bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relationship between thickness of polymer films and their oxidation on copper substrate
Authors: Lin D.G. , Vorobieva E.V. 
Published: November 2002

AbstractThis research was undertaken to understand how the thickness of polyethylene films oxidized on a copper substrate influences the accumulation of carbonyl groups (measured by an IR‐spectroscopy technique) and of metal from the substrate (determined by polarography analysis). It was found that the whole polymer became inhibited by the time the copper stopped transferring into the specimen. Plots of copper concentration versus film thickness have two thickness sections: section I is found between 0 and 70 μm and section II between 80 and 170 μm. Between these two sections the metal concentration varies drastically. This situation can be explained by two schemes by which PE changes to inhibited condition. According to Scheme I (for section I, short oxidation time) this change has only one step: the inhibited layer gradually becomes thicker beginning from the interface and moving toward the outer surface. The second scheme (for section II) shows that the polymer becomes inhibited in two steps. It is typical of thicker films. In this case the oxidation process shifts and localizes in the outer surface because of longer treatment. As a result, transfer of metal and formation of an inhibited layer are interrupted for some time. The metal accumulation in the film only resumes when low‐molecular‐weight products of thermooxidative degradation—formed in the specimen outer surface—enter the region of adhesional contact. A so‐called second transfer stage for metal is realized during which the whole polymer becomes inhibited. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 671–675, 2003
Hydrogels from glycidyl derivatives of poly(vinyl alcohol)
Authors: Ruiz J. , Mantecón A. , Cádiz V. 
Published: November 2002

AbstractPoly(vinyl alcohol) (PVA) was modified with phthalic anhydride to obtain half esters with carboxylic acid groups, which made the reaction with epichlorohydrin easier. The oxirane ring underwent a further crosslinking that led to crosslinked polymers with polar groups capable of interacting strongly with water and therefore with properties of hydrogels. The curing kinetics of the crosslinking were studied by differential scanning calorimetry, and the dependence of the activation energy on conversion degree was studied by isoconversional kinetic analysis. Water absorption was determined gravimetrically as a function of time at room temperature. The swelling behavior of these hydrogels was related to the degree of crosslinking. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 693–698, 2003
Chemical modification of molten polyethylene by thermal decomposition of peroxyesters
Authors: Navarre Sébastien , Saule Myriam , Maillard Bernard 
Published: November 2002

AbstractThe functionalization of polyethylene was realized by the thermal decomposition of peroxyesters in molten polymer in the absence of any other additive. Ester and acid functions were introduced onto the polymer operating with various peroxyesters. This grafting resulted from the combination of a polymer radical, generated in the abstraction of a hydrogen from polyethylene by an alkoxy radical, with an acyloxy or carbon‐centered radical arising from the perester. A complete methodology was set up to identify and to titrate the functions present onto the polyethylene and to determine the extent of crosslinked polymer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 699–707, 2003
Frequent activation of AKT2 kinase in human pancreatic carcinomas
Authors: Altomare Deborah A. , Tanno Satoshi , De Rienzo Assunta , Klein‐Szanto Andres J. , Tanno Sachie , Skele Kristine L. , Hoffman John P. , Testa Joseph R. 
Published: November 2002

AbstractActivation of AKT/protein kinase B promotes a variety of biological activities important in tumorigenesis, such as cell survival and cell cycle progression. We previously demonstrated amplification and overexpression of the AKT2 gene in a subset of human pancreatic carcinomas. In this investigation, we assessed AKT2 catalytic activity in 50 frozen pancreatic tissues (37 carcinomas, four benign tumors, and nine normal pancreata) by in vitro kinase assay. Twelve of 37 (32%) pancreatic carcinomas showed markedly elevated levels of AKT2 activity compared to normal pancreata and benign pancreatic tumors. To delineate mechanisms contributing to AKT2 activation in malignant pancreatic tumors, we examined the status of upstream components of the phosphatidylinositol 3‐kinase (PI3K)/AKT pathway. Western blot analysis revealed loss of PTEN protein expression in two of the 12 pancreatic carcinomas with activated AKT2. In vitro PI3K assays demonstrated high levels of PI3K activity in seven carcinoma specimens that showed AKT2 activation. Immunohistochemical staining confirmed high levels of phosphorylated (active) AKT in malignant pancreatic tumors compared to normal pancreata. Overall, these data suggest that upstream perturbations of the PI3K/AKT pathway contribute to frequent activation of AKT2 in pancreatic cancer, which may contribute to the pathogenesis of this highly aggressive form of human malignancy. J. Cell. Biochem. 87: 470–476, 2002. © 2002 Wiley‐Liss, Inc.
Structural, antigenic and evolutionary analyses of immunoglobulins and T cell receptors
Authors: Marchalonis John J. , Jensen Ingvill , Schluter Samuel F. 
Published: November 2002

