References of "1973"
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See detailActive site-directed inhibition of E. coli DNA-dependent RNA polymerase by pyridoxal 5′-phosphate
Venegas, Alejandro; Martial, Joseph ULg; Valenzuela, Pablo

in Biochemical and Biophysical Research Communications (1973), 55(4), 1053-1059

DNA-dependent RNA polymerase from E. coli is rapidly inhibited by preincubation with pyridoxal 5′-phosphate. The enzyme is not inhibited by pyridoxamine 5′-phosphate or pyridoxine. Pyridoxal is about 10 ... [more ▼]

DNA-dependent RNA polymerase from E. coli is rapidly inhibited by preincubation with pyridoxal 5′-phosphate. The enzyme is not inhibited by pyridoxamine 5′-phosphate or pyridoxine. Pyridoxal is about 10 times less effective than pyridoxal 5′-phosphate. Nucleoside triphosphates but not DNA, protect the enzyme from inhibition. Spectral data from the reaction mixture and NaBH4 reduction products indicate the formation of a Schiff base between the aldehyde group of pyridoxal 5′-phosphate and amino group of the enzyme. The results show that the inhibitor is reacting with a critical amino group presumably at the nucleoside phosphate binding site of the active center of the enzyme. [less ▲]

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See detailMéthodes thermiques d'analyse appliquées aux Sciences du Sol et de la Terre
Marcoen, Jean Marie ULg

Conference (1973, November 28)

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See detailFluorescence and circular dichroism studies on the Streptomyces R61 DD-carboxypeptidase-transpeptidase. Penicillin binding by the enzyme
Nieto, Manuel; Perkins, Harnold R.; Frère, Jean-Marie ULg et al

in Biochemical Journal (1973), 135(3), 493-505

The circular dichroism of the dd-carboxypeptidase-transpeptidase from Streptomyces R61 shows in the near u.v. a set of weak extrema at 289nm (positive) and at 282, 275 and 268nm (all negative). In the far ... [more ▼]

The circular dichroism of the dd-carboxypeptidase-transpeptidase from Streptomyces R61 shows in the near u.v. a set of weak extrema at 289nm (positive) and at 282, 275 and 268nm (all negative). In the far u.v. it shows negative extrema at 217-218 and 208nm, crossover at 202nm and a positive maximum at about 194nm. The u.v. absorption of the enzyme shows it to contain tyrosine and tryptophan in approx. 3.4:1 ratio. The enzyme is fluorescent with a maximum emission at 318-320nm. The near-u.v. circular dichroism of the protein is extensively affected by binding of penicillin G, but the far u.v. is unaffected. Binding of the antibiotic also causes quenching of the fluorescence of the enzyme. The latter effect has been used to study the binding of penicillin G to the enzyme and the influence exerted upon it by salts, denaturants and peptide substrates and inhibitors. High-affinity binding of penicillin appears to be comparatively slow and reversible, and can occur under conditions in which the protein is enzymically inactive. The thermal denaturation of the enzyme in guanidinium chloride at pH7 is affected by binding of the antibiotic. The presence of even large concentrations of beta-mercaptoethanol neither impaired the activity of the enzyme nor prevented its inhibition by penicillin G or cephalosporin C. A new hypothesis for the molecular mechanism of the interaction of the enzyme with penicillin is proposed. [less ▲]

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See detailMolecular weight and amino acid composition of the exocellular DD-carboxypeptidase-transpeptidase of Streptomyces R61
Frère, Jean-Marie ULg; Ghuysen, Jean-Marie ULg; Perkins, Harnold R. et al

in Biochemical Journal (1973), 135(3), 463-468

A procedure allowing the purification of milligram amounts of the exocellular dd-carboxypeptidase-transpeptidase from Streptomyces R61 to protein homogeneity (95% purity) is described. The isolated ... [more ▼]

A procedure allowing the purification of milligram amounts of the exocellular dd-carboxypeptidase-transpeptidase from Streptomyces R61 to protein homogeneity (95% purity) is described. The isolated protein has a molecular weight of about 38000 and consists of one polypeptide chain. Its amino acid composition is presented. [less ▲]

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See detailKinetics of concomitant transfer and hydrolysis reactions catalysed by the exocellular DD-carboxypeptidase-transpeptidase of streptomyces R61
Frère, Jean-Marie ULg; Ghuysen, Jean-Marie ULg; Perkins, Harnold R. et al

in Biochemical Journal (1973), 135(3), 483-492

When Ac(2)-l-Lys-d-Ala-d-Ala and either meso-diaminopimelic acid or Gly-l-Ala are exposed to the exocellular dd-carboxypeptidase-transpeptidase of Streptomyces R61, transpeptidation reactions yielding Ac ... [more ▼]

