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R Benesch

Publications and source records attributed to R Benesch.

At least 37 records · Page 2Linked to original sources
PubMed1977

Location and bond type of intermolecular contacts in the polymerisation of haemoglobin S.

The solubility of 14 hybrid haemoglobins composed of alpha chains with a single substitution and beta chains from HbS was compared with that of sickle haemoglobin. A substantial reduction in the insolubility of native deoxyhaemoglobin S results from surface mutations in certain regions of the alpha chain while changes in other areas have no effect. Also, the chemical nature of the substitution is decisive an points to the type of intermolecular bonding at several loci.

Hemoglobin, Sickle↗
PubMed1977

Reciprocal interaction of hemoglobin with oxygen and protons. The influence of allosteric polyanions.

The interaction of three inositol esters, inositol hexaphosphate (IHP), inositol pentaphosphate (IPP), and inositol hexasulfate (IHS), with hemoglobin has been investigated. The proton uptake method was used to obtain the six binding constants for deoxy- and oxyhemoglobin. These data combined with oxygen binding curves over a range of cofactor concentrations were used to test theoretical and empirical equations relating the affinity of hemoglobin for oxygen and allosteric effectors. The Bohr and Haldane coefficients in the presence of the inositol esters are unequal at low, but not at high, concentration of the cofactors. The maximum value reached by both parameters increases with the number of negative charges of the polyanion. 2,3-Diphosphoglycerate (DPG) differs sharply from the inositol esters since even at high concentrations of this cofactor, the Haldane coefficient remains elevated. This is a reflection of the negligible affinity of DPG for fully oxygenated hemoglobin.

Adult↗
PubMed1977

5'-deoxypyridoxal as a potential anti-sickling agent.

5'-Deoxypyridoxal, which reacts specifically with the terminal amino groups of the alpha chains of hemoglobin, increases the oxygen affinity of hemoglobin solutions as well as of dilute suspensions of normal and sickle red cells and whole blood. As a result, the proportion of deoxyhemoglobin (which is responsible for sickling) is decreased at venous oxygen tensions and this is reflected by a sharply reduced sickle cell count in this range of oxygen pressures.

Anemia, Sickle Cell↗
PubMed1976

The allosteric effect of inositol hexasulfate on oxygen binding by hemoglobin.

Myoinositol hexasulfate (IHS) is a powerful allosteric effector of oxygen binding by hemoglobin. It binds to deoxyhemoglobin at the same site as 2,3-diphosphoglycerate (DPG) and inositol hexaphosphate (IHP) with an affinity which is intermediate between that of the two phosphate esters. The binding constant calculated from the displacement of the oxygenation curve in the presence of low concentrations of IHS is 0.9X10(6) M. The value obtained directly from the number of protons bound as a function of IHS concentration is 1.0X10(6) M. The agreement between these two independent measurements provides an experimental verification of the empirical equation, relating the oxygen affinity to the binding constants, proposed previously (Benesch, R.E., Benesch, R., Renthal, R and Gratzer, W.B. (1971), Nature (London), New Biol. 2348 174).

Binding Sites↗
PubMed1976

alpha-Chain contacts in the polymerisation of sickle haemogloblin.

Five new double-mutant haemoglobins composed of betaS chains and alpha chains with different substitutions, which are located at the surface of the tetramer, have been prepared. Although all the hybrids are more soluble than deoxyhaemoglobin S, the individual differences between these molecules make it possible to evaluate several regions on the alpha chains for intermolecular contacts in the polymerisation of deoxyhaemoglobin S.

Hemoglobin, Sickle↗
PubMed1976

Reaction of haptoglobin with hemoglobin covalently cross-linked between the alpha beta dimers.

Hemoglobin tetramers which cannot split into alphabeta dimers, because they are covalently cross-linked between the beta chains across the polyphosphate binding site, form complexes with haptoglobin. The reaction is biphasic as measured by fluorescence quenching and peroxidase activity. A complex in which one of the alpha beta dimers of the cross-linked hemoglobin is bound to one of the sites in the divalent haptoglobin molecule, is formed reversibly during the initial fast phase. In the subsequent slower step, this product then either polymerizes, adds another cross-linked hemoglobin molecule or, in the presence of excess haptoglobin, combines with a second haptoglobin molecule. This latter complex, in which two haptoglobin molecules are bridged by a cross-linked hemoglobin tetramer, can still combine with normal alpha beta dimers at the vacant haptoglobin combining sites. In spite of the very low oxygen affinity of the cross-linked hemoglobin, combination with haptoglobin shifts if oxygen affinity to the very high value of the normal hemoglobin-haptoglobin complex.

Binding Sites↗
PubMed1974

Chemical modifications that inhibit gelation of sickle hemoglobin.

Substitution of the N-terminal amino groups with pyridoxal compounds inhibits gelation and increases the solubility of deoxy sickle hemoglobin (Hb S). Pyridoxylation of the alpha chains has considerably more effect than that of the beta chains. The increase in minimum gelling concentration of Hb S that results from modification of the alpha N-termini is the same as that produced by dilution of Hb S with an equal amount of Hb A.

Amino Acid Sequence↗