bluuebunny/crossref_metadata_2025_split huggingface dataset:
DFT computational studies on rotation barriers, tautomerism, intramolecular hydrogen bond, and solvent effects in 8‐hydroxyquinoline
Authors: Shchavlev Andrew E. , Pankratov Alexei N. , Shalabay Alexei V. 
Published: October 2005

AbstractIntramolecular hydrogen binding interactions in 8‐hydroxyquinoline, both in its zwitterionic tautomer and in the rotamer without the intramolecular hydrogen bond (IHB), have been computed using the B3LYP and MPW1K density functionals. The rotation of the OH bond and intramolecular proton transfer reactions were studied theoretically. The following theory levels have been applied: B3LYP/6‐31G(d,p), B3LYP/6‐311++G(d,p), MPW1K/6‐311++G(d,p), and MPW1K/6‐311++G(2d,3p)//MPW1K/6‐311++G(d,p). Natural bond orbital (NBO) analysis has also been carried out. The effect of medium (benzene, chloroform, tetrahydrofuran, 1,2‐dichloroethane, acetone, water) was simulated using the self‐consistent reaction field (SCRF) method within the framework of the polarizable continuum model (PCM), at the MPW1K/6‐311++G(d,p) level. The evolution of geometry, relative energies, heights of rotation (around the OH bond) and tautomerization barriers, IHB energies, and ΔG(solv) have been systematically investigated. The results obtained have shown the failure to neglect some changes of the above characteristics in polar media with respect to the gaseous phase. The series of stability of the forms under study in the gaseous phase remains the same in solution. Thus, in spite of the important role of the solvent electrostatic effects, the intrinsic stability of those species overcomes the solvent effects. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Gallium phosphides GAmPn(m+n= 2–5) and their anions: Structures, electron affinities, and vibrational frequencies
Authors: Guo Ling , Wu Haishun 
Published: October 2005

AbstractGeometries, electronic states, and electron affinities of GamPnand GamP(m + n= 2–5) clusters have been examined using four hybrid and pure density functional theory (DFT) methods. Structural optimization and frequency analyses are performed with the basis of a 6‐311+G(2df)one‐particle basis set. The geometries are fully optimized with each DFT method independently. Three types of energy separations reported in this work are the adiabatic electron affinity (EAad), the vertical electron affinity (EAvert), and the vertical detachment energy (VDE). The calculation results show that the singlet structures have higher symmetry than that of doublet structures. The best method for predicting molecular structures was found to be BLYP, while other methods generally underestimated bond lengths. The most reliable adiabatic electron affinities and vertical detachment energy, obtained at the BP86 and B3LYP level of theory, are predicted to be 2.22 and 2.10 eV (GaP), 2.51 and 2.46 eV (Ga2P), 1.86 and 1.94 eV (GaP2), 1.96 and 2.27 eV (GaP3), 1.76 and 1.99 eV (Ga3P), 1.79 and 2.14 eV (Ga2P2), 2.85 and 3.67 eV (GaP4), 2.08 and 2.10 eV (Ga4P), 2.90 and 3.17 eV (Ga2P3), and 2.70 and 3.37 eV (Ga3P2), respectively. Those for Ga2P, Ga3P, Ga2P2, Ga4P, GaP4, Ga2P3, and Ga3P2are in good agreement with experiment, but the predicted EAadvalues for GaP, Ga2P, GaP2, and GaP3are larger than the available experimental values. For the vibrational frequencies of the GamPnseries, the B3LYP method produces good predictions with the average error only ∼10 cm−1from available experimental and theoretical values. The other three methods overestimate or underestimate the vibrational frequencies, with the worst predictions given by the BLYP method. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Theoretical study of the mechanism of CH2CO + CN reaction
Authors: Sun Hao , He Hong‐Qing , Hong Bo , Chang Ying‐Fei , An Zhe , Wang Rong‐Shun 
Published: October 2005

