bluuebunny/crossref_metadata_2025_split huggingface dataset:
Méthode d'estimation de la concentration des cytochromes dans les cellules entières de levure
Authors: Claisse Maurice L. , Péré‐Aubert Geneviève A. , Clavilier Léa P. , Slonimski Piotr P. 
Published: March 2005

A method for the estimation of cytochrome concentrations in whole yeast cells was worked out with strains of Saccharomyces cerevisiae obtained in the laboratory. Differences of cytochrome c content were due to mutations affecting the nature or the quantity of synthetized cytochrome c. Respiratory deficient mutants (without cytochromes a+a3 and b) were also used. Spectra were measured directly on yeast pastes (up to 3 mm thick) with a Cary 15 recording spectrophotometer provided with a Xenon lamp.Absorption differences between the maxima of α and β peaks of cytochrome c in relation to two base lines were measured. The mean value so obtained was in accordance with Lambert's law when the thickness of the sample of the same yeast paste was changed. For a constant optical path, Beer's law has been verified with the strains of different cytochrome c contents due to genotypical differences. There is a linear relation between quantities of cytochrome c extracted and absorptions measured on whole cells pastes.A device for liquid nitrogen temperature recordings is described and the extension of the method to low temperature measurements, and to the estimation of cytochromes a+a3 concentration is discussed.
Structure primaire de la caséine αs1 bovine
Authors: Grosclaude François , Mercier Jean‐Claude , Ribadeau‐Dumas Bruno 
Published: March 2005

Our earlier publications on the primary structure of bovine αs1 casein, which contains 198 amino acid residues in a single polypeptide chain, dealt with the sequence of forty‐eight residues from the COOH‐terminal and also with the various approaches utilised for the elucidation of the primary structure of the molecule: amino acid composition of tryptic peptides, composition and arrangement of the peptides obtained by selective hydrolysis at the arginyl or methionyl bonds and identification of the tryptic peptides in these two series of peptide fragments.In the present communication we report the sequence of sixty amino acid residues from the NH2‐terminal of the bovine αs1 casein with the exception of a fragment consisting of seven amino acid residues (from position 46 to 52) and three phosphate groups whose sequence will be reported in our final publication.The NH2‐terminal of bovine αs1 casein contains markedly different zones which are successively basic (position 1 to 10), non‐polar (position 20 to 33) and acid (position 45 to 60).We will report in another paper that the A variant of αs1 casein is characterised by a deletion of thirteen amino acid residues in this part of the NH2‐terminal.
Cooperative Binding of Manganese (II) to Transfer RNA
Authors: Danchin Antoine , Guèron Maurice 
Published: March 2005

We have measured the binding of manganse ions to tRNA in the concentration range of 1 to 28 bound Mn2+ per tRNA at 23°. The free Mn2+ concentration was monitored by electron spin resonance. The Scatchard plot shows that the first four Mn2+ bind cooperatively, at a free Mn2+ concentration of 3 μM. The cooperativity presumably reflects a conformational change of tRNA. A resulting structure with 6–10 strong binding sites (ks= 1.8 × 105M−1), and 21–25 weak binding sites (kw= 5 × 103 M−1) is suggested.From the bound Mn2+ electron spin resonance we estimate a minimal distance between the strong sites of about 1.5 nm; this shows that the binding sites are spread on the molecule and not clustered together.
Electron Spin Resonance of Pteridine Radicals and the Structure of Hydropteridines
Authors: Ehrenberg Anders , Hemmerich Peter , Müller Franz , Pfleiderer Wolfgang 
Published: March 2005

Cations of monohydropteridine radicals have been obtained in solution and investigated by electron spin resonance. The hyperfine pattern of these signals as well as that of previously described trihydropteridine radical cations has been computed to agreement with experiment. The first mentioned radicals are shown to have 5,8‐H2Pter+‐structure, whereas the latter are 5,6,7,8‐H4Pter+. Substitutions in the pyrimidine part of the system (positions 1–4) do not affect the spin distribution essentially in any case. In monohydropteridine the unpaired electron is delocalized over the whole pyrazine part of the system (positions 5–8), whereas in trihydropteridines it is mainly confined to N(5) and possibly to the bridge carbons.The biochemical implications of pteridine radicals are discussed. While two‐electron oxidoreduction, implying 7,8‐dihydropteridine, is thermodynamically irreversible, one‐electron oxidoreduction appears to be intermediate in the systems Pter/5,8‐H2Pter on the one hand, and 6,7‐H2Pter/H4Pter on the other hand, thus permitting rapid electron transfer. Hence, it is reasonable to assume that trihydropteridine radicals might be of biological importance, though clearly not as the strongly acidic cations described here, but maybe in the stabilized form of metal complexes.In this context, existence, stability and eventual biological importance of the various dihydropteridine isomers is discussed.
Inability of Escherichia coliB to Incorporate Added Deoxycytidine, Deoxyadenosine, and Deoxyguanosine into DNA
Authors: Karlström H. Olle 
Published: March 2005

