bluuebunny/crossref_metadata_2025_split huggingface dataset:
Proton transfer via strained transition states in the elimination of alcohols from MH+ ions of stereoisomeric diethers and hydroxy esters upon chemical ionization and collision‐induced dissociation
Authors: Denekamp Chagit , Mandelbaum Asher 
Published: August 2002

AbstractThe isobutane chemical ionization (CI) mass spectra of cis‐ and trans‐1,4‐di(alkoxymethyl)cyclohexanes, with a tertiary alkoxy group ROH and a primary group R′OH, are identical, and they exhibit exclusive elimination of the alcohol ROH originating from the tertiary alkoxyl. The high abundance of the [MH − ROH]+ ion and the absence of [MH − R′OH]+ and MH+ ions is unexpected in the case of trans‐diethers, and it suggests proton transfer from the primary alkoxyl OR′ to the tertiary OR group prior to the elimination of ROH, despite the large distance between them in the trans configuration. Various isomerization pathways were explored in order to account for the similar behavior of the cis‐ and trans‐isomers upon chemical ionization. The results show that the hydrogens at positions 1 and 4 are not involved in the elimination of ROH. Methyl substitution at positions 1 and 4 leads to the competitive elimination of ROH and R′OH, indicating suppression of the proton transfer. Methyl substitution at position 1 adjacent to the primary alkoxy group has a minor effect on the chemical ionization behavior of the diethers. On the other hand, methyl substitution at position 4, adjacent to the tertiary alkoxy group, suppresses the proton transfer, (i.e. both [MH − ROH]+ and [MH − R′OH]+ are abundant in the CI mass spectra of the trans‐isomers), indicating an effect of steric hindrance. The results suggest that direct proton transfer via a strained proton‐bound transition‐state occurs, and methyl substitution at positions 1 and 4 can affect the relative stability of the transition‐state structures involved. Similar behavior has been observed in the CI and collision‐induced dissociation spectra of 1,4‐hydroxy ester cyclohexanes. Copyright © 2001 John Wiley & Sons, Ltd.
Reaction monitoring of platinum(II) complex–5′‐guanosine monophosphate adduct formation by ion exchange liquid chromatography/electrospray ionization mass spectrometry
Authors: Zöllner Peter , Zenker Andrea , Galanski Mathea Sophia , Keppler Bernhard K. , Lindner Wolfgang 
Published: August 2002

AbstractCisplatin and four structurally related platinum(II) complexes were incubated with guanosine 5′‐monophosphate (5′‐GMP) in water at 37 °C. The adduct formation reactions were monitored with cation‐ and anion‐exchange liquid chromatography/electrospray ionization mass spectrometry. In addition to mono‐ and bis‐adducts of guanosine 5′‐monophosphate with the platinum(II) complexes, other molecular species, presumably with a binuclear structure (two platinum(II) centres), were detected in the reaction mixtures, which have not been reported previously, indicating an unexpected complexity of adduct formation. Anion‐exchange chromatography revealed the presence of isomers of two complexes which presumably result from the restricted rotation at the platinum— N‐7 (5′‐GMP) bonds. All reaction products were characterized in both the positive and negative ion modes. Furthermore, preliminary kinetics and half‐times of complex formation were investigated for cisplatin and two other platinum(II) complexes, monitoring the relative concentrations of free 5′‐GMP and of mono‐ and bis‐GMP adducts as a function of time (250 h) using an internal standard protocol with thymidine 5′‐monophosphate. Copyright © 2001 John Wiley & Sons, Ltd.
A fast atom bombardment and matrix‐assisted laser desorption/ionization mass spectrometry study of doubly charged porphyrins
Authors: Schäfer M. , Budzikiewicz H. 
Published: August 2002

AbstractIn this mass spectrometry (MS) study of doubly charged porphyrin salts, fast atom bombardment (FAB) and matrix‐assisted laser desorption/ionization (MALDI) MS techniques are utilized to examine several unique ionic species. The predominant transformation of preformed doubly charged ions in the desorption/ionization mechanism of FAB and MALDI is the result of deprotonation reactions to form singly charged ions of the type [M2+ − H+]+ and of one‐electron reductions to form radical cations [M2+ + e−]+·. The dependence of this phenomenon and the formation of a number of additional ionic species on the different matrices and the FAB‐matrix additive benzoquinone is examined. The significant analogous behavior of doubly charged porphyrins in FAB‐ and MALDI‐MS leads to the conclusion that one‐electron reductions are of distinct relevance in the desorption/ionization mechanism of MALDI. Copyright © 2001 John Wiley & Sons, Ltd.
In‐gel deglycosylation of sodiumdodecyl sulfate polyacrylamide gel electrophoresis‐separated glycoproteins for carbohydrate estimation by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Kilz S. , Budzikiewicz H. , Waffenschmidt S. 
Published: August 2002

