Showing results 1 to 20 of 109
  Interaction between beta-lactam antibiotics and exocellular DD-carboxypeptidase-transpeptidase of Streptomyces R61Frère, Jean-Marie  ; ; Ghuysen, Jean-Marie et alin European Journal of Biochemistry (1974), 50(1), 203-214 On the basis of steady-state kinetics, inhibition of the exocellular dd-carboxypeptidase-trans-peptidase of Streptomyces R61 by β-lactam antibiotics was competitive with regard to the donor substrate ... [more ▼] On the basis of steady-state kinetics, inhibition of the exocellular dd-carboxypeptidase-trans-peptidase of Streptomyces R61 by β-lactam antibiotics was competitive with regard to the donor substrate. However, the complexes formed between the Streptomyces R61 enzyme and various β-lactam antibiotics were relatively stable, exhibiting half-lives of 40 to 80 min at 37°C and neutral pH. During breakdown of the complexes the protein underwent reactivation, whereas the released antibiotic molecule was chemically altered. With [14C]benzylpenicillin, the released compound was neither benzylpenicillin nor benzylpenicilloic acid. The properties of the Streptomyces R61 enzyme β-lactam antibiotic complexes were compared with those of the complexes formed between the same antibiotics and either the membrane-bound transpeptidase from Streptomyces R61 or the exocellular dd-carboxypeptidase-transpeptidase of Streptomyces R39. [less ▲] Detailed reference viewed: 2 (1 ULg)Critique des catégories de l'histoire de la littérature : téléologie et réalisme chez LansonSeba, Jean-Renaud in Littérature (1974), 16 Detailed reference viewed: 16 (4 ULg) Grandeur, déclin et perspectives de renaissace de l'UniversitéWelsch, Maurice Speech (1974) Detailed reference viewed: 5 (0 ULg)Molecular weight, amino acid composition and physicochemical properties of the exocellular DD-carboxypeptidase-transpeptidase of Streptomyces R39Frère, Jean-Marie ; ; Ghuysen, Jean-Marie in Biochemical Journal (1974), 143(1), 233-240 The exocellular dd-carboxypeptidase-transpeptidase from Streptomyces R39 was purified to protein homogeneity and in milligram amounts. The isolated enzyme consisted of one polypeptide chain of molecular ... [more ▼] The exocellular dd-carboxypeptidase-transpeptidase from Streptomyces R39 was purified to protein homogeneity and in milligram amounts. The isolated enzyme consisted of one polypeptide chain of molecular weight about 53300. Its amino acid composition and several physicochemical properties were determined and compared with those of the exo-cellular dd-carboxypeptidase-transpeptidase from Streptomyces R61. [less ▲] Detailed reference viewed: 4 (0 ULg)Ground-based photometric observations of the type A aurora of 17-18 December 1971Gérard, Jean-Claude in Annales de Géophysique (1974), 30 Ground-based observations have been made during the event of 17-18 Dec. 1971 from northern Norway, using a tilting-filter photometer monitoring the intensities of N2(plus) 1.Neg., H-beta, 6300-A O-I, and ... [more ▼] Ground-based observations have been made during the event of 17-18 Dec. 1971 from northern Norway, using a tilting-filter photometer monitoring the intensities of N2(plus) 1.Neg., H-beta, 6300-A O-I, and 5200-A N-I. The high 6300-A/N2(plus) 1.Neg ratio classes this event among type A auroras. The 6300-A/5200-A ratio varies during the night and remains higher than the usual value of nearly 20. These observations are compatible with a soft electron flux as the origin of the red line enhancement as illustrated by comparison with a model aurora. It is also found that N(2Do) is deactivated by collisions with electrons at a rate foreseen by theoretical calculations. An upper limit of about 40 seconds is derived for the N(2Do) effective lifetime, though no simple relationship gives a good fit to the observations. [less ▲] Detailed reference viewed: 10 (0 ULg)La Musique Cajun de la LouisianeSacré, Robert Article for general public (1974) Detailed reference viewed: 12 (0 ULg)Occurrence of D-alanyl-(D)-meso-diaminopimelic acid and meso-diaminopimelyl-meso-diaminopimelic acid interpeptide linkages in the peptidoglycan of Mycobacteria; ; et al in Biochemistry (1974), 13(17), 3471-3476 Detailed reference viewed: 8 (0 ULg)Membrane-bound transpeptidase and penicillin binding sites in Streptomyces strain R61; ; Ghuysen, Jean-Marie et alin European Journal of Biochemistry (1974), 46(3), 515-523 High-affinity penicillin binding sites from which the antibiotic could not be removed by washings at 4°C in 0.017 M K2HPO4 or 0.05 M Tris-HCl pH 7.5, were shown to occur in the isolated membranes of ... [more ▼] High-affinity penicillin binding sites from which the antibiotic could not be removed by washings at 4°C in 0.017 M K2HPO4 or 0.05 M Tris-HCl pH 7.5, were shown to occur in the isolated membranes of Streptomyces R61. These sites caused