bluuebunny/crossref_metadata_2025_split huggingface dataset:
Charge at the migrating hydrogen in the transition state of hydride transfer reactions from CH groups to hydride acceptors. Dynamics of the redox‐couple NADH‐NAD+
Authors: Buck Henk 
Published: November 2004

AbstractWe consider the controversial conclusions of the charge at the migrating hydrogen in the transition state of hydride‐transfer reactions from CH‐groups to hydride acceptors. Quantum chemical calculations were performed on elementary organic reactions involving carbenium ions, which can be considered as hydride acceptors. We also discuss the biochemical hydride‐transfer reactions in which the coenzyme NADH‐NAD+ plays an important role. With the calculations and the experimental model systems, an answer is given for the stereospecificity of the hydride transfer. Generally, the hydride transfer occurs via a trigonal pyramidal geometry in which the transferred hydride of the CH‐group is located in the axial position. In the case of the coenzyme NADH‐NAD+, the hydride transfer is coupled with an out‐of‐plane orientation of the carboxamide group of the pyridinium moiety, resulting in an increased stereospecificity. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Frontier example in experimental charge density research: Experimental electrostatics of proteins
Authors: Lecomte C. , Guillot B. , Jelsch C. , Podjarny A. 
Published: November 2004

AbstractThe experimental charge density methodology is extended to macromolecular structure and biocrystallography. Ultrahigh‐resolution diffraction data now can be collected at third‐generation synchrotron sources for well‐ordered protein crystals; the data can be refined with a more sophisticated model than the independent atom model (IAM), such as the multipolar atom. A new crystallographic program MoPro combining small molecules and macromolecular refinement method has been developed; first applications are described. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Capillary electrophoresis off‐line matrix‐assisted laser desorption/ionisation mass spectrometry of intact and digested proteins using cationic‐coated capillaries
Authors: Zuberovic Aida , Ullsten Sara , Hellman Ulf , Markides Karin E. , Bergquist Jonas 
Published: November 2004

AbstractCapillary electrophoresis (CE) was coupled off‐line with matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry (MALDI‐TOFMS) for the analysis of proteins and peptides. CE fractions were collected directly on a matrix‐coated MALDI target, using a sheath‐flow interface. Protein adsorption during CE separations was prevented by coating the capillaries with the physically adsorbed, cationic polymer PolyE‐323. The CE/MALDI‐MS system was used for the analysis of model proteins and peptides at physiological pH as well as analysis of proteins in tear fluid. Moreover, tryptic on‐target digestion of the collected protein fractions, with subsequent MALDI‐MS and MS/MS peptide analysis, was demonstrated. Copyright © 2004 John Wiley & Sons, Ltd.
Atmospheric pressure chemical ionisation liquid chromatography/mass spectrometry of the ultraviolet screening pigment scytonemin: characteristic fragmentations
Authors: Squier Angela H. , Airs Ruth L. , Hodgson Dominic A. , Keely Brendan J. 
Published: November 2004

AbstractAtmospheric pressure chemical ionisation reversed‐phase high‐performance liquid chromatography/multistage mass spectrometry has been used to study the mass spectral fragmentation of the cyanobacterial sheath pigment scytonemin and its reduced counterpart. The two pigments exhibit characteristic fragment ions in their MS2 and MS3 spectra that are of value in confirming the identification of the structures in extracts from natural environments. Copyright © 2004 John Wiley & Sons, Ltd.
Interfacial chemistry of adhesives on hydrated aluminium and hydrated aluminium treated with an organosilane
Authors: Watts John F. , Rattana Acharawan , Abel Marie‐Laure 
Published: November 2004