AbstractThe potential energy surface information of the CH2CO + CN reaction is obtained at the B3LYP/6‐311+G(d,p) level. To gain further mechanistic knowledge, higher‐level single‐point calculations for the stationary points are performed at the QCISD(T)/6‐311++G(d,p) level. The CH2CO + CN reaction proceeds through four possible mechanisms: direct hydrogen abstraction, olefinic carbon addition–elimination, carbonyl carbon addition–elimination, and side oxygen addition–elimination. Our calculations demonstrate that R→IM1→TS3→P3: CH2CN + CO is the energetically favorable channel; however, channel R→IM2→TS4→P4: CH2NC + CO is considerably competitive, especially as the temperature increases (R, IM, TS, and P represent reactant, intermediate, transition state, and product, respectively). The present study may be helpful in probing the mechanism of the CH2CO + CN reaction. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Quasi‐classical fluctuation–dissipation description of dielectric loss in oxides with implications for quantum information processing
Authors: Dunne Lawrence J. , Axelsson Anna‐Karin , Alford Neil McN. , Breeze Jonathan , Aupi Xavi , Brändas Erkki J. 
Published: October 2005

AbstractOne of the most important problems in developing devices for quantum computation is the coupling and dissipation of states by thermal noise. We present a study of a two‐state electric dipole in a crystal coupling to noise from a reservoir. As a realization of such an energy‐dissipating dipole, we report and analyze dielectric loss measurements in single crystal and polycrystalline Al2O3 over the temperature range 70–300 K. We are able to model the dielectric loss in terms of a quasi‐classical model that uses the fluctuation–dissipation theorem. Two key parameters in this model are the crystal oscillator energy and reservoir–lattice coupling constant. In polycrystalline samples, it is assumed that the main effect of structural disorder is a modification of the spectrum of the thermal phonons, so that acoustical vibrations acquire some optical mode character. The temperature dependence of the linewidth of the high dielectric strength infrared (IR) mode at 438 cm−1 and the quasi‐degenerate Raman mode of the k = 0 (418 cm−1) transition are also investigated and are shown to be related simply to the dielectric loss. The model reproduces the unusual temperature dependence of the dielectric loss observed experimentally. The implications for the coupling of quantum mechanical objects to noise and quantum information processing are discussed. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Chiral discrimination in hydrogen‐bonded complexes of hydrogen peroxide with methyl hydroperoxide: Theoretical study
Authors: Du Dongmei , Zhou Zhengyu 
Published: October 2005

AbstractFor the first time, the discrimination of different chiral forms of 1:1 complexes with hydrogen peroxide and methyl hydroperoxide have been investigated using density functional theory (DFT) and Møller–Plesset type 2 (MP2) methods at varied basis set levels from 6‐31+G(d,p) to 6‐31++G(2d,2p). Three pairs of chiral enantiomers were considered. The optimized geometric parameters, interaction energies, and chirodiastatic energies for various isomers at different levels are estimated. To take into account the water solvation effect, the polarized continuum model (PCM) method has been used to evaluate the ΔGsolv. The gas phase results show that the heterochiral six‐membered ring complex (structure I) and homochiral five‐membered ring complexes (structures IV and V) are preferred configurations for the three pairs of chiral enantiomers. The solvation effect on six‐membered ring complexes (structures I and II) shows nonsignificant changes in the configurations preferred, but on five‐membered ring complexes, the homo‐/heterochiral preference is found to be inverse in the polar solvent. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Theoretical study of CH…O hydrogen bond in proton transfer reaction of glycine
Authors: Selvarengan P. , Kolandaivel P. 
Published: October 2005

AbstractDensity functional theory (DFT) calculations are used to study the strength of the CH…O H‐bond in the proton transfer reaction of glycine. Comparison has been made between four proton transfer reactions (ZW1, ZW2, ZW3, SCRFZW) in glycine. The structural parameters of the zwitterionic, transition, and neutral states of glycine are strongly perturbed when the proton transfer takes place. It has been found that the interaction of water molecule at the side chain of glycine is high in the transition state, whereas it is low in the zwitterionic and neutral states. This strongest multiple hydrogen bond interaction in the transition state reduces the barrier for the proton transfer reaction. The natural bond orbital analysis have also been carried out for the ZW2 reaction path, it has been concluded that the amount of charge transfer between the neighboring atoms will decide the strength of H‐bond. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Study of the mass spectrometric fragmentation of pseudouridine: comparison of fragmentation data obtained by matrix‐assisted laser desorption/ionisation post‐source decay, electrospray ion trap multistage mass spectrometry, and by a method utilising electrospray quadrupole time‐of‐flight tandem mass spectrometry and in‐source fragmentation
Authors: Dudley Edward , Tuytten Robin , Bond Alison , Lemière Filip , Brenton A. Gareth , Esmans Eddy L. , Newton Russell P. 
Published: October 2005

