The extent of conversion of food protein to microbial protein in the rumen of the sheep.

W. S. REITH AND N. M. WALDRON I954 DDPT is thus a suitable reagent for the determination of the amino-acid sequence in peptides by a process of step-wise degradation from the Nterminal end of the chain, and has in fact been successfully applied for this purpose. The conditions under which the N-terminal amino acid splits off as a substituted DDP-thiohydantoin are so mild that other peptide bonds are not split. The yields of the thiohydantoins vary between 80 and 90% according to the experimental conditions and the type of the thiohydantoin. We found that the yield of the residual peptide (subject to the next step in the sequence determination) is practically equivalent to the yield of the thiohydantoin. Consequently a small but calculable fraction of the DDP-thioureidopeptide is lost during the process of the elimination of the substituted N-terminal group.