title: Spin equilibria in human methemoglobin: effects of bezafibrate and inositol hexaphosphate as measured by susceptometry and visible spectroscopy.
abstract: The effects of inositol hexaphosphate (IHP) and a second allosteric effector, bezafibrate, on the spin-state equilibria of the mixed-spin derivatives of ferric human hemoglobin A are examined. Changes in spin-state equilibrium are monitored by measuring absorption spectra in the visible region (460-700 nm) as well as by direct measurements of magnetic susceptibility by means of a superconducting fluxmeter. The addition of IHP at pH 6.5 results in a measurable shift in the spin equilibria of these derivatives toward higher spin. However, the addition of bezafibrate in the presence of IHP results in still larger shifts toward the high-spin form. The changes in the free energies of the spin-state equilibria resulting from the combination of these two effectors are similar in magnitude to that which results from the R-state to T-state transition in carp hemoglobin.
authors.affiliation: Veteran's Administration Medical Center, State University of New York, Buffalo 14215.
authors.forename: R W
authors.initials: RW
authors.lastname: Noble
authors.forename: A
authors.initials: A
authors.lastname: DeYoung
authors.forename: S
authors.initials: S
authors.lastname: Vitale
authors.forename: M
authors.initials: M
authors.lastname: Cerdonio
authors.forename: E E
authors.initials: EE
authors.lastname: DiIorio
mesh_terms: D000818:Animals; D001629:Bezafibrate; D001665:Binding Sites / Q000187:drug effects; D002347:Carps; D004578:Electron Spin Resonance Spectroscopy; D004735:Energy Transfer; D006441:Hemoglobin A / Q000032:analysis; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008706:Methemoglobin / Q000032:analysis*; D010833:Phytic Acid; D013053:Spectrophotometry
chemical_list: D010833:Phytic Acid; D008706:Methemoglobin; D006441:Hemoglobin A; D001629:Bezafibrate