AbstractMass determination by mass spectrometric methods (electrospray ionization mass spectrometry (ESI‐MS), matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS)) of sodiumdodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE)‐separated proteins is a well known procedure and reliable protocols are available. In our efforts to use the established methods to determine the molecular mass of the disulfide brigded, heterodimeric glycoprotein GP3 and to determine the carbohydrate content of each protein subunit we developed an in‐gel chemical deglycosylation method. For this purpose we established experimental conditions that allow maximum extraction of the high molecular mass protein subunits and developed a routine method to apply the HF–pyridine deglycosylation protocol to proteins isolated from polyacrylamide gel pieces. The novel protocol and extraction procedure described can be used to analyze O‐glycosylated proteins up to 150 kDa after SDS‐PAGE separation. Copyright © 2002 John Wiley & Sons, Ltd.
Quantitative gas chromatographic/mass spectrometric analysis of morphine glucuronides in human plasma by negative ion chemical ionization mass spectrometry
Authors: Leis Hans Jörg , Fauler Günter , Raspotnig Günther , Windischhofer Werner 
Published: August 2002

AbstractA sensitive and specific method for the determination of morphine glucuronides in human plasma is presented. Morphine glucuronides, namely morphine‐6‐glucuronide (M6G) and morphine‐3‐glucuronide (M3G), were extracted from plasma by solid‐phase extraction on C18 cartridges at pH 9.3 and derivatized to their pentafluorobenzyl ester trimethylsilyl ether derivatives. The compounds were measured by gas chromatography/negative ion chemical ionization mass spectrometry without any further purification. Using this detection mode, a diagnostic useful fragment ion at m/z 748 was obtained at high relative abundance for both target compounds. [2H3]‐labeled morphine glucuronides were used as internal standards. Calibration graphs were calculated by polynomial fit within a range of 10–1280 and 15–1920 nmol l−1 for the 6‐ and 3‐glucuronide, respectively. At the limit of quantitation (LOQ), the inter‐assay precision was 2.21% (M3G) and 2.23% (M6G) and the GC/MS assay variability was 1.8% (M3G) and 0.9% (M6G). The accuracy at the LOQ showed deviations of +4.92% (M3G) and +1.5% (M6G). The sample recovery after solid‐phase extraction was 84.7% for both M3G and M6G. The method is rugged, rapid and robust and has been applied to the batch analysis of morphine glucuronides during pharmacokinetic profiling of the drugs. Copyright © 2002 John Wiley & Sons, Ltd.
Structure, energetics and reactivity of ternary complexes of amino acids with Cu(II) and 2,2′‐bipyridine by density functional theory. A combination of radical‐induced and spin‐remote fragmentations
Authors: Seymour Jennifer L. , Tureček František 
Published: August 2002

AbstractThe structures, electron distributions and dissociation energies of gas‐phase ternary complexes of Cu(II) with 2,2′‐bipyridine and leucine, isoleucine and lysine were addressed by density functional theory using the hybrid B3LYP functional, effective core potentials and the 6–31 + G(d) and LANL2DZ basis sets. The calculations confirm the previously suggested structures, in which amino acid carboxylates coordinate to the Cu atom by the carboxylate and α‐amino groups in square‐planar complexes. The dissociation energies for consecutive eliminations of CO2 and alkyl radicals from isomeric singly charged complexes of leucine and isoleucine correlate with the ion relative abundances observed in collisionally activated dissociation mass spectra. Doubly charged lysine complexes show extremely low dissociation energies that are consistent with the <1 eV center‐of‐mass collision energies that were used in previous CAD studies. The calculated charge and spin densities point to radical‐induced dissociations of singly charged complexes with an open‐electron shell. In contrast, the unpaired electron is virtually inert in doubly charged, open‐shell complexes that undergo charge‐induced, spin‐remote dissociations in the amino acid residues. Copyright © 2002 John Wiley & Sons, Ltd.
Mosquito cells bind and replicate hepatitis C virus
Authors: Germi Raphaële , Crance Jean‐Marc , Garin Daniel , Guimet Josette , Thelu Marie‐Ange , Jouan Alain , Zarski Jean‐Pierre , Drouet Emmanuel 
Published: August 2002

