bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flashbulb and factual memories: the case of Rabin's assassination
Authors: Nachson Israel , Zelig Anat 
Published: June 2003

AbstractSimilarities and differences between factual memories (FTM) and flashbulb memories (FBM) of the assassination of Israel's Prime Minister, Itzhak Rabin, were explored. About two weeks after the assassination 61 Israeli students filled out a questionnaire which focused on the event and the circumstances in which they had first learned about it. About 11 months later they filled out again the same questionnaire, and self‐assessed their emotional and cognitive reactions to the assassination, as well as specific properties of their memory; such as confidence in its accuracy, and the amounts of rehearsals and visual representations. Comparative analysis of the participants' responses on the two questionnaires uncovered decrements of about 25% in FTM accuracy, and about 36% in FBM consistency. Rehearsals and visual representations were more common in FTM than in FBM, but the levels of confidence in memory accuracy were similar for both. FTM which were presumably based on information provided by television broadcasts, appeared to have episodic properties. The data seem to support the hypothesis that FTM and FBM of traumatic public events are encoded together; perhaps by the same memory mechanism. Copyright © 2003 John Wiley & Sons, Ltd.
Elektrosprayionisierungs‐Tandem‐Massenspektrometrie im Hochdurchsatz‐Screening homogener Katalysatoren
Authors: Chen Peter 
Published: June 2003

AbstractDer Vortitel enthält eine Illustration von John Tenniel und einen Auszug aus “Alice im Wunderland” von Lewis Carroll in der Ausgabe von 1865. Weil alles im Wunderland der Logik widerspricht, erklärt die Königin im Prozess gegen Alice: “Zuerst die Strafe, dann das Urteil!” Das üblicherweise praktizierte Hochdurchsatz‐Screening von Katalysatoren beruht auf dem Prinzip “zuerst die Synthese, dann das Screening”, worin, wie in diesem Aufsatz diskutiert wird, ebenfalls die Logik umgekehrt ist. Unter den besonderen Zwangsbedingungen für metallorganische Komplexe ist es effizienter, eine selektive Synthese erst dann zu entwickeln, wenn eine bestimmte Struktur der katalytisch aktivste Kandidat unter vielen zu sein scheint. Demzufolge müssen Screening‐Methoden auch für schlecht definierte Mischungen geeignet sein. Die Elektrosprayionisierungs‐Tandem‐Massenspektrometrie bietet eine ausgezeichnete technische Lösung für dieses Problem.
Tyrosine and peptide reorientational mobility in polymer solutions: Time‐dependent fluorescence anisotropy measurements
Authors: Bothwell Troy G. , Unruh Jay R. , Johnson Carey K. 
Published: June 2003

AbstractThe ability of peptides to form biologically active conformations that bind to receptors is governed by their dynamics and their propensity to form stable structures. Such factors are consequently important in the design of peptide drugs. Moreover, the stability of such peptides depends on interactions of the peptide with the surrounding matrix. In this article, we study the effect of the polymer poly(vinyl pyrrolidone) (PVP) on the mobility and orientational dynamics of tyrosine and a model peptide, Val–Tyr–Pro–Asn–Gly–Ala (VYPNGA) in glycerol–water solutions. Orientational dynamics are studied experimentally by time‐resolved fluorescence anisotropy decays of tyrosine. The presence of PVP leads to the possibility of a distribution of environments for the peptide. The orientational dynamics of tyrosine show that the probe molecule experiences two very different environments. In one, tyrosine rotational motion is weakly coupled to PVP, while in the other, tyrosine interacts strongly with PVP leading to much slower rotational times. The dynamics of VYPNGA are more complex. Fast intramolecular, localized reorientations of the tyrosine are detected. The temperature dependence of the reorientational dynamics of the tyrosine side chain reveal that these motions are shielded from solvent friction. In contrast, global motions of the peptide are severely restricted by PVP, suggesting the ability of the polymer to restrict peptide mobility. © 2003 Wiley Periodicals, Inc. Biopolymers 69: 351–362, 2003
Size and shape of the repetitive domain of high molecular weight wheat gluten proteins. II. Hydrodynamic studies
Authors: van Swieten Eric , Friesen Robert R. , de Kruif Cees G. , Robillard George T. 
Published: June 2003

