bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cumulative coordinates for approximations of high‐order atomic multipole moments in aluminosilicate and aluminophosphate sieves*
Authors: Larin A. V. , Vercauteren D. P. 
Published: August 2002

AbstractA scheme to obtain approximate analytical functions for the atomic distributed multipole moments of the crystallographically different atoms within aluminosilicate and aluminophosphate sieves is discussed. Respective atomic multipole moments are derived within the CRYSTAL95 ab initio periodic Hartree–Fock code with different basis sets, from minimal STO‐3G to 6‐21G*. In order to illustrate the possible applications, distributed analyses are carried out for various structural models from all‐siliceous zeolites and aluminophosphates with ratio Al/P=1 to hydrogen forms of aluminosilicates. Simple approximate forms based on charge and geometry coordinates are proposed for the high‐order moments of each atom, which are further required for the calculation of the electrostatic field within the structures. The possibility to use this analytical approach to evaluate the electrostatic field within embedded cluster models is also shortly discussed. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 83: 70–85, 2001
Protein matrix local fluctuations and substrate binding in HRPC: A proposed dynamic electrostatic sampling method
Authors: Schay Gusztav , Galantai Rita , Laberge Monique , Fidy Judit 
Published: August 2002

AbstractHorseradish peroxidase C is an oxidoreductase which catalyzes in plant roots the oxidation of a remarkably wide variety of aromatic compounds by H2O2. The recently available X‐ray structures of the enzyme bound to aromatic substrates are not indicative of significant structural rearrangements as a result of substrate binding when compared to the structure of the unbound enzyme. Our most recent spectral hole‐burning studies on HRPC fluorescent derivatives provided direct experimental evidence indicative of different fields experienced at the heme as a result of substrate binding which can only originate in the protein matrix in which the heme is embedded. In this report, we present results on modeling the fluctuations of these protein matrix electrostatic rearrangements using a combination of molecular dynamics and electrostatic conformational sampling to compare the binding of BHA and NHA to HRPC and to the derivative used in our experimental studies. Our initial results suggest that HRPC does undergo conformational rearrangement on binding aromatic substrates, but of an electrostatic nature, as opposed to major conformational structural changes. This implies that the high versatility of substrate binding in horseradish peroxidase could be due to an electrostatic dynamic selectivity mediated by small‐amplitude internal protein matrix motions. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 290–301, 2001
Self‐association of an amphipathic helix peptide inhibitor of HIV‐1 integrase assessed by electro spray ionization mass spectrometry in trifluoroethanol/water mixtures
Authors: Fermandjian S. , Maroun R. S. , Amekraz B. , Jankowski C. K. 
Published: August 2002

AbstractEstablishing the auto‐associative properties of a molecule in solution can be important for determination of its structure and function. EAA26 (VESMNEELKKIIAQVRAQAEHLKTAY) has been designed to inhibit HIV‐1 integrase via formation of a stable coiled‐coil structure with a nearly homologous segment in the enzyme. The latter catalyzes the permanent incorporation of a DNA copy of the retrovirus genome into host cell DNA, and is thus essential to the life of the retrovirus. This makes integrase an obvious drug target in the therapy of AIDS. The present work has demonstrated, using electrospray ionization mass spectrometry (ESI‐MS), that EAA26 is monomeric in pure water, and tetrameric and dimeric at respectively low and medium concentrations of 2,2,2‐trifluoroethanol (TFE), and again monomeric at higher TFE concentrations. Thus, the apolar solvent TFE may contribute to either stabilization or disruption of the intermolecular hydrophobic contacts depending on its concentration in aqueous solution. Previous NMR and ultracentifugation results are thus confirmed, indicating the reliability of ESI‐MS for defining the self‐association state of biologically relevant peptides in both water and organic‐water solutions. Copyright © 2001 John Wiley & Sons, Ltd.
Collision‐induced dissociation of MCl+ adducts (M = Mg, Mn, Zn, Co, Ni and Cu) and Cu+ and Ag+ adducts of dithioalkyl ketene acetals
Authors: Madhusudanan K. P. , Bhat B. A. , Suryawanshi S. N. 
Published: August 2002