AbstractSeveral studies have demonstrated some hepatitis C virus (HCV) replication in lymphocyte and hepatocyte cell lines such as in African green monkey Vero cells. The aim of the present study was to select other cell lines able to bind and replicate HCV. Human hepatoma PLC/PRF/5 cells, human lymphoma Namalwa cells, Vero and mosquito AP61 cells were inoculated with HCV‐positive plasma, washed six times and examined for the presence of the viral genome at different times post infection, using an RT‐PCR method. Binding of HCV to cells was estimated by HCV RNA detection in cells 2 hr after inoculation and in the last wash of these cells. Successive virus passages in cells were carried out. All the cells studied were able to bind HCV but only AP61 and Vero cells provided evidence of replication and production of infectious virus: virus RNA was detected during 28 days post‐infection in four successive virus passages. CD81 molecules, a putative HCV receptor, were detected by cytofluorometric analysis. Vero cells express CD81 molecules whereas these molecules were not detected on AP61 cells. It is suggested that other receptors are involved in HCV binding to Vero and AP61 cells. J. Med. Virol. 64:6–12, 2001. © 2001 Wiley‐Liss, Inc.
Evaluation of hepatitis C antibody testing in saliva specimens collected by two different systems in comparison with HCV antibody and HCV rna in serum*
Authors: van Doornum G.J.J. , Lodder A. , Buimer M. , van Ameijden E.J.C. , Bruisten S. 
Published: August 2002

AbstractTwo different ELISA assays, the Ortho HCV 3.0 ELISA (Ortho Diagnostics Systems) and the Mono‐Lisa anti‐HCV Plus (Sanofi Diagnostics Pasteur) were evaluated for the detection of hepatitis C virus (HCV) antibody in saliva samples. Specimens were collected from 152 individuals who participated in a longitudinal cohort study on HIV infection, and who used illicit drugs. Saliva specimens were collected using two different systems: Salivette (Sarstedt) and Omni‐Sal (Saliva Diagnostic Systems). Saliva specimens were tested following modified protocols by both ELISAs, and the results were compared with serum specimens that were tested according to the instructions of the manufacturer. Serum samples of 102 (67%) participants were positive by both assays, and 50 persons were negative for HCV antibody. A total of 99 of the 102 serum specimens were confirmed as positive using Ortho Riba HCV 3.0 (Ortho Diagnostics System) and Deciscan HCV (Sanofi Diagnostics Pasteur), and 3 yielded discrepant results. As no cut‐off level is known for testing saliva samples by ELISA, 3 different levels were chosen: mean (M) + 1 standard deviation (SD), M + 2 SD, and M + 3 SD of the optical densities of saliva tests of the 50 HCV serum antibody negative persons. At a level of M + 1 SD and M + 2 SD the Salivette/Mono‐Lisa combination gave the greatest proportion of HCV antibody positive saliva specimens obtained from the 102 HCV serum antibody positive participants, 88% and 79%, respectively. Differences between the various collection systems and assay combinations were not significant statistically. In 76 of the 102 persons with HCV antibodies in serum, HCV RNA was detected in serum. Salivary presence of HCV RNA, however, could not be demonstrated. The results show that the assays compared are unsuitable for diagnostic use, but the sensitivities of the assays are acceptable for use in epidemiological studies. J. Med. Virol. 64:13–20, 2001. © 2001 Wiley‐Liss, Inc.
Antibodies raised to short synthetic peptides with sequences derived from HIV‐1 SF2 gp120 can both neutralize and enhance HIV‐1 SF13: A later variant isolated from the same host
Authors: Davis David , Trischmann Heike , Stephens D. Michael , Lachmann Peter J. 
Published: August 2002

