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Serine and theonine were hydrolyzed in newly designed tubes featuring O-ring joints. Design features of the apparatus include (1) a Teflon stopcock sealed to an O-ring connector tube, (2) a Teflon plug secured by a new sealing clamp, and (3) a Teflon O-ring used in the O-ring joint. This technique was compared with the sealed-tube procedure; the above amino acids were equally decomposed in both types of apparatus. The O-ring joint tube can be reused, thereby eliminating sealing and opening of evacuated hydrolysis tubes. (Author)

The reaction of 20 dipeptides, 2 tripeptides, and 1 heptapeptide with acetic anhydride in anhydrous dioxane was studied. After 6N HC1 hydrolysis the yield of the C-terminal residue was less than that of the penultimate residue in all peptides except three of the dipeptides. The yield of the penultimate residue in the two tripeptides was less than that of the N-terminal residue. Tyrosyl arginine yielded ornithine to partly account for the lost arginine. These results suggest that the acetic anhydride-dioxane reaction can be used as a subtractive method for identifying C-terminal amino acid residues in some peptides. (Author)