AbstractMany nucleosides and their modified forms have been studied by mass spectrometry elaborating the detailed fragmentation pathways under MS2 and MSn conditions. Although the C‐nucleoside pseudouridine has been fragmented and studied briefly, usually amongst many other nucleosides, it has not been investigated to the same extent as other nucleosides. In this report a number of different mass spectrometric techniques are applied to obtain a fuller picture of pseudouridine fragmentation. At the same time this study is used to compare different tandem mass spectrometric techniques, including a novel methodology utilising a quadrupole time‐of‐flight (Q‐ToF) instrument for MSn analysis comparable with that available with an ion trap mass spectrometer. Copyright © 2005 John Wiley & Sons, Ltd.
Noncovalent complex formation of tetratosylated resorcarene with aromatic, aliphatic, and cyclic alkyl ammonium ions: a mass spectrometric study of complex properties
Authors: Ventola Elina , Pirskanen Atte , Vainiotalo Pirjo 
Published: October 2005

AbstractThe ability of tetratosylated resorcarene to form complexes with aromatic ammonium ions was investigated by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. The formation of noncovalent complexes, [1+guest]+ and [1 · 1+guest]+, as observed with singly charged aromatic anilinium and phenylene aminoammonium guests. Comparison of the complexation efficiencies of the aromatic and aliphatic ammonium ions showed the importance of proton affinity of conjugate amines in complex formation. In collision‐induced dissociation experiments, gas‐phase stability was found to be lower for complexes formed with aromatic ions and this behavior was not found to depend on the proton affinity of conjugate amines. Fast oxidation of the para and ortho aminoammonium ions and complexation of these ions with tetratosylated resorcarene was observed. Copyright © 2005 John Wiley & Sons, Ltd.
Dansylation of tryptic peptides for increased sequence coverage in protein identification by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometric peptide mass fingerprinting
Authors: Park Soo‐Jin , Song Jin‐Su , Kim Hie‐Joon 
Published: October 2005

AbstractA database search using peptide mass fingerprints obtained by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry leads to protein identification with incomplete sequence coverage, because certain peptides are preferentially desorbed/ionized and some are not detected at all. We show that certain tryptic peptides mainly with C‐terminal arginine not detected before derivatization become detectable upon dansylation. Others, mainly with C‐terminal lysine, are suppressed. An increase in protein sequence coverage and protein identification score by combined data from underivatized and dansylated peptides in database search is demonstrated using human amnion proteins (human serum albumin precursor, calmodulin, collagen alpha 2(VI) chain precursor, galectin‐3) separated by two‐dimensional gel electrophoresis as well as femtomole amounts of BSA in solution. Copyright © 2005 John Wiley & Sons, Ltd.
Characterization of a new methylated β‐cyclodextrin with a low degree of substitution by electrospray ionization mass spectrometry and liquid chromatography/mass spectrometry
Authors: Jacquet Romain , Elfakir Claire , Lafosse Michel 
Published: October 2005

AbstractA new methylated β‐cyclodextrin (Me‐β‐CD) with a low degree of substitution (DS) was characterized by electrospray ionization mass spectrometry (ESI‐MS) and liquid chromatography coupled with ESI‐MS (LC/ESI‐MS). For ESI‐MS analyses, the composition of the infused sample solution was optimized in order to obtain only singly charged ammoniated CDs without fragmentation. The DS value (i.e. the number of methyl groups per glucopyranose unit) was found to be 0.7, which was in accordance with the values previously obtained by other methods. The LC/ESI‐MS analysis, derived from a method using evaporative light scattering detection, allowed the study of the substitution isomers of each derivative and appears to be an easy and rapid tool for the accurate characterization of Me‐β‐CD mixtures. Copyright © 2005 John Wiley & Sons, Ltd.
Structural determination of the novel fragmentation routes of morphine opiate receptor antagonists using electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry
Authors: Joly Nicolas , Aneed Anas El , Martin Patrick , Cecchelli Roméo , Banoub Joseph 
Published: October 2005

