These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Electrostatic contributions to the energetics of dimer-tetramer assembly in human hemoglobin: pH dependence and effect of specifically bound chloride ions.
    Author: Flanagan MA, Ackers GK, Matthew JB, Hanania GI, Gurd FR.
    Journal: Biochemistry; 1981 Dec 22; 20(26):7439-49. PubMed ID: 7326236.
    Abstract:
    The pH dependence and effects of specifically bound chloride ions on the electrostatic contribution to the energetics of human hemoglobin dimer-tetramer assembly were computed for deoxy- and liganded hemoglobin. In the absence of bound chloride, the electrostatic contribution models the observed contrasting pH dependence of dimer-tetramer assembly for deoxy- and oxyhemoglobin. The effect of specifically bound chloride on the computations depends on the number and placement of the anions. Deoxy assembly shows a greater sensitivity to anion binding, with effects propagating as far as 32 A from the binding site. This sensitivity suggests a mechanism for electronic communication with the heme. At pH 7.4, 24-34% of the experimental value for deoxy and 73-85% for oxy dimer-tetramer assembly stabilization are predicted. Together with the findings of Chu and Ackers [Chu, A. H., & Ackers, G. K. (1981) J. Biol. Chem. 256, 1199] and other recent work, these results suggest that salt bridge formation is not the dominant energetic factor favoring deoxyhemoglobin dimer-tetramer assembly. Results of this work suggest that the marked electrostatic stabilization favoring oxy dimer-tetramer assembly may be a significant contributor to the quaternary enhancement observed in assembly reactions whereas the nonelectrostatic factors favoring deoxy dimer-tetramer assembly may be largely responsible for quaternary constraint.
    [Abstract] [Full Text] [Related] [New Search]