Characterization of the primary thermal degradation processes of peptides using the mass spectrometric technique K(+)IDS, K (+) ionization of desorbed species.

The mass spectrometric technique of K(+) ionization of desorbed species, K(+)IDS, is used here to characterize the primary thermal degradation chemistry of small peptides. In this technique, a small amount of a compound is rapidly heated in the condensed phase. Desorption of the intact molecule can occur. Also, thermal degradation products are formed which quickly desorb as well, rather than remain on the surface and undergo subsequent chemistry. The desorbed molecules form adducts with gas phase K(+) ions, and a mass spectrum is obtained. Deuterium labeling experiments, and the use of derivatizing reagents, allows for the thermal degradation chemistry of small peptides to be elucidated. Apparently, skeletal bond cleavages are accompanied by H-shifts, although the hydrogen atoms shift from "remote" sites, brought into close proximity with the fragmenting skeletal bond via secondary interactions. Experimental results are presented that allow for correlations between thermal degradation chemistry and the resulting K(+)IDS mass spectra to be made.