Comparing simulated and experimental translation and rotation constants: range of validity for viscosity scaling.

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TitleComparing simulated and experimental translation and rotation constants: range of validity for viscosity scaling.
Publication TypeJournal Article
Year of Publication2010
AuthorsVenable, RM, Hatcher, E, Guvench, O, Mackerell, AD, Pastor, RW
JournalJ Phys Chem B
Volume114
Issue39
Pagination12501-7
Date Published2010 Oct 07
ISSN1520-5207
KeywordsDiffusion, Glucose, Maltose, Models, Molecular, Rotation, Trehalose, Viscosity, Water
Abstract

Proper simulation of dynamic properties, including molecular diffusion, is an important goal of empirical force fields. However, the widely used TIP3P water model does not reproduce the experimental viscosity of water. Consequently, scaling of simulated diffusion constants of solutes in aqueous solutions is required to effectively compare them with experiment. It is proposed that scaling by the ratio of viscosities of model and real water is appropriate in the regime where the concentration dependence of simulated and experimental solution viscosities is parallel. With this ansatz, viscosity scaling can be carried out for glucose and trehalose up to 20 wt % for simulations carried out with the CHARMM additive carbohydrate force field C35 and TIP3P water; above this value, the concentration dependence of simulated viscosities lags that of experiment, and scaling is not advised. Scaled translational diffusion constants for glucose and the disaccharides trehalose, maltose, and melibiose at low concentration agree nearly quantitatively with experiment, as do NMR (13)C T(1)'s for glucose, trehalose, and maltose; these results support the use of C35 for simulations of sugar transport properties at low concentration. At high concentrations the scaled diffusion constants for glucose and trehalose underestimate and overestimate experiment, respectively. Hydrodynamic bead model calculations indicate a hydration level of approximately 1 water/hydroxyl for glucose. Patterns for the disaccharides are more complicated, though trehalose binds 0.5 to 1 more water than does maltose depending on the analysis.

DOI10.1021/jp105549s
Alternate JournalJ Phys Chem B
PubMed ID20831149
PubMed Central IDPMC3040444
Grant ListR01 GM070855 / GM / NIGMS NIH HHS / United States
GM070855 / GM / NIGMS NIH HHS / United States
/ / Intramural NIH HHS / United States