AbstractThe adsorption of a commercial adhesive and two of its major components—an amine curing agent [2,4‐toluene diisocyanate urone (TDI urone)] and an adhesive prepolymer resin [diglycidyl ether of bisphenol A (DGEBA)]—on a hydrated aluminium surface and the hydrated surface coated with γ‐glycidoxypropyltrimethoxysilane (GPS) has been investigated by x‐ray photoelectron spectroscopy (XPS) and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). The study of TDI urone adsorption indicated that adsorption was of the chemisorption type, and a specific interaction involving this molecule and the GPS immobilized on the hydrated aluminium surface was identified. From XPS and ToF‐SIMS data it was found that the types of interaction of the curing agent with the bare substrate were of the donor–acceptor type.Study of the DGEBA adsorption showed different‐shaped isotherms for the bare and the GPS‐coated substrates. It was found that the typical Langmuir isotherm type was obtained for the GPS‐coated substrate whereas no adsorption plateau was observed for the bare substrate within the concentration range studied. This resulted from a change in the conformation of the DGEBA molecule on the substrate when the concentration of DGEBA solution was increased. The bonding of DGEBA with both types of substrates was assumed to be via acid–base interactions (i.e. donor–acceptor interactions).Adsorption of the commercial adhesive on the hydrated surfaces was of BET Type IV form, rather than the simple monolayer adsorption isotherm (Langmuir type). This indicates multilayer adsorption, presumably in the pores of the hydrated substrate, as a result of a process analogous to adsorption condensation. Copyright © 2004 John Wiley & Sons, Ltd.
European trials with total mesorectal excision
Authors: Kapiteijn Ellen , van de Velde Cornelis J.H. 
Published: November 2004

AbstractThe outcome after surgery for rectal cancer differs markedly between patient series regarding local recurrence rates and survival. A high incidence of local recurrence is associated with conventional, nonstandardized procedures. To improve results of surgery, various additional treatments, such as radiotherapy, chemotherapy, and immunotherapy, have been tested. The Swedish Rectal Cancer Trial (SRCT) was the first trial to show that better local control achieved with preoperative radiotherapy resulted in improved survival. In recent years local control and survival have been further improved by the introduction of standardized total mesorectal excision (TME) surgery. A major problem of published studies on adjuvant therapy is that surgery was not standardized in these studies. Furthermore, quality control of the surgical technique by standardized pathological examination of the specimen is absent in most studies. In Europe, TME has become the preferred standard of operative management for rectal cancer. Adjuvant therapy studies should now be reexamined based on a platform of standardized, optimal surgery and pathology. We studied the European trials in which TME surgery is intentionally performed. Most of these trials are still in progress, with follow‐up too short for definitive results, apart from interim analyses. However, the Dutch TME trial has already shown that performing a large, multicenter trial with quality control of both surgery and pathology is feasible. Semin. Surg. Oncol. 19:350–357, 2000. © 2000 Wiley‐Liss, Inc.
Nodularin uptake by seafood during a cyanobacterial bloom
Authors: Van Buynder P. G. , Oughtred T. , Kirkby B. , Phillips S. , Eaglesham G. , Thomas K. , Burch M. 
Published: November 2004

AbstractThe problem of blue‐green algal toxin contamination of recreational waters and drinking water catchments is well described, as is the potential contamination of associated seafood. Algal contamination of Victorian waterways is now a widespread annual occurrence and, in some regions, the intersection of blooms and commercial fishing threatens the food safety of large numbers of people. Toxin levels which produce no observed adverse effect in animal studies were used to derive safe tolerable daily intake levels. These ‘acceptable levels’ were then modified to protect against potential acute health risks associated with short‐term exposures. National food surveys were used to derive likely seafood intakes and thus, in combination with ‘safe toxin levels’, health alert levels for seafood were formulated. During the summer of 2001 a bloom of Nodularia spumigena occurred in the Gippsland Lakes area of Southern Victoria. During the bloom, seafood samples were collected and nodularin concentrations were estimated. Nodularin concentrations reached levels of concern in mussels and in prawn viscera at cell counts as low as 30,000 cells/ml. Nodularin concentrations in the flesh of finfish remained low. Boiling the seafood redistributed toxin between viscera and flesh. The results were used to restrict some seafood harvesting. © 2001 John Wiley & Sons, Inc. Environ Toxicol 16: 468–471, 2001
Cytological alterations in isolated hepatocytes from common carp (Cyprinus carpio L.) exposed to microcystin‐LR
Authors: Li XiaoYu , Liu YongDing , Song LiRong 
Published: November 2004