AbstractHIV‐1 SF13 emerged in a patient with immunity to HIV‐1 SF2. This study determined the effect of antibodies raised to HIV‐1 SF2 on the replication of the later variant. Antisera in rats were raised previously to a complete set of overlapping, synthetic 15mer peptides following the sequence of HIV‐1 SF2 gp120. These sera have now been used in neutralization and enhancement assays against viruses derived from molecular clones of both variants. The sets of peptides inducing neutralizing antibodies to the two variants overlap. Antibodies to the third variable region of HIV‐1 SF2 only neutralize the homologous virus whereas those to the second and fourth variable regions neutralize both variants. In contrast, the sets of major epitopes involved in enhancement do not overlap. Epitopes for both variants form two clusters when superimposed on the conformation of the conserved regions. To determine if antibodies with the potential to enhance or neutralize HIV‐1 SF2 change over time in infected individuals sera from chimpanzees were used because no material was still available from the original patient. Antibodies to HIV‐1 SF2 neutralizing epitopes and HIV‐1 SF13 enhancing epitopes were present in the circulation of chimpanzees infected with HIV‐1 SF2. Once antibodies to the neutralizing epitopes were induced they persisted whereas antibodies to the enhancing epitopes varied with time after infection. Conditions may therefore exist within individual hosts where not only neutralizing but also enhancing antibodies have the potential to contribute to the selection pressure operating on the circulating population of polymorphic variants. J. Med. Virol. 64:207–216, 2001. © 2001 Wiley‐Liss, Inc.
Differences between the quantitative antigenemia assay and the cobas amplicor monitor quantitative PCR assay for detecting CMV viraemia in bone marrow and solid organ transplant patients
Authors: Flexman James , Kay Ian , Fonte Rebecca , Herrmann Richard , Gabbay Eli , Palladino Silvano 
Published: August 2002

AbstractThe relationship between quantitative PCR (COBAS Amplicor CMV Monitor, Roche Diagnostics) and quantitative antigenemia (Monofluor pp65, Sanofi Diagnostics) was examined for monitoring CMV viraemia. A total of 469 specimens from immunocompromised haematology and solid organ transplant patients were tested by quantitative antigenemia and qualitative PCR. Quantitative PCR (QPCR) was performed on the 245 specimens in which CMV DNA was detected by qualitative PCR. To exclude any effect due to specific anti‐CMV treatment, analysis of antigenemia and QPCR results was only performed on the 164 of 245 specimens collected from patients not on ganciclovir or foscarnet treatment. Forty seven specimens had <400 CMV copies/mL and a negative antigen result, four specimens were antigen positive (all between 1 to 10 positive CMV cells/2 × 105 leucocytes) and had <400 CMV copies/mL. Fifty‐one specimens had a CMV viral load ≥400 copies/mL and a negative antigen result and 62 specimens had a CMV viral load ≥400 copies/mL and a positive antigen. The viral load was shown to be as high as 43,000 copies/mL in some patients with a negative antigen and occurred in non‐neutropenic patients. The correlation coefficient for antigen and QPCR results for specimens from bone marrow transplant patients, was 0.69 with an average CMV viral load of 3,200 copies/mL (SEM = 800) and an average antigen of nine positive CMV cells/2 × 105 leucocytes (SEM = 3). In the corresponding solid organ transplant group, the correlation coefficient for antigen and QPCR results was 0.71 with an average CMV viral load of 9,900 copies/mL (SEM = 2,100) and an average antigen of 26 positive CMV cells/2 × 105 leucocytes (SEM = 6). Both the average viral load and the average antigen result in specimens from solid organ transplant patients, were significantly higher than the average viral load and antigen result in the corresponding group of bone marrow transplant patients (Two‐Sample‐for‐Means z‐Test, P = 0.001 and P = 0.003, respectively). The differences in the kinetics of the two assays in monitoring CMV and their ability to predict CMV disease was also assessed in a sub‐group of patients. In conclusion, the two assays used in this study do not always show parallel changes in CMV viral load, but may be complementary for the diagnosis and management of CMV disease. The observation that non‐neutropenic patients can have a high viral load in plasma and a negative antigenemia has implications for laboratories using antigenemia alone to monitor patients for CMV disease. J. Med. Virol. 64:275–282, 2001. © 2001 Wiley‐Liss, Inc.
Genetic characterization of hypervariable region 1 in patients chronically infected with hepatitis C virus genotype 2
Authors: Fan Xiaofeng , Di Bisceglie Adrian M. 
Published: August 2002

