Plasma desorption mass spectrometry, an analytical tool in protein engineering: characterization of modified insulins.

Californium-252 plasma desorption mass spectrometry (PDMS) has been employed for the characterization of a series of human insulin derivatives in order to evaluate the performance of this technique as an analytical tool in protein engineering. Several of the characterized modifications result in a 1 a.m.u. mass change. The precision in mass determination obtainable by PDMS analysis is not sufficient for unambiguous verification of such modifications based on the molecular weight alone. It is, however, possible to carry out in situ enzymatic digestion of the sample. Subsequent PDMS analysis will in most cases reveal if the modification has been introduced as intended.