AbstractElectrospray ionization quadrupole time‐of‐flight (ESI‐QqToF) mass spectra of naltrindole hydrochloride 1, naltriben mesylate 2, and naltrexone hydrochloride 3, a common series of morphine opiate receptor antagonists, were recorded using different declustering potentials. Low‐energy collision‐induced dissociation (CID) MS/MS experiments established the fragmentation routes of these compounds. In addition, re‐confirmation of the various established fragmentation routes was effected by conducting a series of ESI‐CID‐QqTof‐MS/MS experiments using non‐conventional quasi MSn (up to MS8) product ion scans, which were initiated by CID in the atmospheric pressure/vacuum interface using a higher declustering potential. Precursor ion scan analyses were also performed with a conventional quadrupole‐hexapole‐quadrupole tandem mass spectrometer and allowed the confirmation of the genesis of some diagnostic ions. Copyright © 2005 John Wiley & Sons, Ltd.
Uniformity of ionization response of structurally diverse analytes using a chip‐based nanoelectrospray ionization source
Authors: Hop Cornelis E. C. A. , Chen Yue , Yu Li J. 
Published: October 2005

AbstractThe major drawback of liquid chromatography/mass spectrometry (LC/MS) for the analysis of mixtures is the non‐quantitative nature of these studies. The ionization efficiency of the various components in the mixture (e.g., a compound and its metabolites) can vary greatly and, therefore, relative intensities of signals cannot be related to relative abundance. A chip‐based nanoelectrospray ionization source was used to compare the ionization efficiencies of compounds with different physical‐chemical characteristics. The data indicate that the ionization efficiencies vary much less with the chip‐based device than by LC/MS. This was ascribed to the generation of a much higher electric field around the nozzles, which supplies a large excess of protons to the small droplets and reduces/eliminates the differences in the ionization efficiency for the analytes. Copyright © 2005 John Wiley & Sons, Ltd.
Identification and mass spectrometric characterization of glycosylated flavonoids in Triticum durum plants by high‐performance liquid chromatography with tandem mass spectrometry
Authors: Cavaliere Chiara , Foglia Patrizia , Pastorini Elisabetta , Samperi Roberto , Laganà Aldo 
Published: October 2005

AbstractA mass spectrometric method for extensive detection and semi‐quantitative determination of flavonoid glycosides in stem and leaves of young Triticum durum plants is presented. About 100 g of sample were lyophilized and ground, and the compounds of interest were then extracted, cleaned‐up, and fractionated using high‐performance liquid chromatography (HPLC). Tandem mass spectrometry analyses were performed using a quadrupole‐linear ion trap instrument with an information‐dependent data acquisition (IDA) protocol that looped two experiments, enhanced MS scan and enhanced product ion scan. Various glycoconjugates, which are all derivatives of only four flavones, apigenin, luteolin, chrysoeriol and tricin, were identified and belong to the following categories: 7 monoglycosides, 31 diglycosides, 15 triglycosides and 1 tetraglycoside. Among these some acylated glycosides were found. Tricin derivatives are present exclusively as O‐glycosides, while apigenin and luteolin are present always as C‐glycosides. Semi‐quantitative estimation was performed by using the monoglycoside and diglycoside of quercetin as internal standards. Copyright © 2005 John Wiley & Sons, Ltd.
PET imaging of striatal dopamine D2 receptors in nonhuman primates: Increases in availability produced by chronic raclopride treatment
Authors: Czoty Paul W. , Gage H. Donald , Nader Michael A. 
Published: October 2005

