Abstract
Eighteen dinitrophenyl (DNP)-amino acids could be separated by reverse phase chromatography using a 20×0.6cm column (NUCLEOSIL 5C18) developed with a stepwise gradient of acetonitrile in aqueous phosphoric acid solution of pH 2.0. DNP-leucine and DNP-isoleucine could not be separated by this method, but excessive dinitroaniline and dinitrophenol formed by side reactions did not interfere with the identification of DNP-amino acids.
N-Terminal amino acids identified for the first time in this report by the micro analytical method are methionine, leucine, lysine and tyrosine for human hair, methionine, lysine and tyrosine for wool and lysine and tyrosine for silk. The above results were supported by the field desorption mass spectra of DNP-amino acids which show only molecular ions of the component DNP-amino acids. The contents of N-terminal methionine found were 0.44μg/g for human hair and 0.28μg/g for wool. N-Terminal amino acids in human hair were also quantitated after the treatments with the permanent wave lotions and the bleach. It was concluded that alkali hydrolysis of peptide bonds and/or N-terminal acetamide bonds took place during the both treatments.
