Plasma desorption mass spectrometry of natural and recombinant peptides and proteins.

Plasma desorption mass spectrometry (PDMS), which utilizes the fission fragments from the spontaneous decay of californium-252 to ionize large biomolecules, has emerged as a powerful analytical tool in the field of protein chemistry. Because of its high mass range and sensitivity, PDMS is an excellent method for direct molecular weight determination of peptides and small proteins, with much better accuracy than that of the most commonly used classical methods of gel permeation chromatography or SDS-gel electrophoresis. Furthermore, PDMS analysis of the peptide mixture resulting from a specific enzymatic or chemical cleavage of the protein, allows rapid and facile checking of DNA-derived protein sequences and protein structures produced by recombinant DNA technology. The relatively nondestructive nature of the PD mass spectrometric analysis allows further confirmation of the sequence assignments of individual peptide fragments through additional chemical or enzymatic reactions on the PDMS matrix-bound peptides. This PD mapping approach, combined with classical gas phase sequencing, can be used to identify and locate post-translational modifications in proteins, such as glycosylation, phosphorylation, disulfide linkages, and also detect the presence of peptide and protein variants in synthetic, native and recombinant peptides and proteins.