When Ac(2)-l-Lys-d-Ala-d-Ala and either meso-diaminopimelic acid or Gly-l-Ala are exposed to the exocellular dd-carboxypeptidase-transpeptidase of Streptomyces R61, transpeptidation reactions yielding Ac(2)-l-Lys-d-Ala-(d)-meso- diaminopimelic acid and Ac(2)-l-Lys-d-Ala-Gly-l-Ala occur concomitantly with the hydrolysis of the tripeptide into Ac(2)-l-Lys-d-Ala. The proportion of the enzyme activity which can be channelled in the transpeptidation and the hydrolysis pathways depends upon the pH and the polarity of the environment. Transpeptidation is favoured both by increasing the pH and by decreasing the water content of the reaction mixtures. Kinetics suggest that the reactions proceed through an ordered mechanism in which the acceptor molecule (meso-diaminopimelic acid or Gly-l-Ala) binds first to the enzyme. Both acceptors behave as non-competitive inhibitors of the hydrolysis pathway. Transpeptidation is inhibited by high concentrations of Gly-l-Ala but not by high concentrations of meso-diaminopimelic acid. The occurrence on the enzyme of an additional inhibitory binding site for Gly-l-Ala is suggested. [less ▲]

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See detailThe wall peptidoglycans of Neisseria perflava, Moraxella glucidolytica, Pseudomonas alcaligenes and Proteus vulgaris strain P18
Martin, Jean-Pierre; Fleck, J.; Mock, M. et al

in European Journal of Biochemistry (1973), 38(2), 301-306

The primary structure of the wall peptidoglycans of Neisseria perflava, Moraxella glucidolytica and Pseudomonas alcaligenes is similar to those of the Enterobacteriaceae Proteus vulgaris and Escherichia ... [more ▼]

The primary structure of the wall peptidoglycans of Neisseria perflava, Moraxella glucidolytica and Pseudomonas alcaligenes is similar to those of the Enterobacteriaceae Proteus vulgaris and Escherichia coli, suggesting that the peptidoglycans of all gram-negative bacteria contain meso-diaminopimelic acid and belong to the same chemotype I. Differences are observed with regard to the thickness of the peptidoglycan layer in the cell envelopes, the extent of peptide crosslinking and the occurrence of N,O-diacetylmuramic acid residues. [less ▲]

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See detailL'Université à l'heure des choix
Welsch, Maurice ULg

Speech (1973)

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See detailSociologische en psychologische aspecten bij reclametaal
Vromans, Joseph ULg

Conference given outside the academic context (1973)

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See detailLes investigations psychologiques en psychiatrie clinique
Mormont, Christian ULg; Servais, J.

in Revue Médicale de Liège (1973), 28(17), 612-614

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See detailDiffusive equilibrium elements
Fraeijs de Veubeke, Baudouin ULg

Scientific conference (1973, July)

Equiliobrium models are characterized by an internal stress field in equilibrium and surface tractions that should obey the diffusivity requirement of reciprocity with adjacent elements at the interfaces ... [more ▼]

Equiliobrium models are characterized by an internal stress field in equilibrium and surface tractions that should obey the diffusivity requirement of reciprocity with adjacent elements at the interfaces. Thepaper discusses the construction of stiffness matices for such elements and the difficulties associated with the presence of mechanisms. The use of first order or second order stress functions is presented together with the possibility of solving the final equations by the force method through a direct flexibility method. Three methods are presented for getting rid of thre machanisms: the classical superelement technique, a method based on the discretization of rotational equilibrium and quasi-diffusivity. [less ▲]

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See detailApplications de la méthode des éléments finis en mécanique des fluides
Debongnie, Jean-François ULg

Master's dissertation (1973)

Investigation of applications of finite elements in fluid problems, with applications.

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See detailSimulation de l'évolution de peuplements forestiers dans le contexte d'une sylviculture intensive
Rondeux, Jacques ULg

in Growth models for tree and stand simulation. Research note n° 30 (1973, June)

Depuis quelques années, la technique de la simulation est de plus en plus utilisée comme moyen de prévision de la production forestière. De façon générale, les premiers modèles mis au point ont d'abord ... [more ▼]

Depuis quelques années, la technique de la simulation est de plus en plus utilisée comme moyen de prévision de la production forestière. De façon générale, les premiers modèles mis au point ont d'abord concerné le développement de forêts de type industriel ou semi-industriel (CLUTTER et BAMPING, 1965; GIBSON et àl., 1969; GOULD et O'REGAN, 1965; etc); tout récemment, en Suisse, l'étude de forêts à sylviculture intensive a été entamée par BARTET et PLEINES (1972). Grâce à des modèles appropriés, il est aussi possible de simuler l'évolution de forêts composées de massifs relativement petits, épars et hétérogènes quant aux essences ou aux milieux de croissance observés. La simulation suppose la connaissance d'une masse très importante d'informations sur le milieu géré; à ce sujet, en Belgique, le nombre de données quantitatives disponibles est nettement insuffisant. Dans les lignes qui suivent, nous montrons très rapidement comment nous proposons d'entreprendre diverses simulations concernant la distribution spatiale du matériel et l'évolution de celui-ci sur la base d'une banque de données que nous avons mise au point. [less ▲]

