Assay of proteins in the presence of interfering materials.

Glycinamidation of aminoethylated α, β, and γ chains of adult and fetal human hemoglobins results in the attachment of a glycinamide residue to each free carboxyl group. The peptides which result from tryptic hydrolysis of such modified chains can be separated by column chromatography or filter-paper finger-printing. Glycinamidation improves the yield of several tryptic peptides and is useful in determining the number and position of aspartyl and glutamyl residues in hemoglobins.