bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interaction of Antibodies with Uridine Diphosphosphate Galactose 4‐Epimerase from Yeast
Authors: Olesen H. A. , Bertland A. U. , Kalckar H. M. 
Published: March 2005

Antibodies from a rabbit immunized with uridinediphosphate galactose 4‐epimerase were shown to inhibit the specific activity of the enzyme and to precipitate [14C]UMP‐labelled epimerase.It comprised about 0.33% of the immunoglobins and its Fab fragments had a binding constant of 0.2 × 109 M‐1 at 25° and 1.1 × 109 M‐1 at 4°. Despite the high energy of interaction the antibody did not liberate [14C]UMP from reduced [14C]UMP‐epimerase. It gave two precipitation lines both with the native and with the reduced epimerase in the immunoelectrophoresis. However, the same pattern was obtained with antibody from a UMP‐epimerase immunized rabbit that could not precipitate [14C]UMP‐epimerase or inhibit the enzymatic activity. It is not clear whether any of the lines represent the epimerase protein unit sensu strictu.
The Effect of Prednisolone Injected in vivo on RNA‐Polymerase Activities in Isolated Rat Thymus Nuclei
Authors: Drews Jürgen , Wagner Lutz 
Published: March 2005

The capacity of isolated rat thymus nuclei to synthesize RNA in vitro was investigated under various experimental conditions. When incubated in the presence of MgCl2 alone thymus nuclei synthesized an RNA product which according to a nearest neighbour frequency analysis contains high proportions of dinucleotide sequences typical for ribosomal precursor RNA: GpC, CpG and GpG. When MgCl2 was replaced in the incubation mixture by MnCl2 and ammonium sulfate the nuclei formed a product of a more DNA‐like nucleotide composition. The time course of the incorporation of tritiated ribonucleosidetriphosphates into acid‐precipitable material was different in the two nuclear polymerase systems: while, in the presence of MgCl2, the incorporation of radioactive AMP or GMP reached a plateau after only 15 min of incubation, the reaction proceeded at a linear rate for at least 40 min in the presence of high concentrations of salt and MnCl2. The absolute amounts of radioactive RNA‐precursor material incorporated into RNA are considerably smaller in the Mg++‐activated system than in the presence of MnCl2 and ammonium sulfate.The administration of prednisolone to adrenalectomized young rats was followed by a decrease in the ability of isolated thymus nuclei to synthesize RNA when MgCl2 was present. The relative frequencies of several dinucleotide pairs in the RNA synthesized by isolated thymus nuclei in the presence of MgCl2 changed significantly in response to steroid treatment. The adminstration of prednisolone, however, did not modify the quantity or the quality of the product formed by thymus nuclei in the Mn++/ammonium sulfate activated reaction. These results further indicate that glucocorticoids exert a preferential inhibitory effect on the formation of ribosomal precursor RNA in rat thymus cells.
A “Proportion Graph” Method for Measuring Binding Systems
Authors: Baulieu Etienne E. , Raynaud Jean‐Pierre 
Published: March 2005

A new graphical methodology is proposed to visualize and estimate the binding at equilibrium of small molecules in protein mixtures, providing each binding system is independent and follows the law of mass action. In many cases, the plots of Lineweaver‐Burk or Eadie‐Scatchard are found to be unsuitable.The method consists in plotting log [fraction bound] vs. log [total ligand]. The determination and statistical approximation of the binding parameters are performed and checked by means of a 360 IBM computer. Therefore instead of the linear method which may lead to arbitrary estimation, a non linear function covering the whole range of informations is used since nowadays computerized analysis is available.Theoretical and experimental examples are given for biological samples containing one or two systems of high affinity (“specific”), in the presence or absence of a system of low affinity and of a relatively large number of binding sites (“non‐specific”). The experimental material consists of steroid hormones and plasma or target tissue proteins.
Excited States of Flavins Characterised by Absorption, Prompt and Delayed Emission Spectra
Authors: Gordon‐Walker Ann , Penzer Geoffrey R. , Radda George K. 
Published: March 2005

