ubvy photometry of some southern field stars.

in Astronomy and Astrophysics. Supplement Series (1975), 22

Abstract image available at: http://cdsads.u-strasbg.fr/abs/1975A&AS...22..323H

Fragmentation of benzylpenicillin after interaction with the exocellular DD-carboxypeptidase-transpeptidases of Streptomyces R61 and R39

in Nature (1975), 258(5531), 168-170

Inactivation of rat liver RNA polymerases I and II and yeast RNA polymerase I by pyrodixal 5'-phosphate. Evidence for the participation of lysyl residues at the active site.

in Biochemistry (1975), 14

Purified DNA-dependent RNA polymerase forms I (A) and II (B) from rat liver and form I from yeast are rapidly inactivated by pyridoxal 5'-phosphate at pH 8.0. The inhibition is relatively specific since ... [more ▼]

Purified DNA-dependent RNA polymerase forms I (A) and II (B) from rat liver and form I from yeast are rapidly inactivated by pyridoxal 5'-phosphate at pH 8.0. The inhibition is relatively specific since pyridoxamine 5'-phosphate is not an inhibitor and pyridoxal is about 12 times less effective than pyridoxal 5'-phosphate. The inactivation is reversed by high concentrations of amines, and can be made irreversible by reduction with NaBH4. Spectral analysis of the inhibited enzyme and its NaBH4 reduction product indicates that a Schiff base forms between the aldehyde group of pyridoxal 5'-phosphate and one or more amino groups of the protein. Nepsilon-Pyridoxyllysine was identified as the only product in acid hydrolysates of the reduced yeast RNA polymerase I-pyridoxal 5'-phosphate complex. Complete inactivation of yeast polymerase I results in the incorporation of 3-4 mol of pyridoxal 5'-phosphate/1 mol of enzyme. DNA and nucleotide substrates partially protect the enzymes from inactivation. These results suggest that one or more lysyl amino groups are critical for the activity of animal RNA polymerases and show that pyridoxal 5'-phosphate is a suitable probe for studying the active sites of these enzymes. Comparison of the present results with those previously obtained with Eschericha coli RNA polymerase in this laboratory suggest a new degree of structural homology between eucaryotic and procaryotic RNA polymerases. [less ▲]

Variation du 17 ß oestradiol au cours du cycle oestral chez la vache

in Comptes Rendus de l'Académie des Sciences de Paris (1975), 281

Le dosage du 17 beta oestradiol plasmatique, sans recours préalable à la chromatographie de partage, a pu être réalisé et ce en raison de la haute spécificité de l'antisérum utilisé. Le 17 beta oestradiol ... [more ▼]

Le dosage du 17 beta oestradiol plasmatique, sans recours préalable à la chromatographie de partage, a pu être réalisé et ce en raison de la haute spécificité de l'antisérum utilisé. Le 17 beta oestradiol augmente à partir du 18e jour du cycle jusqu'à atteindre 8,6 pg/ml (6,4 à 12,6 pg/ml) au début de l'oestrus. Outre ce pic oestral, 3 pics accessoires peuvent être détectés: le premier, pratiquement constant, se situe entre le 4e et le 5e jour, le second moins important et seulement retrouvé chez 75% des sujets survient entre le 12e et le 14e jour. Enfin, le troisième, très inconstant, se retrouve parfois au 8e jour. Le taux basal moyen chez la vache est de 1,75 pg/ml. [less ▲]

Interview: Billy Boy Arnold

Article for general public (1975)

Interaction between the exocellular DD-carboxypeptidase-transpeptidase from Streptomyces R61, substrate and beta-lactam antibiotics. A choice of models

in European Journal of Biochemistry (1975), 57(2), 353-359

The interaction between the exocellular DD-carboxypeptidase-transpeptidase of Streptomyces R61 and beta-lactam antibiotics is a multistep process during which a rather stable enzyme - antibiotic complex ... [more ▼]

The interaction between the exocellular DD-carboxypeptidase-transpeptidase of Streptomyces R61 and beta-lactam antibiotics is a multistep process during which a rather stable enzyme - antibiotic complex is formed. This mechanism of interaction is compatible with Lineweaver-Burk plots that are typical of a competitive inhibition of the hydrolysis of the peptide donor by the antibiotic. In fact, however, the same Lineweaver-Burk plots can be obtained on the basis of a non-competitive type of inhibition. At present, a choice between the two models cannot be made. [less ▲]

Forbidden lines in a newly formed H II region

in Astronomy and Astrophysics (1975), 43

The initial evolution of a spherically symmetric H II region forming around a star of 36 solar masses is calculated numerically using a program based on a finite-difference scheme extrapolated from those ... [more ▼]

