bluuebunny/crossref_metadata_2025 huggingface dataset:
A monoclonal antibody to a synthetic fragment of rabies virus glycoprotein binds ligands of the nicotinic cholinergic receptor
Authors: Rustici Mauro , Santucci Annalisa , Lozzi Luisa , Petreni Simonetta , Spreafico Adriano , Neri Paolo , Bracci Luisa , Soldani Patrizia
Published: May 2005

Rabies virus glycoprotein and snake venom curaremimetic neurotoxins share a region of high homology (30–45 for neurotoxins and 190–203 for the glycoprotein) in the regions that are believed to be responsible for binding the nicotinic acetylcholine receptor. Monoclonal antibodies raised to the 190–203 synthetic fragment of rabies virus glycoprotein were immobilized on a high performance affinity chromatography column and were able to bind neurotoxins. Toxins were displaced from the affinity column by elution at acidic pH and by affinity competition with acetylcholine at neutral pH. Furthermore, the affinity column proved to be useful for the purification of cholinergic ligands. Overall, these results indicate that the paratope of our monoclonal antibodies could behave as an ‘internal image’ of the nicotinic cholinergic receptor acetylcholine binding site.
Binding of basic pancreatic trypsin inhibitor and related isoinhibitors to leukocytic elastase. Determination of thermodynamic parameters
Authors: Fioretti Evandro , Angeletti Mauro , Cottini Maria Teresa , Ascoli Franca
Published: May 2005

The effect of temperature, ionic strength and solvation power of mono‐ and divalent cations on the interaction of BPTI‐like inhibitors with human leukocytic elastase has been determined. The binding process is characterized by a non‐linear dependence of the equilibrium association constant on 1/T indicating a thermal transition at temperature values ranging between 20°C and 35°C depending on the solvent. The marked dependence of the thermodynamic parameters (ΔH°, ΔS°, ΔG°) and of the transition temperature on the concentration and nature of the cations present in solution seems to indicate that the transition, probably of conformational nature, is related to removal of water molecules upon enzyme/inhibitor complex formation.
Chemical and photochemical probing of DNA complexes
Authors: Nielsen Peter E.
Published: May 2005

An overview of the chemical and photochemical probes which over the past ten years have been used in studies of DNA/ligand complexes and of non‐B‐form DNA conformation is presented with emphasis on the chemical reactions of the probes with DNA and on their present ‘use‐profile’. The chemical probes include: dimethyl sulfate, ethyl nitroso urea, diethyl pyrocarbonate, osmium tetroxide, permanganate, aldehydes, methidiumpropyl‐EDTA‐Fell (MPE), phenanthroline metal complexes and EDTA/FeII. The photochemical probes that have been used include: psoralens, UVB, acridines and uranyl salts. The biological systems analysed by use of these probes are reviewed by tabulation.
Prediction of the secondary structure and functional sites of major histocompatibility complex molecules
Authors: Fraga S. , San‐Fabian E. , Thornton S. , Singh Bhagirath
Published: May 2005

A method for the theoretical prediction of the antigenic determinants and the antigen‐interactive receptor sites of immunological proteins from their primary structure would constitute a useful tool for their study. Such a method developed in this laboratory uses hydrophilicity, accessibility, flexibility, and recognition profiles, together with the predicted secondary structure (α‐helices, β‐sheets, and turns). The secondary structure is determined by a modification of the method of Lim (1974), as described below. A study of human and mouse class I and class II major histocompatibility complex (MHC) antigens, central to the regulation of immune responses and to the phenomenon of graft rejection, was carried out using the above method. Comparison of the predictions with some of the available experimental and theoretical information supports the validity and usefulness of the approach.
Recognition of the acetylcholine receptor binding site of a long‐chain neurotoxin by toxin‐specific monoclonal antibodies
Authors: Charpentier Isabelle , Pillet Laurence , Karlsson Evert , Couderc Jacques , Ménez André
Published: May 2005

The present paper reports the preparation and characterization of two neutralizing monoclonal antibodies (Mabs), called MST1 and MST2, which bind at the central loop of a long‐chain neurotoxin from cobra venom. The central loop is a critical region for the binding of the toxin to the nicotinic acetylcholine receptor. Some of the residues incorporated in the epitopes recognized by MST1 and MST2 have been identified on the basis of competition experiments using a set of ‘chemical mutants’ of the toxin. We show that MST1 and MST2 bind at the base and at the tip of the central loop of the toxin, respectively, however, only MST2 actually overlaps the acetylcholine receptor binding site. Accordingly, only MST2 is capable of recognizing all homologous toxins so far examined. MST2, therefore, mimicks, at least partially, the site by which the nicotinic acetylcholine receptor recognizes a long‐chain neurotoxin.
Rabies virus binding to an acetylcholine receptor α‐subunit peptide
Authors: Lentz Thomas L.
Published: May 2005

The binding of 125I‐labeled rabies virus to a synthetic peptide comprising residues 173–204 of the α1‐subunit of the nicotinic acetylcholine receptor was investigated. Binding of rabies virus to the receptor peptide was dependent on pH, could be competed with by unlabeled homologous virus particles, and was saturable. Synthetic peptides of snake venom, curaremimetic neurotoxins and of the structurally similar segment of the rabies virus glycoprotein, were effective in competing with labeled virus binding to the receptor peptide at micromolar concentrations. Similarly, synthetic peptides of the binding domain on the acetylcholine receptor competed for binding. These findings suggest that both rabies virus and neurotoxins bind to residues 173–204 of the α1‐subunit of the acetylcholine receptor. Competition studies with shorter α‐subunit peptides within this region indicate that the highest affinity virus binding determinants are located within residues 179–192. A rat nerve α3‐subunit peptide, that does not bind α‐bungarotoxin, inhibited binding of virus to the α1 peptide, suggesting that rabies binds to neuronal nicotinic acetylcholine receptors. These studies indicate that synthetic peptides of the glycoprotein binding domain and of the receptor binding domain may represent useful antiviral agents by targeting the recognition event between the viral attachment protein and the host cell receptor, and inhibiting attachment of virus to the receptor.
Amino acid side chain interaction with chelate‐liganded crosslinked dextran, agarose and TSK gel. A mini review of recent work
Authors: Porath Jerker
Published: May 2005

