Modification of hemoglobin by ninhydrin

The Strecker degradation reaction was evaluated as a means of modifying hemoglobin in vitro, utilizing ninhydrin as a model compound. Ninhydrin led to modification of hemoglobin (when incubated with hemoglobin or red cells) at physiologic temperature and pH. Isoelectric focusing documented the formation of new hemoglobin bands, all with decreased (more negative) isoelectric points that hemoglobin A. Both alpha and beta chains were modified to an equal degree, although electrophoretic studies documented two modified species of alpha-chains and three modified species of beta-chains. Amino acid analysis of modified hemolysate following NaB3H4 reduction revealed peaks that coeluted with deaminated valine, epsilon-deaminated lysine, and a product with the guanidino group of arginine. The oxygen affinity of hemoglobin increased following its incubation with increasing concentrations of ninhydrin. These studies suggest that ninhydrin is representative of a class of carbonyl compounds that could be utilized to specifically modify that structure and function of hemoglobin variants.