[MOS] TODAY - Modern Optics and Spectroscopy Seminar with Ray Moya (MIT - Schlau-Cohen Group)

[Christine Brooks]

There will be a virtual Modern Optics and Spectroscopy Seminar held today at 12pm. A Q&A segment will immediately follow the conclusion of the seminar.

Zoom link: https://mit.zoom.us/j/97689516052?pwd=K1d2YTlGcHNVSnpZNDRlRFE1akdzUT09
Password: 555033
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Ray Moya
MIT – Schlau-Cohen Group

“Heterogeneous Ultrafast Energy Transfer in Single Photosynthetic Proteins”

In photosynthesis, solar energy capture to conversion occurs with a remarkable near-unity quantum efficiency despite thermally-driven protein fluctuations. These fluctuations are predicted to produce sub-optimal energy transfer rates and thereby decrease overall efficiency. Understanding how high efficiency is maintained despite these fluctuations is a requisite for identifying fundamental design principles for robust light-harvesting devices. Furthermore, the knowledge of the distribution of energy transfer rates arising from protein fluctuations is crucial to understanding the high efficiency in photosynthetic organisms. Herein, we report the further development of a novel technique, single-molecule pump-probe spectroscopy, which utilizes a pump-probe like excitation into a confocal microscope to report femto- to picosecond dynamics into the fluorescence emission of single molecules. This technique directly measures the distribution of energy transfer rates of single molecules, uncovering the variation in rates that underlies the high quantum efficiency of photosynthetic light harvesting.  Specifically, our home-built apparatus reveals the distribution of ultrafast dynamics in two individual photosynthetic light-harvesting subunits from cyanobacteria, allophycocyanin and c-phycocyanin. Broad distributions of energetic relaxation timescales were observed for both subunits and previous single-molecule experiments help to disentangle the contributions from vibrational relaxation and excitation energy transfer. Taken together, these results suggest that the heterogeneous protein environment has little impact on the timescales of energy transfer, a prerequisite for efficient light harvesting.


Christine Brooks
Administrative Assistant
Massachusetts Institute of Technology
Department of Chemistry
77 Massachusetts Ave, 6-333
Cambridge, MA 02139
p: 617.253.7239
e: cbrooks at mit.edu<mailto:cbrooks at mit.edu>

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