Antibodies to indolealkylamines II: site of conjugation of melatonin to protein using formaldehyde.

The site of coupling on the hapten was investigated for melatonin, formaldehyde, and protein conjugates. Model reactions of glycine ethyl ester and piperidine with formaldehyde and melatonin suggested that coupling first occurred through the indole nitrogen and then a stable bond was formed at C-2. Cross-reaction studies of antisera stimulated by melatonin, formaldehyde, and protein conjugates support the hypothesis that C-2 is the site of conjugation of melatonin to protein.