Direct monitoring of sequential enzymatic hydrolysis of peptides by thermospray mass spectrometry.

A procedure for peptide sequencing using an immobilized exopeptidase column directly coupled to a thermospray mass spectrometer is described. The amino acids sequentially released from the C-terminus of the peptide chain are directly introduced into a thermospray ion source by a flowing aqueous buffer. The buffer is essential for the direct production of ions from solution. The method eliminates the need to derivatize the amino acids for detection and, by comparison to standard injections, amino acid sequence information can be obtained in less than two minutes. With the present configuration, detection limits are typically in the low picomolar range.