Coherent Multidimensional Spectroscopy of the Oxygen Evolving Complex in Photosystem II

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, Professor Wright at University of Wisconsin continuously develops coherent multidimensional spectroscopy (CMDS) by expanding its capability of measuring molecular motions. CMDC is a spectroscopic technique to fingerprint a molecule, which helps scientists to distinguish different molecules present in complex samples. In this project, Professor Wright uses a pair of laser pulses to create specific responses from different electrons in a molecule and then follow the change of their energy levels over a very wide range of time scales. He then uses this technique to study how vitamin B12 works and how green plants use sunlight to make oxygen at the molecular level. Studying these two questions could help us to better understand how human body works and how to harness solar energy more effectively. Professor Wright also works with an instrument company on the commercialization of the CMDS technique by reducing the cost and make it easier to use by other scientists. Through this project, Professor Wright provides research opportunities to graduate, undergraduate, and secondary school students. He is also passionate about using active learning methods to prepare future STEM students for better national competitiveness and works closely with summer students from Spelman College. Professor Wright's project has two specific goals - understanding the enzymatic mechanism for vitamin B12's catalysis of ethanolamine degradation and the mechanism by which the oxygen evolving complex in photosystem II makes oxygen. The vitamin B12 mechanism serves as a model for understanding enzymatic reactions. The OEC mechanism is one of the grand challenges of chemistry, particularly for developing solar energy. For both systems, Professor Wright uses CMDS to create quantum mechanical superpositions of vibrational and electronic states that provide the selectivity and structural details required to define the mechanisms with quantum state resolution. Specifically, he is working to (1) develop a pump-CMDS probe to create a 3D spectrum; (2) to study the Co-C bond cleavage in a cobalamin-ethanolamine ammonida lyase (EAL)-ethanolamine (EA) complex to investigate the enzymatic reaction converting ethanolamine to acetaldehyde and ammonia; and (3) to characterize the electronic and vibrational states of oxygen evolving complexes (OEC) in photosystem II to understand the water oxidation mechanism. In addition, Professor Wright (1) continues his development of active learning methods in undergraduate and graduate courses; (2) works with students from Spelman College through a REU program; and (3) plans to disseminate CMDS through web site tutorials, educational materials, publications and conferences.