A highly immunoreactive peptide fragment of human luteinizing hormone alpha subunit, discerned with a new,...

hLHa, whose primary amino acid sequence is known, was reduced and s-carboxymethylated (RCM) to remove secondary and teriary structure. RCM-hLHa was utilized for development of a "sequence specific" ria. RCM-hLHa ria revealed that the NH2-terminal tryptic peptide of hLHa (consisting of only 32 amino acid residues) was nearly as immunoreactive as the entire RCM-hLHa molecule (consisting of 89 residues). No other tryptic peptide was immunoactive. Reduced and s-carbamidomethylated hLHa, differing only slight in structure from RCM-hLHa, was weakly active in the RCM-hLHa ria, demonstrating the utility of this ria for precise study of structure-immunologic activity relationships.