The angles between the two principal long wavelength absorption oscillators of FMN and some other flavins have been measured by two methods. A novel technique involving dichroic bleaching gave a value (approx. 35°) consistent with that obtained from the polarisation of fluorescence extrapolated to infinite viscosity.Flavins trapped in polyacrylamide films display E‐type delayed fluorescence and phosphorescence depending on the temperature. The variations in lifetimes and intensities of these two delayed emissions with temperature have been studied. The Arrhenius activation energies have been analysed in terms of a scheme that gives information about the interrelationships between different electronic states of flavins.
Purification from Calf Thymus of an Inhibitor of Deoxyribonuclease I
Authors: Lindberg M. Uno , Skoog Lambert 
Published: March 2005

A protein inhibitor specific for pancreatic deoxyribonuclease (DNAase I) was purified 10‐ to 20‐fold from calf thymus. This purification resulted in a nearly homogenous protein demonstrating the relative abundance of the inhibitor among the soluble proteins of the crude extract.Like the DNAase inhibitors from calf spleen described earlier the thymus inhibitor showed a high tendency to form high molecular weight aggregates of low specific activity. Conditions which decreased the rate of this self‐aggregation were found as were conditions for the dissociation of already formed inhibitor aggregates.The molecular weight of the purified inhibitor was determined under both stabilizing and disaggregating conditions and values between 45000 and 50000 were obtained.The interaction between the enzyme and the inhibitor was shown to give rise to a stable complex containing one molecule each of the involved protein species.
Étude cinétique de changements conformationnels de la l‐glutamate déshydrogénase provoqués par le couple effecteur GTP + NADH
Authors: Jallon J. M. , di Franco A. , Iwatsubo M. 
Published: March 2005

It is shown by rapid kinetics that when the coenzyme NADH and the effector GTP are added to the enzyme, l‐glutamate dehydrogenase, several changes occur following a multiphasic process. These changes are observed by a variation in the absorbance, and fluorescence intensity of the fixed nicotinamide ring of NADH, as well as by a variation in the fluorescence intensity of the fluorescent probe, ANS, which is fixed to the protein. By all three methods, two phases are generally observed, the slower phase (k2= 1.5 sec–1) being characterized by a change in the molar absorbancy coefficient of the nicotinamide ring (∼15% at 365 nm). The more rapid phase (k1= 60 sec–1) is characterized by a decrease in turbidity without any spectral modifications of the fixed NADH. The binding rates of the two ligands NADH and GTP, presented elsewhere, are too rapid to be taken into consideration as being responsible for the steps observed here.The step (k1= 60 sec–1) which shows a decrease in turbidity is thus associated with a depolymerization of the polymer (composed of an indefinite number of units of molecular weight 310000). Although only partial, such a dissociation, already known to exist by simple dilution of the enzyme, proceeds with a slower rate (k= 12 sec–1) than that of the dissociation provoked by NADH and GTP.A study was also carried out using the coenzyme NADPH instead of NADH. The amplitude of the phase identified with the depolymerization of the enzyme is similar to that observed for NADH. A striking difference is found in the fact that there is but a negligible modification of the nicotinamide ring of NADPH.It should also be noted the order of incubation of these ligands affects only the rate of depolymerization; in particular, pre‐incubation of the enzyme with NADH, but not with NADPH, notably slows down the rate of depolymerization. The results obtained with NADH and NADPH give support to the hypothesis proposed by Frieden from kinetic studies, that NADH, not NADPH, can bind to two distinct sites, an active site and an effector or regulatory site. Correlation of our results with known kinetic data has enabled us to give a functional aspect to each site. The active site is associated with the depolymerization effect, while the regulatory site is the site which we consider to be responsible for the “protector” and “transconforming” effects.A summary of the observed rates is presented in schematic form, in an effort to understand the mechanism of action of NADH and GTP. The process which culminates in the inhibition of the enzyme activity occurs before the two structural modifications which are measured here, since the inhibitory effect of GTP on the oxidation of the coenzyme appears in less than 2 msec. Preliminary results show that the activator ADP reverses both the depolymerization and the spectral modifications of NADH produced by NADH and GTP.
Close Linkage between a Galactose Binding Protein and the β‐Methylgalactoside Permease in Escherichia coli
Authors: Boos Winfried , Sarvas Matti O. 
Published: March 2005

