Phenylthiocarbamyl derivatives

Vasanits, A. and Molnar-Perl, I., Temperature, eluent flow-rate and column effects on the retention and quantitation properties of phenylthiocarbamyl derivatives of amino acids in reversed-phase high-performance liquid chromatography, J. Chromatogr., A, 832,109, 1999. 

KL Woo, QC Hwang, HS Kim. Determination of amino acids in the foods by reversed-phase high-performance liquid chromatography with a new precolumn derivative, butylthiocarbamyl amino acid, compared to the conventional phenylthiocarbamyl derivatives and ion-exchange chromatography. J Chromatogr A 740 31-40, 1996. 

The Edman degradation method for polypeptide sequence determination. The sequence is determined one amino acid at a time, starting from the amino-terminal end of the polypeptide. First the polypeptide is reacted with phenylisothiocyanate to form a polypeptidyl phenylthiocarbamyl derivative. Gentle hydrolysis releases the amino-terminal amino acid as a phenylthiohydantoin (PTH), which can be separated and detected spectrophoto-metrically. The remaining intact polypeptide, shortened by one amino acid, is then ready for further cycles of this procedure. A more sensitive reagent, dimethylaminoazobenzene isothiocyanate, can be used in place of phenylisothiocyanate. The chemistry is the same. 

End-group analysis of proteins. A method introduced by Edmarf involves selective elimination of the amino-terminal group. Reaction of this group with phenyl-isothiocyanate (a) gives the phenylthiocarbamyl derivative (b), which is cleaved... 

Lysine may also present problems because its e-amine couples with phenyl-isothiocyanate to form the e-phenylthiocarbamyl derivative, which is sensitive to any trace of peroxides in the sequencer solvents that may decrease its yield. Its chromatographic elution close to leucine frequently requires special attention to gradient conditions as well. Tryptophan, tyrosine, and methionine are sensitive to severe oxidation, although this is usually an infrequent problem, especially with the latter two. Those residues with sidechains containing only carbon and hydrogen (e.g., Ala, Val, lie. Leu, and Phe) are the most stable and are not known to present any complications from the Edman degradation procedure. 

The phenylthiocarbamyl derivative of the peptide when treated with anhydrous HCl gives the phenylthiohydantoin of the N-terminal amino add which, when treated with Ba(OH)2 in alkaline solution, liberates this terminal amino add. 

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