Peptides minimal protein amount determination

The formation of PTH-amino adds by the Edman degradation [4] of peptides and proteins or by successive modifications of the method constitutes the most commonly used technique for the study of the structure of biologically active polypeptides today. Identification of PTH-amino acids in mixtures may be successfully achieved by TLC. Quantitative determination is based on UV absorption (detection limit 0.1 jLg at 270 nm). An alternative is offered by the chlorine/toUdine test, which is very useful because the minimal amount required for detection is about 0.5 (xg. 

It is clear that the estimation of the amount of a particular peptide in a partial hydrolyzate may in certain cases yield considerably more information concerning the structure of the protein than its mere identification. Unfortunately it is impossible to determine directly the total amount of a particular peptide sequence in a protein molecule. Only a minimal value can be obtained from the composition of a partial hydrolyzate. In the case of the A-terminal peptides of insulin it was possible to estimate certain sequences in the protein from the yields of the peptides by allowing for the rate of breakdown of the bonds involved (p. 52). Such an approach may clearly be useful in the future where the yield of a peptide can be determined. 

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