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Biomedical subjects

M Brunori

Publications and source records attributed to M Brunori.

At least 271 records · Page 15Linked to original sources
PubMed1982

Structural comparison of the haemoglobin components of the armoured catfish Pterygoplichthys pardalis. Evolutionary considerations.

Amino acid analyses and peptide mapping were performed for the four main haemoglobins from the armoured catfish Pterygoplichthys pardalis; component I, which is functionally distinct from the others, is structurally unique, whereas components II, III and IV, functionally indistinguishable, are closely related in structure. Compositional difference indices are calculated for the four components and for the two major haemoglobins from the trout Salmo irideus, and the results are discussed in terms of structural relationships and evolutionary history of fish haemoglobins.

Amino Acids↗
PubMed1982

The kinetics of electron transfer between pseudomonas aeruginosa cytochrome c-551 and its oxidase.

The redox reaction between cytochrome c-551 and its oxidase from the respiratory chain of pseudomonas aeruginosa was studied by rapid-mixing techniques at both pH7 and 9.1. The electron transfer in the direction of cytochrome c-551 reduction, starting with the oxidase in the reduced and CO-bound form, is monophasic, and the governing bimolecular rate constants are 1.3(+/- 0.2) x 10(7) M-1 . s-1 at pH 9.1 and 4 (+/- 1) x 10(6) M-1 . s-1 at pH 7.0. In the opposite direction, i.e. mixing the oxidized oxidase with the reduced cytochrome c-551 in the absence of O2, both a lower absorbance change and a more complex kinetic pattern were observed. With oxidized azurin instead of oxidized cytochrome c-551 the oxidation of the c haem in the CO-bound oxidase is also monophasic, and the second-order rate constant is 2 (+/- 0.7) x 10(6) M-1 . s-1 at pH 9.1. The redox potential of the c haem in the oxidase, as obtained from kinetic titrations of the completely oxidized enzyme with reduced azurin as the variable substrate, is 288 mV at pH 7.0 and 255 mV at pH 9.1. This is in contrast with the very high affinity observed in similar titrations performed with both oxidized azurin and oxidized cytochrome c-551 starting from the CO derivative of the reduced oxidase. It is concluded that: (i) azurin and cytochrome c-551 are not equally efficient in vitro as reducing substrates of the oxidase in the respiratory chain of Pseudomonas aeruginosa; (ii) CO ligation to the d1 haem in the oxidase induces a large decrease (at least 80 mV) in the redox potential of the c-haem moiety.

Azurin↗
PubMed1982

Spectroscopy of (carbon monoxy)hemocyanins. Phosphorescence of the binuclear carbonylated copper centers.

The luminescence of CO-hemocyanin has been studied in several hemocyanins from both arthropods and molluscs. All of them show an emission in the region 550-560 nm with quantum yield = 0.2-0.4, though individual differences are apparent. Solvent composition (as well as the presence of calcium and lanthanides) has no effect on the emission. Lifetimes of this luminescence are in the range 60-140 microseconds, indicating that the emitting state may be a triplet. The presence of both copper atoms (Cu+) per CO binding site is required for the luminescent state since half-met and half-apo derivatives do not show such an emission. Though not clearly related to any of the functional properties, systematic differences in luminescence parameters are apparent between arthropodal and molluscan hemocyanins. Limulus hemocyanin appears to be very different from both types of hemocyanin.

Animals↗
PubMed1982

Ligand binding and stereochemical effects in hemocyanins.

The Bohr effect in the binding of O(2) and CO to Helix pomatia beta-hemocyanin has been estimated by the potentiometric titration method. On the basis of the results, as well as other information available, we conclude that binding of O(2) to hemocyanin is associated with a quaternary allosteric transition (T-->R), while binding of CO is not. This conclusion is in agreement with previous results, which indicate that homotropic interactions are observed only for the binding of O(2) to the active site of hemocyanins. This is in marked contrast to the behaviour of hemoglobins which, otherwise, share with hemocyanins a number of important features, in spite of basic chemical differences. The stereochemical requirements of O(2), which forms a bridge between the two copper atoms in a site, have to be considered essential for the onset of cooperativity in hemocyanins.

Journal Article↗
PubMed1982

Kinetics of reactions within single erythrocytes: studies by microspectrophotometry.

Single cell spectroscopy has been applied to red blood cells along three different lines of research: a) distribution of single hemoglobin components among different erythrocytes, b) chemical reaction with ligands and diffusion in the red blood cell c) dynamics of hemoglobin S aggregation in single red blood cell. The results reported here show, in general, the great possibilities of using single-cell spectroscopy in investigating complex integrated systems.

Anemia, Sickle Cell↗
PubMed1981

Red cell lysis induced by microorganisms as a case of superoxide- and hydrogen peroxide-dependent hemolysis mediated by oxyhemoglobin.

Some bacteria, isolated from the blood of hospitalized patients, have been shown to hemolyze red blood cells through a mechanism which was dependent on the oxygenated state of intracellular hemoglobin, since transformation of hemoglobin into the CO-derivative inhibited the lysis. Hemolysis was also inhibited by superoxide dismutase and catalase, while only catalase prevented the formation of methemoglobin in experiments where isolated oxyhemoglobin was exposed to metabolizing bacteria. Production by bacteria of extracellular superoxide was demonstrated. It is suggested that hemolysis is due to interaction of O-2 and/or H2O2 with intracellular hemoglobin and that some product of such interaction is the lytic agent.

Blood↗
PubMed1981

Equilibrium and kinetic evidence for a transition between six- and five-coordinate ferrous heme in the nitric oxide derivative of Aplysia myoglobin.

The pH dependence in the range 3--7 of the optical absorption and electron paramagnetic resonance of the nitric oxide adduct of ferrous Aplysia myoglobin is reported. Optical spectra in the Soret region show a transition between two conformers with an apparent pK in the range 3.5--5 depending on the presence of carboxylic anions as third component. In the same pH range, the EPR spectrum undergoes a change from a 9-line to a 3-line hyperfine pattern in the g. region, similar to that reported for synthetic heme derivatives and for other hemoproteins. The structural interpretation of the pH-induced transition experienced by Aplysia myoglobin nitric oxide is that of a proton-linked cleavage of the proximal bond as suggested by several lines of evidence. Temperature-jump measurements allowed an estimation of the relaxation time for the process, which is of the order of 0.3 ms at 25 degrees C.

Animals↗
PubMed1981

Purification and functional properties of the hemoglobin components from the rat (Wistar).

Homogeneous components of Wistar rat hemoglobin have been isolated and characterized from the molecular and functional point of view. The O2 equilibrium behaviour of the three main components (HbII, HbIII, HbIVA) has been investigated as a function of pH and organic phosphate concentration. The ligand-binding kinetics of the isolated components have been also studied and are fully consistent with their equilibrium behaviour. It should be remarked that the choice of the system was governed largely by the ability of rat hemoglobins to crystallize very quickly. This almost unique molecular property together with the complete reversibility of the process may allow information to be obtained on the thermodynamics of ligand-linked phase changes.

Animals↗