General Colloquium:

March 28 - 4:00pm Phys 223
(Coffee at 3:30p.m. in room 242)

Hans Frauenfelder

Center for Nonlinear Studies Los Alamos National Laboratory

"The Physics of Proteins"

"Ask not what physics can do for biology, ask what biology can do for physics". (Stan Ulam).

Proteins form a unique state of matter, with some properties characteristic of solids, some of liquids, some of polymers, and some of glasses. 4 Gy of evolution have perfected their structure and function. The study of proteins and other biomolecules yields new concepts and new insights into old problems. Possibly the most important concept is that of the energy landscape: Proteins do not have a unique structure and ground state energy; they can assume a very large number of somewhat different structures. This situation is characterized by a rough energy landscape in a space of 3N dimensions, where N is number of atoms in the protein. Each valley in the landscape corresponds to a particular protein conformation, called a conformational substate. The existence of an energy landscape and of substates has been confirmed by many experiments, in particular by a characteristic Debye-Waller factor, nonexponential time dependence of relaxation phenomena, and spectral and kinetic hole burning. One of the main goal of the protein studies is the exploration of the energy landscape, of the laws governing motions in the landscape, and of their connection to structure and function. Proteins are not isolated systems; they are slaved to the environment. The enthalpy needed for important protein reactions is provided by the solvent; the protein provides entropic control. The entropic control can be understood as an anomalous random walk through the energy landscape. Fractals thus enter the physics of proteins naturally and this concept leads into new, as yet largely unexplored, directions where physicists can contribute much.

Curriculum Vitae