Improved manual sequential analysis of peptides.

Organic solvents can affect the efficiency of peptide sequencing by the Edman degradation method by altering peptide extractive losses during manual sequence analysis. We present a modified phenylisothiocyanate procedure for the degradation of one to five peptides simultaneously with high repetitive yield (90–95%) with an average time per cycle of 75 min. Improvement in average yield per cycle (repetitive yield) varies with the choice of solvent and nature of peptide under investigation. The degree of extraction of a particular thiazolinone similarly can be improved by the selection of appropriate solvents.