Determination of the Amino Acid Sequence of an Unknown Dipeptide

A dipeptide of unknown amino acid composition was subjected to acid hydrolysis and heat to permit breakage of peptide bonds in the sample resulting in each individual amino acid constituent. Chromatography was then employed with a proper solvent system to compare a set of known amino acid standards against the unknown hydrolyzed sample to determine the two amino acids present in the unknown dipeptide. Ninhydrin was used to visualize the amino acid standards and unknown sample. After determination of amino acid composition in the dipeptide sample, the sample was subjected to N-group analysis to determine the aminoterminal end of the digested dipeptide sample. The dansylation technique was chosen to fluorescently label the amino acid that was present at the amino terminus of the dipeptide. Thin-layer chromatography was then selected using a proper solvent system to compare amino acid standards to the fluorescently-labeled dansylated amino acid derivative present at the amino terminus. UV-transillumination revealed the amino acid present at the N-terminus, and the sequence of the dipeptide was deduced from this information.