Bacterial Reaction Centers with New Photochemical Properties

Arizona State University, Scottsdale AZ

Investigators

Abstract

With the support of the Chemistry of Life Processes (CLP) program in the Division of Chemistry, Professor James Allen and Dr. JoAnn Williams of Arizona State University are studying how fundamental biological processes such as respiration and photosynthesis depend on the controlled transfer of protons and electrons in protein complexes. The project is directed towards creating reversible, long-lived electron and proton transfer reactions that mimic the properties of biological processes. An experimental framework will be developed that characterizes proteins modified to gain the capacity to perform proton-coupled electron transfer reactions. Identification of critical interactions among components would aid in predictive algorithms for the management of protons and the accompanying electrons. This convergence of molecular tools should support development of new strategies for the design of proteins. The biochemical expertise of the investigators will be applied to the educational goal of increasing participation in undergraduate research through development of a course that offers a research experience to online students. Because multiple students will be working together in the laboratory course, this powerful and scalable strategy will provide large numbers of students with transferable skills through an enhanced undergraduate experience. Towards understanding the properties of proton-coupled electron transfer processes in biological reactions, this research project seeks to investigate how proteins control these reactions. The experimental approach will involve manipulating bacterial reaction centers, the site of the primary photochemistry in photosynthesis, to contain a four-helix bundle domain that can bind an array of synthetic porphyrins. The unique synthetic compounds include porphyrins with benzimidazole phenol substituents capable of both electron and proton transfer. The four-helix bundle allows probing of the impact of the inhomogeneous protein environment on biological proton transfer. The reaction center provides a light-induced driving force with a range of redox potentials. Modeling of the dependence of the electron and proton transfer rates on the redox properties of the cofactors in the hybrid complex seeks to determine critical parameters concerning the mechanisms. The outcomes should yield new experimental approaches for the design of proteins capable of proton-coupled electron transfer reactions. This project has a goal of increasing the exposure of nontraditional students to scientific research methodology. The proposed approach is to offer a Course-based Undergraduate Research Experience (CURE) that is targeted at the online student population. The course will be supported by a national network of faculty dedicated to using CUREs to engage biochemistry undergraduates in research experiences. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.