Measurement of tryptophan in peptides by acid hydrolysis in the presence of phenol and its application to the amino acid sequence of a sea anemone toxin

The addition of phenol (about 1 % to 6 M HCl largely prevented destruction of tryptophan during hydrolysis of pep tides at 1l0°C for 22hr. Tryptophan recovery depended on the volume of 6 M HCl containing phenol and the concentration of phenol. The maximum tryptophan recovery was 85% for a standard amino acid mixture. The recovery was slightly lower for proteins. This hydrolytic procedure was advantageous for micro amino acid analysis using a conventional high performance liquid chromatography with a precolumn labeling technique. The method was used in the amino acid sequence analysis of a minor component of sea anemone toxins isolated from Anthopleura fuscoviridis. The toxin consisted of 48 amino acid residues with three tryptophan residues.