bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spectrométrie de masse de glycolipides
Authors: Senn M. , Ioneda T. , Pudles J. , Lederer E. 
Published: March 2005

“Cord factors” are diesters of α,α‐trehalose produced by Mycobacteriae and Corynebacteriae. Saponification of the “cord factor” of Corynebacterium diphtheriae gives an equimolecular mixture of homologues of the saturated corynomycolic and of the unsaturated corynomycolenic acids (I and II, R = H). Máss spectrometry of their methyl esters confirms their structures (see Fig. 1, R = CH3).The peracetylated cord factor (IV, a, b, c) gave very weak molecular ions at m/e 1630, 1632 and 1634 showing apparently that it is a mixture of the diesters having respectively two saturated, one saturated and one unsaturated, and two unsaturated acyl radicals. Strong peaks at m/e 809 and 807 are attributed to the oxonium ions (V a and V b).These results as well as chemical degradations show that the “cord factor” of C. diphtheriae is a mixture of glycolipids (III a, b, c).
The Determination of the Order of Lysine‐containing
Authors: Perham R. N. , Jones G. M. T. 
Published: March 2005

A new diagonal electrophoretic technique for determining the order of the lysine‐containing tryptic peptides of a protein is described. The protein is converted into its trifluoracetyl derivative, digested enzymatically (or chemically), and the resulting peptides separated by paper electrophoresis. The paper is then treated with ammonia vapour, which re‐exposes the ɛ‐amino groups of the lysine residues, and submitted to a second electrophoresis at right angles to the first direction. Peptides containing lysine residues, together with the N‐terminal peptide of the protein, are found to lie off a diagonal formed by all other peptides, whence they may be readily purified. A study of these peptides enables the order of the lysine‐containing tryptic peptides in the protein to be deduced.
The technique has been successfully tested with insulin.
When the method was applied to porcine pepsin, the four tryptic peptides isolated were easily ordered and the carboxyl‐terminal sequence of the protein shown to be Arg‐Gln‐Tyr‐Tyr‐Thr‐Val‐Phe‐Asp‐Arg‐Ala‐Asn‐Asn‐Lys‐Val‐Gly‐Leu‐Ala‐Pro‐Val‐Ala. The three basic amino acid residues in the molecule are thus found clustering towards the C‐terminus of the polypeptide chain.
A common ancestral gene for porcine pepsin and bovine (calf) rennin is suggested by the close homology between the C‐terminal sequences of the two proteins.
Interactions entre pigments et acides nucléiques
Authors: Ohba Y. , Fromageot P. 
Published: March 2005

Luteoskyrine can be bound to nucleic acids in presence of Mg2+ ions. Two types of complexes are found. Complex I is made with single stranded nucleic acids containing purine bases such as denatured DNA, heated apyrimidinic acid, poly adenylic acid, poly inosinic acid or heated poly guanylic acid. Its visible spectrum is shifted towards shorter wavelengths compared to that of free luteoskyrine. Complex II is formed with double stranded nucleic acids or with single stranded ones deprived of purine bases such as a purinic acid, poly uridylic or poly cytidylic acid. The visible spectrum of complex II is shifted towards longer wavelengths with respect to that of free pigment. In complex I, one mole of luteoskyrine is associated to one atom of magnesium. Prolonged dialysis or heating does not dissociate the magnesium from the complex I but addition of EDTA does, with the simultaneous appearance of the free dye spectrum. Any purine residue in a polynucleotide is a potential site for complex I formation, but neither the nature of the purine (adenine or guanine) nor the nature of the sugar (ribose or deoxyribose) is relevant. However, the maximum amount of luteoskyrine bound as complex I by poly adenylic acid corresponds to a dye/purine ratio of 1/2. This ratio is somewhat larger with the denatured DNAs studied, being comprised between 1/1,2 and 1/1,7. It is suggested that this limit for complex I formation results from steric hindrance due to the size of the luteoskyrine molecule. Being bound to a given purine residue, a luteoskyrine molecule hinders the approach of another dye molecule to the adjacent purine residue but not to the one second next. According to this hypothesis, the maximum amount of complex I formed with given DNA can be calculated from the frequencies of purines sequences, and the predictions made correspond to the observed values. It is therefore likely that the stoechiometry of complex I corresponds to the association of one purine residue, one molecule of luteoskyrine and one atom of magnesium.To be able to bind luteoskyrine and magnesium as a complex I, a purine‐containing oligo‐nucleotide has to have a certain minimum size of 5 to 6 nucleotides (at 20 °). This suggests that a certain conformation of the relevant purine nucleotide residue is required for the binding of luteoskyrine as complex I.
Carboxyl‐Terminal Region of Human and Bovine Erythrocyte Carbonic Anhydrases
Authors: Andersson B. , Göthe P. O. , Nilsson T. , Nyman P. O. , Strid L. 
Published: March 2005