It has been found that a gene necessary for the production of the galactose binding protein is closely linked, if not identical with the gene(s) determining the β‐methylgalactoside permease. This was determined by crossing a galactose binding protein negative, β‐methylgalactoside permease negative strain of E. coli K‐12 with wild type donor strains.In addition, after mutagenation of a permease positive, binding protein positive strain of E. coli K‐12 with N‐methyl, N‐nitroso, N′‐nitroguanidine, some of the β‐methylgalactoside permease defective mutants showed concomitant changes in the galactose binding protein. Out of 28 independent permease defective mutants two had lost their ability to produce cross reacting material against antibodies specific for the galactose binding protein; four mutants showed temperature sensitive synthesis of cross reacting material; five mutants had immunochemically somewhat changed binding protein. The immunochemical assay showed no changes in the binding protein of the rest of the 17 mutants. However, the galactose binding activity of the crude extract of these mutants varied to a great extent (10–90%) from the activity‐found in the crude extract of the wild type.These results suggest a close relationship between the galactose binding protein and the β‐methylgalactoside permease.
Immunochemical Studies on Structural Proteins of the Red Cell Membrane
Authors: Furthmayr Heinz , Timpl Rupert 
Published: March 2005

Up to one third of the membrane proteins from bovine, ovine and human red cells were solubilized similarily by water pH 9.5, aqueous pyridine, ATP‐mercaptoethanol solutions or urea pH 11. The proteins are heterogeneous but show some common features independent of the extraction method applied. The remaining insoluble proteins are rather different and contain most of the lipids and of the surface antigens.
In the extracts mainly a common membrane‐specific antigen of high anodic mobility was demonstrated which contains neither sialic acids nor lipids. This antigen is species‐specific and is not located on the membrane outside. It is not exposed to the surface after proteolytic treatment of intact red cells. The extracts are contaminated by traces of plasma proteins and surface antigens.
The membrane antigen can be correlated to a characteristic double band demonstrable in the stroma by disc electrophoresis in the presence of sodium dodecylsulfate. The molecular weights were estimated as 190 000 and 210 000, respectively. Evidence is provided that these components represent aggregates.
Zur Biosynthese des Chinazolinalkaloids Arborin
Authors: Johne Siegfried , Waiblinger Konrad , Gröger Detlef 
Published: March 2005

The indian plant Glycosmis arborea (Roxb.) DC. (Rutaceae) contains alkaloids of different types. The main alkaloid of the Glycosmis leaves is the 4‐quinazolone derivative arborine (VI). Previously it has been shown that labelled anthranilic acid (X) and phenylalanine (XI) are specifically incorporated into this alkaloid. This study was performed in order to elucidate the possible pathway of arborine formation in vivo. During these investigations an improved procedure for the isolation of arborine was developed.The following results were obtained: After feeding of [14CH3]methionine the N‐methyl group of VI was specifically labelled. The same result was obtained after the application of [14CH]3N‐methylanthranilic acid. These results seem to indicate that anthranilic acid gets methylated prior to the condensation with phenylalanine which leads to VI. But on the other hand after feeding of [2‐14C] glycosminine (V) labelled arborine was also isolated. However in this case the incorporation rate was much lower compared with those of the two other mentioned precursors. It should be mentioned that V is only sparingly soluble in solvents suitable for feeding experiments. The N‐1 atom of VI is provided by the nitrogen of anthranilic acid. The experiment with [3‐14C, 15N]phenylalanine shows clearly that with the exception of the carboxyl group the aliphatic side chain of XI is incorporated into arborine. Therefore phenylacetic acid can be excluded as an immediate precursor of VI. [U‐3H]anthranoylphenylalanine (XIV) was a very poor precursor of arborine. N‐Methyl‐N‐phenyl‐[14CO‐CH2]acetylanthranilamid (XV) was transformed with high efficiency in Glycosmis into arborine. However it is doubtful whether the N‐phenylacetyl derivative of N‐methylanthranilamide is a true precursor in arborine biosynthesis. Surprisingly it could be shown that the transformation of XV → VI takes also place in pea plants. Apparently the ring closure of XV is catalyzed by an enzym or enzymatic system which is unspecific and widely distributed.
Chemical Structure of Tubular and Glomerular Basement Membranes of Human Kidney
Authors: Mahieu Philippe , Winand Roger J. 
Published: March 2005

