Plasma desorption mass spectrometry (PDMS) (1 ) is a method for the mol-wt determination of peptides and small proteins. The upper mass limit is, in optimal cases, approx 30 kDa, with a precision of about 0.1%. This precision far exceeds that of classical biochemical methods, such as SDS-gel electrophoresis or gel permeation chromatography. The molecular weights determined by PDMS depend only on the atomic composition of the molecule and not, as in other methods, on extraneous properties, such as hydrophobicity or shape.