Protein adsorption and retention data collected from recent chromatographic studies on hydrophilic gels substituted with chelate‐bonded metal ions are discussed. Attempts are made to interpret the adsorption behavior in terms of molecular events caused by the affinity for the immobilized metal ions.
Aspecific and specific intermolecular interactions in aqueous media
Authors: van Oss C. J.
Published: May 2005

Aspecific as well as specific interactions involve the same noncovalent forces, consisting of Lifshitz‐van der Waals, Lewis acid/base, electrostatic, and thermal or Brownian movement interactions. In vivo, aspecific interactions between, e.g., cells and/or biopolymers usually are repulsive, while specific interactions are always attractive. The differences between the two classes of interactions can be shown to lie in the fact that aspecifically interacting bodies are large, while specifically interacting sites are small, or have a small radius of curvature, and in the fact that aspecifically interacting surfaces are homogeneous, whereas specific sites have a heterogeneous composition.
Investigation of dye/protein interaction and its application to enzyme purification
Authors: Glemža Antanas A.
Published: May 2005

In this review the results of the interaction of the active dyes used in the USSR textile industry with microbial enzymes and blood serum proteins are discussed. The complexity of dye/protein interaction and the dependence of this interaction on different factors is demonstrated. Some practical aspects of the use of dye containing sorbents are presented and discussed. Their suitability for RNA ligase and DNA ligase, acetate kinase, alcohol dehydrogenase, lactate dehydrogenase and glucose‐6‐phosphate dehydrogenase purification and blood serum protein fractionation is demonstrated.
Cleavage of double helical DNA by Cu2+ ion in the presence of bisintercalator containing penta(ethylene glycol) connector chain
Authors: Takenaka Shigeori , Ihara Toshihiro , Takagi Makoto
Published: May 2005

In designing new DNA recognizing and cleaving reagents, we introduce herein a bisacridine derivative (referred to as bisacridine) in which two acridine heterocycles are connected by a penta(ethylene glycol) bridging chain. This compound offers two possible functions: 1, stabilization of DNA bisacridine intercalator complex by metal ion. The penta(ethylene glycol) chain stabilizes metal ions binding to the phosphate site of DNA, where the penta(ethylene glycol) chain constitutes a part of a pseudomacrocyclic ligand for metal binding; and 2, enhancement of metal‐assisted hydrolytic cleavage of DNA by means of a metal concentration effect by the pseudomacrocyclic ethereal chain. The binding isotherms of bisacridine with DNA in the presence of metal ions showed that the binding was mainly governed by the cation exchange reaction on the anionic DNA polymer chain, i.e., the exchange between metal ions and the cationic bisacridine. The bisacridine showed an increased DNA binding ability compared to quinacrine, the monoacridine counterpart, and caused an enhancement of DNA cleavage in the presence of Cu2+ ions. Additional experiments which included DNase I footprinting in the presence of bisacridine and the DNA cleavage by Cu2+/bisacridine using a 32P end‐labelled DNA fragment, suggested that the Cu2+‐assisted DNA cleavage sites in the presence of bisacridine were in reasonable overlap with the DNA binding sites of bisacridine.
Haplotype specific homology scanning algorithim to predict T‐cell epitopes from protein sequences
Authors: Guillet J.‐G. , Hoebeke J. , Lengagne R. , Tate K. , Borras‐Herrera F. , Strosberg A. D. , Borras‐Cuesta F.
Published: May 2005

We present a homology scanning microcomputer program to predict functional T‐cell epitopes within proteins. By taking into account particular human or mouse restriction elements the predictions are made haplotype‐sepecific. The generality of this approach is confirmed by (i) identification of well‐characterized immunogenic T‐cell determinants in lysozyme (ii) search for potential T epitopes on unanalysed proteins like the human β2‐adrenoreceptor (iii) modification of non‐immunogenic peptide sequences in order to generate T‐cell determinants.
Ferredoxin electron transfer site on cytochrome c3. Structural hypothesis of an intramolecular electron transfer pathway within a tetra‐heme cytochrome
Authors: Dolla A. , Guerlesquin F. , Bruschi M. , Haser R.
Published: May 2005

To specify electron exchanges involving Desulfovibrio desulfuricans Norway tetra‐heme cytochrome c3, the chemical modification of arginine 73 residue performed. Biochemical and biophysical studies have shown that modified cytochrome retains its ability to both interact and act as an electron carrier with its redox partners, ferredoxin and hydrogenase. Moreover, the chemical modification effects on the cytochrome c3 1H NMR spectrum were similar to that induced by the presence of ferredoxin. This suggests that arginine 73 is localized on the cytochrome c3 ferredoxin interacting site. The identification of heme 4, the closest heme to arginine 73, as the ferredoxin interacting heme helps us to hypothesize about the role of three other hemes in the molecule. A structural hypothesis for an intramolecular electron transfer pathway, involving hemes 4, 3, and 1, is proposed on th basis of the crystal structures of D. vulgaris Miyazaki and D. desulfuricans Norway cytochromes c3. The unique of role of some structural features (α helix, aromatic residues) intervening between the heme groups, is proposed.
Immunological mapping of fine molecular surface structures of citrate synthase enzymes from different cell types
Authors: Nemeth P. , Small W. C. , Evans C. T. , Zhi W. , Persson L. O. , Srere P. A.
Published: May 2005

