A new acid hydrolysis method for determining tryptophan in peptides and proteins

✍ Scribed by B. Penke; R. Ferenczi; K. Kovács

• Publisher: Elsevier Science
• Year: 1974
• Tongue: English
• Weight: 337 KB
• Volume: 60
• Category: Article
• ISSN: 0003-2697
• DOI: 10.1016/0003-2697(74)90129-8

✦ Synopsis

Three different methods for hydrolysis and determination of amino acid composition of peptides and proteins were compared. We found, that the method of Matsubara and Sasaki (using 6N HCI and thioglycolic acid) gives comparatively low recoveries for tryptophan, while Liu and Chang's method, using p-toluenesulfonic acid and tryptamine, is more suitable. TO eliminate the difficulties of the latter method, we used mercaptoethanesulfonic acid, which, in the concentration used, results in total hydrolysis of peptide bonds within 22 hr and gives very high tryptophan recoveries. Both sulfonic acid methods were used for hydrolysis of the pentapeptide "pentagastrine" as well as of the proteins lysozyme, cytochrome c, and chymotrgpsine. Their amino acid composition was determined using an automatic amino acid analyzer. Similarly to the p-toluenesulfonic acid method, the results of our method are totally reliable only for pure peptides and proteins, though the results obtained with our method using samples containing carbohydrates are better than those of all earlier methods.