Non-linear relationships between oxygen saturation and magnitude of fine structure of ultraviolet oxy versus deoxy difference spectrum in human hemoglobin

Abstract

Ultraviolet difference spectra of fully oxygenated hemoglobin vs. successively deoxygenated or reoxygenated hemoglobin were determined in the absence and presence of organic phosphates. Magnitude of fine structure in the difference spectrum around 290 nm, which is considered to be a partial reflection of oxygenation-induced changes in quaternary conformation of hemoglobin, was not linearly related to fractional oxygen saturation of hemoglobin of the reference cell. The non-linear feature was influenced by the organic phosphates as predicted by the allosteric model of Monod et al. The present study suggests that the ultraviolet oxy vs. deoxy difference spectrum measurements provide a useful way to examine the validity of the model.