Oligopeptides as potential antiaggregation agents for deoxyhemoglobin S.

Oligopeptides that mimic segments of the amino acid sequence of hemoglobin S at potential contact sites can be used to inhibit aggregation. These oligopeptide inhibitors raise the minimum gelling concentration of deoxyhemoglobin S so that chemical modification does not have to be used. The hexapeptide amides of both betaS 1-6 which is believed to be one of the contact areas among aggregates, and betaA 1-6 of hemoglobin A increase the minimum gelling concentration by more than 70%. The hexapeptide amide beta79-84 behaves like beta1-6 (beta being betaS or betaA). Shorter oligopeptides, such as betaS3-6, are less effective as an inhibitor but longer ones, such as betaS1-8, are no more effective than beta1-6. Permutations of the sequence, such as betaS125634, do not alter the percent increase in the minimum gelling concentration. Leu- and Met-enkephalin increase the minimum gelling concentration just as beta1-6 does, but (Pro)6 is not very effective. Thus, the use of complementary oligopeptides as inhibitors is extended to include certain "flexible" peptides, which can adapt themselves to interfere with the molecular contacts and thereby gelation of deoxyhemoglobin S.