AbstractWe have had the pleasure of collaborating with Allen Edmundson for the past 15 years on the structure, binding properties and evolution of immunoglobulins and T cell receptors. Among the most significant contributions of our joint efforts were: (1) the predictive use of structural features of immunoglobulin domains to model the three‐dimensional structures of the immunoglobulin domains of human T‐cell receptor α and β chains as well as shark light chains and VH domains; (2) the finding that normal humans and other vertebrates express autoantibodies against combining site epitopes of their own T cell receptors; (3) the mapping of the peptide autoepitopes recognized in health, autoimmunity and retroviral infection; and (4) the determination that epitope recognition promiscuity is a characteristic property of the combining sites of IgM immunoglobulins ranging from those of sharks to those of humans. We briefly review the salient findings and status of these studies and indicate the future directions that we will pursue in their continuation. Copyright © 2002 John Wiley & Sons, Ltd.
Inhibition of HIV protease by monoclonal antibodies
Authors: Rezacova P. , Brynda J. , Fabry M. , Horejsi M. , Stouracova R. , Lescar J. , Chitarra V. , Riottot M. M. , Sedlacek J. , Bentley G. A. 
Published: November 2002

AbstractThe protease of HIV plays a critical role in the maturation of the infectious particles of the virus. The enzyme has therefore been extensively studied with the objective of developing therapeutics that inhibit viral proliferation. We have produced monoclonal antibodies specific for the HIV‐1 protease, and selected those that inhibit enzyme function for use as probes to study the enzyme's activity and as an eventual aid for the development of potential inhibitors targeted to regions other than the active site. We have characterized two such mAbs, F11.2.32 and 1696, which have inhibition constants in the low nanomolar range and which recognize epitopes from different regions of the protease. The crystal structures of the two antibodies, both in the free state as well as complexes with peptide fragments corresponding to their respective epitopes, have been solved. The structural analyses, taken together with other functional data on the antibodies, suggest mechanisms of protease inhibition by these antibodies. Copyright © 2002 John Wiley & Sons, Ltd.
Combinatorial methods for discovery of peptide ligands which bind to antibody‐like molecules
Authors: Tribbick Gordon , Rodda Stuart 
Published: November 2002

AbstractIn the 1980s, new methods of parallel peptide synthesis were used to make large libraries of peptides, which were then screened for binding to Bence–Jones dimers. Subsequent X‐ray crystallography of the Bence–Jones proteins, which had been infiltrated with peptide ligand, was used to determine the structural correlate of the binding data. The mode of binding was found to be not predictable and insight was gained into the forces determining how the so‐called mimotopes interacted with binding sites. Copyright © 2002 John Wiley & Sons, Ltd.
Bifluorophoric molecules as fluorescent beacons for antibody–antigen binding
Authors: Wei Ai‐Ping , Herron James N. 
Published: November 2002

AbstractThe quenching of fluorescence (up to 98%) by anti‐fluorescein antibodies is well documented in the literature. Here we report a system where, instead of quenching, bifluorophoric molecules are designed to increase in fluorescence upon binding by an anti‐fluorescein antibody. Bifluorophoric molecules are made of fluorescein (F) linked to tetramethylrhodamine (T) via varying numbers of methylene units, denoted as F‐(CH2)
n‐T. These F‐(CH2)
n‐T conjugates are almost nonfluorescent when free in solution due to intramolecular dimerization and stacking. Upon binding to an anti‐fluorescein antibody, however, up to 110‐fold increase in fluorescence was observed from the rhodamine moiety. This increase is believed to result from intramolecular dimer dissociation that dequenches the rhodamine fluorescence. Fluorescein fluorescence, on the other hand, remains quenched due to binding and intramolecular resonance energy transfer. Moreover, the excitation wavelength was at the absorption maxima of fluorescein, giving a Stoke's shift of about 90 nm. This system couples directly molecular recognition with a concurrent increase in fluorescence emission, obviating wash and incubation steps required by most assays. It is an important molecular reporter system for developing homogeneous assays. Copyright © 2002 John Wiley & Sons, Ltd.
Expression and functional analysis of recombinant scFv and diabody fragments with specificity for human RhD
Authors: Asvadi Parisa , Fletcher Anne , Raison Robert L. 
Published: November 2002

