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Biomedical subjects

A Garnier

Publications and source records attributed to A Garnier.

At least 55 records · Page 3Linked to original sources
PubMed1981

Spectroscopic and photoreduction studies of copper chromophores in ceruloplasmin.

Photoreduction of native ceruloplasmin, using the 454.5-nm line of an Ar+ laser, enables the identification of type-Ia, type-Ib and type-II copper. The circular dichroic spectra of N--3-bound type-II copper and SCN-- -bound type-II copper are obtained by the same procedure after anionic treatment of ceruloplasmin. From circular dichroic and resonance Raman evidence it appears that some of type-Ia and type-Ib copper ligands differ. Type-Ib copper ligands seem to the same as type-I copper in plastocyanin and azurin. Even though type-Ib copper is coordinated to one sulfur of cysteine and one sulfur of methionine (or disulfide of cystine), the methionine sulfur is not a ligand for type-Ia copper.

Azides↗
PubMed1978

Circular dichroism investigation of the (L lysine)n-Cu(II) (1:1) systems with n = 4 and n = 25.

The study of the (L Lys)n-Cu(II) (1:1) system with n = 4 and n = 25 using circular dichroism (CD) data has provided evidence indicating the formation of two complexes in a two-step process. In the first of these complexes, obtained at pH 6.6, the alpha-amino terminal group and the adjacent deprotonated amide nitrogen are bound to the metal. In the second, additional amino nitrogens of side chains lie at the other two corners of the coordination square. A comprehensive investigation of changes occuring in spectral patterns when coordination takes place enables the assignment of three bands that are characteristic to each type of nitrogen coordination.

Chemical Phenomena↗
PubMed1978

Formation and spectral characterization of Cu(II)-poly(L-ornithine) complexes.

Cu(II)-Poly-(1-ornithine) complexes in aqueous solution have been studied using potentiometric titration and absorption and circular dichroism spectra. As in the case of Cu(II)-poly(L-arginine) complexes studied previously, two types of compounds have been detected, labeled complexes I and II. Complex I contains two amine nitrogens and two water molecules coordinated to the copper. Complex II, two amine and two amide nitrogens. Amide nitrogen coordination confers optical activity to the copper d-d transitions. Furthermore, amine and amide nitrogen coordination to the copper are characterized by charge transfer transitions at 250 and 320 nm respectively which were already identified in Cu(II)-poly(L-arginine) systems.

Cations, Divalent↗
PubMed1976

Ceruloplasmin-anion interaction. A circular dichroism spectroscopic study.

The effect of anion binding to ceruloplasmin has been studied using absorption and cirbular dichroism spectral data. At anion to ceruloplasmin molar ratios approaching infinite, OCN-, N3- and SCN- bind to ceruloplasmin giving rise to similar alterations in circular dichroism and absorption spectra. The positive bands at 610 and 520 nm in circular dichroism spectra disappear, a negative one apperars at 600 nm and the peak at 450 nm is only slightly modified. There is a new negative band at 410 nm well-defined in OCN- ceruloplasmin spectra. The decrease in absorption at 610 nm is ascribed to the disruption of one type I Cu-S(cysteine) bond owing presumably to the changes induced by anions in the protein secondary structure. The new band at 410 nm is assigned to a charge transfer transition from the ligand replacing cysteine at its binding site. Both absorption and circular dichroism spectra show isobestic points indicating that anion binding to the enzyme, disruption of one of the two type I Cu-S bonds and coordination of this Cu to another protein residue take place simultaneously.

Anions↗
PubMedDate not supplied

Crucial role of intracellular effectors on glycogenolysis in the isolated rat heart: potential consequences on the myocardial tolerance to ischemia.

The role played by glycogenolysis in the ischemic heart has been recently put into question because it is suspected that a slowing down of this process could be beneficial for the tolerance of the myocardium to ischemia. The role of the intracellular effectors that control the rate of glycogenolysis has therefore regained interest. We aimed to understand the role played by those intracellular effectors which are directly related to the energy balance of the heart. To this end, we review some of the previously published data on this subject and we present new data obtained from P-31 and C-13 NMR spectroscopic measurement on isolated rat heart. Two conditions of ischemia were studied: 15 min global no-flow and 25 min low-flow ischemia. The hearts were isolated either from control animals or from rats pre-treated with isoproterenol (5 mg.kg-1 b.w. i.p.) 1 h before the perfusion in order to C-13 label glycogen stores. Our main results are as follows: (1) the biochemically determined glycogenolysis rate during the early phase of ischemia (up to 10-15 min) was larger in no-flow ischemia than in low-flow conditions for both groups, (2) direct measurement of the glycogenolysis rate, as determined by C-13 NMR, after labelling of the glycogen pool in the hearts from isoproterenol-treated rats, confirms the estimations from the biochemical data, (3) glycogenolysis was slower in the hearts from pre-treated animals than in control hearts for both conditions of ischemia, (4) the total activity of glycogen phosphorylase (a + b) increased, by 50%, after 5 min no-flow ischemia, whereas it decreased by 42% after the same time of low-flow ischemia. However, the ratio phosphorylase a/a + b was not altered, whatever the conditions, (5) the concentration of inorganic phosphate (Pi) increased sharply during the first minutes of ischemia, to values above 8-10 mM, under all conditions studied. The rate of increase was larger during no-flow ischemia than during low-flow ischemia. The concentration of Pi was thereafter higher in controls than in the hearts from isoproterenol-treated animals. The calculated cytosolic concentration of free 5'AMP increased sharply at the onset on ischemia, reaching in a few minutes values above 30 microM in controls and significantly lower values around 15 microM, in the hearts from isoproterenol-treated rats. (6) The hearts from isoproterenol-treated rats displayed a reduced intracellular acidosis, when compared to controls, under both conditions of ischemia. We conclude that the intracellular effectors, mainly free AMP, play an essential role in the control of glycogenolysis via allosteric control of phosphorylase b activity. The alteration in the concentration of free Pi, the substrate of both forms of phosphorylase, can be considered as determinant in the control of the rate of glycogenolysis. The attenuation of ischemia-induced intracellular acidosis in the hearts from isoproterenol-treated rats could be a consequence of a reduced glycogenolytic rate and is likely to be related to a better resumption of the mechanical function on reperfusion.

Adenosine Triphosphate↗