With this award, the Chemistry of Life Processes Program is funding Delmar Larsen from University of California, Davis and Wouter Hoff from Oklahoma State University to study how light is captured by living organisms and converted into biological activity. All organisms use proteins to tune their response to external stimuli but some have developed specialized proteins that are sensitive to light. An example in the human body is the protein rhodopsin, located in the eye, that absorbs light for sight and initiates a cascade of signaling events that transmit the information in that light to the brain. In this research, a protein known as Photactive Yellow Protein, or PYP, is being investigated since it has become a well-studied model for many light-initiated process involving proteins. Understanding the molecular basis for the activity of proteins is important in a fundamental sense. It is also necessary for the development of new tools by which investigators might design proteins with new functions for both biomedical use and industrial use, such as hydrogen fuel generation or waste remediation. The work has a broad impact on a wide array of fields. The investigators are further broadening the impact of their work by developing new modules for their online library ChemWiki, which is currently being used by millions of students every month enrolled in over thirty courses at multiple universities. As part of the current project, the investigators are now constructing UltraWiki and PhotoWiki that will provide new platforms for disseminating information about light-induced biological processes to both students and the general public.
Photoreceptor proteins are ideal systems to study functional protein reaction activity since they are triggered with short pulses of light, and their signaling activity may be directly followed via spectroscopic techniques. This project focuses on investigating the photoinduced reaction mechanisms underlying the conversion of photons into biological activity within novel PYP photoreceptor systems via the application of transient spectroscopic approaches. Specifically, the research is examining the photochemical and conformational changes in the PYP class of photosensors. These reaction mechanisms are being characterized through a synergistic combination of molecular biology approaches to generate novel photoreceptor systems and multipulse ultrafast spectroscopic techniques capable of resolving transient electronic, vibrational, and structural dynamics on a timescale of femtoseconds to milliseconds. Interrogation of the electronic dynamics, primarily via pump-probe or pump-dump-probe approaches, is being used to resolve inhomogeneity, excited-state and ground-state evolution, and photoproduct formation kinetics. These signals are complemented with mid-IR probing and novel dynamic Förster Resonant Energy Transfer (FRET) experiments to provide structural insight into the transient changes in molecular interactions and configuration of photoreceptors systems upon light activation.