AbstractElectrospray ionization mass spectra of equimolar solutions of dithioalkyl ketene acetals 1 and 2 and metal chlorides (MgCl2, MnCl2, ZnCl2, CoCl2, NiCl2 and CuCl2) produced abundant ligated metal ion adducts [1 + MCl]+ and [2 + MCl]+. In addition, CuCl2 also gave rise to Cu+ adducts. The ligated metal ion adducts upon collision‐induced dissociation (CID) showed characteristic fragmentation pathways reflecting the favoured site of coordination. The results show that MgCl+ prefers oxygen over sulfur, whereas the reverse is true for ZnCl+ adducts, exemplified by the preferred fragmentation of [1 + MgCl]+ as elimination of MgCl(OH), while that of [1 + ZnCl]+ is expulsion of ZnCl(SCH3). Co and Ni chloride adducts tend to give stable metal coordinated species. Cleavage of the dithiolane ring followed by elimination of C2H4S is the preferred pathway during the CID of [2 + MCl]+ adducts. The CuCl+ adducts of 1 and 2 showed reduction of Cu(I) to Cu(0) resulting in the M+· ions of 1 and 2. Abstraction of .CH3 resulting in elimination of CuCH3 was observed during CID of Cu+ adducts of 1 and 2. A comparative study of the corresponding Ag+ adducts revealed a similar behaviour. Copyright © 2001 John Wiley & Sons, Ltd.
Infrared matrix‐assisted laser desorption/ionization of polycyclic aromatic hydrocarbons with a sulfolane matrix
Authors: Jackson Shelley N. , Murray Kermit K. 
Published: August 2002

AbstractInfrared matrix‐assisted laser desorption/ionization (IR‐MALDI) of the polyaromatic hydrocarbons (PAHs) anthracene, benzo[a]pyrene, and dibenz[a,h]anthracene was performed using a 10.6‐µm CO2 laser and a liquid matrix. Sulfolane (tetrahydrothiophene 1,1‐dioxide) was found to be an effective matrix for PAH ionization: mass spectra obtained with a sulfolane matrix contain an intense molecular ion peak; interference from PAH fragment and matrix peaks is negligible in all cases. The main limitation of the sulfolane matrix is sample evaporation after 3 to 5 min in vacuum. This sample lifetime can be increased to between 15 and 30 min using a 2:1 (v/v) mixture of sulfolane and glycerol, but the resulting spectra have greater matrix interference and decreased shot‐to‐shot signal stability. Copyright © 2001 John Wiley & Sons, Ltd.
Use of matrix‐assisted laser desorption/ionization time‐of‐flight mass mapping and nanospray liquid chromatography/electrospray ionization tandem mass spectrometry sequence tag analysis for high sensitivity identification of yeast proteins separated by two‐dimensional gel electrophoresis
Authors: Poutanen Marjo , Salusjärvi Laura , Ruohonen Laura , Penttilä Merja , Kalkkinen Nisse 
Published: August 2002

