bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative study of folate cofactor models
Authors: Kang Congmin , Feng Dacheng , Qi Chuansong , Zhao Weian , Cai Zhengting 
Published: August 2002

AbstractThe structures of a type of tetrahydrofolate cofactor models, asymmetric substituted imidazolinium, have been studied theoretically, and the relation of reactivities to the electronic structures of these compounds has been analyzed. It is found that the reactivity of one‐carbon unit transfer of this type of tetrahydrofolate cofactor models has a tight relation to properties of the two nitrogen atoms that link to the transferring carbon atom. The followed regularity is obtained. With the group on the para‐position of benzenesulfonyl changing from an electronic acceptor to an electronic donor, the difference between N3 and N6 is smaller step by step, and the model becomes more active to transfer one‐carbon unit gradually. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Wavepacket propagation in simple molecular systems
Authors: Burrows B. L. , Amos A. T. 
Published: August 2002

AbstractA combinatorial method for solving the time‐dependent Schrödinger equation is used with the tight‐binding approximation to consider the motion of wavepackets in chains and rings. A discussion of the relationship between the uncertainty principle and our results is given. We present calculations of charge densities, currents, and transmission coefficients, which illustrate the changes in the motion due to an impurity atom in the system and the effects of an imposed field with leads connected to the molecule. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Theoretical study of reactions between MH (M=B, Al) and the H2S molecule
Authors: Chen Xian‐Yang , Zhao Cheng‐Xue , Ping Yin , Ju Guan‐Zhi 
Published: August 2002

AbstractReaction mechanisms between MH (M=B, Al) and the H2S molecule have been theoretically studied. The G3 ab initio and DFT calculations demonstrate that only one stable addition complex (HM:SH2, M=B, Al) can be formed, and that, starting from the addition complex (HM:SH2) two parallel reaction channels have been found: one is an addition reaction to give H2MSH via the three‐membered ring transition state (TS), and the other is a dehydrogenation reaction to give MSH+H2 via the four‐membered ring TS. Thermodynamics and Eyring transition state theory (TST) with the Wigner correction are also used to compute the thermodynamic functions, the equilibrium constants, A factors, and the rate constants of these reaction channels at 300–1500 K. The calculated results predict that the product H2BSH in the system of BH+H2S and the product AlSH+H2 in the system of AlH+H2S will be mainly observed. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Stochastic molecular dynamics in simulations of metalloid impurities in metals
Authors: Fuks David , Dorfman Simon , Mundim Kleber C. , Ellis Donald E. 
Published: August 2002

AbstractA hybrid approach is described, which combines stochastic classical molecular dynamics and first‐principles density functional theory to model the atomic structure and properties of large solid‐state systems. The stochastic molecular dynamics using generalized simulated annealing (GSA) is based on nonextensive statistical mechanics and thermodynamics. Examples of applications are given on metalloid impurities in metals. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Wigner localization and dynamics in two‐electron semiconductor rings
Authors: Puente Antonio , Serra Llorenç 
Published: August 2002

AbstractWe present a theoretical analysis of the electronic structure and the linear‐response dynamics for two‐dimensional rings in a perpendicular magnetic field containing two electrons. The exact lower eigenstates are found by numerically solving the Schrödinger equation and are used to build the pertubative dipole response. We show the equivalence of this technique with the integration in real time used in a previous work. Comparison with the predictions of local spin density approximation theory is also done. In narrow rings the solution is shown to correspond to a rigid rotor and thus to a localized structure in the intrinsic frame, i.e., a rotating Wigner molecule. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Shape‐dependent molecular polarizabilities
Authors: Apell S. Peter , Sabin John R. , Trickey S. B. , Oddershede J. 
Published: August 2002

AbstractIn a series of papers we have considered the overall effects of geometrical shape on molecular electronic properties. Molecules are mapped into ellipsoids, based on tabulated bond lengths and van der Waals radii. The main advantage of the approach is to make predictions of the influence of shape itself on important physical properties and their trends, particularly for systems which are computationally difficult or time‐consuming. The results include insight into the effect of shape on molecular stopping anisotropy, stopping in ultra‐thin films, and anisotropic Compton profiles. In this paper we extend the treatment to polarizability anisotropies and to the scaling of the polarizability of long objects in terms of the number of basic building blocks. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
The use of particle beam mass spectrometry for the measurement of impurities in a nabumetone drug substance, not easily amenable to atmospheric pressure ionisation techniques
Authors: Wolff Jean‐Claude , Hawtin Philip N. , Monté Soraya , Balogh Michael , Jones Tim 
Published: August 2002