Citrate synthase (EC 4.1.3.7), which is present in all living organisms as a key enzyme in aerobic energy metabolism, is one of the most highly phylogenetically conserved enzymes known in terms of its primary and active site structure. However, in terms of other parameters such as in vitro stability, tolerance to changes in pH, degree of self‐polymerization, etc., citrate syntheses different sources are markedly different. These divergences can be observed even between isoforms of the enzyme within the same species. Data documenting these diversities suggest that a high degree of difference in tertiary structures may occur. Therefore, the surface profiles of citrate synthase enzymes from yeast, pig, rat, tomato and Escherichia coli were investigated with immunological methods using monoclonal antibody families generated against either pig citrate synthase (α‐PCS) or yeast citrate synthase‐2 (α‐YCS‐2). A high degree of homology of enzyme epitopes was detected on the mitochondrial citrate synthases originating from yeast, tomato, pig and rat cells. Major differences were found between the hexameric citrate synthase originating from E. coli compared with those dimeric forms prepared from eukaryotic cells. Only modest similarities were detected between the highly homologous peroxisomal and mitochondrial yeast citrate syntheses. Furthermore, a point mutation of one of the catalytic residues (H274R on recombinant pig and H313R on yeast enzyme) of mitochondrial citrate synthase (CS‐1) resulted in a significant increase in immunological similarity with the peroxisomal isoenzyme (CS‐2). These findings are discussed in terms of the possible mechanism of evolution of CS‐2 in yeast.
Studies of the binding activity of phage G13 to synthetic trisaccharides analogous to binding structures in Salmonella typhimurium and Escherichia coli C core saccharide. Correlation between conformation and binding activity
Authors: Bruse Gert W. , Wollin Ralfh , Oscarson Stefan , Jansson Per‐Erik , Lindberg Alf A.
Published: May 2005

Phage G13 binds to the carbohydrate part of lipopolysaccharides from rough mutants of Salmonella and Escherichia coli as the first event of infection. Equilibrium dialysis inhibition studies with native and synthetic trisaccharides as inhibitors suggested that phage G13 recognizes branched oligosaccharides having 6‐O‐α‐ or 7‐O‐α‐glycosyl groups with α‐Man(1→3) [α‐Man(1→6)]Man (Man[Man]Man) and α‐Glc(1→3)‐[α‐Hep(1→7)α‐Hep(1→3)α‐Hep(1→5) Kdo as the smallsest saccharides with inhibitory activity (Wollin et. al., 1989). Of four synthetic analogues to Man[Man]Man only Man(1→3)[α‐Gal(1→6)]α‐Man‐Ome (Man[Gal]‐Man) and α‐Glc(1→3)]α‐Hep(1→7)α‐Hep‐Ome (Glc[Hep]Hep) inhibited the binding of labelled E. coli. C core nonasaccharide ligand to G13 with activities which were 10‐ and 15‐fold lower than Man[Man]Man. The trisaccharides α‐Man(2→3)[α‐Glc(1→6)]α‐Man‐OMe (Man[Glc]Man) and α‐Man(1→3)[α‐Tal(1→6)]α‐Man‐OMe (Man[Tal]Man) showed no inhibition at concentrations 75‐fold higher than Man[Man]Man. Minimum energy conformation calculations of the saccharides using the GESA method showed that the 6‐O‐α‐Man group in Man[Man]Man and the 7‐O‐α‐Hep group in SL805 pentasaccharide expose their OH‐2 and OH‐3 groups in a similar way and these are postulated to be key structural features for binding activity. The importance of hydroxy groups at certain positions is implied from the fact that both manno‐ and galacto‐isomers are active. We also conclude that the O6‐C6‐C5‐O5‐C1 region of the 3‐O‐α‐glycosyl group in the Man[Man]Man trisaccharide, or part of it, is important for the G13 binding activity.
Making sense from antisense: A review of experimental data and developing ideas on sense–antisense peptide recognition
Authors: Tropsha Alexander , Kizer John S. , Chaiken Irwin M.
Published: May 2005

Peptides encoded in the antisense strand of DNA have been predicted and found experimentally to bind to sense peptides and proteins with significant selectivity and affinity. Such sense–antisense peptide recognition has been observed in many systems, most often by detecting binding between immobilized and soluble interaction partners. Data obtained so far on sequence and solvent dependence of interaction support a hydrophobic‐hydrophilic (amphipathic) model of peptide recognition. Nonetheless, the mechanistic understanding of this type of molecular recognition remains incomplete. Improving this understanding likely will require expanding the types of characteristics measured for sense–antisense peptide complexes and hence the types of analytical methods applied to such interactions. Understanding the mechanism of sense–antisense peptide recognition also may provide insights into mechanisms of native (sense) peptide and protein interactions and protein folding. Such insight may be helpful to learn how to design macromolecular recognition agents in technology for separation, diagnostics and therapeutics.
Quantitative structure–activity relationship studies on benzodiazepine receptor binding: Recognition of active sites in receptor and modelling of interaction
Authors: Gupta Satya P. , Saha Ranendra N. , Mulchandani Veena
Published: May 2005

A quantitative structure‐activity relationship study was carried out for the binding of a series of ‘classical’ benzodiazepines (BZs) and some β‐carbolines with BZ receptors to investigate the active sites in the latter and the nature of the binding of compounds with them. Using the Hansch approach, an attempt was made to correlate binding affinities of compounds with various physico‐chemical and electronic properties of substituents. The correlations obtained showed the main roles were played by the hydrophobic constant π and the Hammett constant σ (an electronic parameter) of various substituents. This led to the suggestion that BZ receptors have many additional hydrophobic, hydrogen bonding and polor sites other than those suggested by Hollinshead et al. (1990). From the present study, the Hollinshead model of interaction was found to be inadequate to account fully for the binding of all types of compounds.
Epitope analysis using kinetic measurements of antibody binding to synthetic peptides presenting single amino acid substitutions
Authors: Zeder‐Lutz Gabrielle , Altschuh Danièle , Denery‐Papini Sandra , Briand Jean Paul , Van Regenmortel Marc H. V. , Tribbick Gordon
Published: May 2005