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See detailContribution à l'étude du Strychnos usambarensis GILG, principal constituant d'un poison de flèche curarisant africain
Angenot, Luc ULg

Doctoral thesis (1973)

The thesis is subdivided in four parts and two annexes . The first part concerns the choice of Strychnos usambarensis based on ethnobotanical considerations; the second part is dedicated to the study of ... [more ▼]

The thesis is subdivided in four parts and two annexes . The first part concerns the choice of Strychnos usambarensis based on ethnobotanical considerations; the second part is dedicated to the study of arrow poisons in the World and particularly in Africa; the third part describes the isolation of eight indole alkaoids ( 5 new and 3 known ones) and their structure determination thanks to modern spectroscopic methods.The fourth part is applied to the biosynthesis of these alkaloids and to the identification of loganic acid.The first appendix describes the phytochemical screening of 33 Rwandan plants mainly collected in the National Park of Akagera. The second appendix relates pharmacological experiments on crude fractions and some isolated alkaloids. [less ▲]

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See detailProblèmes posés par l'aspect structural de la théorie de Piaget
Beckers, Jacqueline ULg

in Education : tribune libre (1973), 141

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See detailEtude du Rorschach d'une jeune épileptique ne présentant pas de paroxysme
Mormont, Christian ULg; Servais, J.

in Acta Psychiatrica Belgica (1973), 73(3), 379-386

Reports the case study of a 12-yr-old female epileptic who was not presenting seizures but who appeared to suffer from a behavior disorder. The study exemplifies the role the Rorschach test can play in ... [more ▼]

Reports the case study of a 12-yr-old female epileptic who was not presenting seizures but who appeared to suffer from a behavior disorder. The study exemplifies the role the Rorschach test can play in the early detection of such disorders. The epileptic component had been overlooked but was later confirmed by EEG. Specific treatment produced improvement of the behavior disturbance. [less ▲]

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See detailEtude du Rorschach d'une enfant suicidante
Mormont, Christian ULg

in Acta Psychiatrica Belgica (1973), 73

Describes the case of 10-yr-old girl whose suicidal ideation was reflected in her Rorschach record.

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See detailStreptomyces DD-carboxypeptidases as transpeptidases. The specificity for amino compounds acting as carboxyl acceptors
Perkins, Harnold R.; Nieto, Manuel; Frère, Jean-Marie ULg et al

in Biochemical Journal (1973), 131(4), 707-718

The ability of the water-soluble dd-carboxypeptidases of Streptomyces strains albus G, R61, K11 and R39 to perform transpeptidation was studied. The donor was diacetyl-l-lysyl-d-alanyl-d-alanine, and a ... [more ▼]

The ability of the water-soluble dd-carboxypeptidases of Streptomyces strains albus G, R61, K11 and R39 to perform transpeptidation was studied. The donor was diacetyl-l-lysyl-d-alanyl-d-alanine, and a whole range of amino acids, peptides and structurally related amino compounds were tested for acceptor function. No compound tested was an acceptor for the enzyme from strain albus G whereas the enzymes from strains R61 and K11 could utilize with varying efficiency a wide range of substances including peptides with N-terminal glycine or d-alanine, omega-amino acids, aminohexuronic acids, 6-aminopenicillanic acid and d-cycloserine. Certain peptides, when present in higher concentration, inhibited the transpeptidation observed at lower concentration. The enzyme from strain R39 would not use any dipeptide as an acceptor, but a few compounds that were not glycine or alpha-amino acids of the d-configuration did function thus. These were d-cycloserine and the lactams of meso- or racemic-diaminoadipic acid. [less ▲]

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See detailQuelques aspects psychologiques du comportement suicidaire
Mormont, Christian ULg

in Revue Médicale de Liège (1973), 28(5), 151-154

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See detailDD-carboxypeptidase-transpeptidase and killing site of β-lactam antibiotics in Streptomyces strains R39, R61, and K11
Dusart, Jean; Marquet, Alberto; Ghuysen, Jean-Marie ULg et al

in Antimicrobial Agents and Chemotherapy (1973), 3(2), 181-187

Additional evidence is given that in Streptomyces strains R39, R61, and K11 the same enzyme performs dd-carboxypeptidase and transpeptidase activities and that this enzyme is the killing site of beta ... [more ▼]

Additional evidence is given that in Streptomyces strains R39, R61, and K11 the same enzyme performs dd-carboxypeptidase and transpeptidase activities and that this enzyme is the killing site of beta-lactam antibiotics. With strain R61, it was found that the exocellular enzyme has a sensitivity towards some antibiotics different from that of the membrane-bound enzyme. Under the growth conditions used in the present investigations, beta-lactamase activity was not involved in susceptibility to beta-lactam antibiotics. [less ▲]

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