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Biomedical subjects

E Vitrano

Publications and source records attributed to E Vitrano.

32 records · Page 2Linked to original sources
PubMed1986

The interaction of sodium maleate with human haemoglobin.

We have studied the effect of sodium maleate on the reaction of haemoglobin with oxygen at various temperatures between 10 degrees C and 30 degrees C. At all the temperatures investigated, the presence of sodium maleate causes a significant increase of log p50. Analysis of the experimental data in terms of Wyman's linkage theory indicates that one oxygen-linked maleate molecule bound to the haemoglobin tetramer in the deoxy conformation is released when the tetramer is oxygenated. Further analysis within the framework of the Monod-Wyman-Changeux model, considering maleate as a classical allosteric inhibitor, enabled us to obtain the equilibrium constant for the binding of maleate to deoxyhaemoglobin at various temperatures and therefore the values of the standard binding entropy and enthalpy. These last values indicate that the binding of maleate to deoxyhaemoglobin is an exothermic enthalpy-driven process.

Depression, Chemical↗
PubMed1986

Effect of organic co-solvents on the dimer/tetramer equilibrium of human haemoglobin.

We have studied the effect of organic co-solvents (monohydric alcohols and formamide) on the dimer-tetramer equilibrium of human haemoglobin by measuring the dependence of oxygen affinity upon haemoglobin concentration over a 100-fold concentration range and analysing the data with a modified Monod-Wyman-Changeux model in which the equilibrium (tetramer) in equilibrium with (dimer) + (dimer) was taken into account. This procedure enabled us to obtain the dimer-tetramer equilibrium constant and to find its dependence upon co-solvent concentration. Then by following the procedure already reported for the tense----relaxed state transition of haemoglobin, we separated the co-solvent effects into bulk electrostatic and non-bulk electrostatic (hydrophobic) contributions. We believe that our results demonstrate that during haemoglobin dissociation, just as we have already shown for the tense to relaxed state transition, both charged groups and hydrophobic surfaces became exposed to the solvent.

1-Propanol↗
PubMed1986

Effects of organic co-solvents on the oxygen equilibrium of N-ethylmaleimide-treated human haemoglobin.

We have studied the effects of monohydric alcohols and formamide on the oxygen equilibrium of native and N-ethylmaleimide-treated human haemoglobin. Comparison of the results obtained for the two haemoglobins gives further and compelling evidence in favour of the model, proposed recently by our group, on the role played by the solvent in the conformational equilibria of haemoglobin; moreover the results provide direct functional evidence of the relevance of the electrostatic free energy of salt bridges to the T in equilibrium with R equilibrium of haemoglobin.

1-Propanol↗
PubMed1986

Optical absorption spectra of deoxy- and oxyhemoglobin in the temperature range 300-20 K. Relation with protein dynamics.

We have studied the optical absorption spectra of human deoxy- and oxyhemoglobin in the temperature range 300-20 K and in the wavelength range 350-1350 nm. By lowering the temperature, a narrowing and a shift of all bands were observed together with a sizeable increase of the integrated intensities of the charge-transfer bands of deoxyhemoglobin. At all temperatures the spectra are in full agreement with the band assignment previously suggested in the literature and no new relevant bands have been detected for both deoxy- and oxyhemoglobin. Analysis of the first and second moment of the bands, within the framework of the harmonic Franck-Condon approximation, gave information on the dynamic properties of the heme in the heme pocket.

Freezing↗
PubMed1984

Oxygen affinity of bovine haemoglobin. Relevance of electrostatic and hydrophobic interactions.

We have studied the effects of organic cosolvents (monohydric alcohols and formamide) on the oxygen equilibrium of bovine haemoglobin and have compared them with the effects of the same cosolvents on the oxygen equilibrium of human haemoglobin. Our results indicate: (1) that in agreement with previous suggestions, the lower affinity of bovine haemoglobin for oxygen is not due to an increased number of salt bridges stabilizing the T structure; (2) that, following T----R transition, more hydrophobic surface is exposed to the solvent by bovine than by human haemoglobin. We suggest, therefore, that a relevant role in keeping the oxygen affinity of bovine haemoglobin lower than that of human haemoglobin is played by the higher free energy needed to expose this more hydrophobic surface to the solvent. We stress, however, that our analysis does not enable us to say which particular amino acid residues are concerned in these effects.

1-Propanol↗
PubMed1980

Thermal stability of poly(A) and poly(U) complexes in H2O and D2O: isotopic effects on critical temperatures and transition widths.

This is a study of the effect of total and partial deuteration of solvent on critical temperatures and profiles of all four reactions occurring in poly(A) x n poly(U) (n = 1 or 2) aqueous systems. The study was done at observational times not longer than hydrogen exchange times at base pairs in helically ordered structures, and it was extended to a wide range of salt concentrations at neutral pH. The dependence of stability of polymer helical order on hydrogen mass does not appear to be merely attributable to the stronger intrahelical deuterium bonding. Substituting Deuterium for Hydrogen implies a probably predominant modulation of the entrophy term of polymer-solvent interactions. Effects of deuteration on the width of the 2(poly(A) x poly (U)) leads to poly(A) x 2poly(U)+poly(A) interconversion reaction were also observed. They bear on the role of polymer-solvent interaction on pattern recognition leading to formation of ordered structures. They also bear on the role of the same interaction on the "breathing" of ordered structures of this type.

Deuterium↗