The fine modulation of peptide–antibody interactions was investigated with anti‐peptide monoclonal antibodies recognizing peptide 125–136 of the coat protein of tobacco mosaic virus. Nine synthetic peptides presenting single amino acid substitutions were selected for detailed analysis on the basis of their reactivity in ELISA. Kinetic measurements of the binding of four antibodies to these peptides performed with a biosensor instrument (BIAcoreTM, Pharmacia) were used to quantify the contribution of individual residues to antibody binding. The results showed that even conservative exchanges of some residues in the epitope results in a small but significant decrease of the equilibrium affinity constant due mostly to a higher dissociation rate constant of the monoclonal antibodies. Two amino acid residues directly adjacent to the epitope, which appeared to play no role when tested by ELISA, were shown to influence the kinetics of binding. These data should be useful for computer modelling of the peptide–antibody interactions.
Effect of high of pressure of EcoRI reactions
Authors: Kabata Hiroyuki , Nomura Akihiko , Shimamoto Nobuo , Kunugi Shigeru
Published: May 2005

The effect of pressure on reactions of restriction endonucleases was investigated. No obvious irreversible (after) effect was observed for EcoRI, while a considerable irreversible inactivation was found for BamHI. Thus the EcoRI reactions against λ DNA, pBR322 and pBluescript were studied under high pressure and little effect was observed on the overall reaction. The Dna concentration dependence of the kinetic data apparently fits the Michaelis‐Menten type equation and the evaluated rate parameters were: Vmax = 6.2±0.24 and 7.0±0.22 (×10−2 nM/min) at 0.1 and 200 MPa, respectively; Km = 19±1.8 and 28±1.7 nM at 0.1 and 200 MPa, respectively. The apparent activation volume corresponding to kcat/Km was ca + 1 mL/mol. a characteristics effect of pressure on the sequence specificity of these enzymes was seen in their star activity. Relaxed specificity was tightened by increasing pressure (200 MPa) with respect to that induced by low salt concentration or by the presence of organic solvent.
Selective oxidation of methionyl residues in the human recombinant secretory leukocyte proteinase inhibitor. Effect on the inhibitor binding properties
Authors: Tomova Svetlana , Cutruzzolà Francesca , Barra Donatella , Amiconi Gino , Ascenzi Paolo , Carugo Kristina Djinović , Menegatti Enea , Sarti Paolo , Schnebli Hans Peter , Bolognesi Martino
Published: May 2005

Binding of the human recombinant secretory leukocyte proteinase inhibitor (SLPI) [native and with the methionyl residues at positions 73, 82, 94 and 96 of domain 2 oxidized to the sulfoxide derivative (Met(O) SLPI)] to bovine α‐chymotrypsin (α‐chymotrypsin) [native and with the Met192 residue converted to the sufoxide derivative (Met(O) α‐chymotrypsin)] as well as to native bovine β‐trypsin (β‐trypsin), which does not contain methionyl residues, has been investigated between pH 4.0 and 8.0, and between 10.0°C ad 30.0°C, from thermodynamic and/or kinetic viewpoints. By increasing the number of oxidized methytonyl residues present at the proteinase: inhibitor contact interface (from 0 to 3), the adducts investigated are increasingly destabilized and the relaxation time of the complexes into conformers less stable is enhanced. On the other hand, the selective oxidation methionyl residues of SLPI and α‐chymotrypsin, by the reaction with chloramines T, does not affect the proteinase inhibition recognition mechanism. Therefore, even though conformational changes may occur in the conversion native SLPI and native α‐chymotrypsin to their Met(O) derivatives, a localized steric hindrance can be considered as the main structural determinant accounting for the reported results.
Interaction of mithramycin with isolated GC and CG sites
Authors: Carpenter Mark L. , Cassidy Sarah A. , Fox Keith R.
Published: May 2005

We have studied the interaction of the GC‐specific, minor groove‐binding ligand, mithramycin, with cloned DNA inserts containing isolated GC and CG sites flanked by regions of (AT)n and An · Tn using DNase I and hydroxyl radical footprinting. We find that mithramycin binds to GC better than CG and that AGCT is a better site than TGCA. Sites flanked by (AT)n appear to be bound better than those surrounded by An · Tn. Although no footprints are produced at T9GCA9 and T15CGA15, DNase I cleavage is enhanced with the GC sites suggesting that there is some interaction with the ligand. Mithramycin also alters the DNase I cleavage of (GA)n · (CT)n.
Identification and analysis of a template‐primer (ds‐DNA) binding cleft in E. coli DNA polymerase I: An electrostatic potential contour pattern of the modeled structure
Authors: Yadav Prem N. S. , Modek Mukund J. , Yadav Janardan S.
Published: May 2005

In the modeled structure of the Klenow fragment of E. coli DNA polymerase I, we have identified a distinct region that exhibits a strong electropositive potential contour. The examination of the distribution of the electropositive and negative potential across the two‐dimensional slices of the modeled structure revealed that the positive potential was concentrated around the cleft. The approximate size and shape of the region appears well suited to accommodate eight base pairs of duplex DNA and is consistent with the position of the dsDNA binding cleft reported in the crystal structure [Beese et al., Science (1993) 260, 352–355].
In search of the ‘bio‐active conformation’—Is it induced by the target cell membrane?
Authors: Schwyzer Robert
Published: May 2005

Conformations of regulatory peptides interacting lipid membranes were compared with those of chemically constrained molecules that react‐selectively with different receptor classes. Striking similarities in the topochemistry of molecules with similar activity were observed, The membrane‐induced topomers were almost congruent with the topomers that are selectively recognized by the same receptors. Finally, the ideas developed in the membrane compartments theory allow a quantitative prediction of receptor preference are compatible with our present knowledge of receptor structure.
Topological templates as tool in molecular recognition and peptide mimicry: Synthesis of a TASK library
Authors: Silla Ursula , Mutter Manfred
Published: May 2005