AbstractThe hypervariable region 1 (HVR1) has been most reliably identified in the genome of HCV genotype 1 isolates and thought to possibly play a role in immune evasion and development of chronic infection. There are few studies, however, of other HCV genotypes to determine if they also have such a hypervariable region present, and it is unclear whether or not there is any genotype‐dependent difference in the genetic characteristics of HVR1. We determined the nucleotide sequence of 5′ end of E2/NS1 region of the HCV genome spanning HVR1 of multiple genotype 1 and 2 HCV isolates and carried out a detailed genetic analysis. Similarity plots identified two hypervariable regions within the genotype 2 sequences, a larger one corresponding to HVR1 as well as a smaller 27‐nucleotide region of hypervariability. The synonymous substitutions per synonymous site (ds) was greater than nonsynonymous substitutions per nonsynonymous site (dn) within genotype 1 group whereas dn and ds were similar in the genotype 2 group. Analysis of amino acid sequences revealed several conserved sites across genotype 1 and 2 (amino acid numbers 2,6, 20 and 26) and overall similar hydropathic profiles were found within two genotypes. Still, despite the hypervariability, the HVR1 showed a genotype‐specific phylogenetic clustering. Thus, HVR1 appears to be conserved between genotypes in keeping with it having an important survival function. Genotype 2 appears to have a greater rate of nonsynonymous substitutions within HVR1, suggesting a greater positive evolutionary pressure. J. Med. Virol. 64:325–333, 2001. © 2001 Wiley‐Liss, Inc.
Identification of a DNA encapsidation sequence for human polyomavirus pseudovirion formation
Authors: Ou Wei‐Chih , Hseu Tzong‐Hsiung , Wang Meilin , Chang Han , Chang Deching 
Published: August 2002

AbstractHuman polyomavirus is a naked capsid virus containing a closed circular double‐stranded DNA genome. The mechanism of DNA encapsidation for the viral progeny formation is not fully understood. In this study, DNA encapsidation domain of the major capsid protein, VP1, of the human polyomavirus JCV was investigated. When the first 12 amino acids were deleted, the E. coli expressed VP1 (ΔN12VP1) failed to encapsidate the host DNA although the integrity of the capsid‐like structure was maintained. In addition, capsid‐like particles of ΔN12VP1 did not package exogenous DNA in vitro, which is in contrast to that of the full‐length VP1 protein. These findings suggest that the N‐terminal of the first 12 amino acids of VP1 were responsible for DNA encapsidation. The importance of amino acids in the DNA encapsidation domain was determined further using site‐directed mutagenesis. All of the positively charged amino acids at the N‐terminal region of VP1 were essential for DNA encapsidation. The results indicate that the N‐terminal region of the human polyomavirus major capsid protein VP1 may be involved in viral genome encapsidation during progeny maturation. J. Med. Virol. 64:366–373, 2001. © 2001 Wiley‐Liss, Inc.
Longitudinal study of serum neutralization of HIV‐1 in infected plasma donors
Authors: Abelian Arthur V. , Saurya Shreesh , Ash Stephen , Karpas Abraham 
Published: August 2002

AbstractEarlier studies provided suggestive evidence about the effectiveness of passive immunotherapy for AIDS patients using plasma donated by healthy HIV‐1 infected individuals and revealed beneficial effects of plasmapheresis for the immune system of the donors. In this study, anti‐HIV‐1 neutralizing activity in 31 healthy HIV‐1 infected donors of plasma participating in a passive immunotherapy study was investigated as a function of time. Average studied period was 33 months. Using the highly cytopathic HIV‐1 NDK strain and MOLT4 cells, it was shown by means of syncytia formation inhibition assay and polyclonal HIV‐1 antigen‐capture assay that viral neutralizing titers tend either to remain unchanged or increase over time. These findings support the notion that the immune system is not affected adversely in HIV‐1 infected plasma donors and lend further support to the feasibility of passive immunotherapy for AIDS patients. J. Med. Virol. 65:649–658, 2001. © 2001 Wiley‐Liss, Inc.
Detection of human group C rotaviruses in Nigeria and sequence analysis of their genes encoding VP4, VP6, and VP7 proteins
Authors: Adah Mohammed Ignatius , Wade Abel , Oseto Mitsuaki , Kuzuya Mitsutaka , Taniguchi Koki 
Published: August 2002

AbstractIn a survey on the etiology of acute gastroenteritis in infants and young children in Nigeria, group C human rotaviruses were detected in two of 112 rotavirus positive stool specimens collected between 1999 and 2000. The VP7, VP6, and VP4 genes of the two Nigerian human group C rotavirus strains (Jajeri and Moduganari) were sequenced in this study. Comparative sequence analysis with other published human group C rotaviruses showed that the genes encoding the three structural proteins were remarkably conserved in primary structure with few mutations. The VP4 and VP7 genes from the two Nigerian strains were related more closely to each other than to those of other published strains, and formed a separate cluster on the phylogenetic tree. In contrast, it was of note that VP6 gene of strain Moduganari was related more closely to the Brazilian strain Belem than to the other Nigerian strain Jajeri. This is the first report of identification of human group C rotavirus in Nigeria and constitutes the first sequence data of human group C rotaviruses in the African continent. J. Med. Virol. 66:269–275, 2002. © 2002 Wiley‐Liss, Inc.