Glycans can decorate either proteins or lipids and serve a variety of functions from modulating extra cellular signals to mediating direct cell-cell interactions or serving as binding sites for pathogenic organisms and their toxins. In order to fully comprehend the biological roles of glycans, it is necessary to determine their structures. Several methodologies are available and each has its strengths and weaknesses. NMR spectroscopy represents the gold standard in structural elucidation since it gives the linkage and anomeric configuration of each monosaccharide. However, rarely is there enough material of sufficient purity for NMR analysis. Gas chromatography with mass spectrometric detection of partially methylated alditol acetates suffers from similar limitations. High pH anion exchange chromatography with pulsed amperometric detection gives only retention times. Mass spectrometry is playing an increasing important role in defining glycan structure. It can be applied to mixtures of glycans. The monosaccharide composition of a glycan can be deduced simply from the molecular weight of the glycan. Fragmentation of glycosidic bonds gives the branching pattern of the glycan and cross-ring cleavages yields information about linkage position. Here we request funding for an ABI QSTAR XL QqTOF mass spectrometer and MALDI source for the structural characterization of glycans and glycopeptides. This instrument will support the research aims of a diverse group of well-funded investigators with a common interest in the biological significance of glycans. The requested instrument will be housed in the UCSD Glycotechnology Core. Established 10 years ago, the Core specializes in the characterization of glycans and glycoproteins and serves glycobiologists both in the San Diego area and elsewhere. The Director (Dr. Bradley Hayes) has considerable experience using mass spectrometry. He has developed methods for determining sites of O-glycosylation using ESI mass spectrometry and has implemented methods for analyzing mixtures of permethylated glycans using MALDI-TOF mass spectrometry. He will be responsible for consulting with investigators, for implement new MS methods for the analysis of glycans, for ensuring the instrument is properly operated and cared for and for helping with the interpretation of data, as requested. Sufficient floor space and electrical service is available within the Glycotechnology Core to accommodate the requested instrument.