Topological templates disposing orthogonally protected reactive sites in defined spatial positions of a variable degree of flexibility can serve as a pool for the selective functionalizations by groups thought to interact with an acceptor molecule. This strategy is exemplified by the chemo‐selective ligation of amino‐acid residues to a cyclic peptide as a structural motif (template‐assembled side chains; TASK) applying the concept of combinatorial libraries. Binding assays to a monoclonal antibody allow for the delineation of a lead compound mimicking the structural features of a discontinuous epitope. The conceptually novel approach may serve as a tool in molecular recognition studies and in drug development.
Trimeresurus flavoviridis venom gland phospholipase A2 isozymes genes have evolved via accelerated substitutions
Authors: Ogawa Tomohisa , Nakashima Kin‐ichi , Oda Naoko , Shimohigashi Yasuyuki , Ohno Montonori , Hattori Shosaku , Hattori Masahira , Sakaki Yoshiyuki , Kihara Hiroshi
Published: May 2005

As a step towards understanding the structure and function of phospholipases A2 (PLA2s), five cDNAs encoding Trimeresurus flavoviridis venom gland PLA2 isozymes have been sequenced. They revealed that the 5′ and 3′ un translated regions are much more homologous than the protein‐coding regions and that mbase substitutions have occurred at similar rates for the three positions of codons in the protein‐coding regions. Such novel findings are of great interest from the viewpoint of molecular evolution. To gain a further insight into this evolutional phenomenon, we have isolated and sequenced six T. flavoviridis PLA2 isozyme genes. Each gene consisted of four exons and three introns and encoded protein of 138 amino‐acid residues, including the signal sequence of 16 amino‐acid residues. The introns were much more homologous than the protein‐coding regions of exons except for the signal peptide‐coding region of the first exon. The absence of apparent functional role in the introns suggested that the protein‐coding regions, expect for the signal peptide‐coding domains, have evolved at greater substitution rates than introns. The fact that the numbers of nucleotide substitutions per non‐synonymous site are close to or larger than the number of nucleotide substitutions per synonymous site for relevant pairs of genes revealed that Darwinian‐type accelerated substitutions have occurred in the protein‐coding regions of exons. This is compatible with the presence of PLA2 species with diverse physiological activities in the venom.
Transformation of an irreversible MSH antagonist into an irreversible MSH agonist by differential receptor crosslinking using the photo‐affinity technique
Authors: Eberle Alex N.
Published: May 2005

Photocrosslinking of receptor for α‐melanocyte‐stimulating hormone (α‐MSH) on melanophores of frogs and lizards has been shown to induce long‐lasting receptor stimulation whereby the photoreactive α‐MSH may contain one or two photolables in positions 1, 7, 9, or 13. The chemical synthesis and biological testing of an α‐MSH analogue is now described which contains three photoreactive groups in positions 1, 9 and 13, on eof which with a cleavable SS disulphide bridge: [ApSSpr‐Ser1, Trp(Naps)9 Pap13]‐α‐MSH. Photocrosslinking of MSH receptors on melanophores of Anolis carolinensis with this analogue led to almost complete receptor blockade which could be transformed into long‐lasting receptor stimulation by exposure to a thiol reagents. By contrast, the analogue containing only two photoreactive groups in positions 9 and 13, [Trp(Naps)9, Pap13]‐α‐MSH, produced long‐lasting receptor stimulation which was not altered by the thiol reagent. These results demonstrate that one and the same peptide ligand may contain structural information for both receptor activation and inhibition and that the receptor may become arrested in an activated or inhibited state by multiple photocrosslinking, depending on the relative positions of these crosslinks.
Specific hemoglobin (poly)saccharide recognition
Authors: Jacques Wilfrid , Mateescu Mircea‐Alexandru
Published: May 2005

Hemoglobin (Hb) is not a glycoprotein but can easily by glycosylated by a non‐enzymatic mechanism. Based on some kinetic particularities, consisting in a faster glycosylation of the amine terminal group of the β‐chain located on the allosteric site, a hypothesis of a recognition center for specific sugars has been advanced.

Affinity chromatography materials based on epichlorohydrin crosslinked amylose, agarose and dextran (Sephadex®), were used. A specific interaction with the CL‐amylose (α‐1,4‐glycosidic links) was found, while for Sephadex® (α‐1,6‐glycosidic links), no Hb retention was observed. An affinity retention of hemoglobins (human and bovine) on agarose (a galactose containing carbohydrate) has also been established.

Chromatographic studies of Hb competitive elution with several monosaccharides (glucose, fructose, galactose) and disaccharides (saccharose, cellobiose, maltose, lactose) indicated that Hb retained by affinity onto CL‐Amylose columns, can be eluted only with galactose and lactose; with the other tested saccharides, very poor or no desorption at all, has been observed. These new data suggest: (1) a selective recognition of a limited number of (poly)saccharidic materials; and (2) a different behavior towards various sugars, the best interaction being observed with galactose‐containing sugars (lactose). These aspects fit well with the hypothesis of a hemoglobin recognition center for sugars.
Characterization of the high affinity heparin binding site of the Alzheimer's disease βA4 amyloid precursor protein (APP) and its enhancement by zinc(II)
Authors: Maulthaup Gerd , Mechler Hans , Masters Colin L.
Published: May 2005