AbstractThis study describes the hydrodynamic properties of the repetitive domain of high molecular weight (HMW) wheat proteins, which complement the small‐angle scattering (SANS) experiments performed in the first paper of this series. The sedimentation coefficients, s0, and diffusion coefficients, D0, were obtained from the homologuous HMW proteins dB1 and dB4 that were cloned from the gluten protein HMW Dx5, and expressed in Escherichia coli. Monodisperse conditions for accurate determination of s0 and D0, were obtained by screening a series of buffers using dynamic light scattering. For the first time, hydrodynamic parameters were obtained on monodisperse samples that enabled the determination of the monomeric size and shape. The hydrodynamic values determined on dB1 and dB4 were used to test the worm‐like chain (WLC) model that was proposed in the SANS studies. The successful matching of two separately obtained hydrodynamic parameters of dB1 and dB4 using the WLC model provides further evidence for the WLC model. The small discrepancy between the hydrodynamic and scattering data, possibly coming from the excluded volume effect, was compensated by a solvation layer of 1–2 water molecules thick around the protein in the WLC model. The solvation of the central domain is much higher than those of the terminal domains of the HMW subunits. This difference emphasizes the dual role of HMW wheat gluten proteins in water‐binding and aggregation. © 2003 Wiley Periodicals, Inc. Biopolymers 69: 325–332, 2003
Contribution of Raman spectroscopy to identification of biominerals present in teeth of Acanthopleura rehderi, Acanthopleura curtisiana, and Onithochiton quercinus
Authors: Lee Alasdair P. , Brooker Lesley R. , Van Bronswijk Wilhelm , Macey David J. , Webb John 
Published: June 2003

AbstractRaman spectroscopic investigations of the major lateral teeth of the chitons Acanthopleura rehderi and Acanthopleura curtisiana indicate that, in addition to the magnetite of the cutting surface and a carbonated hydroxyapatite in the central tooth core, these species deposit limonite in place of the lepidocrocite reported for other members of the genus Acanthopleura. A comparison of the spectra from these species with those of Onithochiton quercinus, which also deposits limonite, indicates that the current assignment of these species to Acanthopleura may not be appropriate. Biomineralization of the major lateral teeth may be a useful parameter to include in the taxonomic classification of chiton species. © 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy), 2003
Recognition of thymine by triazine fluorescent probe through intermolecular multiple hydrogen bonding
Authors: Nie Lihua , Ma Huimin , Li Xiaohua , Sun Ming , Xiong Shaoxiang 
Published: June 2003

AbstractIn order to design a fluorescent probe with a long wavelength and multiple hydrogen bond sites for thymine, 3‐(4‐chloro‐6‐methylamino‐1,3,5‐triazinylamino)‐7‐dimethylamino‐2‐methylphenazine is synthesized by subsequently reacting neutral red and methylamine with cyanuric chloride. Its recognition behavior for thymine and its spectroscopic properties in different solvents are studied. The probe's fluorescence can be selectively quenched by thymine instead of guanine, indicating that fully complementary hydrogen bonding plays a key role in such recognition processes. In addition, the recognition mechanism of the probe for thymine and the bathochromic shift of its fluorescence spectra with the solvent polarity are also discussed. © 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy), 2003
Resonance Raman spectroscopy study of change of iron spin state in horseradish peroxidase C induced by removal of calcium
Authors: Huang Qing , Laberge Monique , Szigeti Krisztian , Fidy Judit , Schweitzer‐Stenner Reinhard 
Published: June 2003

