Evolution of Algal Light Harvesting Proteins & the Emergence of Coherent Beats: Does Quantum Mechanics Play a Role in Biology?

Professor Paul Curmi

School of Physics, University of New South Wales, Sydney

Thursday, 28 November 2013, 11:00 am
EN515 Lecture Theatre (EN Building), Hawthorn

Abstract:
A key unanswered question in molecular biophysics is whether quantum phenomena play a non-trivial role in biology.  If they do, then one would assume that they are under the control of evolution and natural selection.  Most processes in molecular biology occur on time and length scales where classical physics is sufficient to explain the underlying mechanisms.  One exception to this is light harvesting and photosynthetic energy transduction.
The first hints that quantum phenomena may be involved in photosynthesis came from the study of aquatic organisms that live under low light environments.  These organisms have evolved elaborate light harvesting antennae that can efficiently capture photons and transfer the energy to the photosystem reaction centre with high photon efficiencies (>90%). Two-dimensional electronic spectroscopy (2DES) studies of several different light harvesting proteins have shown the existence of long-lived (~500 fs) quantum beats under near physiological conditions.
We have characterized a series of light harvesting proteins from single-celled algae (the crptophytes) by x-ray crystallography.  These proteins display a rich evolutionary history that includes several dramatic structural changes in the light harvesting proteins.  These changes have affected the characteristics of the 2DES.  Thus it appears that evolution through genetic mutation is controlling the organism’s ability to access quantum phenomena in optimizing photosynthetic processes.

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