The Alzheimer's disease βA4 amyloid precursor protein (APP) has been shown to be involved in a diverse set of biological protein precursor‐like proteins (APLP1 and APLP2) belong to a superfamily of proteins that are probably functionally related. In order to characterize the cell adhesion properties of APP the brain specific isoform APP695 was purified and used to assess the binding to herparin, a structural and functional analogue of the glycosaminoglycan heparan sulfate. We show that APP binds in a time dependent and saturable manner to heparin. The salt concentration of 620 mM at which APP elutes from heparin Sepharose is greater than physiological. Tha apparent equilibrium constant for dissociation was determined to be 300 pM for APP binding to heparin Sepharose. A high affinity heparin binding site was identified within a region conversed in rodent and human APP, APLP1 and APLP2. This binding site was located between residues 316‐337 of APP695 which is within the carbohydrate domain of APP. We also demonstrate an interaction between this heparin binding site and the zinc(II) binding site which is conserved in all members of the APP superfamily. We show by using an automated surface plasmon resonance biosensor (BIAcore, Pharmacia) that the affinity for heparin is increased two‐ to four‐fold in the presence of micromolar zinc(II). The identification of zinc‐enhanced binding of APP to heparin sulfate side chains of proteoglycans offers a molecular link between zinc(II), as a putative environmental toxin for Alzheimer's disease, and aggregation of amyloid βA4 protein.
Conservation of water molecules in an antibody–antigen interaction
Authors: Braden Bradford C. , Fields Barry A. , Poljak Roberto J.
Published: May 2005

The solvation of the antibody–antigen Fv D1.3–lysozyme complex is investigated through a study of the conservation of water molecules in crystal structures of the wild‐type Fv fragment of antibody D1.3, 5 free lysozyme, the wild‐type Fv D1.3–lysozyme complex, 5 Fv D1.3 mutants complexed with lysozyme and the crystal structure of an idiotope (Fv D1.3)‐abti‐idiotope (Fv E5.2) complex. In all, there are 99 water molecules common to the wild‐type and mutant antibody–lysozyme complexes. The antibody–lysozyme interface includes 25 well‐ordered solvent molecules, conserved among the wild‐type and mutant Fv D1.3–lysozyme complexes, which are bound directly or through other water molecules to both antibody and antigen. In addition to contributing hydrogen bonds to the antibody–antigen interaction the solvent molecules fill many interface cavities. Comparison with x‐ray crystal structures of free Fv D1.3 and free lysozyme shows that 20 of these conserved interface waters in the complex were bound to one of the free proteins. Uo to 23 additional water molecules are also found in the antibody–antigen interface, however these waters do no bridge antibody and antigen and their temperature factors are much higher than those of the 25 well‐ordered waters. Fifteen water molecules are displaced to form the complex, some of which are substituted by hydrophilic protein atoms, and 5 water molecules are added at the antibody–antigen interface with the formation of the complex. While the current crystal models of the D1.3–lysozyme complex do not demonstrate the increase in bound waters found in a physico‐chemical study of the interaction at decreased water activities, the 25 well‐ordered interface water contribute a net gain of 10 hydrogen bonds to complex stability.
Metabolic engineering of a non‐allosteric citrate synthase in an Escherichia coli citrate synthase mutant
Authors: Evans Claudia T.
Published: May 2005

This study examined the organization of the Krebs tricarboxylic acid (TCA) cycle by metabolic engineering and high‐resolution 13C NMR. The oxidation of [1,2,3‐13C]propionate to glutamate via the TCA cycle was measured in wild‐type (WT) and a citrate synthase mutant (CS−) strain of Escherichia coli transformed with allosteric E. coli citrate synthase (ECCS) or non‐allosteric pig citrate synthase (PCS). The 13C fractional enrichment in glutamate C‐2, C‐3, and C‐4 in ECCS and PCS were similar; although quantitative differences in total citrate synthase activity and total C‐4 labeling of glutamate were observed in ECCS and PCS. Allosteric ECCS cells contained 10‐fold less total enzyme activity than PCS but only 50% less total labeling in glutamate C‐4 and equivalent doubling times. The observed spectra were mathematically fitted using an iterative procedure(TCACALC) and yielded an acetate/succinyl‐CoA flux ratio of 10 for both ECCS and PCS, a result that is in agreement with the isotopomer analyses of the 13C spectra of cells presented with [3‐13C] propionate or [2‐13C]propionate. The results are consistent with the presence of an allosteric citrate synthase in ECCS and a non‐allosteric citrate synthase in PCS. The former maintains TCA cycle flux via alternative propionate pathways activated by positive allosteric mechanisms and the latter via elevated enzyme levels.
Die Korrosion durch Schwefelsäure
Authors: Bünger Johannes
Published: May 2005

Mit den hochlegierten Cr‐Ni‐Mo‐Cu‐Stählen, welche insbesondere bei Schwefelsäureangriff empfohlen werden, und mit modernen Mo‐haltigen Nickellegierungen wurden Korrosionsversuche über das gesamte Temperatur‐Konzentrations‐gebiet bis zu den atmosphärischen Siedepunkten durchgeführt. Die Resultate wurden in Form won Korrosionsdiagrammen dargestellt, wobei die Beständigkeitsgebiete durch Isokorrosionslinien abgegrenzt wurden. Die Cr‐Ni‐Mo‐Cu‐Stähleverhalten sich korrosionschemisch in Lösungen über 50% sehr ähnlich und sind in diesem Gebiet nur sehr beschränkt verwendbar. Dagegen sind sie bei niedrigeren Konzentrationen bis zu höheren Temperaturen technisch gut verwendbar, wobei sich die Grenzen der Verwendbarkeit im wesentlich nach dem Nickelgehalt richten.

Die hochlegierten Nickellegierungen weisen im allgemeinen eine erhöhte Schwefelsäurebeständigkeit auf, wobei für die Ni‐Mo‐Legierung 70/30 (Euzonit 70) im Gegensatz zu allen anderen untersuchten Werkstoffen gerade in dem Konzentrationsgebiet um 80% die beste Korrosionsbeständigkeit bis zur relativ hohen Temperaturen gefunden wurde. Diese Erscheinung wird mit dem geringen Eisengehalt der Legierung erklärt, die Gegenwart von Chrom hat in den Legierungen offenbar eine ähnliche Wirkung wie der Eisengehalt.
Flammgespritzte nichtmetallische Überzüge
Authors: Reininger Hans
Published: May 2005