the attachment of 25 picomoles of [14C]benzylpenicillin per milligram membrane protein. Penicillins and cephalosporins competed for the same binding sites. The antibiotic concentrations which excluded [14C]benzylpenicillin from 50% of the binding sites were those which inhibited by 50% the membrane-bound transpeptidase. The same rate constant (about 1 × 10−4 s−1) for the dissociation of the benzylpenicillin membrane complex at 37°C and in 0.017 M K2HPO4, was calculated either from the release of the radioactivity (using [14C]benzylpenicillin) or from the recovery of the transpeptidase activity. These observations supported the conclusion that the high-affinity binding sites in the isolated membranes were the transpeptidase molecules. All the complexes formed between the membranes and the various penicillins and cephalosporins examined were reversible at 37°C and in 0.017 M K2HPO4 at least with regard to the transpeptidase. Depending upon the antibiotics, the rate constants for the dissociation of these complexes varied from 3.3 × 10−3 to 0.73 × 10−4 s−1. The radioactivity released through the dissociation of [14C]benzylpenicillin membrane complex occurred mainly in the form of a compound which behaved as [W]-benzylpenicilloic acid both by paper electrophoresis and thin-layer chromatography. It was impossible to choose between several possible mechanisms for the release of the antibiotic molecule. [less ▲] Detailed reference viewed: 4 (0 ULg)Un procédé rapide de cartographie forestière par ordinateurRondeux, Jacques in Schweizerische Zeitschrift für Forstwesen = Journal Forestier Suisse (1974), 125(7), 429-434 La cartographie automatique a pris un essor considérable ces dernières années, mais il semble bien qu'elle soit encore très souvent liée à l'utilisation de systèmes de traitement puissants avant tout ... [more ▼] La cartographie automatique a pris un essor considérable ces dernières années, mais il semble bien qu'elle soit encore très souvent liée à l'utilisation de systèmes de traitement puissants avant tout rentables dans le cadre de réalisations à grande échelle (aménagement du territoire, inventaires) ou dans des problèmes nécessitant des représentations graphiques rapides, voire instantanées. A défaut de disposer d'un matériel perfectionné, à utilisation généralement coûteuse (tables traçantes à commande numérique, plotters, etc.), il est possible d'exploiter directement l'imprimante de l'ordinateur. Si ce procédé présente l'inconvénient d'être moins précis, il peut toutefois s'avérer utile dans certains types de travaux. Dans cet ordre d'idées, à l'occasion de la révision d'un aménagement forestier, nous avons envisagé la représentation cartographique, par ordinateur, de diverses informations. Nous définirons d'abord les conditions générales de travail dans lesquelles nous nous trouvions (paragraphe 2), nous verrons ensuite comment nous avons conçu et réalisé la cartographie proprement dite d'une forêt donnée (paragraphe 3), nous évoquerons les principales limitations du système proposé (paragraphe 4), puis nous terminerons par quelques conclusions (paragraphe 5). [less ▲] Detailed reference viewed: 27 (1 ULg)The stiff-man syndrome. Clinical, polygraphical and histoenzymological study (author's transl); ; et al in Acta Neurologica Belgica (1974), 74(4), 221-40 Detailed reference viewed: 2 (0 ULg)Application de la méthode des éléments finis à l'étude du comportement dynamique d'un fluide incompressible et non visqueux contenu dans une structure élastique de révolutionDebongnie, Jean-François ; Report (1974) This report is devoted to the bases of the formulation which is implemented in SAMCEF in order to treat fluid-structure interactions in launcher tanks. Detailed reference viewed: 13 (2 ULg)Effects of donor and acceptor peptides on concomitant hydrolysis and transfer reactions catalyzed by the exocellular DD-carboxypeptidase-transpeptidase from Streptomyces R39Ghuysen, Jean-Marie ; ; et alin Biochemistry (1974), 13(12), 2539-2547 Detailed reference viewed: 2 (0 ULg)A simple model of stellar atmosphere; Manfroid, Jean in Orion: Zeitschrift für Amateur-Astronomie (1974), 32 Not Available Detailed reference viewed: 5 (0 ULg)Par delà les miroirs: chapitre XII de Au dessous du volcanPagnoulle, Christine in Les Lettres nouvelles (1974) Detailed reference viewed: 18 (3 ULg)Elément de coque à géométrie de révolutionDebongnie, Jean-François Report (1974) The first par of this report is focused on the formulation of the conical shell element in SAMCEF. In chapter 2, benchmark applications of this element in statics are discussed. Chapter 3 is devoted to ... [more ▼] The first par of this report is focused on the formulation of the conical shell element in SAMCEF. In chapter 2, benchmark applications of this element in statics are discussed. Chapter 