The initial evolution of a spherically symmetric H II region forming around a star of 36 solar masses is calculated numerically using a program based on a finite-difference scheme extrapolated from those previously proposed for solving hydrodynamic problems involving shock waves. The helium abundance is assumed to be 10 per cent, and no account is taken of magnetic fields, turbulent motions, or interstellar grains. The evolution of the positions of the hydrogen and helium ionization fronts is plotted as a function of time, and the total spectra of the forbidden emission lines of C II, N II, N III, O II, O III, Ne II, and Ne III are computed at each time. The intensities of the 29 strongest lines at five different epochs are compared with a rough estimate of the total strength of H-beta. The temporal evolution of the nebula and the emission lines is described qualitatively. [less ▲]

The catalytic activity and penicillin sensitivity in the liquid and frozen states of membrane-bound and detergent-solubilised transpeptidase of Streptomyces R61

in European Journal of Biochemistry (1975), 56(1), 57-65

The Km, app. values of the membrane-bound transpeptidase of Streptomyces R61 for the donor Ac2-L-Lys-D-Ala-D-Ala and the acceptor Gly-Gly are not affected by temperature variations when the reaction ... [more ▼]

The Km, app. values of the membrane-bound transpeptidase of Streptomyces R61 for the donor Ac2-L-Lys-D-Ala-D-Ala and the acceptor Gly-Gly are not affected by temperature variations when the reaction mixtures are incubated in liquid suspensions. At -5 degrees C, the incubation can be carried out either in the liquid or in the frozen state. The enzyme is active in the latter state. In the frozen state, the Km, app. value for the acceptor remains unchanged but there is a 3-fold increase in the maximum velocity, a 10-fold decrease of the Km, app. value for the donor and a 10-fold increase of the benzylpenicillin concentration required to inhibit the enzyme activity by 50% (ID50 value). Temperatures of -35 degrees C or below are required to completely inhibit the membrane-bound enzyme in the frozen state. Cetyltrimethylammonium bromide extracts the transpeptidase both from the isolated membranes and, with a much higher yield, from the intact mycelium. The extracted enzyme is not active in the frozen state, requires detergent for activity, has decreased Km, app. values for both donor and acceptor, exhibits the same sensitivity to benzylpenicillin and cephalosporin C as the membrane-bound transpeptidase (in liquid suspensions) and, like this latter enzyme, has no DD-carboxypeptidase activity. The detergent-extracted transpeptidase penetrates gels of Sephadex-100 and is not sedimented at 200 000 X g. [less ▲]

Inactivation of E. coli RNA polymerase by pyridoxal 5′-phosphate: Identification of a low pKa lysine as the modified residue

in Biochemical and Biophysical Research Communications (1975), 64(4), 1152-1159

The inactivation of E. coli RNA polymerase (3.3 × 10−7M) by pyridoxal 5′-phosphate (1 × 10−4M to 5 × 10−4M) is a first order process with respect to the remaining active enzyme. Studies of the variation ... [more ▼]

The inactivation of E. coli RNA polymerase (3.3 × 10−7M) by pyridoxal 5′-phosphate (1 × 10−4M to 5 × 10−4M) is a first order process with respect to the remaining active enzyme. Studies of the variation of the first order rate constant with the concentration of pyridoxal 5′-phosphate show that the inactivation reaction follows saturation kinetics. The formation of a reversible enzyme-inhibitor intermediate is postulated. Kinetic studies at different pH values indicate that the inactivation rate constant depends on the mole fraction of one conjugate base with pKa 7.9. The apparent equilibrium constant (association) for the inactivation reaction is independent of the pH and is 1.8 × 104 M−1. By electrophoretic and chromatographic analysis of enzyme hydrolyzates after pyridoxal 5′-phosphate and NaBH4 treatment only N-ε-pyridoxyllysine was found. It is postulated that a lysine ε-amino group with a low pKa is critical for the activity of the enzyme. [less ▲]

Analyse dynamique des structures pouvant être incompressibles et application à un élément fini de tore triangulaire

Report (1975)

This report is the continuation of a former report about incompressible structures in statics. Its essential purpose is to derive the mass matrix of the triangular tor element based on Herrmann's ... [more ▼]

This report is the continuation of a former report about incompressible structures in statics. Its essential purpose is to derive the mass matrix of the triangular tor element based on Herrmann's formulation. A special focus is brought on the problem of teh condensation of the pressure d.o.f.'s. Examples are presented, in order to assess the correct working of the program. In one of these, details are given on the approprate way of condensing the pressures in the incompressible case. Finally, chapter 4 is devoted to the problem of the convergence of pure displacement models to the correct solution when Poisson's ratio converges to 0.5. [less ▲]