Electron paramagnetic resonance study of carp methemoglobin.
The g anisotropy of the EPR spectra of carp azidomethemoglobin is found to be pH-dependent, whereas, the spectra of human azidomethemoglobin are not. The two hemoglobins have the same g values at alkaline pH values. Crystal field analysis yielded values of 2.25 and 3.31, respectively, for the rhombic distortion, V/lambda, and the tetragonal distortion, delta/lambda. The spin orbit coupling constant is lambda. At pH 4.0 the values of V/lambda and delta/lambda for carp azidomethemoglobin became 1.95 and 4.76, respectively, whereas those for the human hemoglobin are virtually unchanged. The results are interpreted to mean an increase of out-ofplane displacement of the iron atom and stabilization of the T form of carp azidomethemoglobin by high proton concentration. At pH 6.0 and lower, the EPR spectra of carp azidomethemoglobin showed the presence of about 1.5% of high spin species, the amount is not affected by excess of either inositol hexaphosphate or sodium azide. The EPR spectra of aquo- and fluoroderivatives of carp methemoglobin were not affected by pH changes.
D000818:Animals; D001386:Azides; D001665:Binding Sites; D002347:Carps; D004578:Electron Spin Resonance Spectroscopy; D006441:Hemoglobin A; D006801:Humans; D008433:Mathematics; D008706:Methemoglobin; D011485:Protein Binding; D011487:Protein Conformation; D013045:Species Specificity
D001386:Azides; D008706:Methemoglobin; D006441:Hemoglobin A