GlycoMod - A software tool for determining glycosylation compositions frommass spectrometric data

GlycoMod (http://www.expasy.ch/tools/glycomod/) is a software tool designed to find all possible compositions of a glycan structure from its experimen tally determined mass. The program can be used to predict the composition o f any glycoprotein-derived oligosaccharide comprised of either underivatise d, methylated or acetylated monosaccharides, or with a derivatised reducing terminus. The composition of a glycan attached to a peptide can be compute d if the sequence or mass of the peptide is known. In addition, if the prot ein is known and is contained in the SWISS-PROT or TrEMBL databases, the pr ogram will match the experimentally determined masses against all the predi cted protease-produced peptides (including any post-translational modificat ions annotated in these databases) which have the potential to be glycosyla ted with either N- or O-linked oligosaccharides. Since many possible glycan compositions can be generated from the same mass, the program can apply co mpositional constraints to the output if the user supplies either known or suspected monosaccharide constituents. Furthermore, known oligosaccharide s tructural constraints on monosaccharide composition are also incorporated i nto the program to limit the output.