AbstractResonance Raman spectroscopy is used to probe the effect of calcium depletion on the heme group of horseradish peroxidase C at pH 8. Polarized Raman spectra are recorded with an argon ion laser at eight different wavelengths to provide a sound database for a reliable spectral decomposition. Upon calcium depletion, the spectrum is indicative of a predominantly pentacoordinated high spin state of the heme iron coexisting with small fractions of hexacoordinated high and low spin states. The dominant quantum mixed spin state of native ferric horseradish peroxidase, which is characteristic for class III peroxidases, is not detectable in the spectrum of the enzyme with partial distal Ca2+ depletion. The quenching of the quantum mixed spin state and the predominance of the pentacoordinated high spin state are likely to arise from distortions induced by distal calcium depletion, which translates into a weaker Fe‐Nϵ(His) bond and a more tilted imidazole. A correlation is proposed between the lower enzyme activity and the elimination of the pentacoordinated quantum mixed state upon Ca2+ depletion. © 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy), 2003
Simultaneous determination of leflunomide and its active metabolite, A77 1726, in human plasma by high‐performance liquid chromatography
Authors: Schmidt Andreas , Schwind Bianca , Gillich Martin , Brune Kay , Hinz Burkhard 
Published: June 2003

AbstractThe isoxazol derivative leflunomide [N‐(4′‐trifluoromethylphenyl)‐5‐methylisoxazole‐4‐carboxamide] is an inhibitor of de novo pyrimidine synthesis used for the treatment of rheumatoid artrithis. In the present study, a liquid–liquid extraction‐based reversed‐phase HPLC method with UV detection was validated and applied for the analysis of leflunomide and its active metabolite, A77 1726, in human plasma. The analytes were separated using a mobile phase, consisting of acetonitrile, water and formic acid (40/59.8/0.2, v/v), at a flow rate of 0.5 mL/min, and UV detection at 261 nm. The retention times for A77 1726, leflunomide and warfarin (internal standard) were 8.2, 16.2 and 12.2 min, respectively. The validated quantification range of the method was 0.05–100 µg/mL for leflunomide and 0.1–100 µg/mL for A77 1726. The developed procedure was applied to assess steady‐state plasma concentrations of A77 1726 in patients with rheumatoid arthritis treated with 10 or 20 mg leflunomide per day. Copyright © 2003 John Wiley & Sons, Ltd.
A Catalytic Antibody Programmed for Torsional Activation of Amide Bond Hydrolysis
Authors: Aggarwal Ranjana , Benedetti Fabio , Berti Federico , Buchini Sabrina , Colombatti Alfonso , Dinon Francesca , Galasso Vinicio , Norbedo Stefano 
Published: June 2003

AbstractAmidase antibody 312d6, obtained against the sulfonamide hapten 4 a that mimics the transition state for hydrolysis of a distorted amide, accelerates the hydrolysis of the corresponding amides 1 a–3 a by a factor of 103 at pH 8. The mechanisms of both the uncatalyzed and antibody‐catalyzed reactions were studied. Between pH 8 and 12 the uncatalyzed hydrolysis of N‐toluoylindoles 1 a and 3 a shows a simple first‐order dependence on [OH−], while hydrolysis of 3 a is zeroth‐order in [OH−] below pH 8. The pH profile for hydrolysis of the corresponding tryptophan amide 2 a is more complex due to the dissociation of the zwitterion into an anion with pKa 9.74; hydrolysis of the zwitterionic and the anionic form of 2 a both show simple first‐order dependence on [OH−]. Absence of 18O exchange between H218O/18OH− and the substrate, a normal SKIE for both 1 a (kH/kD=1.12) and 3 a (kH/kD=1.24) and the value of the Hammett constant ρ for hydrolysis of p‐substituted amides 3 a–e are consistent with an ester‐like mechanism in which formation of the tetrahedral intermediate is rate‐determining and the amine departs as anion. The 312d6‐catalyzed hydrolysis of 3 a was studied between pH 7.5 and 9, and its independence of pH in this range indicates that water is the reacting nucleophile. Hydrolysis of 3 a is only partially inhibited by the sulfonamide hapten, and this indicates that non‐specific catalysis by the protein accompanies the specific process. Only the nonspecific process is observed in the hydrolysis of amides 3 with para substituents other than methyl. Binding studies on the corresponding series of p‐substituted sulfonamides 5 a–e confirm the high specificity of antibody 312d6 for p‐methyl substituted substrates.
Interaction of the Benzenium Ion with Inert Ligands: IR Spectra of C6H7+Ln Cluster Cations (L=Ar, N2, CH4, H2O)
Authors: Solcà Nicola , Dopfer Otto 
Published: June 2003