AbstractPrevious research using positron emission tomography (PET) in monkeys has shown that attaining social dominance can result in increased DA D2 receptor availability and attenuated sensitivity to the reinforcing effects of cocaine. The present study utilized a within‐subjects design to determine whether chronic treatment with the D2 receptor antagonist raclopride could similarly increase D2 receptor availability. Using the D2‐selective radioligand [18F]fluoroclebopride (FCP), three adult male cynomolgus monkeys were scanned before and after chronic treatment with raclopride (0.01 mg/kg per h for 30 ± 1 day) administered by a subcutaneous osmotic pump. Food‐reinforced operant behavior was assessed during treatment. A transitory decrease in responding was observed during the initial eight days of raclopride treatment. Tolerance developed by the tenth session, and responding remained at baseline levels for the duration of treatment and after treatment was discontinued. Averaged across monkeys, chronic raclopride administration increased FCP distribution volume ratios (DVRs) between 12 and 20% in the caudate nucleus, putamen, and anterior cingulate cortex. When monkeys were re‐scanned 9–12 months after termination of raclopride treatment, FCP DVRs remained elevated in two subjects, and decreased below baseline levels in the third monkey. Considering the reported 2% test/retest variability for FCP, these findings indicate that chronic treatment with a D2 receptor antagonist can produce large increases in D2 receptor availability as measured with PET. Individual differences in rates of recovery were observed, such that the increases in DVR persisted in two of three subjects. Synapse 58:215–219, 2005. © 2005 Wiley‐Liss, Inc.
Dopamine agonist action of phencyclidine
Authors: Seeman Philip , Lasaga Mercedes 
Published: October 2005

AbstractAlthough the psychotomimetic action of phencyclidine is often used to model a hypoglutamate theory of psychosis or schizophrenia, work also exists showing that phencyclidine has a significant affinity for the dopamine D2 receptor. The present study was done to determine whether phencyclidine has a direct functional dopamine‐like action on cells. The effect of phencyclidine was tested on the release of prolactin from rat cultured anterior pituitary cells. It was found that the release of prolactin was 50% inhibited by 4 nM phencyclidine. This strong dopamine‐like agonist action at the functional high‐affinity state of the dopamine D2 receptor by the phencyclidine psychotomimetic is consistent with the dopamine hypothesis of psychosis. Synapse 58:275–277, 2005. © 2005 Wiley‐Liss, Inc.
Pain and pain‐related fear are associated with functional and social disability in an occupational setting: Evidence of mediation by pain‐related fear
Authors: Gheldof Els L.M. , Vinck Jan , Van den Bussche Eva , Vlaeyen Johan W.S. , Hidding Alita , Crombez Geert 
Published: October 2005

AbstractThis study examined the role of work‐related, psychosocial and psychological factors in predicting functional and social disability in working employees. In a cross‐sectional design, 890 working employees (reporting at least 1 day of back pain during the past year) completed self‐report measures of back pain, disability, pain‐related fear, negative and positive affectivity, job satisfaction, job stress and physical work load. Regression analyses revealed that pain intensity was a strong predictor of functional (β = .69, p < .001) and social disability (β = .67, p < .001). Fear of (re)injury due to movement (β = .25, p < .001; β = .28, p < .001) had additional predictive value in both models. Further, (singular) mediation tests indicated that fear for (re)injury partially mediated the relation between pain intensity and disability, and between negative affectivity and disability. Finally, path analyses revealed both fear and pain intensity as mediators between negative affectivity and disability. Overall, our findings point at the relevance of the cognitive‐behavioral model of avoidance in occupational settings.
The NK1‐receptor antagonist TKA731 in painful diabetic neuropathy: A randomised, controlled trial
Authors: Sindrup Søren H. , Graf Ana , Sfikas Nikolaos 
Published: October 2005

AbstractSubstance P is one of the neurotransmitters released by primary nociceptive neurons in the dorsal horn of the spinal cord and it binds postsynaptically to NK1‐receptors. This receptor is therefore an obvious target for analgesic drugs. The aim of this multicenter, randomised, double‐blind, placebo‐controlled and parallel‐group study was to test if the non‐peptide NK1‐receptor antagonist TKA731 would relieve painful diabetic polyneuropathy. Eighty‐seven patients completed a treatment period of 2 weeks' duration with TKA731 (150 mg daily) or placebo preceded by one week for baseline observations. There was no significant difference between TKA731 and placebo in change in pain rating from baseline to study end neither for rating of total pain (mean −13.4 mm vs. −11.6 mm, p = 0.664) nor for change in ratings of different pain symptoms (touch‐ or pressure‐evoked pain, pain paroxysms, steady burning or deep aching pain) (p = 0.169‐0.834).