AbstractIn an attempt to generate recombinant anti‐D reagents for possible diagnostic and therapeutic use we cloned the genes encoding the variable (V) domains of a human anti‐D antibody secreted by the lymphoblastoid cell line BTSN4. A single‐chain Fv (scFv) fragment was constructed using a 21 amino acid linker to join the genes encoding the variable domains of the BTSN4 heavy (VH) and light chains (VL). A diabody construct was also generated by reducing the length of the scFv linker from 21 to 10 residues. The scFv and diabody constructs were cloned into the pFLAG‐CTS vector, expressed in E. coli host cells and the recombinant proteins were affinity‐isolated from bacterial culture medium. Analysis of the recombinant proteins indicated that they retained the D antigen binding specificity of the parental BTSN4 IgG. Furthermore, both fragments mediated agglutination of papain‐treated D positive erythrocytes in the absence of a cross‐linking second antibody. While the agglutinating property of BTSN4 diabody was readily explained by the non‐covalent association of this protein as a bivalent dimer, oligomeric forms of BTSN4 scFv were not detected when the protein was analysed by size exclusion chromatography. Thus, the agglutinating property of the scFv is not the result of the formation of non‐covalently associated multimeric forms of the antibody fragment. Copyright © 2002 John Wiley & Sons, Ltd.
Mcg light chain dimer as a model system for ligand design: a docking study
Authors: Yuriev Elizabeth , Ramsland Paul A. 
Published: November 2002

AbstractMcg light chain dimer has been extensively studied by crystallography and peptide binding studies to investigate its peptide cross‐reactivity as well as to use it as a model system for designing space filling peptide ligands. Here we extend these investigations by utilizing automated docking. Mcg light chain dimer is an ideal model system for such study due to the availability of experimental data for both the native structure and the 14 complexes with various peptide ligands. We show the ability of the docking approach to reproduce the experimental structures and discuss the limitations associated with such outcomes. We demonstrate the usefulness of the docking approach in generating structural information otherwise not available from the experiment. Copyright © 2002 John Wiley & Sons, Ltd.
Dealing with intractable protein cores: protein sequencing of the Mcg IgG and the Yvo IgM heavy chain variable domains
Authors: Shaw Denis C. , Shultz Brandon B. , Ramsland Paul A. , Edmundson Allen B. 
Published: November 2002

AbstractThe VH domains of two human monoclonal antibodies, designated Mcg IgG1(λ) and Yvo IgM(κ), were particularly intractable to standard protein sequencing protocols. Peptides liberated from the VH domains of these proteins, using standard enzymatic or chemical cleavages, invariably precipitated during the procedures. Boiling in SDS containing buffers dissolved precipitates and the peptides were separated using SDS–PAGE. Fully overlapped VH sequences were obtained with a series of ‘in‐gel’ cleavages, followed by passive/differential transfers of peptides onto PVDF membranes. Both the in‐gel cleavages and passive transfers could be applied to ‘wet’ or ‘dry’ gels so that gels could be archived and used at a later date to obtain additional sequence information from a fragment of interest. Repetitive yields of even the most insoluble peptides were such that the sequences of various peptides from relatively complex mixtures of peptides could be assigned with confidence. Despite the overall success of the sequencing, we occasionally referred to electron density maps, calculated for crystals of the Fab of Yvo IgM, to resolve particular sequences and confirm ambiguous amino acid assignments. Methods we describe in this report should be generally useful for obtaining sequences of proteins with intractable cores and may find many applications in the ‘post genomic era’. Copyright © 2002 John Wiley & Sons, Ltd.
Fiber‐ring laser‐based fiber grating sensor system using self‐healing ring architecture
Authors: Peng Peng‐Chun , Tseng Hong‐Yih , Chi Sien 
Published: November 2002

AbstractThis paper presents a self‐healing fiber grating sensor system and demonstrates its effectiveness. The self‐healing function is constructed by using a primary ring architecture incorporated with several ring sub‐networks. To enhance the sensing signal when a breakpoint suddenly occurs in the network, we employ a fiber‐ring laser‐based sensor system. The network survivability of an 11‐point FBG sensor is experimentally examined. The proposed fiber grating sensor system can increase the reliability of a sensing network. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 441–444, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10633
Theoretical studies on the structures and electronic spectra of C75B−
Authors: Teng Qiwen , Wu Shi , Zhu Zheying 
Published: November 2002