AbstractIR photodissociation spectra of mass‐selected clusters composed of protonated benzene (C6H7+) and several ligands L are analyzed in the range of the CH stretch fundamentals. The investigated systems include C6H7+Ar, C6H7+(N2)n (n=1–4), C6H7+(CH4)n (n=1–4), and C6H7+H2O. The complexes are produced in a supersonic plasma expansion using chemical ionization. The IR spectra display absorptions near 2800 and 3100 cm−1, which are attributed to the aliphatic and aromatic CH stretch vibrations, respectively, of the benzenium ion, that is, the σ complex of C6H7+. The C6H7+(CH4)n clusters show additional CH stretch bands of the CH4 ligands. Both the frequencies and the relative intensities of the C6H7+ absorptions are nearly independent of the choice and number of ligands, suggesting that the benzenium ion in the detected C6H7+Ln clusters is only weakly perturbed by the microsolvation process. Analysis of photofragmentation branching ratios yield estimated ligand binding energies of the order of 800 and 950 cm−1 (≈9.5 and 11.5 kJ mol−1) for N2 and CH4, respectively. The interpretation of the experimental data is supported by ab initio calculations for C6H7+Ar and C6H7+N2 at the MP 2/6‐311 G(2df,2pd) level. Both the calculations and the spectra are consistent with weak intermolecular π bonds of Ar and N2 to the C6H7+ ring. The astrophysical implications of the deduced IR spectrum of C6H7+ are briefly discussed.
Chiral [RuCl2(dipyridylphosphane)(1,2‐diamine)] Catalysts: Applications in Asymmetric Hydrogenation of a Wide Range of Simple Ketones
Authors: Wu Jing , Ji Jian‐Xin , Guo Rongwei , Yeung Chi‐Hung , Chan Albert S. C. 
Published: June 2003

AbstractThe dipyridylphosphane/diamine–Ru complex combined with tBuOK in 2propanol acts as a very effective catalyst system for the enantioselective hydrogenation of a diverse range of simple ketones including heteroaromatic ketones, substituted benzophenones, alkenyl ketones, and cyclopropyl ketones. The combination of desirable features, such as quantitative chemical yields within hours, broad substrate scope, excellent enantioselectivities (up to 99 %), and high substrate‐to‐catalyst ratios, among others, makes the present catalyst system of high practical interest.
Density Functional Characterization of the Chemoselective Oxidation of Catechol by using Molecular Oxygen: Thermodynamics of the Reaction between [(triphos)Ir(dtbc)]+ and O2
Authors: Bencini Alessandro , Bill Eckhard , Scozzafava Andrea , Totti Federico 
Published: June 2003

