PHYSICS AND ASTRONOMY COLLOQUIUM
		      Tuesday, October 25, 2001
		   Room 118 Physics-Astronomy Bldg.
			     4:10 p.m.
		Refreshments at 3:45 p.m. - Room 224 PA


                             Steven Chu
                         Stanford University
                     1997 Nobel Prize in Physics

                "Biology at the Single Molecule Level"

ABSTRACT

Virtually all knowledge of chemical and biochemical processes has been deduced
from ensemble measurements. This has led us to think of molecular processes as
well-ordered sets of events. However, biological processes are not so simple:
many of these reactions involve multiple kinetic paths and transient
intermediate states.  Single molecule measurements allow one to look beyond the
ensemble average and measure the behavior of individual molecules. The ability
to record the current changes in a single ion channel revolutionized the study
of ion transport in cellular membranes. Our polymer studies using DNA have
fundamentally altered our thinking of polymer dynamics by showing that
identical molecules placed under identical conditions take several distinct
paths to a new equilibrium state.  We have been applying fluorescence resonance
energy transfer (FRET) to study the behavior of individual biomolecules. With
this technique, a change in fluorescence from the two dyes can be used as an
indicator of a change in the conformation of the host molecule.  Using this
technique to a variety of biological problems including the observation of
enzymatic activity and RNA folding. We have also begun to study more complex
interacting systems such as neuro transmission at the synapse and the
manufacture of proteins by the ribosome.