Detail:
Abstract: Elucidating the mechanism by which a protein folds—the protein folding problem—has blossomed into a large, interdisciplinary field. Single-molecule methods provide a powerful tool for probing complex folding pathways as in protein folding and misfolding. In this talk I will share two of my stories on using single-molecule force spectroscopy (SMFS) to study protein folding. I will first discuss our work on the structural dynamics of the prion protein PrP, which misfolds through an unknown mechanism into an infectious form that causes "mad cow" disease. We use optical tweezers to observe the structural dynamics of individual PrP molecules in real time as they either fold natively or misfold and aggregate into larger structures, focusing on the microscopic mechanisms that determine the structural outcome (native or misfolded). Then I will introduce our effort in developing AFM-based force spectroscopy with ~1-µs resolution. With that, individual membrane proteins within their native lipid bilayers were mechanically unfolded. A dramatically more complex folding pathway, including numerously previously invisible states and equilibrium dynamics, was revealed via improved resolution: an important result likely to impact many, if not all, SMFS studies. Throughout the talk, I will focus on quantitative descriptions of folding as a physical process, showing how single-molecule probes can be used to address unsolved problems in biology.
