Proton nuclear nagnetic resonance characterization of heme disorder in monomeric insect hemoglobins.

High field proton nuclear magnetic resonance spectroscopy has been utilized to determine the physical origin of the structural difference which leads to two interconvertible forms of the monomeric hemoglobins from the insect Chimnomus thummi thummi.Chironomous hemoglobin-111 and -IV were reconstituted with protohemins which have been specifically deuteriumlabeled at the peripheral methyls, leading to the assignment of individual methyl resonances for each isomer for the met-cyano form of the proteins.The methyl hyperfine shift patterns for the two isomers for each of the hemoglobins were found to differ characteristically, with pairwise exchange of environments of methyls 1 and 5 with methyls 3 and 8. Previous studies with both model compounds and deuterohemin-reconstituted myoglobin (La Mar, G. N.,