Abstract: When an inkjet printer places a dot on a page with 40 micron precision, it finds its mark using an optical encoder -- a mechanism that produces a periodic signal synchronized with the motion of the print head. By incorporating fluorescent dye molecules into DNA, we have scaled down this device by a factor of ten thousand, enabling continuous tracking of individual biomolecular motors with nanometer-scale precision in tens of milliseconds. Our measurements of DnaB helicase, which separates the two strands of DNA prior to replication, indicate that it travels more than 30 times farther than was previously believed, and suggest that it may rotate as it moves. It appears that improved encoder measurements will soon allow us to resolve single-base steps during DNA replication.

Bio: Everett Lipman is an assistant professor of physics at UC Santa Barbara. He received a B.A. in physics
from the University of Chicago in 1991, and a Ph.D. in physics from UC Berkeley in 1998. His thesis project,
supervised by Professor Charles H. Townes, involved the development of adaptive optics for observing red giant stars. After graduation, he moved from astrophysics to biological physics, working as a postdoctoral fellow at the National Institutes of Health and teaching physics at George Washington University before coming to UCSB in 2003. With his coworkers at the NIH, he did some of the first experiments using single-molecule fluorescence to study protein folding, and pioneered the use of microfluidic mixing for single-molecule kinetics measurements. He continues to use ultra-sensitive light detection to make new measurements of the assembly and behavior of individual biological molecules.

Host: Brad Paden