A methionine‐containing tryptic peptide from acetamidinated human carbonic anhydrase B has been isolated. This peptide has been shown to bridge a previously known carboxyl‐terminal fragment prepared by CNBr degradation with the rest of the enzyme molecule. Sequence studies on the methionine‐containing peptide have extended the previous knowledge of the carboxyl‐terminal sequence of the enzyme.Corresponding bridge peptides from human carbonic anhydrase C and acetamidinated bovine carbonic anhydrase B have also been isolated and their amino acid compositions have been determined.
Études sur les fractions glucidiques de la trame fibreuse insoluble du stroma cornéen
Authors: Moczar E. , Robert L. , Moczar M. 
Published: March 2005

Calf corneas were extracted with a buffer containing M CaCl2, 0.05 M Tris and 0.02 M citric acid, at pH 7.5. The residual stroma was digested successively by collagenase and pronase. The glycopeptides obtained were separated by gel filtration and high voltage electrophoresis. The sugar and amino acid content of the isolated glycopeptides was determined. Two types of sugar chains were detected: (a) chains with a more complicated structure, containing galactose, glucose, mannose and glucosamine; (b) disaccharidic and monosaccharidic side chains containing galactose and glucose or galactose alone and linked O‐glycosidically to the OH groups of hydroxylysine. The Hyl‐Gal‐Glc compound was isolated and identified with the compound isolated by Butler and Cunningham from calf skin collagen, by the study of its composition, thin layer chromatography and high voltage electrophoresis.The stroma of the calf cornea contains about 4 times more hexoses in the small glycopeptides of type b (di‐ and monosaccharides) than in the higher molecular weight mannose‐containing chains.
The Association of Brain Hexokinase with Mitochondrial Membranes and its Functional Implications
Authors: Vallejo Carmen G. , Marco Roberto , Sebastián Jesús 
Published: March 2005

The intracellular location of brain hexokinase and the nature of its association with mitochondria were studied in calf and rat. Three different media were used in order to minimize possible artifacts in the homogenization process.Subcellular fractionation was followed testing, in addition to hexokinase, certain enzymes known as markers for the different cellular fractions. In the conditions used, hexokinase was almost entirely associated with mitochondria in calf, but only partially associated in rat. This is at variance with the rest of the enzymes involved in the glucose 6‐phosphate crossroads. The use of a “physiological saline” homogenization medium resulted in a considerable increase in the proportion of soluble hexokinase in rat brain.Repeated washings of mitochondria from calf brain released little hexokinase, but in rat brain a rapid release was observed.Upon submitochondrial fractionation by Sottocasa's method, a substantial amount of hexokinase appeared bound to the inner membrane in the case of calf brain. In rat brain, the evidence found also points to the binding of the greater part of hexokinase to the inner membrane.Brain mitochondria were found to be sensitive to atractyloside, which made it possible to locate mitochondrial bound hexokinase as external to the ATP barrier, both in calf and rat.These results indicate that mitochondrially bound hexokinase is only active on substrates located in the cytosol.
Interactions entre l'acide désoxyribonucléique et les histones
Authors: Touvet‐Poliakow Marie‐Claire , Daune Michel P. , Champagne Madeleine H. 
Published: March 2005