Enzymatic digestion with pronase and collagenase of glomerular and tubular basement membranes isolated from human kidneys yields soluble glycopeptides which can be separated by gel filtration and ion exchange chromatography.Two different glycopeptides were isolated from both types of membranes. One contains a disaccharide composed of an equimolecular quantity of glucose and galactose probably linked to hydroxylysine. The second contains a heterosaccharide composed of galactose, fucose, mannose, hexosamine and sialic acids. The heterosaccharide from glomerular basement membrane had a molecular weight of 3600 and twice as much sialic acid as the heterosaccharide from tubular basement membrane which had a molecular weight of 3400.
Separation of Contributions of Tryptophans and Tyrosines to the Ultraviolet Circular Dichroism Spectrum of Hen Egg‐White Lysozyme
Authors: Teichberg Vivian I. , Kay Cyril M. , Sharon Nathan 
Published: March 2005

Ultraviolet circular dichroism measurements over the wavelength range of 190–300 nm have been carried out on hen egg‐white lysozyme and on an iodine‐oxidized derivative of lysozyme in which Tryptophan‐108 has been selectively modified. The contribution of Tryptophan‐108 to the aromatic circular dichroism profile has been ascertained from a difference spectrum generated between the native and the modified protein. This tryptophyl residue is exceptional in its properties, as it is the principal contributor to the circular dichroism pattern in this wavelength range. The chemically modified protein shows only minor differences from the native molecule in terms of the magnitude of the conformation‐dependent ellipticity bands at 209 and 192 nm. Separation of the partial contributions of tyrosines was obtained from circular dichroism difference spectra constructed from circular dichroism profiles of both the native and iodine oxidized proteins at pH 7 and 11.2. Oligomers of N‐acetyl‐d‐glucosamine, which are inhibitors of lysozyme, markedly affect the circular dichroism spectrum of the enzyme at the aromatic region. It is postulated that this effect on the spectrum is a result of a change in orientation of Tryptophan‐108, which occurs on binding of the inhibitors to the active site of the enzyme.These results are discussed with respect to the proposed three‐dimensional model of lysozyme.
Inhibition and Modification of Human Carbonic Anhydrase B with Bromoacetate and Iodoacetamide
Authors: Whitney Philip L. 
Published: March 2005

Bromoacetate and iodoacetamide reversibly inhibit human erythrocyte carbonic anhydrase B. The binding of these inhibitors is competitive with that of the other inhibitors, chloride and sulfanilamide. However, bromoacetate and iodoacetamide are only partially competitive with each other. That is, both can bind at the same time, but the binding of one inhibitor increases the Ki for the second by about 50%.
While bound as a reversible inhibitor, bromoacetate or iodoacetamide reacts with the basic form of a specific histidine residue in the enzyme. The half‐times of reaction are 0.44 h and 2.7 h, respectively. The pH‐dependence of reaction shows that the pK of this histidine is 5.6 when bromoacetate is bound as a reversible inhibitor, and the pK when iodoacetamide is bound is below 5.0.
Reaction with bromoacetate introduces a carboxymethyl group in the region of the active center. This group perturbs the active site of the enzyme. This specific carboxymethylation causes about a five‐fold decrease in esterase activity and a shift in the midpoint of the pH‐dependence curve of activity from about pH 7.3 to 9.2. The affinity for several inhibitors is decreased.
Results of titration of the carboxymethyl enzyme with acetazolamide are consistent with 1.0 binding sites per enzyme molecule. This is the same number of sites as for native enzyme, but the Ki is higher with modified enzyme.
Studies of the visible spectrum of cobaltous carbonic anhydrase B have revealed two pH‐dependent transitions. The first occurs below pH 7 and produces relatively small changes in the spectrum. Introduction of the carboxymethyl group has little effect on the first transition, but shifts the midpoint of the second transition from pH 7.1 to 9.2.
Several lines of evidence indicate that the carboxymethyl group in the modified enzyme occupies a position different from the bromoacetate ion in the reversible complex.
Structure primaire de la caséine αs1 bovine
Authors: Mercier Jean‐Claude , Grosclaude François , Ribadeau‐Dumas Bruno 
Published: March 2005

