How Nature Harvests Sunlight
Klaus Schulten, Theoretical Biophysics Group
2pm, Tuesday, March 30, 1999
Room 5602, Beckman Institute
Photosynthetic organisms fuel their metabolism with light energy and
have developed for this purpose an efficient apparatus for harvesting
sunlight that involves aggregates of hundreds of chlorophyll molecules.
The underlying physical mechanisms had been conceptually established
long ago in an interdisciplinary collaboration of US biologist Arnold and
US physicist Oppenheimer.
Recently, the atomic structure of the main protein constituent of the
apparatus, as it evolved in purple bacteria, has been solved through a
combination of modeling, x-ray crystallography and electron microscopy.
This permitted the modeling of the entire light harvesting system, a
complex nanometric aggregate of trans-membrane proteins. Spectroscopists
have resolved the underlying physical processes of light abosrption and
migration of electronic excitation at femtosecond resolution.
The seminar will show how in a still ongoing analysis an explanation,
based on quantum physics, of the extremely efficient light harvesting
function is wrestled from the atomic level structure of the aggregate.
The investigations of the light harvesting system of purple bacteria
demonstrate particularly clearly the course typical for research in
biological physics that starts from a simply stated, known function and
proceeds through experimental and theoretical investigations carried out
at more and more refined levels of molecular reality: first the
macromolecular components of the underlying system are identified and
their role characterized, e.g., through spectroscopy; then the complex
structures of these components are established at atomic resolution and
functionally relevant architectural elements are recognized; finally,
through refined observation and theoretical analyses of these elements
the physical mechanisms exploited by the organism to achieve the cellular
function are determined.
The route described had been taken in the past for single protein
systems. The seminar will demonstrate that the Theoretical Biophysics
Group, having developed at Beckman Institute since the institute's
opening in 1989 computational and conceptual tools for biological
nanomaterials, can take this route today for entire nanometric
aggregates.
(see also http://www.ks.uiuc.edu/Research/psu/psu.html)
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