Reconstitution in vitro of complexes between DNA and histone fractions (F1 and F3), each properly purified, is performed at high salt concentrations (∼ 1 M), followed by a progressive dialysis of the mixtures against decreasing ionic strengths.In a first approach, we study at pH = 5.4, the formation of a coacervate inside these mixtures, using low speed centrifugation, and measuring DNA and histone concentrations in the supernatants, as a function of the ratio of histone/DNA (w/w) in the initial mixture, and the molarity of the salt (NaCl). Interactions between DNA and histones are essentially electrostatic. However, the total number of positive charges on the histone molecules cannot explain the greater efficiency of F1 to precipitate DNA compared with F3. Uneven distribution of positive charges along histone molecules are to be considered, together with hydrophobic interactions between histones.Then by means of appropriate sucrose gradients, the existence of two complexes can be clearly demonstrated, the relative amount of each depending upon the ionic strength and the initial ratio histone/DNA in the mixture. The first complex, called “soluble”, is obtained alone only for very small values of histone/DNA ratio. With increasing amounts of histone, there appears a second complex called “aggregate”, which is in fact the first step in the formation of the coacervate.Distinct physico‐chemical factors govern each step of the binding process and it must be pointed out that the first step (soluble complex) only can be used to characterize the affinity of histone to DNA.The second step (coacervate) appears as an insoluble precipitate in the case of F1. In the case of F3, an intermediary state in the formation of the coacervate consists of stable aggregates, whose size and polydispersity are related to the initial F3/DNA ratio.The former case is somewhat similar to the complexes of DNA with polylysine, but the latter one resembles the artificial complexes between lysozyme and DNA.A tentative model is proposed for F3‐DNA aggregates where DNA is first folded into rodlike particles which in turn are organized into quasi‐spherical and highly hydrated micelles.
Some Aspects of the Process of DNA Synthesis in Mammalian Cells
Authors: Harrison Paul R. 
Published: March 2005

The process of DNA synthesis has been investigated in Ehrlich ascites tumour cells in suspension either in vivo or in vitro, in continuous cell lines growing as monolayers (HeLa and L cells), and in primary explants of normal embryonic tissue growing as monolayers.Newly‐synthesized DNA was detected by pulse‐labelling with tritiated thymidine and isolated by extraction with phenol/sodium dodecyl sulphate at pH 8.0. By chromatography on methylated albumin/kieselguhr, rapidly‐labelled DNA has been resolved into four components. One component, P1, was eluted with bulk DNA by about 0.65 M NaCl. In the case of DNA labelled during a very short pulse, a second component, P2, was eluted by about 0.8 M NaCl. Two further components, (β1 and β2) were eluted by 0.75 M and 6 M guanidine thiocyanate. The proportion of the latter components in total rapidly‐labelled DNA decreased only slightly as the time of incubation with label was increased from 7 to 60 min.P2 and the β components were precipitated by 2 M potassium acetate plus 35% ethanol, whereas about 70% of P1 remained in solution. Furthermore, the proportion of single‐stranded regions in the rapidly‐labelled DNA (measured by binding to nitrocellulose) decreased with increasing time of incubation with label. However, at all times, rapidly‐labelled DNA resembled double‐stranded DNA by chromatography on hydroxyapatite.There was no evidence for a different mechanism of DNA synthesis in the normal cells and the malignant cells or continuous cell lines. However, the timing of labelling of P2 varied between the cells.
Spectroscopic Studies on the Reduction and Reformation of the Disulfide Bonds of Papaya Lysozyme
Authors: Barel André O. , Dolmans Marcel , Léonis José 
Published: March 2005

The study of the reduction and reformation of the four disulfide bonds cross‐linking the single polypeptide chain of papaya lysozyme (molecular weight 28000) has been undertaken. The four disulfide bonds were quantitatively reduced and carboxymethylated. Various physicochemical measurements, such as optical rotatory dispersion, circular dichroism and fluorescence showed that the polypeptide chain of the reduced inactive papaya lysozyme appears to behave as a random coil. The conformational changes can be characterized as a complete loss of helical structure and an extensive exposure of the aromatic chromophores. Partial reduction of the protein (with splitting of, most probably, a single disulfide bond) does not affect the enzymatic activity. Physico‐chemical studies indicated that the secondary and tertiary structure of this derivative are very similar with those of the native enzyme.Reoxidation of the completely reduced enzyme, on exposure to air, produces a protein which could not be distinguished from the native molecule with respect to optical rotatory dispersion, fluorescence, solvent perturbation and enzymatic activity. The results of this study show that the primary structure of papaya lysozyme is sufficient to direct the refolding of the reduced protein in order to reform the native three‐dimensional conformation.
Structure primaire de la caséine β bovine Séquence partielle
Authors: Brignon Ghislaine , Ribadeau Dumas Bruno , Grosclaude François , Mercier Jean‐Claude 
Published: March 2005