AbstractMicrocystin‐LR (MC‐LR) is the most commonly encountered of the toxic cyclic peptide hepatotoxins occurring in China. It is a model compound for toxicological studies. In this study, the toxicity of MC‐LR (50 and 500 μg/L) on isolated carp hepatocytes was determined and the ultrastructural alterations of cells induced by MC‐LR were observed. The alterations noted when hepatocytes were exposed to 50 μg/L MC‐LR were blebbing of cell membrane, shrinking and deformation of nuclei, vesiculation and transformation into concentric membrane whorls of RER, and swelling and rearrangement of the cytoskeleton. However, when the cells were exposed to 500 μg/L MC‐LR, broken cell membranes, nuclei and cytoskeleton could be observed. These ultrastructural changes paralleled the pathological events, which lead to apoptosis or necrosis of hepatocytes. These results suggest that disruption of the cytoskeletal structures could account for the blebbing of cell membrane and apoptosis induced by MC‐LR. © 2001 John Wiley & Sons, Inc. Environ Toxicol, 16: 517–522, 2001
Characterisation of a gene cluster involved in bacterial degradation of the cyanobacterial toxin microcystin LR
Authors: Bourne David G. , Riddles Peter , Jones Gary J. , Smith Wendy , Blakeley Robert L. 
Published: November 2004

AbstractA novel pathway for degradation of the cyanobacterial heptapeptide hepatotoxin microcystin LR was identified in a newly isolated Sphingomonas sp. (Bourne et al. 1996 Appl. Environ. Microbiol. 62: 4086–4094). We now report the cloning and molecular characterisation of four genes from this Sphingomonas sp. that exist on a 5.8‐kb genomic fragment and encode the three hydrolytic enzymes involved in this pathway together with a putative oligopeptide transporter. The heterologously expressed degradation pathway proteins are enzymatically active. Microcystinase (MlrA), the first enzyme in the degradative pathway, is a 336‐residue endopeptidase, which displays only low sequence identity with a hypothetical protein from Methanobacterium thermoautotrophicum. Inhibition of microcystinase by EDTA and 1,10‐phenanthroline suggests that it is a metalloenzyme. The most likely residues that could potentially chelate an active‐site transition metal ion are in the sequence HXXHXE, which would be unique for a metalloproteinase. Situated immediately downstream of mlrA with the same direction of transcription is a gene mlrD, whose conceptual translation (MlrD, 442 residues) shows significant sequence identity and similar potential transmembrane spanning regions to the PTR2 family of oligopeptide transporters. A gene mlrB is situated downstream of the mlrA and mlrD genes, but transcribed in the opposite direction. The gene encodes the enzyme MlrB (402 residues) which cleaves linear microcystin LR to a tetrapeptide degradation product. This enzyme belongs to the “penicillin‐binding enzyme” family of active site serine hydrolases. The final gene in the cluster mlrC, is located upstream of the mlrA gene and is transcribed in the opposite direction. It codes for MlrC (507 residues) which mediates further peptidolytic degradation of the tetrapeptide. This protein shows significant sequence identity to a hypothetical protein from Streptomyces coelicolor. It is suspected to be a metallopeptidase based on inhibition by metal chelators. It is postulated on the basis of comparison with other microorganisms that the genes in this cluster may all be involved in cell wall peptidoglycan cycling and subsequently act fortuitously in hydrolysis of microcystin LR. © 2001 John Wiley & Sons, Inc. Environ Toxicol, 16: 523–534, 2001
Population growth impairment of sulfur‐containing compounds to Tetrahymena pyriformis
Authors: Schultz T. Wayne , Sinks Glendon D. , Miller Lisa A. 
Published: November 2004

AbstractA series of 37 aliphatic and aromatic sulfur‐containing compounds were evaluated in 2‐day Tetrahymena pyriformis population growth impairment assay. The results indicate that, except for select compounds, the in‐ring sulfur‐containing compounds, sulfates, sulfites, thiols, sulfones, and sulfoxides model as neutral and noncovalent‐reacting narcotics. Abiotic loss due to volatility appears to interfere in accurate model prediction because actual toxicity was less than predicted. Vinyl sulfones and sulfoxides are more toxic than predicted using neutral narcosis. Tetrahymena exposed to methyl vinyl sulfone exhibits a direct relationship between the exposure concentration and the generation times with no lag phase in growth. As such, these population growth kinetics mimic those reported for hydrophilic neutral narcotics (i.e., ethanol and acetone). Tetrahymena exposed to phenyl vinyl sulfone exhibit a long concentration‐dependent lag phase, which is followed by population growth at rates not different from controls. These population growth kinetics are similar but more dramatic than those reported for hydrophobic neutral narcotics (i.e., butylbenzene and 2‐decanone). These results are useful in that they imply that sulfur‐containing compounds for the most part act as simple narcotics. Therefore, their toxicity can be modeled with simple structure‐toxicity relationships without much fear of underestimation of potency. © 2001 John Wiley & Sons, Inc. Environ Toxicol, 16: 543–549, 2001
Comparative sensitivity of embryo–larval toxicity assays with African catfish (Clarias gariepinus) and zebra fish (Danio rerio)
Authors: Nguyen Lien T. H. , Janssen Colin R. 
Published: November 2004