AbstractThe catalytic mechanism of intra and extra catechol cleaving dioxygenases is still a matter of debate, because the intermediate transient oxygen adduct has never been isolated in these enzymes. The complex [(triphos)Ir(dtbc)]+ (triphos=MeC(CH2PPh2)3, DBTC2−=3,5‐di‐tert‐butylcatecholate), reacts with molecular oxygen and exhibits a ring‐cleaving catalytic activity, and a stable oxygen intermediate appears; this stimulates an opportunity for obtaining information that can be transferable to the above‐mentioned enzymatic catalytic centers, therefore, giving a breakthrough into the strategy of oxygen activation in these natural systems. Here, we present the results of our computational approach, based on density functional theory, focusing on the following aspects: to explain the interaction with molecular oxygen and how to avoid the existing spin problem, to understand the formation of the bridging moiety, to clarify, if any, the possible influence on the structure of the formed adduct of the bidentate versus monodentate binding of the catechol ligand, and to disclose, eventually, the nature of final decomposition products with the aim to rationalize the intra versus extra cleavage of the catechol molecule itself.
Greener Solvents: Room Temperature Ionic Liquids from Biorenewable Sources
Authors: Handy Scott T. 
Published: June 2003

AbstractRoom temperature ionic liquids (RTILs) have attracted a great deal of interest as environmentally benign (green) solvents for organic synthesis. More recently, RTILs that are chiral, less expensive, or functionalized (protic or Lewis basic) have been developed. In many cases, these new solvents are based on the modification of natural products. This paper is an overview of these new biorenewable RTILs.
Cyclodextrin Phosphanes as First and Second Coordination Sphere Cavitands
Authors: Engeldinger Eric , Armspach Dominique , Matt Dominique , Jones Peter G. 
Published: June 2003

AbstractThe binding properties of two α‐cyclodextrins, each containing two C(5)‐linked “CH2PPh2” units, L 1 (A,D‐substituted) and L 2 (A,C‐substituted), have been investigated. Both ligands readily form transition‐metal chelate complexes in which the metal centres are immobilised at the cavity entrance. Although diphosphane L 1 displays a marked tendency to behave only as a trans‐spanning ligand, the ligand possesses a certain degree of flexibility, for example, allowing the stabilisation of a trigonal silver(I) complex in which the bite angle drops to 143°. Another feature of L 1 concerns its ability to function as an hemilabile ligand. Together with four methoxy groups anchored onto the primary face, the two PIII centres of L 1 form a circularly arranged P2O4 12‐electron donor set able to complex an Ag+ ion in a dynamic way, each of the four oxygen atoms coordinating successively to the silver ion. Furthermore, the particular structures of L 1 and L 2, characterised by the presence of PIII units lying close to the cavity entrance, lead upon complexation to complexes whereby the first coordination sphere is partly entrapped in the cyclodextrin. Thus, when treated with metal chlorides, both ligands systematically produce complexes in which the MCl unit is maintained inside the cyclodextrin through weak Cl⋅⋅⋅H‐5 interactions. The chelate complex [Ag(L 1)]BF4 reacts with acetonitrile in excess to afford a mixture of two equilibrating complexes, [Ag(acetonitrile)(L 1)]BF4 and [Ag(acetonitrile)2(L 1)]BF4, whose coordinated nitriles lie inside the cyclodextrin cavity. The inner‐cavity ligands can be substituted by a benzonitrile molecule. The present study provides the first identification of an [Ag(acetonitrile)2(phosphane)2]+ ion. The unexpected stabilisation of this species probably rests on a cavity effect, the cyclodextrin walls favouring recombination of the complex after facile dissociation of the nitrile ligands.
A Systematic Exploration of Nickel–Pyrazolinato Chemistry with Alkali Metals: New Cages From Serendipitous Assembly
Authors: Aromí Guillem , Bell Aidan R. , Helliwell Madeleine , Raftery James , Teat Simon J. , Timco Grigore A. , Roubeau Olivier , Winpenny Richard E. P. 
Published: June 2003