Earlier work in this laboratory on the determination of the primary structure of bovine αs1 casein [1–5] established that this phosphoprotein is composed of only one single peptide chain of 198 residues. The sequence of 101 residues have already been determined: the substitution of Glu/Gly at position 191 in the COOH‐terminal region differentiates the B and C genetic variants [1–3]. The sequence of 53 amino acid residues in the NH2‐terminal region was also determined [5].This publication deals with the sequence of the central part of the chain. Sequence determinations have been made on various tryptic [2], CNBr and chymotryptic [4] peptides obtained earlier, which have been further broken down with the help of endopeptidases or mild acid hydrolylysis into smaller fragments to which classical methods of degradation have been applied: exopeptidase hydrolysis and substractive Edman's degradation.The results obtained and previously published results establish the sequence of 172 amino acid residues in the molecule. The residues of which the positions have not been established so far are situated in 2 regions of the chain, between position 46 to 52 and position 61 to 77. These 2 regions are characterized by the presence of phosphorus and their sequences will be dealt with in our final publication.
Enzymes from Human Gastric Mucosa Conferring Blood‐Group A and B Specificities upon Erythrocytes
Authors: Schenkel‐Brunner Helmut , Tuppy Hans 
Published: March 2005

Enzyme preparations obtained from human gastric mucosa microsomes are able to provide human erythrocytes with blood‐group A and B specificities, the newly conferred serological properties being dependent on the blood‐group of the tissue donor. The time‐course and the extent of the enzyme‐catalyzed change in antigenic properties of the erythrocytes were assessed by the serum absorption method.The enzyme preparation from gastric mucosa of group A1 individuals, when incubated with O or B erythrocytes in the presence of UDP‐acetylgalactosamine, rendered them agglutin‐able by anti‐A serum. The enzymatically converted erythrocytes behaved like A2 cells. After treatment with enzyme from B individuals and UDP‐galactose, O, A1 and A2 erythrocytes could be agglutinated by anti‐B serum. When the enzymes from A1 and B individuals were allowed to act together upon O erythrocytes in the presence of UDP‐acetylgalactosamine and UDP‐galactose, the red cells became susceptible to agglutination with both anti‐A and anti‐B serum. The blood‐group specificity of red cells was not changed upon exposure to microsomal extracts from O individuals.
Biosynthesis of Salmonella Lipopolysaccharide
Authors: Mühlradt Peter F. 
Published: March 2005

Several transfer reactions involved in the biosynthesis of the core part of Salmonella lipopolysaccharide have been studied in a cell free system. This system contained three components: (1) enzymes which were solubilised by repeated washings of EDTA‐lysozyme spheroplasts; (2) acceptor which consisted of either a heated cell wall fraction sedimenting at 20 000 x g, or heated, partially lysed, EDTA‐lysozyme treated cells; and (3) radioactively labelled precursors ([32P]ATP, UDP‐[14C]Glc, UDP‐[14C]Gal).The following results were obtained with this transfer system: (1) only the γ‐phosphate group of ATP is transferred to the heptose moiety of the core; (2) polyphosphate which is synthesised enzymatically in a a side‐reaction by the system is not involved in the heptose phosphorylation; (3) there is a definite sequence of addition of the core substituents glucose, phosphate, and galactose to the incomplete core stub. This sequence is as follows:(Hep)2‐(KDO, ethanolamine, phosphate, lipid A) → Glc‐(Hep)2‐(KDO, ethanolamine, phosphate, lipid A) → Glc‐(Hep)2P‐(KDO, ethanolamine, phosphate, lipid A) → (Gal)2‐Glc‐(Hep)2P‐(KDO, ethanolamine, phosphate, lipid A).