farkas Viktor , Majer Zsuzsa , Joniau Marcel , Van Dael Herman , Hanssens Ignace 
Published: April 2005

AbstractTo test the occurrence of local particularities during the unfolding of Ca2+‐loaded goat α‐lactalbumin (GLA) we replaced Trp60 and ‐118, either one or both, by Phe. In contrast with alternative studies, our recombinant α‐lactalbumins are expressed in Pichia pastoris and do not contain the extra N‐terminal methionine. The substitution of Trp60 leads to a reduction of the global stability. The effect of the Trp118Phe substitution on the conformation and stability of the mutant, however, is negligible. Comparison of the fluorescence spectra of these mutants makes clear that Trp60 and ‐118 are strongly quenched in the native state. They both contribute to the quenching of Trp26 and ‐104 emission. By the interplay of these quenching effects, the fluorescence intensity changes upon thermal unfolding of the mutants behave very differently. This is the reason for a discrepancy of the apparent transition temperatures derived from the shift of the emission maxima (Tm,Fl λ) and those derived from DSC (Tm,DSC). However, the transition temperatures derived from fluorescence intensity (Tm,Fl int) and from DSC (Tm,DSC), respectively, are quite similar, and thus, no local rearrangements are observed upon heat‐induced unfolding. At room temperature, the occurrence of specific local rearrangements upon GdnHCl‐induced denaturation of the different mutants is deduced from the apparent free energies of their transition state obtained from stopped‐flow fluorescence measurements. By ϕ‡‐value analysis it appears that, while the surroundings of Trp118 are exposed in the kinetic transition state, the surroundings of Trp60 remain native. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Spectroscopic and DFT studies of donor–acceptor molecules containing phenylquinoline and phenothiazine moieties in various redox states
Authors: Ponce Ortiz R. , Malavé Osuna R. , Ruiz Delgado M. C. , Casado J. , Jenekhe S. A. , Hernandez V. , Lopez Navarrete J. T. 
Published: April 2005

AbstractWe report the ultraviolet (UV)‐Vis, Fourier transform‐infrared (FT‐IR), and FT‐Raman spectroscopic study of an electrogenerated chemiluminescence (ECL) emitting compound containing two electron‐accepting phenylquinoline end groups covalently attached to an electron‐donating 10‐methylphenothiazine central moiety. The optimized molecular geometry of the neutral compound as determined from quantum chemical density functional theory (DFT)//B3LYP/3‐21G* calculations shows that the phenyl groups appended onto the quinolines are twisted by ≈62° from these moieties. The sulfur atom is also tilted with respect to the plane defined by the phenyl rings of the phenothiazine, in both the neutral and singly oxidized species. The highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbitals (LUMO) of the neutral systems partially overlap, so that the lowest‐energy visible absorption band implies a certain degree of charge transfer from the phenothiazine toward the phenylquinolines. In contrast, the removal of the first electron mainly affects the structure and equilibrium charge distribution of the phenothiazine, and much less in those of the quinolines. In addition, the DFT//UB3LYP/3‐21G* topologies of the molecular orbitals around the bandgap region of the radical cation reveal no molecular orbital overlap between the two types of constituent building blocks, thus inhibiting the delocalization of the injected positive charge over the whole molecule. This feature could be in line with the ability of this system to generate localized radical ions capable of displaying chemiluminescence upon annihilation, as previously observed experimentally. The UV‐Vis and FT‐Raman spectra of the singly oxidized species generated upon treatment with FeCl3 in CH2Cl2 solution have also been recorded. The experimental data were interpreted with the help of DFT calculations. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Control of the Molecular Alignment Inside Liquid‐Crystal Droplets by Use of Laser Tweezers
Authors: Murazawa Naoki , Juodkazis Saulius , Matsuo Shigeki , Misawa Hiroaki 
Published: April 2005

AbstractHere, we demonstrate how the light‐induced birefringence due to the dipole molecular realignment and anisotropic polarizability of a nematic liquid crystal inside a droplet changes the droplet’s radial (and thus optically isotropic) structure into a birefringent one. This intensity‐dependent change of birefringence can be understood in terms of the anisotropic polarizability and orientational optical nonlinear effect. Birefringence induced by laser tweezers changes the momentum of the passing light. In turn, for the circularly polarized tweezers, this change generates an angular momentum change large enough to spin micrometer‐sized droplets. For the linearly polarized tweezers, the molecular ordering generates momentum, which laterally displaces the droplet. It is shown that the optical nonlinearity can be “large” enough to have mechanical (ponderomotive) implications, that is, it allows control of the movement and position of micro‐objects with submicrometer resolution. The optically induced molecular alignment controlled by the polarization and power of the laser tweezers allows one to actuate, rotate, and translate objects which are up to 103–104 times larger than the constituent molecules themselves.
Flow Focusing: A Versatile Technology to Produce Size‐Controlled and Specific‐Morphology Microparticles
Authors: Martín‐Banderas Lucía , Flores‐Mosquera María , Riesco‐Chueca Pascual , Rodríguez‐Gil Alfonso , Cebolla Ángel , Chávez Sebastián , Gañán‐Calvo Alfonso M. 
Published: April 2005

AbstractThe Flow Focusing platform is especially advantageous for micro‐ and nanoparticle production. This versatile technique is amenable to designing the size, surface treatment and internal topology of the particles; mechanical stresses are minimal—an optimal feature for the manipulation of delicate substances. Multiplexing and high‐rate production are readily implemented. Adaptive operational design can lead, in one single step, to finely tuned microcapsules encasing different products within a targeted morphology. This achievement is of great significance for most microcapsule applications in the biosciences (for example, drug delivery, cell encapsulation, and the production of bead arrays).