title: Conformation dynamics and polarization effect of α,α-trehalose in a vacuum and in aqueous and salt solutions.
abstract: Conformational changes of α,α-trehalose in a vacuum, water, and 0-20 wt % NaCl solutions were investigated by means of molecular dynamics (MD) simulations at different levels of density function theory (DFT) and with fixed-charge nonpolarizable and variable-charge force fields (FFs), respectively. The relative thermodynamic stability of trehalose is enhanced by the formation of intercycle and/or intracycle hydrogen bonds, but some thermodynamically unfavorable structures can be sampled in the DFT-based ab initio MD simulation. The polarization effects of polar trehalose molecule in aqueous and NaCl solutions were studied by a series of MD simulations with both the conventional nonpolarizable and polarizable force field models. In the polarizable model, the partial charges of trehalose were updated every 2 ps using DFT calculations and fused with the other FF parameters for the energy calculation and MD simulation. Around the trehalose, water molecules located in an asymmetry model and trehalose have a stronger tendency to bind with water molecules than Na(+) and Cl(-) ions. When the trehalose concentration is increased from 3.26 to 6.31 wt % in salt aqueous solution, the two trehalose molecules periodically approach each other in a nearly anhydrate state and leave a way to keep the favorable hydration structure with the mean trehalose-trehalose distance of 8.6 Å. The similarity between the solvated dimer packing styles (shoulder-by-shoulder or head-to-head) and crystal stacking can be used to make an extrapolation to higher sugar concentrations and to rationalize the bioprotection function of trehalose in high salt concentration.
authors.affiliation: School of Chemistry and Chemical Engineering, Key Laboratory of Mesoscopic Chemistry of MOE, Nanjing University , Nanjing 210093, People's Republic of China.
authors.forename: Zigui
authors.initials: Z
authors.lastname: Kan
authors.forename: Xiufen
authors.initials: X
authors.lastname: Yan
authors.forename: Jing
authors.initials: J
authors.lastname: Ma
mesh_terms: D008968:Molecular Conformation; D056004:Molecular Dynamics Simulation; D012965:Sodium Chloride / Q000737:chemistry*; D012996:Solutions; D014199:Trehalose / Q000737:chemistry*; D014618:Vacuum; D014867:Water / Q000737:chemistry
chemical_list: D012996:Solutions; D014867:Water; D012965:Sodium Chloride; D014199:Trehalose