3 is devoted to numerical tests in modal analysis. [less ▲] Detailed reference viewed: 38 (2 ULg)High Achievers in Belgium: A Partial Analysis of I. E. A. Science, Literature and Reading Comprehension DataDe Landsheere, Gilbert ; ; in Comparative Education Review (1974), 18(2), 188-195 In this article, we examine what IEA data tell us about the situation of the gifted in Belgium. (Author) Detailed reference viewed: 4 (0 ULg)Membrane-bound DD-carboxypeptidase and LD-transpeptidase of Streptococcus faecalis ATCC 9790; ; et al in European Journal of Biochemistry (1974), 44(2), 459-468 Isolated membranes of Streptococcus faecalis ATCC 9790 exhibit DD-carboxypeptidase activity (standard reaction: Ac2-l-Lys-d-Ala-d-Ala →d-alanine + Ac2-l-Lys-d-Ala) and ld-trans-peptidase activity ... [more ▼] Isolated membranes of Streptococcus faecalis ATCC 9790 exhibit DD-carboxypeptidase activity (standard reaction: Ac2-l-Lys-d-Ala-d-Ala →d-alanine + Ac2-l-Lys-d-Ala) and ld-trans-peptidase activity (standard reaction: Ac2-l-Lys-d-Ala + acceptor →d-alanine + Ac2-l-Lys-acceptor). The DD-carboxypeptidase activity has a considerable specificity for peptides with a C-terminal l-R3-d-Ala-d-Ala sequence where R3 is an amino acid residue and a long side-chain at the l-R3 position. A corresponding DD-transpeptidation reaction yielding the product Ac2-l-Lys-d-Ala-d-[14C]Ala from the system Ac2-l-Lys-d-Ala-d-Ala-f-d-[14C] alanine was not detected. The ld-transpeptidase activity has a considerable specificity for peptide donors that have an Nα-substituted, C-terminal l-R3-d-Ala sequence with a free ω-amino group at the end of a long side-chain at the l-R3 position, and a considerable specificity for amino group acceptors that are located on a d-carbon in α-position to a free carboxyl group. In the absence of acceptor, hydrolysis of the dipeptide Ac2-l-Lys-d-Ala (ld-carboxypeptidase activity) was not observed. Both DD-carboxypeptidase and ld-transpeptidase activities are inhibited by β-lactam antibiotics, but their relative sensitivity differs according to the particular antibiotic used. [less ▲] Detailed reference viewed: 8 (0 ULg)The DD-carboxypeptidase-transpeptidase system in Escherichia coli mutant strain; Nguyen-Distèche, Martine ; Ghuysen, Jean-Marie et alin Annals of the New York Academy of Sciences (1974), 235 Detailed reference viewed: 8 (0 ULg)The penicillin receptor in StreptomycesGhuysen, Jean-Marie ; ; Frère, Jean-Marie et alin Annals of the New York Academy of Sciences (1974), 235 Detailed reference viewed: 7 (1 ULg)Quelques réflexions relatives à l'utilisation de banques de données écologiques de petite dimension; Rondeux, Jacques ; Conference (1974, May) L'expression "banques de données" évoque presque inévitablement une masse considérable d'informations et, aussi, un matériel important de traitement automatique de ces informations. De ce fait même, cette ... [more ▼] L'expression "banques de données" évoque presque inévitablement une masse considérable d'informations et, aussi, un matériel important de traitement automatique de ces informations. De ce fait même, cette expression peut faire peur notamment à nombre de biologistes, déjà peu enclins bien souvent à avoir recours à l'ordinateur et à l'analyse statistique. Il nous semble cependant que, dans un sens peut-être plus restreint, la notion de banque de données peut s'appliquer aussi à des ensembles d'informations plus limités, qui ne représenteraient par exemple que quelques mois de travail continu, voire même un travail occasionnel de collecte pour un chercheur isolé ou pour une petite unité de recherche. Nous voudrions montrer que l'organisation rationnelle de telles banques de données "à la carte" peut conduire à des résultats pratiques fort intéressants, tant au niveau des chercheurs isolés ou des petites unités de recherche, qu'au niveau des institutions auxquelles ils appartiennent. Subsidiairement, nous voudrions montrer aussi que la création de banques de données même assez complexes peut être réalisée à l'aide d'un matériel de capacité relativement modeste. Nous pensons qu'il s'agit là d'un facteur important, car il nous semble que les centres de traitement de l'information de petite dimension, restant à une échelle plus humaine, peuvent avoir une action de promotion de l'informatique beaucoup plus efficace que les centres de grande dimension. Nous définirons tout d'abord brièvement les conditions dans lesquelles nous avons abordé le problème (paragraphe 2). Nous présenterons ensuite les principaux exemples que nous avons traité (paragraphe 3, 4 et 5) et nous parlerons de leur coordination et de quelques perspectives d'avenir (paragraphe 6). Nous terminerons enfin par quelques conclusions (paragraphe 7). [less ▲] Detailed reference viewed: 10 (3 ULg) |
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