Conformational free energy maps for globobiose (α-d-Galp-(1→4)-β-d-Galp) in implicit and explict aqueous solution

Four Ramachandran maps of the conformational potential of mean force (PMF) for the galactose disaccharide globobiose (α-d-Galp-(1→4)-β-d-Galp) were calculated in vacuum, explicit water, with a simple high dielectric constant and a distance-dependent dielectric coefficient, respectively. This simple model of the galactan α-(1→4)-linkage is shown to be conformationally restricted, with only a small range of syn-ϕ/syn-ψ conformations predominating at standard temperature and pressure. This has implications for the preferred conformation and chain dynamics of α-galactosides. In addition, comparison of the relevant PMF surfaces reveals the substitution of a high dielectric constant for explicit water solution to be a valid approximation for reproducing the minimum energy conformation of this glycosidic linkage.

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