A Multifaceted Strategy for the Characterization of Recombinant gD-2, a Potential Herpes Vaccine

Abstract

Any number of individual mass spectrometric techniques may be used alone to characterize a protein, but the availability of several techniques in the same laboratory together with the use of a broad array of proteases and glycosidases and sophisticated data processing tools greatly facilitates the characterization process. The advent of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS, henceforth referred to as MALDIMS), with its high sensitivity and tolerance for a broad range of excipients (e. g., 50 mM phosphate, 100 mM Tris, 1M guanidine, 0.1% detergent, 0.01% SDS, 1 M alkali metal salts, 1% glycerol, 1 mM sodium azide) provides a tool for rapid screening of digests with little or no sample cleanup required [1, 2]. Such a tool can be useful for monitoring digestion conditions to find the most appropriate strategy for the protein of interest while consuming only a few picomoles of sample. MALDI can also provide a preliminary indication of the presence of posttranslational modifications based on mass shifts or, in the case of typically heterogeneous glycosylation, based on increased peak widths. After isolating glycopeptides as described below, it is possible to rapidly determine aspects of the carbohydrate structure by MALDI, using combinations of glycosidases on only a few picomoles of material [3].