"Quantum Mechanics and Biology: Elucidating Design Principles of Photosynthetic Energy Transfer"
Presented by Greg Engel, University of Chicago
Hosted by Wei Min
Thursday, October 24, 2013
1:30 - Meet the Speaker, Room 328 Havemeyer
4:00 - Tea & Cookies, Room 328 Havemeyer
4:30 - Seminar, Room 209 Havemeyer
Photosynthetic
antenna complexes harvest light with near perfect quantum efficiency
and steer excitonic motion with exquisite precision. Optimized by
evolution, these complexes exploit both incoherent (Förster) energy
transfer along with coherent (wavelike) motion of energy. We seek to
isolate and copy the microscopic details of this mechanism to enable
coherent energy transfer in synthetic systems. The talk will show
evidence for long-lived quantum coherence in photosynthetic complexes
along with new spectroscopic techniques to probe these effects. For
example, we have created a new femtosecond optical spectroscopy by
exploiting spatiotemporal gradients to image the underlying excited
state dynamics within photosynthetic antenna complexes. From our 2D
electronic spectra, we find a strong and unexpected mixing between
states of the chromophores and some bath modes within the system. At
the end of the talk, three new results will be discussed. First, a new
theoretical model using non-equilibrium Green’s functions will be
presented; this model demonstrates that the coherences observed in time
domain spectroscopy report on underlying physics with direct
implications for light harvesting under incoherent excitation. Second,
new results will be shown demonstrating that long-lived coherence can be
engineered into a family of novel synthetic small molecules using the
insights extracted from the photosynthetic work. Finally, evidence for
sequence-specific dephasing rates will be demonstrated with single amino
acid substitutions lending credence to hypotheses of evolutionary
fine-tuning of quantum dynamics in photosynthetic complexes.