This paper is the fifth of a series devoted to the primary structure of the bovine β‐casein A2. The first two communications dealt with the isolation, analysis and positioning in the peptide chain of the tryptic and “CNBr” peptides [1,2]. The last two described the sequence of 65 residues from the carboxyl‐terminus and of 32 residues from the amino‐terminus [3,4].We report here a partial sequence which includes 156 residues (out of the 209 residues of the β‐casein A2) exactly positioned in the peptide chain. Two segments including 53 residues (from position 36 to 68 and from 73 to 92) remain to be analyzed.In addition to the tryptic and “CNBr” peptides originating from β‐casein A2, two peptides issued from a tryptic digest of β‐casein B were used as starting material.The position of the substitution His→Gln which differenciates the β‐casein A2 from the β‐casein A3, already given in a preliminary communication [5], is indicated, as it is for the substitution Ser→Arg which represents one of the two differences occurring between the β‐casein A2 and the β‐casein B.Four of the five phosphorus atoms of the β‐casein A2 have been previously located in the NH2‐terminal tryptic peptide [4]. The fifth has been located at position 35. All the phosphorus atoms of the β‐casein A2 occur as phosphoserine.The complete structure of the β‐casein A2 will be given and discussed in the next and last paper.
Evidence that Protein is Bound to the Rapidaly Labelled RNA in Polyribosomes in vivo
Authors: Olsnes Sjur 
Published: March 2005

When ribosomal subunits were liberted from polysomes by puromycin treatment the rapidly labelled RNA banded in a CsCI gradient with the same low buoyant density as when the polysomes were treated with EDTA.A complex of cRNA and ribosomes was prepared in vitro and incubated with a cytoplasmic postribosmal fraction. The low buoyant density of the cRNA after such treatment indicated that protein had been adsorbed. However, after prior sedimentation through sucrose, the cRNA banded with a considerably higher buoyant density indicating that most of the adsorbed protein had been removed during the sedimentation in sucrose.It is concluded that the protein bound to the rapidly labelled RNA in polysomes cannot represent ribosomal strctural protiens, adsorbed nuclear material or cytoplasmic protein adsorbed during the homogenization. Most likely protien is bound to the rapidly labelled RNA in polysomes in vivo
Heterogeneity and Polymorphism of Human‐Liver Alcohol Dehydrogenase
Authors: Schenker Toni M. , Teeple Leslie J. , von Wartburg Jean‐Pierre 
Published: March 2005

Seven isoenzymes of human liver alcohol dehydrogenase have been ascertained by means of starch gel electrophoresis and chromatography on ion‐exchange celluloses. Six of them have been isolated and purified.
Catalytic properties of the isolated isoenzymes and the results of their reversible monomerization suggest that they are formed by the possible dimeric combinations of three subunits A, B and B′.
The same isoenzymes as observed in normal livers have been found in livers containing the atypical, variant enzyme described previously. The predominating isoenzyme isolated from atypical livers exhibits the catalytic features characteristic for the atypical enzyme in liver homogenates. One isoenzyme with normal kinetic properties, however, is also found in atypical livers.
Formes natives et globulaires de l'acétylcholinestérase dans la moëlle épinière et le cerveau de gymnote, Electrophorus electricus
Authors: Rieger François , Tsuji Shigeru , Massoulié Jean 
Published: March 2005

Acetylcholinesterase was studied in subcellular fractions of the spinal cord and brain from electric eel: the enzyme species we found were identical to the native forms which were characterized in electric organ extracts. On the contrary, the soluble protein fraction contains only globular species: mainly Gb (11.8 S) and a variable proportion of G'b (7.7 S), depending on the age of the homogenate and the tissue studied. A significant proportion of Gb is also found in particulate fractions.It seems probable that endogenous proteases cause the solubilization of the enzyme, yielding globular species Gb and G'b. Addition of benzethonium, an inhibitor of proteolytic enzymes, to spinal cord preparations results in a decrease of the proportion of globular species. This inhibitor also slows down the conversion of added “native” species A, C, and D into globular forms.Using a modified Koelle staining technique, we have not been able to detect any soluble acetylcholinesterase activity in the cytoplasm of the spinal cord neurons in electron microscopy. Most of the activity seems to be bound to the endoplasmic reticulum, which further suggests that proteases are responsible for the formation of globular species in the spinal cord homogenate.
Consequences of Lysine Oversynthesis in Pseudomonas Mutants Insensitive to Feedback Inhibition
Authors: Hermann Monique , Thevenet Nicole J. , Coudert‐Maratier Michèle M. , Vandecasteele Jean‐Paul 
Published: March 2005

