Krzysztof KuczeraKrzysztof Kuczera
Professor, Chemistry and Molecular Biosciences
University of Kansas



Fast processes in optogenetic systems: Experiments and modeling (2017-18)

Optogenetics refers to the control of cellular processes via genetic encoding of light-sensitive elements, such as chromophoric proteins. Recent advances in this field have led to exciting progress in neurobiology, with improved understanding of synaptic protein defects, modulation of cardiovascular function, breathing and blood pressure control, depression and addiction. The success of optogenetics rests on finely crafted molecular systems.

The long-term goal of this project is the design of new and improved optogenetic tools, in order to expand the scope of neurological research and disease treatment. The general principles of optogenetics, including cycles of spectroscopic and long-term conformational change, are largely well understood. However, advances in optogenetics require controlling of optical properties. These features are dictated by the atomic-level details of the earliest processes, knowledge of which is only beginning to emerge. In particular, a description of the chromophore excited states in the protein environment and the microscopic paths of energy flow and structural changes in protein-chromophore systems are needed.

The goal of this pilot project is to understand the early stages of light-induced signal transduction in a model system, the phytochrome from Deinococcus radiodurans (drBphP). This system exhibits near-infrared absorption and utilizes the biliverdin chromophore, which is advantageous for mammalian cell applications. We propose interdisciplinary, collaborative studies joining novel experiments and computational modeling with quantum and classical methods. The specific aims are: (1) To perform classical molecular dynamics to model energy flow and structural change and quantum calculations to describe influence on protein matrix on electronic energy levels and (2) to employ novel ultra-fast spectroscopic studies to characterize basic structural and energetic features of the phytochrome-biliverdin system. The role of crucial residues identified by modeling will be verified by design and spectroscopic characterization of mutant proteins. Through combination of results from our interdisciplinary studies, an improved understanding of the microscopic mechanism of light energy transduction in drBphP will be gained. Identification of crucial residues for early stages of photoexcitation, energy flow and conformational change will provide the basis for rational design of drBphP mutants with tailored time response and wavelength sensitivity, for applications in neurobiology and other biomedical areas.