Tuesday, 11:00 am Room 1315 January 31, 2017 Chemistry Building

Professor Peng Chen Department of Chemistry

Cornell University

Host: Professor Randy Goldsmith

Refreshments will be available prior to the seminar at 10:45 a.m. outside room 1315

Graduate Students can meet with the speaker in Room 8305F at 1:00 pm

Single-molecule chemistry: from solar energy conversion to transcription regulation

I will present two stories that use single-molecule fluorescence imaging to interrogate the mechanism and dynamics of chemical and biological processes. In the first story, I will present our work in using redox-selective super-resolution reaction imaging and sub-particle photocurrent measurements to determine the relation between charge-carrier surface activity and water oxidation efficiency on a semiconductor photoanode during photoelectrochemical water oxidation. We determine that on a semiconductor nanostructure, how much the sites reactive for water oxidation also contribute to recombination, and how the photocurrent efficiency and onset potential are correlated at the nanoscale. Guided by hole and electron reactivity maps, site-selective catalyst deposition on individual nanorods reveals the optimal sites for oxygen evolution catalysts, leading to a strategy for rationally engineering photoelectrodes with catalysts. In the second story, I will present our work in using super-resolution single-molecule tracking to study transcription regulation in living cells. Binding and unbinding of transcription regulators on chromosome constitute a primary mechanism for gene regulation. While many cellular factors are known to regulate their binding, little is known on how cells can modulate their unbinding for regulation. I will describe that two metal-sensing transcription regulators show unusual concentration and chromosome-conformation dependent unbinding kinetics in bacterial cells, which provide novel mechanisms for facile switching between transcription activation and deactivation in vivo and in coordinating transcription regulation of resistance genes with the cell cycle