Regulation of lysine biosynthesis was studied in Pseudomonas putida and Pseudomonas acidovorans. In both species, aspartokinase was subject to feedback inhibition by lysine and threonine and dihydrodipicolinate synthetase was inhibited by lysine. P. acidovorans could not degrade lysine whereas P. putida degraded lysine through an inducible lysine oxygenase. P. putida mutants with an aspartokinase insensitive to lysine inhibition were obtained. They did not excrete lysine but their lysine oxygenase was endogenously induced. However mutants obtained from a mutant lacking lysine oxygenase still did not excrete lysine. P. acidovorans mutants with a dihydrodipicolinate synthetase desensitized towards lysine inhibition were obtained. From them double mutants with both dihydrodipicolinate synthetase and aspartokinase desensitized were also obtained. All of these mutants excreted lysine.
Purification of Methionyl‐tRNA Synthetase from Escherichia coli K12 by Affinity Chromatography
Authors: Robert‐Gero Malka , Waller Jean‐Pierre 
Published: March 2005

An affinity column for the purification of methionyl‐tRNA synthetase has been prepared. Cyanogen‐bromide‐activated Sepharose 4B was reacted successively with hexamethylene‐diamine and N‐nitrophenylsulphenylmethionine succinimide ester. The nitrophenylsulphenyl protecting group of the polymer was removed under mild conditions with aqueous sodium thiosulfate. The affinity columns were equilibrated in 200 mM potassium phosphate buffer; this ionic strength proved to be sufficiently high to avoid the retention of methionyl‐tRNA synthetase by ion exchange.On columns with high methionine concentration (8–20 μmol/ml gel bed), the enzyme was strongly retained but could be selectively eluted by addition of 20 mM methionine to the buffer. However this resulted in excessive dilution of the enzyme. Highly purified enzyme could be obtained in high yield by lowering the methionine substitution of the polymer to 4.5 μmol/ml gel and by introducing the affinity chromatography after the first DEAE‐Sephadex step of the conventional purification procedure. Under these conditions no retention but sufficient retardation of the enzyme on the column was observed.The possibility of generalizing the method for the purification of other proteins recognizing an amino acid with its free amino group is discussed.
Ribonucleoprotein Particles in HeLa Cells
Authors: Wengler Gerd , Wengler Gisela , Scherrer Klaus 
Published: March 2005

We have investigated some properties of a class of cytoplasmic ribonucleoprotein particles in HeLa cells. After 3.5 h of labelling in the presence of 0.04 μg/ml actinomycin D to inhibit rRNA synthesis, about 20% of the newly synthesized cytoplasmic RNA, that sediments faster than 7 S, is contained in two types of particles sedimenting at 45 S and 30 S in sucrose gradients. We have examined this material in more detail with the following results.

The fixed particles band as two sharp peaks of density o= 1.440 g/cm3 for the 45‐S and density o= 1.460 g/cm3 for the 30‐S material. We call them the 45‐S‐M and 30‐S‐M particles, respectively.
The RNA of the 45‐S‐M and 30‐S‐M particles sediment in sucrose gradients as sharp peaks at 16 S and 12 S, respectively.
The synthesis of these two RNA species is inhibited by ethidium bromide, but resistant to low concentrations of actinomycin D. Two RNA species with these drug sensitivities and sedimentation characteristics have been found in the mitochondria of HeLa cells [1].
If cell homogenization and fractionation are carried out without detergents, the 45‐S‐M and 30‐S‐M particles are quantitatively bound to mitochondria.
Under most of the conditions commonly used for cell lysis and fractionation, these particles are extracted into the postmitochondrial‐cytoplasmic fraction.