Vernon Reinhold University of New Hampshire, Durham, NH Office: 603-862-2527 FAX: 603-862-4278 E-mail: vernon.reinhold@unh.edu Job Title: Director, Center for Structural Biology Ph.D. in Biochemistry from the University of Vermont

Speaker: Vernon Reinhold, Department of Chemistry, University of New Hampshire, Durham, NH

Topic: The Details of Carbohydrate Structure by MSⁿ; Sequencing with Contiguous Glycan Segments (CGS), and Bioinformatics

Place: Building 549, Auditorium, NCI at Frederick, Frederick, MD

Time: Wednesday, October 20, 2004, at 10:00 AM

Abstract: Comprehensive structural details of monomers, anomers, inter-residue linkage, and branching are observed in spectra of small methylated oligosaccharides as products of gas-phase MSn disassembly. These details are a feature of 1,2-dehydroglycans (DHG), a common CID gas-phase product ion of glycosidic bond rupture. These fragments increased with decreasing oligomer size, (consistent with the quasi-equilibrium theory and number of oscillators), exposing stereochemical differences, and all the structure features essential for organic synthesis. A set of carbohydrate monomers and dimers have been studied with variations in equatorial and axial positions. These samples were easily characterized by CID with significant mass and abundance differences. Sodium chelation appears to account for this stereo specificity, a conjecture supported by minimal energy modeling studies. Larger oligomers disassembled to identical products yield indistinguishable spectra, even though disassembled by different MSn pathways. This basic feature documents the iso-energetic character of products essential for building a library of finger-print segments currently underway. Glycans released from porcine submaxillary mucin (PSM) were chosen to demonstrate comprehensive sequencing when guided by this library of segments and products. Fundamental aspects of this sequencing strategy were methylation, (which defines topology limits), positive ion extraction of sodiated precursors, (which imparts stereochemical selectivity upon CID), MSn that exposes sequence continuity, and a searchable library of segments, (aids and confirms accurate glycan reassembly). Glycans were profiled by MALDI and/or ESI mass spectrometry in both linear and Paul traps (MSn). Molecular isobars were readily detected when spectra failed to match library standards. In this manner four isobars were identified.