9. Phenylisothiocyanate (PITC) is called Edman’s Reagent and used in sequencing proteins, an unknown decapeptide is treated with PITC and after the chemical cycle is completed, HPLC of the product shows a retension time equal to leucine. Another cycle is run and the HPLC again shows leucine as the product. a) the sequence is LLXXXXXXXX b) the sequence is XXXXXXXXLL c) the sequence is LXXXXXXXXL
a) the sequence is LLXXXXXXXX
Because the Edman degradation proceeds from the N-terminus of the protein.
Phenyl isothiocyanate is reacted with an uncharged N-terminal amino group, under mildly alkaline conditions, to form a cyclical phenylthiocarbamoyl derivative. Then, under acidic conditions, this derivative of the terminal amino acid is cleaved as a thiazolinone derivative. The thiazolinone amino acid is then selectively extracted into an organic solvent and treated with acid to form the more stable phenylthiohydantoin (PTH)- amino acid derivative that can be identified by using chromatography or electrophoresis. This procedure can then be repeated again to identify the next amino acid.
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