MMC and LD simulations of alpha-D-Manp-(1-->2)-beta-D-Glcp-OMe: comparison to long-range heteronuclear NMR coupling constants and to the crystal structure.

Abstract

The conformational flexibility and the dynamics of alpha-D-Manp(1-->2)-beta-D-Glcp-OMe have been investigated by Metropolis Monte Carlo (MMC) and Langevin dynamics (LD) simulations. The two simulation techniques employ different force fields, namely the HSEA force field and a CHARMm-based force field. The former shows less conformational flexibility than the latter, in which a multiple energy minima conformational space is sampled. Long-range heteronuclear nuclear magnetic resonance (NMR) coupling constants have been measured by selective excitations of the carbons at the glycosidic linkage. Calculated 3J(C,H) values from MMC and LD simulations show excellent agreement to those from NMR experiments. The X-ray crystal structure has a conformation within a region of the conformational space populated in both force fields.