Electron and Proton Transfer Reactions in Photobiological H2 Production
EMSL Project ID
35410
Abstract
The biological photoproduction of hydrogen by microbial photosynthetic organism requires light as the energy source, an electron-donating substrate, and a catalyst that combines electrons and protons to generate molecular hydrogen. At the heart of this process lies electron and proton transfer reactions mediated by structural changes at femto to picosecond timescales. Although high-resolution X-ray structures of many of the protein complexes involved in photosynthesis and metabolism are available, the mechanistic details of how proton and electron transfer reactions occur at a molecular level are not well understood. Relevant time and spatial resolution are notoriously difficult to access experimentally, and therefore computational simulations are the methods of choice to investigate the relationship between electron/proton transfer rates and molecular dynamics underlying photobiological H2 production. Electron and proton transfer reactions will be studied for two constituents of oxygenic photosynthesis, hydrogenases and the photosynthetic reaction center of Blastochloris viridis. We will use electron transfer simulation methodologies based on Marcus' theory, and classical molecular dynamics simulation to sample representative molecular environments for the electron transfer between redox sites, the simulation of proton hopping using the semi-classical QHOP and QM/MM methodologies, and thermodynamic integration to evaluate relative free energies of the possible redox states of the reaction center complex and hydrogenases. Ultimately, our research aims to provide a detailed molecular-level characterization and understanding of microbial processes that may play an important role in biological light harvesting and hydrogen production. The proposed research project will take advantage of the computational chemistry software system NWChem which, in addition to a wide range of electronic structure capabilities for density functional theory and ab initio molecular orbital theory calculations, also supports molecular dynamics (MD) calculations with a variety of empirical (classical mechanical) force fields for the simulation of macromolecular and solution systems.
Project Details
Project type
Capability Research
Start Date
2009-10-01
End Date
2012-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Smith, D.M.A., Xiong, Y, Straatsma, T.P., Rosso, K.M., and Squier, T.C., Classical Force Field Development and Molecular Dynamics of [NiFe] Hydrogenase. Journal of Chemical Theory and Computation 2012 (In press. DOI: 10.1021/ct300185u)