Conformational Preferences of Glycans from the Use of 13C Chemical Shifts

GARAY, PABLO G.; MARTIN, OSVALDO A.; VILLEGAS, MYRIAM E.; SCHERAGA, HAROLD A.; VILA, JORGE A.

San Javier, Tucumán

Congreso; XLI Reunión Anual de la Sociedad Argentina de Biofísica; 2012

The addition of oligosaccharides to proteins is a significant post-translational modification that modulates protein structure and function. Glycans are vital for development in all eukaryotes and are profoundly connected to a large number of human diseases, ranging from glycan genetic diseases to auto-immune disorders and cancer. Knowledge of the three-dimensional structures of the carbohydrate molecules isindispensable for a full understanding of the molecular processes in which carbohydrates are involved, such as protein glycosylation or protein?carbohydrate interactions. Unfortunately, many carbohydratemoieties in Protein Data Bank (PDB) contain inconsistencies or errors and, hence, the need for accurate and fast validation methods to detect flaws in glycan structures appears to be crucial. Because 13C isubiquitous in glycans, this makes the 13C nucleus an attractive candidate for computation of theoretical chemical shifts at the quantum chemical level of theory in order to determine, refine and validate glycanstructures. For an accurate computation of the 13C chemical shifts in glycans, at the DFT level of theory, it is very important to determine the influence of all factors that affect the computation of the 13C-shielding,among them the density functional model and the basis set adopted. Consequently 10 density functional models and 10 basis sets will be tested here for their ability to reproduce 13C chemical shifts in glycansaccurately