Hybrid quantum/classical path integral approach for simulation of hydrogen transfer reactions in enzymes.
A hybrid quantum/classical path integral Monte Carlo (QC-PIMC) method for calculating the quantum free energy barrier for hydrogen transfer reactions in condensed phases is presented. In this approach, the classical potential of mean force along a collective reaction coordinate is calculated using umbrella sampling techniques in conjunction with molecular dynamics trajectories propagated according to a mapping potential. The quantum contribution is determined for each configuration along the classical trajectory with path integral Monte Carlo calculations in which the beads move according to an effective mapping potential. This type of path integral calculation does not utilize the centroid constraint and can lead to more efficient sampling of the relevant region of conformational space than free-particle path integral sampling. The QC-PIMC method is computationally practical for large systems because the path integral sampling for the quantum nuclei is performed separately from the classical molecular dynamics sampling of the entire system. The utility of the QC-PIMC method is illustrated by an application to hydride transfer in the enzyme dihydrofolate reductase. A comparison of this method to the quantized classical path and grid-based methods for this system is presented.
Wang
Qian
Q
Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, USA. shs@chem.psu.edu
Hammes-Schiffer
Sharon
S
D003198:Computer Simulation; D004735:Energy Transfer / Q000502:physiology*; D004798:Enzymes / Q000378:metabolism*; D006859:Hydrogen / Q000378:metabolism*; D008956:Models, Chemical; D011789:Quantum Theory
D004798:Enzymes; D006859:Hydrogen