Hydrophobic interactions in urea-trimethylamine-N-oxide solutions.
The influence of osmolytes urea and trimethylamine- N-oxide (TMAO) on hydrophobic interactions is investigated employing molecular dynamics simulations. These osmolytes are of interest because of their opposing influence on proteins in solution; the denaturing effect of urea can be countered with TMAO. A neopentane pair is used to model typical nonpolar entities. Binary water-urea and water-TMAO as well as ternary water-urea-TMAO systems are considered. Neopentane-neopentane potentials of mean force, neopentane-water, and neopentane-osmolyte distribution functions are reported. Urea is found to have only modest influence on the neopentane-neopentane potential of mean force, but the hydrophobic attraction is completely destroyed by the presence of TMAO. It is shown that TMAO tends to act as a simple "surfactant" displacing water and urea (if it is present) from the first solvation shell of neopentane. It is likely the surfactant-like influence of TMAO that accounts for the elimination of the hydrophobic attraction. The implications of our results for explanations of the action of TMAO in protein solutions are discussed.
Paul
Sandip
S
Department of Chemistry, University of British Columbia, Vancouver BC V6T 1Z1, Canada.
Patey
G N
GN
D057927:Hydrophobic and Hydrophilic Interactions; D008744:Methylamines / Q000737:chemistry*; D010420:Pentanes / Q000737:chemistry; D012996:Solutions; D013501:Surface-Active Agents / Q000737:chemistry; D013696:Temperature; D014508:Urea / Q000737:chemistry*
D008744:Methylamines; D010420:Pentanes; D012996:Solutions; D013501:Surface-Active Agents; D014508:Urea; C005855:trimethyloxamine; C039752:neopentane