AbstractEmbryo–larval toxicity tests with the African catfish (Clarias gariepinus) were conducted with five chemicals (Cr, Cd, Zn, NaPCP and malathion) and three environmental samples. The sensitivity of the 5‐day assay was compared to that of the 12‐day embryo–larval toxicity tests with the zebra fish (Danio rerio). The ratios of the C. gariepinus and D. rerio LC50 values ranged from 0.4 for Cr to 8.9 for Zn. The ratios of subchronic values ranged from 0.25 for NaPCP to 3.1 for Cd indicating a more comparable sensitivity of the two species. For the three sediment pore waters, the ratios were 0.6, 1.1, and 2.4 and the subchronic values were identical for the two species. The results suggest that, considering the short‐test duration and its sensitivity, the 5‐day embryo–larval tests with C. gariepinus may be a potential alternative for short‐term embryo–larval toxicity testing with fish. © 2001 John Wiley & Sons, Inc. Environ Toxicol 16: 566–571, 2001
The cross‐sectional study of the health effects of occupational exposure to carbon disulfide in a Chinese viscose plant
Authors: Tan Xiaodong , Wang Fuyuan , Bi Yongyi , Su YongJun , Li Yang , He Jun , Yi Pinfan , Yan Jun , de Bacquer Dirk , Braeckman Lutgart , Vanhoorne Michel 
Published: November 2004

AbstractThis article presents results of carbon disulfide exposure assessment in a Chinese viscose rayon factory and represents the cross‐sectional study beginning phase of the occupational epidemiological project. The authors measured external exposure levels to carbon disulfide at a Chinese viscose rayon factory and monitored results as internal exposure indexes by testing urine samples of workers exposed to carbon disulfide levels. The rate at which carbon disulfide is metabolized by exposed subjects was demonstrated by 2‐thio‐thiazolidine‐4‐carboxylic acid (TTCA) concentrations in urine of exposed subjects, which was studied to determine best time points for internal exposure sampling. Carbon disulfide concentrations in the air of the workplace were analyzed with gas chromatography with flame photometric detector (GC‐FPD); presence of TTCA in urine samples of subjects was determined using a modified high‐performance liquid chromatography method. Kinetics of TTCA excretion was studied by analysis at different time points during and after exposure of workers to carbon disulfide. A total of 155 personal samples were obtained. Carbon disulfide concentration at staple viscose hall was found to be 13.72±1.12 mg/m3 in terms of geometric mean and geometric standard deviation. Carbon disulfide concentration at filament spinning hall was found to be 20.05±1.33 mg/m3. TTCA values of subjects at staple spinning hall were 1.18±0.43 and 1.07±0.38 mg/g creatinine for subjects working at filament spinning hall. The best time for TTCA sampling is at the end of the exposure–working shift. © 2001 John Wiley & Sons, Inc. Environ Toxicol 16: 377–382, 2001
Deletion of the Chloroplast-Localized Thylakoid Formation1 Gene Product in Arabidopsis Leads to Deficient Thylakoid Formation and Variegated Leaves
Authors: Wang Qin , Sullivan Rusty W. , Kight Alicia , Henry Ralph L. , Huang Jirong , Jones Alan M. , Korth Kenneth L. 
Published: November 2004

