Allocution de M. Georges Schnek

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L'hémoglobine - poumon moléculaire

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Oxygen‐Affinity Studies of Avian Hemoglobins: Chicken and Pigeon

The oxygenation of hemoglobin is under the control of the regulatory function of organic phosphates. The one in mammals corresponds to 2,3‐bisphosphoglycerate but in birds and turtles appears to be inositol hexakisphosphate. The latter component decreases the oxygen affinity of the two chicken hemoglobin compounds (the minor and the major) and the lone pigeon hemoglobin component. The Bohr effects have also been determined for the two hemoglobin samples. As has already been observed by electrophoresis and by chromatography, pigeon hemoglobin seems to behave more like that of the major chicken component by disclosing analogous log p50 values, i.e. the partial pressure of oxygen corresponding to a 50% load of the hemoglobin. Copyright © 1971, Wiley Blackwell. All rights reservedSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Sulfhydryl groups of chicken hemoglobins. Effect of the reaction with para-mercuribenzoate on subunits dissociation and oxygen affinity

After quantitative reaction of the sulfhydryl groups of chicken hemoglobins with para mercuribenzoate, α and β chains cannot be separated by chromatography from either major or minor component. Ultracentrifugations show that dissociation into dimers occurs, but at protein concentrations much lower than those observed for mammalian hemoglobins. Oxygen equilibrium is affected: cooperative effects are weakened and oxygen affinity increases, the amplitude of the alteration being different for each component in presence or in absence of inositol hexaphosphate. Comparison with the behaviour of some mammalian hemoglobins is discussed. © 1973.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Tritium labelling of ribonuclease by the gas exposure method, as improved by an electric discharge

When lyophilized samples of bovine pancreatic ribonuclease are exposed to tritium gas, the exchange process can be markedly improved by applying high frequency electric discharges. Labelling was carried out for 5, 15 or 30 min periods. Labile radioactivity was then removed by means of molecular sieving and repeated lyophilizations, the tritiated protein being submitted to further purification by ion exchange chromatography. The specific radioactivity of such purified samples is in the Curie/mmole range, and the biological activity of the enzyme remains well preserved. The distribution of tritium atoms among component aminoacids was determined, after acid hydrolysis of the labelled protein.SCOPUS: NotDefined.jFLWNAinfo:eu-repo/semantics/publishe

Separation and characterization of four enzyme forms of beta-galactosidase from Saccharomyces lactis.

beta-Galactosidase from Saccharomyces lactis has been purified to serve as a model for the kinetic behavior of human lactase in adult lactase deficiency. Enzymes from both species are neutral and follow Michaelis-Menten kinetics. beta-Galactosidase of S. lactis is more readily available than the human lactase. An enzyme preparation from S. lactis (Maxilact 40,000), which is used commercially to hydrolyze lactose in milk, has been found to contain four isozymes of beta-galactosidase. Methods have been developed for the separation and purification of each of the four enzymes. The enzymes were found to differ in molecular mass, kinetic behavior, isoelectric point, response to pH, specific volume and sensitivity to metal ions. The four enzymes had apparent molecular masses of 630 kDa, 550 kDa, 41 kDa and 19 kDa. Their specificity constants (kcat/Km) were found to be 42.0, 355.2, 0.38 and 0.48 mM-1 s-1, respectively. The techniques of reiterated ultrafiltration used for the isolation of these isozymes may be applicable to other purification processes.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

N terminal amino acid sequences of the α and β chains of the two chicken hemoglobin components

Amino acid sequences corresponding approximately to the N terminal third of the α and β chains of the minor chicken hemoglobin component (P1) were determined. When each subunit is compared to the corresponding chain belonging to the major chicken hemoglobinic component (P2),a high number of amino acid substitutions can be observed between both chicken α chains while no difference can be noticed between the 2 β subunits.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Penguin hemoglobin (Aptenodytes forsteri). A 45 residue N terminal sequence

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Oxygen affinity of avian hemoglobins

1. 1. Blood from different avian species displays the presence of either two major hemoglobin components, type 1 and type 2, or a unique one similar to type 2. 2. 2. Some aspects of oxygen equilibrium are reported for both types of hemoglobin obtained from several species, namely oxygen affinity in the absence or presence of inositolhexaphosphate, the Bohr effect and the heme-heme interaction. 3. 3. The analogies and differences illustrated at the level of the physicochemical parameters are also observed at the level of the physiological properties. © 1973.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

The thiol proteinases from the latex of Carica papaya L. I. Fractionation, purification and preliminary characterization.

Three thiol proteinases, namely papain, chymopapain and proteinase omega were purified to homogeneity from the latex of Carica papaya L. During the purification procedure, the thiol function of the cysteinyl residues were protected either as mixed disulfides with cysteamine or 2-thiopyridone or as S-sulphenylthiosulfate derivative or after blocking with p-chloromercuribenzoic acid. In marked contrast with earlier publications, chymopapain also was found to be a monothiol proteinase as papain and proteinase omega. The active sites of chymopapain and proteinase omega could not be distinguished from that of papain neither by the analysis of the pH dependence of kcat/Km nor by the examination of the pH dependence of the fluorescence emission spectra.Journal ArticleSCOPUS: ar.jinfo:eu-repo/semantics/publishe