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- Title
Conformation of glycosaminoglycans by ion mobility mass spectrometry.
- Authors
Lan Jin; Barran, Perdita E.; Lyon, Malcolm; Uhrín, Dušan
- Abstract
Glycosaminogycans (GAGs) are polysaccharides found on most animal cell surfaces and extracellular matrices. They constitute an important class of biologically active macromolecules that are implicated in the biological activity of morphogens, growth factors, cytokines, chemokines and enzymes. Intervention in signalling pathways they are involved in, represents a valuable therapeutical opportunity for cancer treatment, wound healing and specific organ regeneration. GAGs are linear polysaccharides with alternating uronic acid and hexosamine residues. Their polysaccharide precursors are extensively modified (epimerization, N-deacetylation N-, O-sulfation) creating a wide heterogeneity to their structures. The binding specificity of GAGs is encoded in their primary structures but ultimately depends on how this basis set of functional groups is presented to a protein in three-dimensional space. As a part of our efforts to characterize the conformation of GAGs, we present here our preliminary results of conformational studies of heparin-derived oligosaccharides by ion mobility mass spectrometry. This MS technique is designed to study conformation of mass-selected gas-phase ions. When ions drift through an inert gas under the influence of a weak electric field, their arrival time depends on their collisional cross sections. From this data, the experimental cross sectional areas are easily derived. These are then compared with those obtained from candidate geometries generated from molecular modelling, and hence conformation(s) of studied compounds can be determined. We have measured the cross sectional areas of four heparin oligosaccharides: one disaccharide and three tetrasaccharides. Amongst these are two fully sulfated species and also two tetrasaccharides each with one sulfate group missing. Our samples were prepared by enzymatic digestion of heparin and contain a nonreducing terminal unsaturated glycosyluronic acid ring. We employ the GLYCAM 2000 force field (Woods) and the AMBER ( ) suite of programs to model the gas-phase conformations of the oligosaccharides. We have generated AMBER parameters for sulfate groups using ab initio calculations and are in the process of generating structures for which we calculate the cross sectional areas using a projection approximation ( ). We present a comparison of experimental cross sections with those of calculated models. We also compare them with cross sections calculated using oligosaccharide fragments extracted from X-ray and NMR structures of heparin oligosaccharides – protein complexes.
- Subjects
GLYCOSAMINOGLYCANS; MUCOPOLYSACCHARIDES; CELL membranes; GROWTH factors; OLIGOSACCHARIDES; MASS spectrometry
- Publication
International Journal of Experimental Pathology, 2004, Vol 85, Issue 4, pA68
- ISSN
0959-9673
- Publication type
Abstract
- DOI
10.1111/j.0959-9673.2004.390ae.x