AbstractCurrent analytical techniques in protein identification by mass spectrometry are based on the generation of peptide mass maps or sequence tags that are idiotypic for the protein sequence. This work reports on the development of the use of mass spectrometric methods for protein identification in research on metabolic pathways of a genetically modified strain of the baker's yeast Saccharomyces cerevisiae. This study describes the use of matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass mapping and liquid chromatography/quadrupole time‐of‐flight electrospray ionization tandem mass spectrometry (LC/Q‐TOF‐ESI‐MS/MS) sequence tag analysis in identification of yeast proteins separated by two‐dimensional polyacrylamide gel electrophoresis (2D‐PAGE). The spots were selected for analysis in order to collect information for future studies, to cover the whole pI range from 3 to 10, and to evaluate information from spots of different intensities. Mass mapping as a rapid, high‐throughput method was in most cases sensitive enough for identification. LC/MS/MS was found to be more sensitive and to provide more accurate data, and was very useful when analyzing small amounts of sample. Even one sequence tag acquired by this method could be enough for unambiguous identification, and, in the present case, successfully identified a point mutation. Copyright © 2001 John Wiley & Sons, Ltd.
The nature of collision‐induced dissociation processes of doubly protonated peptides: comparative study for the future use of matrix‐assisted laser desorption/ionization on a hybrid quadrupole time‐of‐flight mass spectrometer in proteomics
Authors: Cramer R. , Corless S. 
Published: August 2002

AbstractComparative MS/MS studies of singly and doubly charged electrospray ionization (ESI) and matrix‐assisted laser desorption/ionization (MALDI) precursor peptide ions are described. The spectra from these experiments have been evaluated with particular emphasis on the data quality for subsequent data processing and protein/amino acid sequence identification. It is shown that, once peptide ions are formed by ESI or MALDI, their charge state, as well as the collision energy, is the main parameter determining the quality of collision‐induced dissociation (CID) MS/MS fragmentation spectra of a given peptide. CID‐MS/MS spectra of singly charged peptides obtained on a hybrid quadrupole orthogonal time‐of‐flight mass spectrometer resemble very closely spectra obtained by matrix‐assisted laser desorption/ionization post‐source decay time‐of‐flight mass spectrometry (MALDI‐PSD‐TOFMS). On the other hand, comparison of CID‐MS/MS spectra of either singly or doubly charged ion species shows no dependence on whether ions have been formed by ESI or MALDI. This observation confirms that, at the time of precursor ion selection, further mass analysis is effectively decoupled from the desorption/ionization event. Since MALDI ions are predominantly formed as singly charged species and ESI ions as doubly charged, the associated difference in the spectral quality of MS/MS spectra as described here imposes direct consequences on data processing, database searching using ion fragmentation data, and de novo sequencing when ionization techniques are changed. Copyright © 2001 John Wiley & Sons, Ltd.
Alkaline liquid chromatography/electrospray ionization skimmer collision‐induced dissociation mass spectrometry for phosphopeptide screening
Authors: Beck Alexander , Deeg Martin , Moeschel Klaus , Schmidt Eckhart K. , Schleicher Erwin D. , Voelter Wolfgang , Häring Hans U. , Lehmann Rainer 
Published: August 2002

AbstractA rapid on‐line method for the identification of phosphorylated peptides in enzymatic protein digests by specific marker ion signals is described. In our study we investigated the use of alkaline conditions together with a previously described method for selective and sensitive detection of phosphopeptide ions combining high‐performance capillary liquid chromatography (LC) and electrospray ionization mass spectrometry (ESI‐MS).1,,
2 Phosphorylation‐specific marker ions (m/z 79, PO3−, and m/z 97, H2PO4−) were generated by skimmer collision‐induced dissociation (sCID) in the negative‐ion mode. The method was evaluated and validated for mono‐phosphorylated synthetic peptides using different alkaline pH values and CID offsets. Alkaline conditions (pH 10.5) enhance the generation of phosphopeptide‐specific fragment ions from serine‐ and tyrosine‐phosphorylated peptides, and enable the use of m/z 79 (PO3−) and m/z 97 (H2PO4−) as phosphorylation‐specific marker traces. Note that HPLC separation in trifluoroacetic acid containing solvents impairs the use of m/z 97 (C2F3O− fragment ion at m/z 97) as a phosphorylation‐specific marker. The optimized method was applied for the detection of phosphorylated peptides in a tryptic β‐casein digest. The expected mono‐ and tetra‐phosphorylated peptides were detected and rapidly identified by µLC/ESI‐sCID‐MS and µLC/ESI‐MS analysis. Copyright © 2001 John Wiley & Sons, Ltd.
Femtosecond laser time‐of‐flight mass spectrometry of labile molecular analytes: laser‐desorbed nitro‐aromatic molecules
Authors: Hankin S. M. , Tasker A. D. , Robson L. , Ledingham K. W. D. , Fang X. , McKenna P. , McCanny T. , Singhal R. P. , Kosmidis C. , Tzallas P. , Jaroszynski D. A. , Jones D. R. , Issac R. C. , Jamison S. 
Published: August 2002

