DESCRIPTION: MALDI mass spectrometry has become one of the two important methods driving the application of mass spectrometry in biochemistry. A problem that stands in the way of broad application is the extensive metastable-ion decay exhibited by some molecules. This is a particular problem when a class of molecules has one or more labile groups that undergo reactions with significantly lower fragmentation barriers than those for analytically useful fragmentations. An example is the loss of water, for which there is little information content. The problem is made worse when a mixture is encountered. The composite fragmentation is difficult, if not impossible, to assign. A promising development to overcome this limitation is to initiate the desorption process in the presence of a bath gas. This idea will be pursued for the analysis of samples containing oligosaccharides, glyco and phosphopeptides, sialylated glycolipids, sulfated oligosaccharides, and peptides containing oxidized cysteine residues. Many of these samples are of interest to collaborators of the BU research resource.