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Biomedical subjects

B Giardina

Publications and source records attributed to B Giardina.

At least 235 records · Page 13Linked to original sources
PubMed1977

Functional properties of partially oxidized trout hemoglobins.

This paper reports on a study of the effect of partial oxidation on oxygen and carbon monoxide binding by components I and IV of trout hemoglobin. The O2 binding equilibria of the various oxidation mixtures show a decrease in the heme-heme interactions as the number of oxidized sites is increased. However, the large Bohr effect, characteristic of Hb Trout IV, is maintained unchanged. Similarly the time course of CO combination changes on increasing the fractional oxidation, and the autocatalytic character of the CO binding kinetics is lost; however the pH dependence of the apparent "on" constant in the oxidation mixtures is similar to that characteristic of the native molecule. The results of the O2 equilibria and of CO binding kinetics may be interpreted in accordance with the two state concerted model suggesting that in the oxidation intermediates there is an increase in the fraction of the high affinity (R) conformation. Additional experiments on the effect of azide, and fluoride, ferric ligands which produce a change of spin state of the heme iron, suggest that additional second order conformational changes may also come into play.

Animals↗
PubMed1975

Kinetics of binding of carbon monoxide to lumbricus erythrocruorin: a possible model.

This paper represents a kinetic study of the binding of carbon monoxide by Lumbricus erythrocruorin. Observations on the quantum and the relaxation of the system both to equilibrium and to the steady state realized in the presence of constant illumination under various conditions are reported. The results, besides indicating the existence of at least two types of binding sites, give indications as to the behavior of a complex polyfunctional molecule, such as an enzyme, working under steady-state conditions.

Animals↗
PubMed1972

Partial restoration of normal functional properties in carboxypeptidase A-digested hemoglobin.

In the absence of organic phosphates human hemoglobin A digested with carboxypeptidase A (des His, Tyr beta) has high ligand affinity, a greatly reduced Bohr effect, and no heme-heme interaction. Under these conditions, it shows the simple, homogeneous ligand-binding kinetics characteristic of noncooperative heme proteins in which the high combination velocity for both O(2) and CO accounts, to a larger extent, for the increased affinity for both these ligands. Addition of inositol hexaphosphate dramatically alters the functional properties of this digested hemoglobin. The Bohr effect is greatly increased, and at neutral pH the protein shows significant, though still reduced, heme-heme interaction, together with a 5-fold decrease in affinity. In the presence of saturating amounts of the organic phosphate, the value of n is pH dependent, dropping from 1.9 at pH 5.8 to 1.3 at pH 8.6. After inositol hexaphosphate addition, the combination of the deoxy form of the digested hemoglobin with CO is 10-times slower than that observed in the absence of the inorganic phosphate; also the combination with CO after flash photolysis is biphasic and is similar, in many respects, to that observed for unmodified hemoglobin. Besides these functional changes, addition of inositol hexaphosphate to the modified deoxyhemoglobin results in an increase in the extinction coefficient at 430 nm similar to that observed on mixing the isolated alpha and beta chains of normal hemoglobin. The results are consistent with the idea that inositol hexaphosphate shifts an equilibrium between high- and low-affinity forms of the protein.

Carbon Monoxide↗