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L Esclade

Publications and source records attributed to L Esclade.

6 recordsLinked to original sources
PubMed1986

Effect of glutaraldehyde on haemoglobin: oxidation-reduction potentials and stability.

Glutaraldehyde is a reagent widely used for the cross-linking of haemoglobin for use as a blood substitute. Most of the previous studies were limited to oxygen binding equilibria of the glutaraldehyde-modified haemoglobin. This paper concerns the impact of glutaraldehyde on oxidation-reduction equilibria, autoxidation kinetics and stability towards heat and urea of haemoglobin cross-linked in the oxy, deoxy and ferri states. The oxidation-reduction potentials and homotropic effects were reduced; however, the oxidation Bohr effect was not significantly different when compared with native haemoglobin. Haemoglobin immobilized in the oxy or ferri state exhibited a lower redox potential than when immobilized in the deoxy state. The autoxidation rates were increased after cross-linking, particularly at basic pH. Cross-linking stabilizes ferrihaemoglobin better than oxy or deoxyhaemoglobin against thermal- and urea-induced denaturation. Glutaraldehyde cross-linking does not stabilize haemoglobin against urea-denaturation. The experimental results were interpreted as indicating a chemical modification of the protein without 'conformation freezing' and by an opening of the haem pocket to the aqueous solvent.

Aldehydes↗
PubMed1986

Aromatic hydroxylations in peroxidations by haemoglobin systems.

The catalytic activity of haemoglobin on aromatic substrates was studied in three systems: NADH-methylene blue-haemoglobin, ascorbic acid-haemoglobin, and red blood cells. Aniline and phenol but not acetanilide or p-toluidine are hydroxylated by haemoglobin. Dealkylations are not observed. Hydroxylations are postulated to be intermediate reactions in peroxidations catalysed by haemoglobin. The lifetime of the products depends on the presence of electron donors, such as NADH or ascorbic acid, in the medium. In the red blood cells where endogenous electron donors are recycled, levels of the products are higher and their lifetime is longer. This could have implications on drug metabolism by haemoglobin, as haemoglobin is present in large quantities in the organism.

Animals↗
PubMed1985

Determination of metabolites of cytochrome P-450 model systems using high-performance liquid chromatography.

High-performance liquid chromatographic techniques were developed for the simultaneous detection of metabolites in a cytochrome P-450 model system composed of NADH, haemoglobin and methylene blue. Monohydroxylated metabolites were determined following aniline, acetanilide and phenol hydroxylations. 4-Aminoantipyrine, 7-hydroxycoumarin and p-nitrophenol were determined after dealkylation of 4-N,N-dimethylamino-antipyrine, 7-ethoxycoumarin and p-nitroanisole. These substrates are commonly used for measuring cytochrome P-450 activities. Treatment of the samples was minimal, consisting of a simple deproteinization, and did not involve any organic extraction. Separations were carried out on reversed-phase columns and the products were detected by UV adsorption. Separations were completed in less than 15 min and the detection limits were between 0.5 and 4 microM.

7-Alkoxycoumarin O-Dealkylase↗
PubMed1981

Studies on haemoglobin immobilized by cross-linking with glutaraldehyde. Cross-linked soluble polymers and artificial membranes.

Human haemoglobin was immobilized by cross-linking with glutaraldehyde as soluble polymers and artificial membranes. Effects of pH and 2,3-diphosphoglycerate on oxygen binding and cross-linking were studied with haemoglobin immobilized in both the oxy and deoxy states. The cooperativity is suppressed and the affinity is increased when compared with native haemoglobin. Haemoglobin immobilized in the oxy state exhibited a higher oxygen affinity than that immobilized in the deoxy state. The alkaline Bohr effect is not significantly different from that of native haemoglobin. The 2,3-diphosphoglycerate influence on oxygen binding was reduced by one third with immobilization. In order to separate the chemical and the "conformation freezing' effects on the properties of immobilized haemoglobin, glutaraldehyde-modified haemoglobin in oxy and deoxy states was produced. Oxygen binding was studied and chemical modifications were checked by electrophoresis and gel filtration. This chemically modified haemoglobin without polymerization and without intra-chain bridging exhibits a behaviour similar to that of cross-linked soluble polymers or membranes of haemoglobin.

2,3-Diphosphoglycerate↗