AbstractLiquid chromatography/particle beam mass spectrometry (LC/PB‐MS) was used for the structural elucidation of some impurities in nabumetone as this compound poorly ionises by atmospheric pressure ionisation (API) techniques. PB‐MS was optimised for nabumetone and a sensitivity study was carried out. To obtain full scan electron ionisation spectra a minimum of 100 ng of compound on column was needed. By using 20 mg/mL solutions of nabumetone, impurities at levels of about 250 ppm mass fraction relative to nabumetone could be detected. Results were compared with LC/API‐MS and previous GC/MS. Copyright © 2001 John Wiley & Sons, Ltd.
Genotyping short tandem repeats using flow injection and electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry
Authors: Hannis James C. , Muddiman David C. 
Published: August 2002

AbstractCharacterizing polymerase chain reaction (PCR) amplicons has been accomplished for the first time using flow injection analysis coupled to electrospray ionization mass spectrometry (ESI‐MS). The PCR amplicons were amplified at the human tyrosine hydroxylase short tandem repeat locus from an individual homozygotic for the 9.3 allele. One product was amplified using Pfu polymerase and yielded a blunt‐ended amplicon of 82 base‐pairs (bp) in length. The second PCR product was amplified using Taq polymerase that resulted in an amplicon with cohesive termini of 82 bp plus either mono‐ or diadenylation. The two PCR amplicons were alternatively injected using a 0.5‐µL loop at 2 µM for the Pfu amplicon and 1 µM for the Taq amplicon with a flow rate of 200 nL/min during data acquisition. Both PCR amplicons were accurately identified using mass measurements illustrating the compatibility of ESI‐MS for genotyping short tandem repeat sequences and the potential for high‐throughput genotyping of large PCR amplicons. Copyright © 2001 John Wiley & Sons, Ltd.
In‐line coupling of low‐pressure short capillary electrochromatography columns to electrospray ionisation mass spectrometry
Authors: Walhagen Karin , Gaspari Marco , Tjaden Ubbo R. , Rozing Gerard P. , Greef Jan van der 
Published: August 2002

AbstractA new in‐house designed and constructed injection valve for capillary electrochromatography (CEC) based on a rotating injection part with compartments for the eluent as well as for the sample has been coupled to a mass spectrometer via a sheath flow electrospray ionisation (ESI) interface, using short capillary columns of 15 cm length. The CEC columns were packed with 3 µm C18 bonded silica particles, and a mixture of peptides was analysed using an ammonium acetate/acetonitrile eluent. A significant increase in the signal‐to‐noise ratio was obtained when the peptides were dissolved in water with the same content of organic modifier as in the eluent with an addition of 0.5% (v/v) acetic acid. When the CEC analysis was performed without any additional pressure, the separation current sometimes dropped tremendously due to bubble formation, caused by different permeability in the frits and packed part of the column causing an extremely low electroosmotic flow. The separation current was restored to its original value by applying only 7 bar at the inlet of the CEC column, and the separation performance for the test peptides was recovered. A comparison of the CEC performance of peptides in pure CEC mode and in low‐pressure CEC mode is reported. Copyright© 2001 John Wiley & Sons, Ltd.
A comprehensive on‐line digestion‐liquid chromatography/mass spectrometry/collision‐induced dissociation mass spectrometry approach for the characterization of human fibrinogen
Authors: Vecchione Gennaro , Casetta Bruno , Santacroce Rosa , Margaglione Maurizio 
Published: August 2002