AbstractFemtosecond laser time‐of‐flight mass spectra of solid samples of trinitrobenzene (TNB), trinitrotoluene (TNT) and trinitrophenol (TNP) have been recorded. Desorption of the solid samples was enacted by the fourth harmonic output (266 nm) of a 5 ns Nd:YAG laser. Subsequent femtosecond post‐ionisation of the plume of neutral molecules was achieved using 800 nm laser pulses of 80 fs duration. Mass spectra have been recorded for desorption laser intensities from 2–6 × 109 W cm−2with ionisation laser intensities between 2 × 1014and 6 × 1015 W cm−2. Femtosecond laser ionisation has been shown to be capable of generating precursor and characteristic high‐mass fragment ions for labile nitro‐aromatic molecules commonly used in high‐explosive materials. This feature is critical in the future development of femtosecond laser‐based analytical instruments that can be used for complex molecular identification and quantitative analysis of environmentally important labile molecules. Furthermore, a comparison of femtosecond post‐ionisation mass spectra with standard 70 eV electron impact data has revealed similarities in the spectra and hence the fragmentation processes. Copyright © 2001 John Wiley & Sons, Ltd.
Analysis of flavonoid constituents from leaves of Acanthopanax senticosus Harms by electrospray tandem mass spectrometry
Authors: Chen Maolian , Song Fengrui , Guo Mingquan , Liu Zhiqiang , Liu Shuying 
Published: August 2002

AbstractThree known flavonoids, quercetin, quercitrin (quercetin‐3‐0‐rhamnoside) and rutin (quercetin‐3‐0‐rutinoside), have been identified for the first time in the leaves of Acanthopanax senticosus Harms by using electrospray tandem mass spectrometry techniques (ESI−MSn). The flavonoid hyperin (quercetin‐3‐0‐β‐galactoside), already known to be present, was also investigated. The diagnostic fragment ions of the aglycone quercetin were obtained in the ESI−MSn experiments, and a fragmentation mechanism proposed. Copyright © 2002 John Wiley & Sons, Ltd.
Characterisation of combinatorial libraries of mucin‐2 antigen peptides by high‐resolution mass spectrometry
Authors: Windberg Emöke , Hudecz Ferenc , Marquardt Andreas , Sebestyén Ferenc , Kiss Andrea , Bösze Szilvia , Medzihradszky‐Schweiger Hedvig , Przybylski Michael 
Published: August 2002

AbstractAn epitope motif, TX1TX2T, of mucin‐2 glycoprotein was identified by means of a mucin‐2‐specific monoclonal antibody, mAb 994, raised against a synthetic mucin‐derived 15‐mer peptide conjugate. For determination of the epitope sequence recognised with highest affinity by mAb 994, a combinatorial approach was applied using the portioning‐mixing technique excluding Cys. Antibody binding of libraries was most profound when Gln was at the X1 position. Analytical characterisation of the TQTX2T library was conducted by amino acid analysis and matrix‐assisted laser desorption/ionisation time‐of‐flight (MALDI‐TOF) and electrospray ionisation Fourier transform ion cyclotron resonance (ESI‐FTICR) mass spectrometric methods. Control libraries were prepared by mixing 19 individual peptides corresponding to the TQTX2T sequence. Thus, mixtures of 6, 10 and 19 pentapeptides were analysed and compared with the combinatorial mixture. MALDI‐TOFMS was able to detect only partially the components in the 6‐ and 10‐member mixtures, but failed to characterise a more complex 19‐member mixture. In contrast, ESI‐FTICRMS resolved all mixtures of higher complexity and provided direct identification at monoisotopic resolution, such as for a peptide library containing ‘isobaric’ lysine and glutamine (Δm = 0.0364 Da). The results of this study suggest that ESI‐FTICRMS is a powerful tool for characterisation of combinatorial peptide libraries of higher complexity. Copyright © 2002 John Wiley & Sons, Ltd.
Simultaneous separation of 17 inorganic and organic arsenic compounds in marine biota by means of high‐performance liquid chromatography/inductively coupled plasma mass spectrometry
Authors: Kohlmeyer Ute , Kuballa Jürgen , Jantzen Eckard 
Published: August 2002

