Matrix-assisted laser desorption ionization mass spectrometry: applications in peptide and protein characterization

Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) has quickly gained notoriety as an analytical tool that can accurately determined the molecular weight of proteins up to (and exceeding) 100 kDa from low-picomole amounts of sample. Beyond simple molecular weight determinations, investigators are developing this mass spectrometric technique to obtain more structural information from proteins using a combination of chemical and enzymatic modifications of the analyte prior to analysis by MALDI-MS. Covalent post-translational modifications such as phosphorylation and disulfide bond formation can be identified and localized. MALDI-MS also can be used to rapidly mass-map protein digests for sequence confirmation, often without requiring peptide fractionation. The potential for direct sequencing of peptides and proteins of unknown structure has been successfully demonstrated using several different MALDI-MS approaches. The objective of this report is to introduce MALDI-MS to the non-mass-spectrometrist and to describe applications of this new analytical technique for acquiring information related to peptide and protein structure.