AbstractAn automatic on‐line digestion‐liquid chromatography/mass spectrometry/collision‐induced dissociation mass spectrometry (LC‐MS/CID‐MS) protocol has been developed for detection of errors in the biosynthesis of human fibrinogen, such as amino acid (AA) mismatch or incorrect post‐translational modification (PTM). Using on‐line digestion on an immobilized‐enzyme column, the reaction time is significantly reduced (less than 20 min) and the entire approach is suitable for automation. The two‐loop MS experiments (full‐scan acquisition and sugar moieties monitoring by SIM) allow checking both the correct AA mapping via the peptides generated by the digestion of the PTM. Since the protocol was designed for application on a routine basis, as a proof‐of‐concept detection of a rare case of ‘abnormal’ fibrinogen has been demonstrated. The advantage of the proposed approach is exemplified by the fact that the DNA sequence information for the case investigated had not shown any evidence of the abnormality. Copyright © 2001 John Wiley & Sons, Ltd.
Multiple‐sprayer tandem mass spectrometry with parallel high flow extraction and parallel separation for high‐throughput quantitation in biological fluids
Authors: Deng Yuzhong , Zeng Hang , Unger Steve E. , Wu Jing‐Tao 
Published: August 2002

AbstractIn this work, an on‐line four‐column high‐flow parallel extraction device was set up and interfaced to a four‐column parallel separation system with a four‐sprayer tandem mass spectrometric detector. This system allowed for the direct and simultaneous sampling, extraction, separation, and detection of four samples in biological fluids, resulting in significantly increased throughput. The performance of this system was evaluated using rat plasma samples spiked with methotrexate as a test compound. The results showed that the relative standard deviation for responses across the four parallel channels was less than 10% for a concentration range from 10 to 2500 nM, resulting in comparable sensitivity (slope of curve) for the analyte on all channels. A ruggedness test was performed using a mixed set of new and used extraction columns and the relative standard deviation in analyte response was found to be below 15%. The inter‐channel crosstalk was measured to be about 0.1%. A comparison between the data generated on this system and on a conventional system for a rat pharmacokinetic study showed no more than 20% difference in measured concentrations. This parallel system is a viable tool for high‐throughput bioanalysis in a drug discovery environment. Copyright © 2001 John Wiley & Sons, Ltd.
Study of the mass spectrometric behaviour of phthalocyanine and azo dyes using electrospray ionisation and matrix‐assisted laser desorption/ionisation
Authors: Conneely A. , McClean S. , Smyth W. F. , McMullan G. 
Published: August 2002

AbstractThe negative ion MALDI‐MS and ESI‐MS behaviour of sulphonated copper phthalocyanine dyes has shown the presence of both anionic and radical anionic species. Substituent groups such as sulphonates and linker arms, as are present in commercial dyes such as Remazol TB and Everzol TB, are found to be labile and the dyes undergo in‐source fragmentation in both MALDI‐MS and ESI‐MS. Ions corresponding to sodium salts can be formed. It appears that Cu is firmly bound in the phthalocyanine structure, unlike the corresponding Mg and Al chelates that can undergo demetallation. The application of ESI‐MSn confirmed that these labile groups can be fragmented from the dye molecules and, in addition, SO2 losses are observed as for EI‐MS. Hydrolysed commercial azo dyes such as Remazol Black B (I) and Remazol Red RB (III) showed both singly and doubly charged molecular anion species as well as sodium salts using negative ion ESI‐MS, but did not desulphonate like the copper phthalocyanine dyes. The application of ESI‐MSn revealed fragmentation of the dye molecules with the loss of entities such as HOCH2CH2SO2C6H4N2 (for both dyes) and SO2 (for Remazol Black B). MALDI‐MS, ESI‐MS and ESI‐MSn can therefore be used for the characterisation of such dyes by exploiting these fragmentation processes, and some structural information can be obtained for the dyes whose structures are not in the public domain. Copyright© 2001 John Wiley & Sons, Ltd.
Negative ion electrospray mass spectra of caerulein peptides: an aid to structural determination
Authors: Boontheung Pinmanee , Alewood Paul F. , Brinkworth Craig S. , Bowie John H. , Wabnitz Paul A. , Tyler Michael J. 
Published: August 2002

AbstractMS/MS data derived from the [M − H]− ions of desulfated caerulein peptides provide (i) sequencing information from a combination of α, β and γ backbone cleavages, and (ii) identification of specific amino acid side chains by side‐chain cleavages [e.g. Ser (−CH2O), Thr (−CH3CHO) and Asp (−H2O)] (fragmentations having no counterparts in positive ion spectra). In addition, δ and/or γ backbone cleavage ions from Asp residues identify the position of these residues in the peptide. In contrast, neither δ nor γ cleavage ions are observed from either the Gln2 residue nor from Phe residues. Full structural information can be obtained from a consideration of the positive and negative ion MS/MS data in concert. Copyright © 2002 John Wiley & Sons, Ltd.
Rotating ball inlet mass spectrometry enhanced by electrochemical effects
Authors: Degn Hans , Christensen Torben , Sørensen René 
Published: August 2002