AbstractA method using high‐performance liquid chromatography/inductively coupled plasma mass spectrometry (HPLC/ICP‐MS) has been developed to determine inorganic arsenic (arsenite, arsenate) along with organic arsenic compounds (monomethylarsonic acid, dimethylarsinic acid, arsenobetaine, arsenocholine, trimethylarsine oxide, tetramethylarsonium ion and several arsenosugars) in fish, mussel, oyster and marine algae samples. The species were extracted by means of a methanol/water mixture and a dispersion unit in 2 min, with extraction efficiencies ranging from 83 to 107% in the different organisms. Up to 17 different species were determined within 15 min on an anion‐exchange column, using a nitric acid gradient and an ion‐pairing reagent. As all species are shown in one chromatogram, a clear overview of arsenic distribution patterns in different marine organisms is given. Arsenobetaine is the major compound in marine animals whereas arsenosugars and arsenate are dominant in marine algae. The method was validated with CRM DORM‐2 (dogfish muscle). Concentrations were within the certified limits and low detection limits of 8 ng g−1 (arsenite) to 50 ng g−1 (arsenate) were obtained. Copyright © 2002 John Wiley & Sons, Ltd.
Homocysteine thiolactone and protein homocysteinylation: mechanistic studies with model peptides and proteins
Authors: Hop Cornelis E. C. A. , Bakhtiar Ray 
Published: August 2002

AbstractIn vitro incubations were performed to show that homocysteine thiolactone could generate covalent adducts with model peptides and proteins. MS and MS/MS data suggest that the thiolactone reacts with the side‐chain amino group of lysine residues as well as with the N‐terminal amino group or C‐terminal carboxy group. For larger peptides and proteins, the contribution from the ∈‐amino groups of lysine residues should be predominant. These data could help explain the detrimental effects of elevated levels of homocysteine and homocysteine thiolactone. Copyright © 2002 John Wiley & Sons, Ltd.
Novel direct detection method for quantitative determination of intracellular nucleoside triphosphates using weak anion exchange liquid chromatography/tandem mass spectrometry
Authors: Shi Guoen , Wu Jing‐tao , Li Yu , Geleziunas Romas , Gallagher Karen , Emm Tom , Olah Timothy , Unger Steve 
Published: August 2002