AbstractIntermediate neglect of differential overlap (INDO) calculations were used to study the structure of C75B−—the isoelectronic molecule of C76. It was found that the boron atom mainly substitutes the second carbon atom (there are 19 types of carbon atoms in C76). The electronic spectra of all the possible isomers of C75B− were calculated based on the optimized geometries. It was shown that the UV‐Vis spectra of C75B− and C76 resemble each other in many ways with the exception of the absorptions beyond 700 nm. The red shift of the absorptions was rationalized and nature of transition of the peaks discussed. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Identification and Characterization of Two Temperature-Induced Surface-Associated Proteins of
Streptococcus suis
with High Homologies to Members of the Arginine Deiminase System of
Streptococcus pyogenes
Authors: Winterhoff Nora , Goethe Ralph , Gruening Petra , Rohde Manfred , Kalisz Henryk , Smith Hilde E. , Valentin-Weigand Peter 
Published: November 2002

ABSTRACT

The present study was performed to identify stress-induced putative virulence proteins of
Streptococcus suis
. For this, protein expression patterns of streptococci grown at 32, 37, and 42°C were compared by one- and two-dimensional gel electrophoresis. Temperature shifts from 32 and 37 to 42°C induced expression of two cell wall-associated proteins with apparent molecular masses of approximately 47 and 53 kDa. Amino-terminal sequence analysis of the two proteins indicated homologies of the 47-kDa protein with an ornithine carbamoyltransferase (OCT) from
Streptococcus pyogenes
and of the 53-kDa protein with the streptococcal acid glycoprotein (SAGP) from
S. pyogenes
, an arginine deiminase (AD) recently proposed as a putative virulence factor. Cloning and sequencing the genes encoding the putative OCT and AD of
S. suis
,
octS
and
adiS
, respectively, revealed that they had 81.2 (
octS
) and 80.2% (
adiS
) identity with the respective genes of
S. pyogenes
. Both genes belong to the AD system, also found in other bacteria. Southern hybridization analysis demonstrated the presence of the
adiS
gene in all 42 serotype 2 and 9
S. suis
strains tested. In 9 of these 42 strains, selected randomly, we confirmed expression of the AdiS protein, homologous to SAGP, by immunoblot analysis using a specific antiserum against the SAGP of
S. pyogenes
. In all strains AD activity was detected. Furthermore, by immunoelectron microscopy using the anti-
S. pyogenes
SAGP antiserum we were able to demonstrate that the AdiS protein is expressed on the streptococcal surface in association with the capsular polysaccharides but is not coexpressed with them.
Mutant Forms of theAzotobacter vinelandiiTranscriptional Activator NifA Resistant to Inhibition by the NifL Regulatory Protein
Authors: Reyes-Ramirez Francisca , Little Richard , Dixon Ray 
Published: November 2002

ABSTRACTTheAzotobacter vinelandiiσ54-dependent transcriptional activator protein NifA is regulated by the NifL protein in response to redox, carbon, and nitrogen status. Under conditions inappropriate for nitrogen fixation, NifL inhibits transcription activation by NifA through the formation of the NifL-NifA protein complex. NifL inhibits the ATPase activity of the central AAA+ domain of NifA required to drive open complex formation by σ54-RNA polymerase and may also inhibit the activator-polymerase interaction. To analyze the mechanism of inhibition in greater detail, we isolated NifA mutants which are resistant to the inhibitory action of NifL. Mutations in both the amino-terminal GAF domain and the catalytic AAA+ domain of NifA were isolated. Several mutants blocked inhibition by NifL in response to both nitrogen and redox status, whereas some of the mutant NifA proteins were apparently able to discriminate between the forms of NifL present under different environmental conditions. One mutant protein, NifA-Y254N, was resistant to NifL under conditions of anaerobic nitrogen excess but was relatively sensitive to NifL under aerobic growth conditions. The properties of the purified mutant protein in vitro were consistent with the in vivo phenotype and indicate that NifA-Y254N is not responsive to the nitrogen signal conveyed by the interaction of NifL withA. vinelandiiGlnK but is responsive to the oxidized form of NifL when ADP is present. Our observations suggest that different conformers of NifL may be generated in response to discrete signal transduction events and that both the GAF and AAA+ domains of NifA are involved in the response to NifL.
Isolation of Three New Surface Layer Protein Genes (
slp
) from
Lactobacillus brevis
ATCC 14869 and Characterization of the Change in Their Expression under Aerated and Anaerobic Conditions
Authors: Jakava-Viljanen Miia , Åvall-Jääskeläinen Silja , Messner Paul , Sleytr Uwe B. , Palva Airi 
Published: November 2002

