Computational Investigation of the Oxygen Evolving Complex of Photosystem II and Related Models via Density Functional Theory

Abstract

The first step of photosynthetic metabolism effects the facile oxidation of water to dioxygen and hydrogen cations. This is achieved through an incompletely-understood process of light-driven four-electron oxidation at the Mn4CaO5 cofactor of the Oxygen Evolving Complex (OEC) of the Photosystem II (PSII) holoenzymatic complex in photosynthetic autotrophs. Biomimesis of this reaction—artificial photosynthesis—may offer energy-efficient routes to industrial hydrogen generation and value-added derivatives, with implications for solar energy fixation. This thesis consists of a compilation of four publications relating to Density Functional Theory (DFT) studies of structural and spectroscopic aspects of the OEC of PSII. These publications consist of research resolving the basis of structural anomalies in metal-substituted PSII, combinatoric simulation of difference spectra corresponding to proton-coupled oxido-reduction scenarios of PSII models, simulation of the hyperfine and superexchange magnetic interactions in PSII models, and the development of a methodology for obtaining vibrational intensities in the Mobiel Block Hessian (MBH) approximation, with applications to accelerated modeling of the vibrational structure of complex models of PSII, as well as other large molecules. These publications are presented alongside explanatory introductions and preceded by a general survey of the state of the art of photosynthesis research, context for the relevance of this research, and methodological discussion. Concluding remarks are also presented.