Molecular Simulations of Dodecyl-β-maltoside Micelles in Water: Influence of the Headgroup Conformation and Force Field Parameters
Résumé
This paper deals with the development and validation of new potential parameter sets, based on the CHARMM36 and GLYCAM06 force fields, to simulate micelles of the two anomeric forms ($\alpha$ an $\beta$) of N-dodecyl-maltoside (C$_{12}$ G$_2$), a surfactant widely used in the extraction and purification of membrane proteins. In this context, properties such as size, shape, internal structure, and hydration of the C$_{12}$ G$_2$ anomer micelles were thoroughly investigated by molecular dynamics simulations and the results compared with experiments. Additional simulations were also performed with the older CHARMM22 force field for carbohydrates (Kuttel, M.; et al. J. Comput. Chem. 2002, 23, 1236-1243). We find that our CHARMM and GLYCAM parameter sets yield similar results in the case of properties related to the micelle structure but differ for other properties such as the headgroup conformation or the micelle hydration. In agreement with experiments, our results show that for all model potentials the$\beta$-C$_{12}$ G$_2$ micelles have a more pronounced ellipsoidal shape than those containing $\alpha$ anomers. The computed radius of gyration is 20.2 and 25.4 Å for the $\alpha$-and-$\beta$ anomer micelles, respectively. Finally, we show that depending on the potential the water translational diffusion of the interfacial water is 7-11.5 times slower than that of bulk water due to the entrapment of the water in the micelle crevices. This retardation is independent of the headgroup in $\alpha$- or-$\beta$ anomers.
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