Development of Karplus equations for 1,6-linked disaccharides
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251st American Chemical Society (ACS) National Meeting
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Oligosaccharides are biochemically very important and are associated with a multitude of processes central to disease and are equally important to the human body’s response to such disease. Structural diversity because of constitution and configuration is greater than in any other category of biomacromolecules. An additional dimension to this “sugar code” is the glycan’s conformational flexibility. The glycosidic bond geometry in glycans describes an important part of the overall oligosaccharide conformation. Conformational flexibility influences the glycans’ biochemistry and is dependent on time-averaged changes in dihedral angles across the glycosidic linkages, especially in methyleneoxy linkages. We report on experimental 1H-13C-coupling constants from J-HMBC experiments fitted to computationally derived Karplus equations of the form 3J = Acos2(θ)+Bcos(θ)+C and 3J = Acos2(θ)+Bcos(θ)+Dsin2(q)+Esin(θ)+C. Results from calculations in AMBER 08/GLYCAM 06, from statistical distributions of dihedral angles in MD-simulations, and from Gaussian ’09 single point NMR calculation of coupling constants are presented. Preliminary data showed good fit between computed and experimental coupling constants in several monosaccharides and disaccharides.