Tryptophan fluorescence of human hemoglobin. II. Effect of inositol hexaphosphate on the T-R transition.

Fluorescence spectra of tryptophan residues of human hemoglobin in the absence and presence of inositol hexaphosphate were measured at room temperature. The tryptophan fluorescence intensity of deoxy HbA was observed to decrease in accordance with the binding with inositol hexaphosphate. The fluorescence intensity of HbA, Hb Kempsey (beta 99 Asp-Asn), Hb Chesapeake (alpha 92 Arg-Leu) and NES-des-Arg Hb (des-141 alpha Arg and beta 93 Cys-N-ethylsuccinimide derivative) in the presence of inositol hexaphosphate exhibits a considerable decrease in the deoxy to oxy transition, while no or slight fluorescence intensity change was observed in the deoxy to oxy transition of Hb Kempsey and NES-des-Arg Hb in the absence of inositol hexaphosphate. The tryptophan fluorescence behavior suggest that the inositol hexaphosphate-induced structural change in these hemoglobins is attributable to the formation of a different T type of structure from that of the normal T-R transition.