It is known that Escherichia coli can incorporate labeled thymidine into its DNA, but it has not been previously possible to measure the incorporation of the other deoxyribonucleosides deoxycytidine, deoxyadenosine, and deoxyguanosine because of degradation of these compounds.The present experiments utilize a mutant of E. coli B lacking deoxyribonucleoside‐catabolizing enzymes. This strain, OK441, has mutations affecting the following enzymes: thymidine phosphorylase, purine nucleoside phosphorylase, eytidine deaminase, and adenosine deaminase.The results with OK441 show that E. coli, in contrast to lactobacilli and mammalian cells, does not incorporate any deoxyribonucleoside other than thymidine into its DNA.E. coli may be unable to phosphorylate deoxyeytidine, deoxyadenosine, and deoxyguanosine. In agreement with this suggestion, only thymidine kinase but no other deoxyribonucleotide kinase could be detected in extracts of OK441.
Glycopeptides des immunoglobulines
Authors: Jouanneau Jacqueline , Razafimahaleo Edmond , Bourrillon Roland 
Published: March 2005

An immunoglobulin M from Waldenström's disease (IgM Ga) was hydrolysed by papain and a glycopeptide fraction was isolated by gel filtration on Sephadex G‐100. This fraction was then successively resolved into fourteen glycopeptides by gel filtration on Sephadex G‐50 and by preparative paper electrophoresis at pH 1.9.The amino acid and carbohydrate content of these glycopeptides was determined by ion‐exchange chromatography in an autoanalyzer.All of them contain aspartic acid and serine, but they are quite different from one another, in amino acid composition and sequence about the carbohydrate‐peptide linkage, especially with respect to histidine, tyrosine, threonine, valine, glutamic acid, lysine and proline.Furthermore, a number of glycopeptides contain only mannose and glucosamine, while others contain in addition, galactose, fucose, and N‐acetylneuraminic acid, in variable amounts.These results suggest the presence of several linkage sites of the oligosaccharide chains on the H‐chain and the true heterogeneity of these oligosaccharide chains.The peptide sequence of a few glycopeptides was reported, especially the following: Tyr‐Asn‐(carbohydrates)‐Ser‐Thr, also present in the Fc fragment of Immunoglobulin G.
The Trapping of Uridine Phosphates byd‐Galactosamine,d‐Glucosamine, and 2‐Deoxy‐d‐galactose
Authors: Keppler Dietrich O. R. , Rudigier Jürgen F. M. , Bischoff Erwin , Deckker Karl F. A. 
Published: March 2005

The effects ofd‐galactosamine,d‐glucosamine, and 2‐deoxy‐d‐galactose on rat liver uracil nucleotides were studiedin vivo. Enzymic and isotope dilution analyses of the UDP‐sugars and of uridine phosphates revealed three major, related changes: an accumulation of the respective UDP‐sugar derivatives, a marked decrease of UTP, UDP, and UMP, and a subsequent increase of the sum of hepatic uracil nucleotides. The decrease of uridine phosphates was accompanied by diminished contents of UDPG and UDP‐galactose. UMP of total liver RNA was not altered significantly. Inhibition of uridylate synthesis by use of 6‐azauridine resulted in a suppression of thed‐galactosamine‐induced stimulation of uridine phosphate synthesis and of the increase in total acid soluble uracil nucleotides. The trapping of uridine phosphates by formation of UDP‐sugar derivatives was most pronounced and most prolonged after administration ofd‐galactosamine. The uridine phosphate content was lowered to less than 10% of normal within three hours, while the sum of uracil nucleotides increased by 0.35 μmole x g liver−1x hour−1, from an initial value of 1.24 μmole/g. The quantitative analysis of the time dependent changes of UDP‐hexosamines, UDP‐N‐acetylhexosamines, UDPG, and UDP‐galactose revealed a pronounced alteration byd‐galactosamine of the UDP‐sugar pattern.Corresponding changes in the distribution of liver uracil nucleotides were obtained after administration ofd‐glucosamine and 2‐deoxy‐d‐galactose. Both, however, are ineffective in provoking hepatitis. In contrast tod‐galactosamine,d‐glucosamine and 2‐deoxy‐d‐galactose do not lead to the formation of UDP‐hexosamines; furthermore they are less efficient in trapping uridine phosphatesin vivo. These observations contribute to an understanding of the orotate‐mediated prevention of the galactosamine‐induced liver damage, and of the role of pyrimidine nucleotides in this experimental hepatitis.
The Cleavage of Prolyl Peptides by Kidney Peptidases
Authors: Dehm Peter , Nordwig Arnold 
Published: March 2005