AbstractThe sample compartment in a rotating ball inlet mass spectrometer is made into an electrochemical cell where the rotating platinum ball can be electrically polarised relative to the sample liquid. Positive polarisation of the ball increases the mass peak intensities of weak acids and reduces those of weak bases. Negative polarisation of the ball reduces the mass peak intensities of weak acids and increases those of weak bases. These effects are caused by local changes in pH at the ball surface due to the electrolysis of water. When aliphatic alcohols are present in the sample solution positive polarisation of the ball results in the appearance of peaks due to electrochemical oxidation products of these alcohols. The effects of electric polarisation of the ball are potentially useful in the identification of analytes. Rotating ball inlet mass spectrometry with electric polarisation of the ball offers an alternative to conventional differential electrochemical mass spectrometry (DEMS). Copyright © 2002 John Wiley & Sons, Ltd.
Backbone cleavages of [M − H]− anions of peptides. Cyclisation of citropin 1 peptides involving reactions between the C‐terminal [CONH]− residue and backbone amide carbonyl groups. A new type of β cleavage: a joint experimental and theoretical study
Authors: Brinkworth Craig S. , Dua Suresh , Bowie John H. 
Published: August 2002

AbstractThis paper reports the study of backbone cleavages in the collision‐induced negative‐ion mass spectra of the [M − H]− anions of some synthetic modifications of the bioactive amphibian peptide citropin 1 (GLFDVIKKVASVIGGL‐NH2). The peptides chosen for study contain no amino acid residues which could effect facile side‐chain cleavage, i.e. Ser (−CH2O, side‐chain cleavage) and Asp (−H2O) are replaced by Ala or Lys. We expected that such peptides should exhibit standard and pronounced peaks due to α cleavage ions (and to a lesser extent β cleavage ions) in their collision‐induced negative‐ion spectra. This expectation was realised, but the spectra also contained peaks formed by a new series of cleavage anions. These are produced following cyclisation of the C‐terminal CONH− moiety at carbonyl functions of amide groups along the peptide backbone; effectively transferring the NH of the C‐terminal CONH− group to other amino acid residues. We have called the product anions of these processes β′ ions, in order to distinguish them from standard β ions. Some β′ ions also fragment directly to some other β′ ions of smaller mass. The reaction coordinates of α,β and β′ backbone processes have been calculated at the HF/6‐31G*//AM1 level theory for simple model systems. The initial cyclisation step of the β′ sequence is barrierless and exothermic. Subsequent steps have a maximum barrier of +40 kcal mol−1, with the overall reaction being endothermic by some 30 kcal mol−1 at the level of theory used. These calculations take no account of the complexity of the conformationally flexible peptide system, and it is surprising that each of the two reacting centres can ‘find’ each other in such a large system. Copyright © 2002 John Wiley & Sons, Ltd.
Using a high‐resolution magnetic sector mass spectrometer for fast analysis of transient reaction processes in automotive catalytic converters
Authors: Harmsen J. M. A. , Bijvoets Th. , Hoebink J. H. B. J. , Hachiya T. , Bassett J. , Brooker A. D. , Schouten J. C. 
Published: August 2002

AbstractA high‐resolution magnetic sector mass spectrometer has been developed and used for transient kinetic measurements on reactions that are important for automotive exhaust gas catalysis. This instrument allows separation of the isobaric masses of CO and N2 as well as CO2 and N2O, which are separately monitored in time at a sampling rate of 48 Hz. The time resolution is sufficient to determine individual kinetic rate parameters for reactions under transient conditions. A description of the experimental set‐up as well as the software used is given. The results are illustrated by the catalytic reduction of NO by CO. To the best knowledge of the authors, this is the first application of a magnetic sector mass spectrometer for kinetic research under dynamic operation conditions. Copyright © 2002 John Wiley & Sons, Ltd.
A Case Study of the Beneficial Reuse of Treated Groundwater
Authors: Elmore Andrew Curtis , Graff Thomas 
Published: August 2002