Die Abhandlung gibt einen weitgehend vollständigen Überblick über den Korrosions‐ und Verschleißschutz metallischer Werkstoffe durch flammgespritzte nichtmetallische, insbesondere Kunststoff‐Überzüge. Im ersten Teil werden die verschiedenen Spritzgerätekonstruktionen einander kritisch gegenübergestellt und die derzeitigen Spritzverfahren ausführlich behandelt. Sodann werden die nach dem gegenwärtigen Stande des Flammspritzens gebräuchlichen Kunststoffe unter Darlegung ihrer besonderen Vor‐ und Nachteile und die an den Spritzguß zu stellenden Anforderungen behandelt. Die Haftgrundvorbereitung, die ebenso wie der Spritzvorgang selbst spezielle Maßnahmen erfordert, werden im einzelnen ausführlich beschrieben. Abschließend zeigen Beispiele aus der Praxis in Wort und Bild, an welchen Stellen sich das Flammspritzen nichtmetallischer Überzüge und Schutzschichten bewährt oder nicht bewährt hat.
Das Pulverkaltspritzverfahren
Authors: Reininger Hans
Published: May 2005

Ein neuartiges Verfahren wird beschrieben, das mittels einer Zweidüsenspritzpistole für gewünschte Überzugstypen geeignete Pulver gemeinsam mit Kaltklebern unter 6 atü Treibluftdruck fest haftend dicht auf metallischen oder nichtmetallischen Haftgrund kalt aufgespritzt.
Das Verhalten der Werkstoffe gegenüber Fluor
Authors: Lingnau E.
Published: May 2005

In der Fachliteratur der letzten fünf Jahre ist eine große Zahl von Mitteilungen über das Verhalten der Werkstoffe gegenüber gasförmigem und flüssigem Fluor veröffentlicht worden. Eine Zusammenfassung und Sichtung dieser zerstreut vorliegenden Erkenntnisse führt zu einem Überblick über den heutigen Stand unseres Wissens hinsichtlich der Handhabung dieses aggressiven Stoffes.

Die gegen Fluor beständigsten Metalle sind Nickel und seine Legierungen mit etwa 30% Kupfer, aber auch unlegierter Stahl sowie Kupfer und Aluminium sind gegen trockenes Fluor resistant. Kohlenstoff wird als Elektrodenmaterial für die elektrolytische Fluor‐Herstellung verwendet. Oxydkeramische Stoffe und einige säurebeständige Spezialkitte sind für die Handhabung von Fluor geeignet und auch Glas und Quarz werden von dem trockenen Gas bis zu recht hohen Temperaturen kaum angegriffen. Organische Werkstoffe sind im allgemeinen nicht beständig.
Oxydation von Titan
Authors: Kofstad Per , Hauffe Karl
Published: May 2005

Es wird der Versuch unternommen, die von den einzelnen Autoren gefundenen Zeitgesetze zu deuten. Die in den verschiedenen Temperaturbereichen und Oxydationszeiten beobachteten Zeitgesetze stehen in einem sinnvollen Zusammenhang. Unterhalb 300° C, wo das logarithmische Zeitgesetz der Oxydation herrscht, ist eine nennenswerte Sauerstofflöslichkeit im Titan während der Oxydation nicht zu beobachten. Erst oberhalb dieser Temperatur wird die Sauerstoffaufnahme durch Titan beachtlich. In diesem Temperaturbereich wird ein Übergang zunächst in das kubische und anschließend in das parabolische Zeitgesetz gefunden. Oberhalb 700° C ist ferner nach längeren Oxydationszeiten mit einem Aufreißen der Zunderschicht zu rechnen.
Über die Prüfung und die Korrosion von Weinflaschenkapseln aus dünnverzinntem Blei („Stanniol‐Kapseln”︁)
Authors: Schikorr G. , Bergner K. G.
Published: May 2005

Es wurden Verfahren für die Prüfung der Dicke und der Porigkeit der Zinnauflage auf den üblichen sogenannten “Stanniol” ‐ Flaschenkapseln entwickelt. Kapseln von aus dem Handel bezogenen Weinflaschen waren fast stets unter 0,001 mm dick verzinnt und meist erheblich porig.

Zur Prüfung der Korrosionsbeständigkeit der Kapseln wurden Laboratoriumsversuche mit Kapseln und praktische Lagerversuche mit handelsüblich verkapselten Flaschen ausgeführt. Unter gewissen Bedingungen, die in der Praxis durchaus vorkommen können, wurden die Kapseln unter Bildung von Bleisalzen erheblich korrodiert, in einigen Fällen sogar völlig zerfressen.
Neue Wege des Korrosionsschutzes von Eisen in Böden
Authors: Markovic T.
Published: May 2005

In der vorliegenden Arbeit werden zuerst die Bedingungen für das Zustandekommen eines aktiven bzw. passiven Verhaltens des Eisens gegeben, wobei Bodenstruktur bzw. Änderungen der kapillaren und nichtkapillaren Porosität des Bodens eine entscheidende Rolle spielen. Anschließend werden die die im Boden ablaufenden Korrosionsprozesse beeinflussenden Faktoren diskutiert, and zwar Bodenwasser, Bodenluft, Bodenwiderstand und Wasserstoffionen‐Konzentration. Dabei wurde das Verhältnis, „Bodenwasser zu zu Bodenluft”︁ als maßgebender, die Eisenkorrison im Erdboden regulierender Faktor, gefunden. Jeder Boden besitzt eine spezifisches Aggressivität, die durch das Annahmevermögen des Bodens an Wasser bestimmt ist.