Carboxypeptidase activity was detected in swine kidney microsomes. The enzyme was solubilised by treatment with trypsin and toluene. Approximately 330‐fold purification was achieved by subsequent chromatography on DEAE‐cellulose and hydroxylapatite.As shown by polyacrylamide gel investigation, the carboxypeptidase preparation thus obtained was practically pure. It still contains trace impurities of aminopeptidase M which is quite similar in physical properties. The molecular weight of the carboxypeptidase was 240000 as determined by Sephadex gel filtration. It is activated by manganese ions and exhibits a pH‐optimum at 7.75.The carboxypeptidase preferentially attacks substrates with a prolyl residue in the last but one position. No chain length dependence was found. Peptides free of proline were also cleaved, but normally at a rather low rate. The designation carboxypeptidase P (indicating its preference of proline peptide bonds) is therefore suggested.The physiological role of the new peptidase is discussed.
Hefe‐Phosphofructokinase
Authors: Freyer Renate , Liebe Stefan , Kopperschläger Gerhard , Hofmann Eberhard 
Published: March 2005

The effect of trypsin treatment with respect to the allosteric properties of yeast phosphofructokinase as well as its molecular weight has been studied. In the presence of fructose 6‐phosphate trypsin desensitizes yeast phosphofructokinase to ATP inhibition. Under the same conditions, activation of this enzyme by the positive allosteric effector AMP, however, remains uneffected. Addition of MgATP instead of fructose 6‐phosphate to the incubation medium containing trypsin protects the enzyme against ATP‐desensitization. After prolonged incubation of yeast phosphofructokinase with trypsin the enzyme becomes inactivated both with fructose‐6‐phosphate and with MgATP.Using density gradient centrifugation in sucrose media the effects of trypsin treatment on the sedimentation behaviour of yeast phosphofructokinase has also been investigated. With fructose 6‐phosphate, trypsin converts the 560000 form of yeast phosphofructokinase into two enzymatically active forms of 510000 and 350000 daltons respectively, which are both insensitive to ATP inhibition.On the other hand, in the presence of MgATP the peak of enzymatic activity sediments with 160000 daltons. This molecular form has the same high sensitivity to ATP inhibition as the untreated enzyme of molecular weight 560000. After the addition of fructose 6‐phosphate, the 160000‐molecule seems to dimerize giving an ATP‐sensitive form with a molecular weight of 340000.In the light of studies about the existence of several interconvertible forms of yeast phosphofructokinase published recently by our laboratory, the results described in this paper are discussed in terms of the existence of dimeric and trimeric states, regarding the 160000‐moiety as the trypsin modified monomer of the enzyme. Kinetic and allosteric properties of these states including conditions for their formation and stabilization are summarized and the peculiarities of the trypsin‐unmodified and trypsin‐modified enzyme are compared.
Studies on Nucleolar Liver DNA
Authors: Ittel Marie‐Elisabeth , Wintzerith Marguerite , Zahnd Jean‐Pierre , Mandel Paul 
Published: March 2005

Rat liver nucleoli were isolated from nuclear rat liver preparations. The nucleolar DNA and extranucleolar DNA, i.e. chromosomal DNA were examined. After deproteinization, nucleolar and chromosomal DNA were separated from RNA on 6 M CsCl isopycnic gradient.Nucleolar and chromosomal DNA were of the same density (1.703 g/cm3) in CsCl. The specific activity of nucleolar DNA from normal adult rat liver was significantly higher than chromosomal DNA after 32P incorporation in vivo, independent of the time after the label. Nucleolar DNA is metabolically distinct from chromosomal DNA. Results are discussed and a possible role of nucleolar DNA replication in ribosomal RNA synthesis is suggested.
Occurrence and Function of a High‐Km Hexokinase in Immature Red Blood Cells
Authors: Gerber Gerhard K. G. , Schultze Maria , Rapoport Samuel M. 
Published: March 2005

