Abstract: A protein micro sequencing method for use in conjunction with the thiocylation degradation of polypeptides and proteins is disclosed. The process involves reaction of the N-terminal amino acid of a polypeptide with an excess of a thioacylating reagent. After sufficient time to insure quantitative coupling and removal of excess reagent, the derivatized polypeptide is subjected to cleavage by acid which affords a 2-substituted-5(4H)-thiazolinone. After removal of excess acid, the thiazolinone is reacted with a small excess of a fluorescent or enhanced ultraviolet absorbance reagent having a reactive carboxylic acid chloride, sulfonic acid chloride, chloroformate, isocyanate or anhydride functionality, in the presence of a tertiary amine catalyst, to yield the corresponding 5-O-acyl-2-(substituted)thiazole derivative, detectible by enhanced ultravoilet absorobance or fluorescence emission at extremely low concentration thereby providing a method of sequencing very small amounts of protein.