The role of pH in the light-harvesting properties of PC645

Abstract

The PC645 is a pigment-protein complex that plays a key role in light harvesting algae by absorbing photons and facilitating energy transfer within the photosynthetic apparatus. In this work, we investigate the relation between pH and the light harvesting mechanisms of PC645. We perform classical molecular dynamics (MD) simulations combined with quantum/molecular mechanical polarizable (QM/MMPol) models to derive the exciton Hamiltonian of the system. Using this Hamiltonian, we compute the absorption spectrum of the complex and simulate the energy transfer dynamics between pigments. Our results reveal two effects of acidic pH: a decrease in the site energy of one of the pigments of the complex and a slower Electronic Energy Transfer (EET) rate, a parameter which quantifies how quickly energy is transferred between pigments. This preliminary work establishes the basis for future research, suggesting avenues for improvement and more advanced simulations to be performed.