The formation of 14C02 from [1‐14C]glucose and [6‐14C]glucose by reticulocytes of rabbit and rat is dependent on the concentration of glucose over a wide range, indicating reactions preceding the formation of glucose‐6‐phosphate to be dependent on glucose concentration.In haemolysates of rabbit reticulocytes a high‐Km hexokinase was demonstrated by its kinetic properties. It corresponds to the glucokinase of liver. This enzyme does not occur in mature red blood cells of man and rabbit, nor in reticulocytes of newlyborns with erythro‐blastosis fetalis. The presence of glucokinase in reticulocytes introduces a metabolic path of glucose utilization which is not subject to regulation by the phosphofructokinase.
Optical Rotatory Dispersion and Circular Dichroism of DNA from Various Sources at Alkaline pH
Authors: Luck Gerhard , Zimmer Christoph , Snatzke Günther , Söndgerath Gertrud 
Published: March 2005

The effect of deprotonation and alkaline denaturation on the conformation of DNA from various sources has been investigated by optical rotatory dispersion and circular dichroism measurements.Upon transition to alkaline pH, changes in the optical rotatory dispersion at the characteristic peaks around 228 and 290 nm are observed. The variation of the optical rotations in case of A. T‐rich DNA is more pronounced than in case of G . C‐rich DNA. For G . C‐rich DNA, changes of rotations are mainly observed at pH values beyond 11.5; the transition ranging between pH 11.6 and 11.7. The transition is accompanied by a shift of the “cross‐over” point towards longer wavelengths presumably due to deprotonation of guanine residues.Native DNAs show characteristic differences in their circular dichroism spectra dependent on the G · C content. Increasing the temperature (below the melting region) reveals enhancement of the circular dichroism band of native DNA around 270 nm whereas the opposite effect is found in the denatured state. As a possible explanation an increase of the chirality in the native helical DNA structure or a structure of intermediary character is considered. Titration up to pH 12 or higher produces a drastic increase of the rotational strength around 228 nm as well as changes in the other two circular dichroism‐maxima which may be correlated to a diminuition of the chiral and helical structure.
The Effects of Magnesium and Manganese on the Purine Ratio of RNA Transcribed in vitro by Rat Liver Nuclei
Authors: Moulé Yvonne , Rousseau N. 
Published: March 2005

It is currently accepted that the base composition of the RNA synthesized in vitro by RNA polymerase of rat liver nuclei, depends on both the nature of the cation added to the incubation medium and the ionic strength of this medium. However, up to the present time, the foregoing results have been obtained on nuclei isolated in sucrose solution containing Mg2+ (1 to 3 mM). The influence of the isolation medium of nuclei has so far never been considered.The present results demonstrate that the ratio A/G of the RNA synthesized in vitro is much more determined by the cation added to the isolation medium than that present in the incubation assay. Nuclei isolated either in the presence of 1 mM Mn2+ or in the absence of cation added to sucrose solution synthesize (at low ionic strength) RNA molecules with a ratio A/G 1 regardless of the ion present in the standard assay. Thus, presence of Mg2+ during the isolation of nuclei appears to suppress their ability to transcribe in vitro DNA‐like RNA although allowing an optimal synthesis of ribosomal RNA.The properties of liver nuclei isolated in various conditions have been studied in relation to their transcriptional ability, and the results have been discussed taking into account the different possibilities of action of the cations upon the nucleus.
Hydrocarbon‐Utilizing Microorganism
Authors: Fujii Katsuhiko , Fukui Saburo 
Published: March 2005

Cellular fatty acids of Corynebacterium simplex ATCC 6946 were studied using various chain length of n‐alkanes as a sole source of carbon substrate. The organism contained appreciable amounts of odd‐numbered fatty acids even when grown on even‐numbered n‐alkane, suggesting the involvement of α‐oxidation of fatty acids. Moreover various homologues of tuberculostearic acid (10‐methylstearic acid) and iso branched acids were derived specifically depending on the chain length of n‐alkane.The compositions of monounsaturated and 10‐methyl branched‐chain fatty acids were remarkably affected by the level of intracellular vitamin B12, while those of normal saturated ones remained essentially constant. Namely, B12‐sufficient cells contained more 10‐methyl fatty acids than Δ9‐monounsaturated ones, and vice versa.From the study concerning the enzymatic synthesis of 10‐methyl fatty acids, these acids were found to be formed by methyl group transfer from S‐adenosylmethionine to unsaturated fatty acid moieties of certain lipids, and methyl‐B12 did not serve as a direct methyl donor in this reaction. In the test organism, the presence of B12‐dependent N5‐methyltetrahydrofolate‐homocysteine transmethylase was confirmed, the activity of which decreased significantly in the cells of low B12‐level. These results indicated that the reduced activity of methionine‐synthesizing system causes a lowering in the transformation of Δ9‐monounsaturated acids into 10‐methyl fatty acids in C. simplex.
3‐Phosphoglycerate Kinase from Rabbit Sceletal Muscle and Yeast
Authors: Krietsch Wolfgang K. G. , Bücher Theodor 
Published: March 2005