AbstractThe preparation and properties of fourteen novel paramagnetic [NiIIx] aggregates bridged by pivalate, pyrazolinolate and in most cases hydroxide are reported. A rich structural diversity has been achieved by changing the nature of the alkali of the base used during the synthesis, leading to the nuclearities [NiII4NaI4] (2, 3, 4), [NiII5NaI4] (5, 6, 7), [NiII5LiI6] (8), [NiII8MI2] (M=K (9, 10), Rb (11, 12), Cs (13, 14) and [NiII8] (15). All compounds have been characterised by single‐crystal Xray diffraction; however, full crystallographic details are given only for the representative molecules [Ni4Na4(fpo)4(piv)8(Hpiv)8] (2), [Ni5Na4(OH)2(mpo)4(piv)8(Hpiv)2(MeCN)2] (5), [Ni5Li6(OH)2(fpo)2(piv)12(Hpiv)4] (8), [Ni8K2(OH)4(ppo)4(piv)10(Hppo)2(Hpiv)2(MeCN)2] (9), [Ni8Rb2(OH)4(ppo)4(piv)10(Hppo)2(Hpiv)2(MeCN)2] (11), [Ni8Cs2(OH)4(ppo)4(piv)10(Hppo)2(Hpiv)2(MeCN)2] (13) and [Ni8(OH)4(mpo)2(PhCH2CO2)10(Hmpo)8] (15). Variable‐temperature bulk magnetisation measurements have been performed for each type of complex. The [NiII4NaI4] clusters show intramolecular antiferromagnetic coupling and a spin ground state of S=0. Complexes of the type [NiII5NaI4] also display antiferromagnetic superexchange, leading to an S=1 spin ground state. The molecule with nuclearity [NiII5LiI6], in contrast, exhibits ferromagnetic interactions, resulting in the presence of low energy states with high multiplicity, and a spin ground state S>1. The [NiII8MI2] and [NiII8] clusters have the same topology of spin carriers, which display predominantly antiferromagnetic interactions to yield a diamagnetic ground state. The coupling within these octanuclear NiII clusters is rationalised in terms of the nature of the Ni‐O‐Ni angles within the core.
Discrete Cyanide‐Bridged Mixed‐Valence Co/Fe Complexes: Outer‐Sphere Redox Behaviour
Authors: Bernhardt Paul V. , Bozoglian Fernando , Macpherson Brendan P. , Martínez Manuel , González Gabriel , Sienra Beatriz 
Published: June 2003

AbstractThe outer‐sphere redox behaviour of a series of [LnCoIIINCFeII(CN)5]− (Ln = n‐membered pentadentate aza‐macrocycle) complexes have been studied as a function of pH and oxidising agent. All the dinuclear complexes show a double protonation process at pH ≈︁ 2 that produces a shift in their UV/Vis spectra. Oxidation of the different non‐protonated and diprotonated complexes has been carried out with peroxodisulfate, and of the non‐protonated complexes also with trisoxalatocobaltate(III). The results are in agreement with predictions from the Marcus theory. The oxidation of [Fe(phen)3]3+ and [IrCl6]2− is too fast to be measured, although for the latter the transient observation of the process has been achieved at pH = 0. The study of the kinetics of the outer‐sphere redox process, with the S2O82− and [Co(ox)3]3− oxidants, has been carried out as a function of pH, temperature, and pressure. As a whole, the values found for the activation volumes, entropies, and enthalpies are in the following margins, for the diprotonated and non‐protonated dinuclear complexes, respectively: ΔV≠ from 11 to 13 and 15 to 20 cm3 mol−1; ΔS≠ from 110 to 30 and −60 to −90 J K−1 mol−1; ΔH≠ from 115 to 80 and 50 to 65 kJ·mol−1. The thermal activation parameters are clearly dominated by the electrostriction occurring on outer‐sphere precursor formation, while the trends found for the values of the volume of activation indicate an important degree of tuning due to the charge distribution during the electron transfer process. The special arrangement on the amine ligands in the isomer trans‐[L14CoIIINCFeII(CN)5]− accounts for important differences in solvent‐assisted hydrogen bonding occurring within the outer‐sphere redox process, as has been established in redox reactions of similar compounds. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)