ABSTRACT

Two new surface layer (S-layer) proteins (SlpB and SlpD) were characterized, and three
slp
genes (
slpB
,
slpC
, and
slpD)
were isolated, sequenced, and studied for their expression in
Lactobacillus brevis
neotype strain ATCC 14869. Under different growth conditions,
L. brevis
strain 14869 was found to form two colony types, smooth (S) and rough (R), and to express the S-layer proteins differently. Under aerobic conditions R-colony type cells produced SlpB and SlpD proteins, whereas under anaerobic conditions S-colony type cells synthesized essentially only SlpB. Anaerobic and aerated cultivations of ATCC 14869 cells in rich medium also resulted in S-layer protein patterns similar to those of the S- and R-colony type cells, respectively. Electron microscopy suggested the presence of only a single S-layer with an oblique structure on the cells of both colony forms. The
slpB
and
slpC
genes were located adjacent to each other, whereas the
slpD
gene was not closely linked to the
slpB
-
slpC
gene region. Northern analyses confirmed that both
slpB
and
slpD
formed a monocistronic transcription unit and were effectively expressed, but
slpD
expression was induced under aerated conditions.
slpC
was a silent gene under the growth conditions tested. The amino acid contents of all the
L. brevis
ATCC 14869 S-layer proteins were typical of S-layer proteins, whereas their sequence similarities with other S-layer proteins were negligible. The interspecies identity of the
L. brevis
S-layer proteins was mainly restricted to the N-terminal regions of those proteins. Furthermore, Northern analyses, expression of a PepI reporter protein under the control of the
slpD
promoter, and quantitative real-time PCR analysis of
slpD
expression under aerated and anaerobic conditions suggested that, in
L. brevis
ATCC 14869, the variation of S-layer protein content involves activation of transcription by a soluble factor rather than DNA rearrangements that are typical for most of the S-layer phase variation mechanisms known.
Regulation of Expression of
mas
and
fadD28
, Two Genes Involved in Production of Dimycocerosyl Phthiocerol, a Virulence Factor of
Mycobacterium tuberculosis
Authors: Sirakova Tatiana D. , Fitzmaurice Ann Marie , Kolattukudy Pappachan 
Published: November 2002

ABSTRACT

Transcriptional regulation of genes involved in the biosynthesis of cell wall lipids of
Mycobacterium tuberculosis
is poorly understood. The gene encoding mycocerosic acid synthase (
mas
) and
fadD28
, an adjoining acyl coenzyme A synthase gene, involved in the production of a virulence factor, dimycocerosyl phthiocerol, were cloned from
Mycobacterium bovis
BCG, and their promoters were analyzed. The putative promoters were fused to the
xylE
reporter gene, and its expression was measured in
Escherichia coli
,
Mycobacterium smegmatis
, and
M. bovis
BCG. In
E. coli
, the
fadD28
promoter was not functional but the
mas
promoter was functional. Both
fadD28
and
mas
promoters were functional in
M. smegmatis
, at approximately two- and sixfold-higher levels, respectively, than the BCG
hsp60
promoter. In
M. bovis
BCG, the
fadD28
and
mas
promoters were functional at three- and fivefold-higher levels, respectively, than the
hsp60
promoter. Primer extension analyses identified transcriptional start points 60 and 182 bp upstream of the translational start codons of
fadD28
and
mas
, respectively. Both promoters contain sequences similar to the canonical −10 and −35 hexamers recognized by the σ
70
subunit of RNA polymerase. Deletions of the upstream regions of both genes indicated that 324 bp of the
fadD28
and 228 bp of the
mas
were essential for promoter activity. Further analysis of the
mas
promoter showed that a 213-bp region 581 bp upstream of the
mas
promoter acted as a putative transcriptional enhancer, promoting high-level expression of the
mas
gene when present in either direction. This represents the identification of a rare example of an enhancer-like element in mycobacteria.