Professor Holten’s research interests include the initial reactions of photosynthesis and studies of tetrapyrrole chromophores and arrays. The goal of his lab's photosynthesis research is to achieve a molecular-level understanding of charge separation in the bacterial reaction center.
In this pigment-protein complex, light energy is converted into chemical potential energy by a series of fast electron transfers across the membrane from the photoexcited bacteriochlorophyll special dimer along a chain of electron acceptors on the photoactive A-branch with a quantum yield of ~1. His lab is studying mutants to (1) probe the contributions of energetics versus electronic interactions to the directionality of electron transfer, (2) modulate the rate constants and yields of charge separation versus recombination at each step on both branches, and (3) give electron transfer fully down the normally inactive B branch. Their studies of tetrapyrrole chromophores (porphyrin, chlorin, bacteriochlorin) chromophores are aimed at elucidating the fundamental interplay between molecular composition, electronic structure, and photophysical properties. These properties include absorption and emission spectra and the rate constants and yields of the singlet excited-state decay pathways (fluorescence, internal conversion, intersystem crossing). Studies of multichromophore arrays probe fundamental aspects of energy and electron transfer and include design and characterization of biohybrid light-harvesting architectures that integrate designer chromophores with native-like peptide scaffolds to enhance solar coverage.
