Colloquium Double-Header by Professors Steven M. Block and Robert H. Austin
Host: Prof. Liviu Movileanu. For other questions: Yudaisy Salomon Sargenton, email@example.com
Room 202/204 Physics
Steven M. Block, Ph.D.
S.W. Ascherman Professor of the Sciences
Department of Applied Physics
Department of Biology
Stanford University CA 94305
Optical Tweezers: Gene Regulation, Studied One Molecule at a Time
Advances have led to the new field of single molecule biophysics. Single-molecule techniques can record characteristics that are obscured by traditional biochemical approaches, revealing behaviors of individual biomolecules. Prominent among the techniques is the laser-based optical trap, or ‘optical tweezers,’ which uses radiation pressure. Optical traps now measure biomolecular properties with a precision down the atomic level—achieving a resolution of 1 angstrom over a bandwidth of 100 Hz—while exerting controlled forces in the piconewton range. Among the successes for optical traps have been measurements of the steps produced by motor proteins (for example, kinesin and myosin) and by processive nucleic-acid enzymes (for example, RNA polymerase), as well as determinations of the strengths of noncovalent bonds between proteins, and the kinetics of structure formation by DNA and RNA. Optical trapping instruments have been particularly useful in mapping the energy landscapes for folding macromolecules. We’re now able to follow the co-transcriptional folding of RNA in real time, as it is synthesized, revealing how such folding can regulate downstream genes, mediated by structured RNAs called ‘riboswitches.’ In recent developments, optical traps have been used in conjunction with single-molecule FRET (Förster Resonance Energy Transfer) to report on folding configurations and internal degrees of freedom in biomolecules.
Robert H. Austin
Professor of Physics
Department of Physics
The Collective Brain of Bacteria and Applications to Antibiotics and Cancer
No bacterium is an island. The bacterium E. coli’s motility not only responds to a number of input parameters (5 chemicals, heat, maybe pressure, maybe electric field), and it modifies these parameters by virtue of metabolism, movement and growth. The result is that bacteria interact in a collective manner. My most recent question is: do bacteria collectively compute in some sense solutions to biological and physical problems? I’ll show how we have used microfabrication techniques to probe the problem solving abilities in a collective manner. I’ll speculate that this insight can be applied (perhaps) to how antibiotic resistance arises, and how cancer cells evade chemotherapy in a tumor.