AbstractA novel analytical method has been developed for direct quantification of intracellular nucleoside triphosphates (NTPs). Lysates of human peripheral blood mononuclear cells (PBMCs) were extracted by protein precipitation, and the filtered extracts were analyzed by weak anion exchange liquid chromatography (WAX‐LC) coupled to detection by mass spectrometry (MS). Compared with ion pairing (IP)‐LC/MS/MS, the only MS‐compatible direct detection method for NTPs currently available, the new method completely avoids the usage of ion‐pairing reagents and has a shorter analytical time of only 2 min. The method was validated and is being used to determine the amount of the triphosphate metabolite of D‐D4FC (DPC817), an investigational HIV nucleoside reverse transcriptase inhibitor (NRTI), in human PBMC samples from clinical studies. By using a PE Sciex API 4000 triple quadrupole instrument operating in positive ion MRM mode, the method was able to achieve a lower limit of quantitation (LLOQ) of 5 fmol/106 cells in samples containing 3 × 106 lysed cells (6 fmol on‐column). With minor adaptation, the method described here may be suitable for analyzing other NTPs. This paper also provides a discussion of the unique retention characteristics of WAX‐LC, the principles of which may prove to be valuable for designing other forms of directly coupled ion‐exchange (IX)‐LC/MS methods suited for high sensitivity quantitative analysis. Copyright © 2002 John Wiley & Sons, Ltd.
Determination of glutathione in spruce needles by liquid chromatography/tandem mass spectrometry
Authors: Guček Marjan , Makuc Simon , Mlakar Anita , Beričnik‐Vrbovšek Julija , Marsel Jože 
Published: August 2002

AbstractFor the determination of glutathione (GSH) and its oxidized form (GSSG) in spruce needles their electrospray mass and MS/MS spectra were recorded with an ion trap mass spectrometer (ITMS, LCQ, Finnigan) and a triple stage quadrupole mass spectrometer (TSQ, Quattro II, Micromass). A study of the stability of GSH in aqueous solutions shows the presence of dimeric and trimeric forms of GSH, as well as GSSG, GSH‐sulfonate and GSH‐sulfinic acid. The same components were also found in extracts of spruce needles. We developed an assay which is suitable for monitoring low concentrations of GSH and similar compounds in plant tissues, employing the sensitivity and specificity of LC/MS/MS. Preliminary results on the mass spectrometric determination of GSH in spruce needles are given. Copyright © 2002 John Wiley & Sons, Ltd.
Matrix‐assisted laser desorption/ionization mass spectrometry compatible β‐elimination of O‐linked oligosaccharides
Authors: Huang Yunping , Konse Tomonori , Mechref Yehia , Novotny Milos V. 
Published: August 2002

AbstractA new β‐elimination procedure has been introduced to cleave O‐linked oligosaccharides from low‐ to sub‐microgram amounts of glycoproteins prior to analysis by mass spectrometry. Borane‐ammonia complex in aqueous ammonia is used as a cleaving solution alternative to the sodium borohydride/sodium hydroxide medium conventionally used in β‐elimination. The procedure results in minimum sample purification, leading to minimal sample loss and consequently an overall enhancement in sensitivity. It was applied successfully in the analysis of bovine fetuin and submaxillary mucin, as well as to a complex bile‐salt‐stimulated lipase glycoprotein isolated from human milk. Copyright © 2002 John Wiley & Sons, Ltd.
Persistence of arboviruses and antiviral antibodies in vertebrate hosts: its occurrence and impacts†
Authors: Kuno Goro 
Published: August 2002

AbstractThe recent isolation of West Nile virus from a bird in mid‐winter in New York immediately raised, as one of a few explanations, the possibility of long‐term persistence of arboviruses in vertebrate hosts. Although it was a highly popular topic for research many years ago, generally it has since been neglected and its meaning under appreciated. This comprehensive survey of literature worldwide uncovered, contrary to the general perception that it is a rather infrequent phenomenon, a large number of important observations involving all groups of arboviruses that have been accumulating over the years without drawing much attention. In this review, the data and observations were analysed in terms of the occurrence, role in natural transmission, mechanisms and genesis of persistence, source of problems in research and impact. The outcome of the analyses clearly demonstrates that asymptomatic, long‐term infection in the absence of viraemia with or without the induction of neutralising antibody, the most frequent characteristics of arboviral persistence, presents a serious question about the validity of some of the past animal experiments that were conducted without the consideration of such a possibility. Likewise, significant impacts are felt on diverse fields ranging from epidemiology to diagnostic virology and from veterinary medicine to agricultural commerce. Published in 2001 by John Wiley & Sons, Ltd.