Phosphoglycerate kinase, isolated from rabbit muscle in highly purified crystalline form, was compared in terms of chemical, physical and kinetic properties to yeast phosphoglycerate kinase. A summary of the data is presented.Both proteins are composed of a single polypeptide chain, and in electrophoresis only one band was found. The N‐terminus is masked. The C‐terminal amino acid of the muscle enzyme is valine.Muscle and yeast enzyme have nearly identical molecular weights, Michaelis‐Menten constants, optimal pH values and Vmax. On the other hand, they differ significantly in their amino acid composition, especially in the content of sulfur and aromatic amino acids, in electrophoretic mobility and in heat stability. The muscle enzyme has an essential SH group. The single SH group of the yeast enzyme is apparently without importance for enzyme activity.Differences in the same direction as those observed with yeast and muscle phosphoglycerate kinase are discussed in connection with other glycolytic enzymes from the same organisms.
Staphylococcal Ornithine Carbamoyltransferase
Authors: Zaharia O. , Soru Eugenia 
Published: March 2005

A procedure for the purification of an ornithine carbamoylphosphate transferase isolated from a Staphylococcus aureus strain is reported. The procedure consists of the following steps: water extraction of the crude enzyme by autolysis under a toluene layer of the acetone dried bacteria cells, lyophilization of the crude extract, molecular sieving chromatography on a Bio Gel P‐150 column and as a final step the electrophoresis on Sephadex G‐200 plates.A 100‐fold purification with a 50% yield is realized. The purified preparation so obtained appeared to be pure on the basis of acrylamide gel electrophoresis, thin layer chromatography, immunodiffusion and immunoelectrophoresis.The apparent molecular weight of the enzyme as determined by molecular sieve chromatography is 200 000 ± 30 000.The Km value for l‐ornithine as substrate is 3 mM and for carbamoylphosphate 0.7 mM. Arrhenius activation energy is 13 775 cal/mol. NH2‐terminal amino acid is glycine: COOH‐terminal amino acid is glutamic acid.Two unmasked SH‐groups and two S‐S interchain bridges per molecule were found.
Effects of Valine Deprivation on the Biosynthesis of Ribosomal and Messenger RNA in a Mammalian Cell Line (L 5178 Y)
Authors: Tiollais Pierre , Galibert Francis , Boiron Michel 
Published: March 2005

It has been well demonstrated in bacteria that RNA syntheses are non‐coordinated. In order to study this problem in mammals, qualitative and quantitative studies of rRNA, polysomal mRNA, and RNA of heterogeneous ribonucleoproteic particles syntheses have been performed, during exponential growth and valine starvation. During the latter, the residual synthesis of these three classes of RNA were respectively calculated as 38, 70 and 90% of the control. Whatever is the physiological significance of these particles one can conclude that the RNA syntheses in mammals are not coordinated. This result resembles those observed in stringent bacteria strains.In addition, the “45 S fraction” isolated from sucrose gradient appears to be heterogeneous in CsCl gradient. This could be interpreted by the existence of several classes of particles, heterogeneous ribonucleoproteic particles and small ribosomal subunits more or less mature.Finally, some heterogeneous ribonucleoproteic particles with high density (ϱ= 1.60 g/cm 3) were found. This is not in complete accordance with the generally finding, that these particles are characterized by a low density.
Observations on the Biosynthesis of Ubiquinones by Animals
Authors: Whistance Geoffrey R. , Field Frederick E. , Threlfall David R. 
Published: March 2005

Tissues of a number of avian and mammalian species have been examined for the presence of 2‐polyprenylphenols, 6‐methoxy‐2‐polyprenylphenols, 6‐methoxy‐2‐polyprenyl‐1,4‐benzoquinones and 5‐demethoxyubiquinones. In no instance was evidence found of the presence of any of these compounds, although most tissues contained at least two ubiquinones and one ubiquinol.
Tracer studies wiht p‐hydroxy[U‐14C]benzoic acid have been carried out to detect the precursor of ubiquinone‐9, “5‐demethoxyubiquinone‐9”, reported by Olson and co‐workers [14, 15] in rat liver. The results obtained provided good evidence that this compound is ubiquinol‐9.