In der Arbeit werden weiter Ratschläge für der Verminderung der Eisenkorrosion im Erdreich ohne und mit kathodischem Korrosionsschutz, durch Zusatz chemischer Hemmstoffe und durch Erzeugung eines künstlichen Belüftungselementes gegeben.
Anstrich‐ und rostschutzgerechte Gestaltung der Konstruktion. Der Rostschutz beginnt am Reißbrett
Authors: van Oeteren K. A.
Published: May 2005

Zu vermeiden sind unzugängliche Ecken und schmale Fugen. U‐Eisen und Winkeleisen sollen mit der Öffnung nach unten angeordnet werden, um Wassersäcke zu vermeiden. Anstrichtechnisch mangelhaft sind auch spitze Winkel und schwer zu reinigende Anschlüsse bei Gittermasten, Rohrbrücken und Stützen. Geschweißte Konstruktionen sind den genieteten vorzuziehen, Rohrkonstruktionen solchen aus Profileisen. Waagerechte Flächen sind durch Wasseransammlungen, Staub‐ und Rußablagerung und Bildung von Moospolstern gefährdet. Bei Eisenbahnbrücken sind Rauchgase durch Holzschilder abzuwehren. Nietstellen und Fugen sind gut zu verkitten, Trägerfüße sind zweckmäßig nicht einzubetonieren. Durch Aufhängevorrichtungen für die Rüstung kann der Erneuerungsanstrich verbilligt werden. Bei Brücken sind stationäre Wagen zur Befahrung der Unteransicht am Platze. Verdeckte Träger sowie sich überdeckende Laschen und Knotenbleche müssen den endgültigen Anstrich vor der Montage erhalten.

Geschweißte Konstruktionen haben gegenüber genieteten den Vorteil, weniger Ansatzpunkte zur Rostbildung zu bieten, während im besonderen Nietköpfe häufig Ausgangspunkte vorzeitigen Rostens sind.
Vergleichende Untersuchungen über die korrosionshemmende Wirkung organischer Verbindungen in wäßriger Lösung
Authors: Funke W. , Hamann K.
Published: May 2005

Eine Reihe organischer Verbindungen aus verschiedenen Verbindungsklassen wurde auf die Schutzwirkung gegenüber der Korrosion von Eisenblech in wäßrigem Medium geprüft. Die Korrosionsgeschwindigkeit wurde durch Bestimmung des Gewichtsverlustes der Blechproben ermittelt. Ferner wurde die Abhängigkeit des Korrosionsbeginns von der Konzentration der zu untersuchenden Verbindung und vom pH‐Wert ihrer Lösungen untersucht. Bei basischen Verbindungen war die Schutzwirkung im allgemeinen vom Überschreiten einer Mindestbasizität der Lösung abhängig. Bei sauren, in Form ihrer Natriumsalze untersuchten Verbindungen trat eine Schutzwirkung dann ein, wenn die Dissoziationskonstante innerhalb eines bestimmten Bereiches lag.
Das korrosive Verhalten des Magnesiums bei Inhibierung und Aktivierung der Auflösung und dessen Darstellung im io‐pH‐Diagramm
Authors: Markovic T. , Rubinic L.
Published: May 2005

Die Auflösungsgeschwindigkeit des Magnesiums in Säuren und Alkalien wurde mittels Korrosionsstrom‐pH‐Diagramm dargestellt. Die Umrechnung des Korrosionsstroms i0 in der üblichen Meßeinheit g/m2. Tg. erfolgte für eine Magnesium‐Elektrode von 25 cm2 geometrischer Oberfläche.

Ferner war der Gegenstand der Untersuchung das Verhalten des Magnesiums bei Zusatz von Aktivatoren und Passivatoren auf die Korrosionsreaktion. So ergab es sich, daß die Anwesenheit von KF auf die Korrosionsreaktion des Magnesiums abhängig von pH‐Wert der Säure hemmend oder fördernd wirken kann.
Die Ionendurchlässigkeit von Anstrichfilmen
Authors: Bartoň Korel , Čermáková Dagmar , Beránek Eduard , Akimow G. W.
Published: May 2005

Auf Grund der Auffassung des Anstrichfilmes als ionenselektive Membran wurde versucht, durch Zusatz von Kationen‐ oder Anionenaustauschern und einer Mischung von beiden, die Ionendurchlässigkeit eines Alkydharzfilmes zu steuern. Es wurde gefunden, daß der Zusatz von diesen Stoffen den Durchtritt von Ionen (mikroskopisch gemessen) stark beeinflußt. Dabei wurde eine bremsende Einwirkung der Grenze zwischen den einzelnen Filmschichten auf die Diffusion beobachtet. Durch Zusatz einer Mischung von Kationen‐ und Anionenaustauschern zu Grundanstrichen, kann die Unterrostung von gestrichenen, angerosteten Eisenmetallen unterbunden werden. Dies wird durch die Bindung der korrosionsfördernden Stoffe im Rost (lösliche Salze) durch die Ionenaustauscher erklärt.
Korrosion des Aluminiums und seiner Legierungen in Wässern verschiedener Zusammensetzung
Authors: Sverepa Otakar , Akimow G. W.
Published: May 2005

Korrosionsversuche mit Aluminium und seinen Legierungen wurden in den Fluß‐ und Kühlwässern von Zirkulations‐systemen unter natürlichen Bedingungen durchgeführt. In Flußwässern war die Korrosion gering und gleichmäßig, in den Zirkulationswässern erfolgte Lochfraßkorrosion. Die Zusammensetzung und Verunreinigungen des Wassers übten einen wesentlichen Einfluß auf die Korrosion aus. Die Unterschiede in der Korrosion der einzelnen Werkstoffe waren gering. Durch die laboratoriumsmäßigen Untersuchungen wurde bestätigt, daß bei den Legierungen AlMn und AlMg die intensivste Korrosion durch komplexe Einwirkung von Cu++, Cl′, Ca++, HCO3′ bei gleichzeitiger Anwesenheit von O2, bewirkt wird. Die Lochfraßkorrosion hängt von der Konzentration der angeführten Ionen stark ab. Andere Kationen und Anionen bewirkten geringere oder keine Lochfraßkorrosion. Quantitativ wurden die Gewichtsverluste, die Anzahl der Löcher, die von der Lochfraßkorrosion befallene Oberfläche, die maximale Korrosionstiefe und die Natur der Korrosionsprodukte in Abhängigkeit von der Konzentration von Cu++, Cl′, Ca(HCO3)2 und pH verfolgt.