Abstract
Development of thylakoid membranes depends upon the transport of membrane vesicles from the chloroplast inner envelope and subsequent fusion of vesicles within the interior of the plastid. The Arabidopsis (Arabidopsis thaliana) Thylakoid formation1 (Thf1) gene product is shown here to control an important step required for the normal organization of these vesicles into mature thylakoid stacks and ultimately for leaf development. The Arabidopsis Thf1 gene encodes an imported chloroplast protein, as shown by in vitro import and localization of a Thf1-green fluorescent protein fusion product in transgenic plants. This gene is conserved in oxygenic photoautotrophs ranging from cyanobacteria to flowering land plants. Transcript levels for Thf1 are induced in the light and decrease under dark conditions, paralleling profiles of light-regulated nuclear genes involved in chloroplast function. Disruption of the Thf1 gene via T-DNA insertion results in plants that are severely stunted with variegated leaf patterns. Nongreen sectors of variegated leaves lacking Thf1 expression contain plastids that accumulate membrane vesicles on the interior and lack organized thylakoid structures. Green sectors of Thf1-disrupted leaves contain some chloroplasts that form organized thylakoid membranes, indicating that an inefficient compensatory mechanism supports thylakoid formation in the absence of Thf1. Genetic complementation of a Thf1 knockout line confirms the role of this gene in chloroplast and leaf development. Transgenic plants expressing the Thf1 gene in antisense orientation are stunted with altered thylakoid organization, especially in young seedlings. The data indicate that the Thf1 gene product plays a crucial role in a dynamic process of vesicle-mediated thylakoid membrane biogenesis.
A Stromal Hsp100 Protein Is Required for Normal Chloroplast Development and Function in Arabidopsis
Authors: Constan Diane , Froehlich John E. , Rangarajan Sowkya , Keegstra Kenneth 
Published: November 2004

Abstract
Molecular chaperones are required for the translocation of many proteins across organellar membranes, presumably by providing energy in the form of ATP hydrolysis for protein movement. In the chloroplast protein import system, a heat shock protein 100 (Hsp100), known as Hsp93, is hypothesized to be the chaperone providing energy for precursor translocation, although there is little direct evidence for this hypothesis. To learn more about the possible function of Hsp93 during protein import into chloroplasts, we isolated knockout mutant lines that contain T-DNA disruptions in either atHSP93-V or atHSP93-III, which encode the two Arabidopsis (Arabidopsis thaliana) homologs of Hsp93. atHsp93-V mutant plants are much smaller and paler than wild-type plants. In addition, mutant chloroplasts contain less thylakoid membrane when compared to the wild type. Plastid protein composition, however, seems to be largely unaffected in atHsp93-V knockout plants. Chloroplasts isolated from the atHsp93-V knockout mutant line are still able to import a variety of precursor proteins, but the rate of import of some of these precursors is significantly reduced. These results indicate that atHsp93-V has an important, but not essential, role in the biogenesis of Arabidopsis chloroplasts. In contrast, knockout mutant plants for atHsp93-III, the second Arabidopsis Hsp93 homolog, had a visible phenotype identical to the wild type, suggesting that atHsp93-III may not play as important a role as atHsp93-V in chloroplast development and/or function.
Class II Integrase Mutants with Changes in Putative Nuclear Localization Signals Are Primarily Blocked at a Postnuclear Entry Step of Human Immunodeficiency Virus Type 1 Replication
Authors: Lu Richard , Limón Ana , Devroe Eric , Silver Pamela A. , Cherepanov Peter , Engelman Alan 
Published: November 2004

ABSTRACT

Integrase has been implicated in human immunodeficiency virus type 1 (HIV-1) nuclear import. Integrase analyses, however, can be complicated by the pleiotropic nature of mutations: whereas class I mutants are integration defective, class II mutants display additional assembly and/or reverse transcription defects. We previously determined that HIV-1
V165A
, originally reported as defective for nuclear import, was a class II mutant. Here we analyzed mutants containing changes in other putative nuclear localization signals, including
186
KRK
188
/
211
KELQKQITK
219
and Cys-130. Previous work established HIV-1
K186Q
, HIV-1
Q214L/Q216L
, and HIV-1
C130G
as replication defective, but phenotypic classification was unclear and nuclear import in nondividing cells was not addressed. Consistent with previous reports, most of the bipartite mutants studied here were replication defective. These mutants as well as HIV-1
V165A
synthesized reduced cDNA levels, but a normal fraction of mutant cDNA localized to dividing and nondividing cell nuclei. Somewhat surprisingly, recombinant class II mutant proteins were catalytically active, and class II Vpr-integrase fusion proteins efficiently complemented class I mutant virus. Since a class I Vpr-integrase mutant efficiently complemented class II mutant viruses under conditions in which class II Vpr-integrases failed to function, we conclude that classes I and II define two distinct complementation groups and suggest that class II mutants are primarily defective at a postnuclear entry step of HIV-1 replication. HIV-1
C130G
was also defective for reverse transcription, but Vpr-integrase
C130G
did not efficiently complement class I mutant HIV-1. Since HIV-1
C130A
grew like the wild type, we conclude that Cys-130 is not essential for replication and speculate that perturbation of integrase structure contributed to the pleiotropic HIV-1
C130G
phenotype.