Hydrogen Bonds in GlcNAc( β1,3)Gal( β)OMe in DMSO Studied by NMR Spectroscopy and Molecular Dynamics Simulations

Abstract

IDRTech Inc., 461-6 Jeonmin-dong, Yusung-gu, Daejeon 305-390, KoreaReceived October 29, 2003Hydrogen bond is an important factor in the structures of carbohydrates. B ecause of great strength, short range,and strong angular dependence, hydrogen bonding is an important factor stabilizing the structure ofcarbohydrate. In this study, conformational properties and the hydrogen bonds in GlcNAc( β1,3)Gal(β)OMe inDMSO are investigated through NMR spectroscopy and molecular dynamics simulation. Lowest energystructure in the adiabatic energy map was utilized as an initial structure for the molecular dynamics simulationsin DMSO. NOEs, temperature coefficients, SIMPLE NMR data, and molecular dynamics simulations provedthat there is a strong intramolecular hydrogen bond between O7' and HO3' in GlcNAc(β1,3)Gal(β)OMe inDMSO. In aqueous solution, water molecule makes intermolecular hydrogen bonds with the disaccharides andthere was no intramolecular hydrogen bonds in water. Since DMSO molecule is too big to be inserted deep intoGlcNAc(β1,3)Gal(β)OMe, DMSO can not make strong intermolecular hydrogen bonding with carbohydrateand increases the ability of O7' in GlcNAc( β1,3)Gal(β)OMe to participate in intramolecular hydrogen bonding.Molecular dynamics simulation in conjunction with NMR experiments proves to be efficient way to investigatethe intramolecular hydrogen bonding existed in carbohydrate.Key Words : GlcNAc(β1,3)Gal(β)OMe, NMR spectroscopy, SIMPLE NMR, Molecular dynamics simula-tion, Hydrogen bondIntroductionNMR is a good method to obtain structural data ofcarbohydrate in solution where motional variations are lessrestricted than in crystals. Also, in many cases, the crystalstructures of carbohydrates are not available. However,because of severe spectral overlaps, NMR experiments donot provide enough NOE distance constraints to allow acomplete structure determination of carbohydrates.