AbstractThe future disposal of treated groundwater at the former Nebraska Ordnance Plant (NOP) Superfund
site has been a topic of interest to the local property owners, the U.S. Army Corps of Engineers, and the local
regulatory agencies. The Record of Decision for the site includes the extraction, treatment, and disposal of
almost 3,000 gpm of groundwater with an estimated restoration time period exceeding 100 years. Interest from
property owners and the Nebraska agency charged with regulating groundwater supply prompted the Corps of
Engineers to consider several strategies for beneficially reusing the treated water. Alternatives included the
establishment of a rural water district or local distribution system; delivery of the water to the municipal
supply system of Lincoln, Nebraska, andsol;or other nearby municipalities; and consideration of innovative
remedial technologies to reduce the quantity of treated water requiring disposal. The selected disposal plan
consists of providing treated groundwater to interested parties for agricultural use with excess treated
groundwater discharged to two streams. Multiple feasibility studies were generated, public input was solicited,
and interagency agreements were executed during the course of the project. The remediation project is currently
being constructed, and at least one property owner has constructed a new center‐pivot irrigation system
to use the treated groundwater. © 2001 John Wiley & Sons.
Synergistic Effects of Multiple Metal Contaminants on Electrokinetic Remediation of Soils
Authors: Reddy Krishna R. , Chinthamreddy Supraja , Al‐Hamdan Ashraf 
Published: August 2002

AbstractThis article presents a bench‐scale study performed to investigate the removal of heavy metals when
they exist individually and in combination in soils. Electrokinetic experiments were conducted using two types
of clayey soils, kaolin and glacial till. These soils were contaminated with Cr(VI) only, with
Ni(II) only, and with Cr(VI), Ni(II), and Cd(II) combined. It was found
that in kaolin, a significant pH variation occurred due to electric potential application, affecting the
adsorption‐desorption and dissolution‐precipitation, as well as the extent of migration of the
contaminants. In glacial till, however, pH changes were not affected significantly. In both kaolin and glacial
till, the migration of Cr(VI) and Ni(II) was higher when they were present individually
compared to when they existed together with Cd(II). Cr(VI) migration as single or combined
contaminant was lower in kaolin as compared to that in glacial till. This result was due to the low pH
conditions created near the anode region in kaolin that led to high Cr(VI) adsorption to the clay
surfaces. In glacial till, however, nickel precipitated with or without the presence of co‐contaminants
due to high pH conditions in the soil. Overall, this study demonstrates that adsorption, precipitation, and
reduction are the significant hindering mechanisms for the removal of heavy metals using electrokinetic
remediation. The direction of the contaminant migration and overall removal efficiency depend on the polarity of
the contaminant, the presence of co‐contaminants, and the type of soil. © 2001 John Wiley &
Sons.
Receptor for the group B coxsackieviruses and adenoviruses: CAR
Authors: Carson Steven D. 
Published: August 2002

AbstractConsiderable progress towards the characterisation of the long‐sought receptor, CAR (coxsackievirus and adenovirus receptor), shared by group B coxsackieviruses (CVB) and most adenoviruses (Ad) has been made since it was isolated and cloned in 1997. The primary sequence of CAR shows that it is a member of the immunoglobulin superfamily of proteins, containing two Ig superfamily domains: an amino‐terminal V‐like module and a C2‐like module. The CAR cytoplasmic domain, representing nearly one‐third of the protein, is separated from the C2‐like module by a single membrane‐spanning sequence. The structure of the CAR V‐like module complexed with the Ad fibre knob has been determined using recombinant proteins, and reveals three CAR modules associated with a single knob. Although recombinant CAR expressed in mammalian cells confers permissivity to CVB infection, details of the interaction between CAR and CVB remain to be elucidated. The expression of CAR appears to be highly regulated with respect to both cell type and developmental age. In rodents, CAR is expressed at high levels just before birth, and declines thereafter. Expressed levels have been found to increase in regenerating muscle and in response to immunological mediators or inflammation, and in RD cells and umbilical vein endothelial cells in response to high cell density. These studies indicate that CAR expression is highly regulated, but the mechanisms and molecules that mediate the expression remain to be discovered. The physiological function of CAR and its natural ligand also remain to be discovered. In addition, while CAR expression generally correlates with viral tropism, the relationship between the physiological function of CAR and the pathologies of CVB and Ad infections remain to be described. Copyright © 2001 John Wiley & Sons, Ltd.