TY - JOUR
T1 - Effects of pH, 2,3-diphosphoglycerate and salts on gelation of sickle cell deoxyhemoglobin
AU - Briehl, Robin W.
AU - Ewert, Sandra
N1 - Funding Information:
We are grateful to Dr Sherman Weissman of the Department of Medicine, Yale University and Dr Samuel Charache, Department of Medicine, Johns Hopkins School of Medicine for gifts of the homozygous sickle cell blood used in the viscosity studies. This work wm supported in part by U.S. Public Health Service grant no. HL07451 from the National Heart and Lung Institute and in part by a Grant-in-aid from the American Heart Association.
PY - 1973/11/5
Y1 - 1973/11/5
N2 - Gelation of fully deoxygenated sickle cell hemoglobin was assayed by (1) determination of the temperature at which viscosity increased sharply and (2) a high-speed sedimentation equilibrium method in which three zones are seen. These are a pre-gelation zone, a narrow transition zone exhibiting aggregation, followed by a phase change and a zone of gelation. Only the first zone is seen with deoxyhemoglobin A and CO hemoglobins A and S up to about 0·35 g protein/ml. Minimal gelling temperatures by the viscosity method and, by ultracentrifugation, minimal gelling concentrations determined at the onset of aggregation and at the phase change showed: (a) lowering the pH toward 6·7 favors gelation; (b) deoxyhemoglobin S gels more readily in 6 mm-2,3-diphosphoglycerate than in its total absence; (c) 1 m-NaCl and l m-KCl inhibit gelation. The known favoring of gelation by warming is confirmed by the equilibrium method and is about 2% change in minimal gelling concentration per degree. The effects of pH and high ionic strengths are consistent with contributions of specific polar interactions to gel structure. The effect of 2,3-diphosphoglycerate probably depends on known structural changes which this cofactor induces rather than on alteration of the allosteric quaternary structure equilibrium.
AB - Gelation of fully deoxygenated sickle cell hemoglobin was assayed by (1) determination of the temperature at which viscosity increased sharply and (2) a high-speed sedimentation equilibrium method in which three zones are seen. These are a pre-gelation zone, a narrow transition zone exhibiting aggregation, followed by a phase change and a zone of gelation. Only the first zone is seen with deoxyhemoglobin A and CO hemoglobins A and S up to about 0·35 g protein/ml. Minimal gelling temperatures by the viscosity method and, by ultracentrifugation, minimal gelling concentrations determined at the onset of aggregation and at the phase change showed: (a) lowering the pH toward 6·7 favors gelation; (b) deoxyhemoglobin S gels more readily in 6 mm-2,3-diphosphoglycerate than in its total absence; (c) 1 m-NaCl and l m-KCl inhibit gelation. The known favoring of gelation by warming is confirmed by the equilibrium method and is about 2% change in minimal gelling concentration per degree. The effects of pH and high ionic strengths are consistent with contributions of specific polar interactions to gel structure. The effect of 2,3-diphosphoglycerate probably depends on known structural changes which this cofactor induces rather than on alteration of the allosteric quaternary structure equilibrium.
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U2 - 10.1016/0022-2836(73)90415-4
DO - 10.1016/0022-2836(73)90415-4
M3 - Article
C2 - 4762563
AN - SCOPUS:0015851091
SN - 0022-2836
VL - 80
SP - 445-452,IN1-IN2,453-458
JO - Journal of Molecular Biology
JF - Journal of Molecular Biology
IS - 3
ER -