It’s Complex: Probing Protein Interactions from Single-Molecule to Cellular Scales


Biological molecules rarely act alone. Instead, molecular complexes carry out a range of cellular functions from DNA repair to cell motility and protein folding. Dysfunction of complexes is implicated in numerous diseases. For example, altered cellular distributions of actin cytoskeletal protein monomers and complexes result in highly motile and invasive cancer cells. Such dysfunction arises biochemically, biophysically, or both. Biochemical and biophysical changes occur on the length and force scales of the complexes themselves—micro/nanoscale and ultra-low forces. Microscale tools, such as size-based electrophoretic (EP) cytometry protein separations, and piconewton-scale magnetic tweezers, can measure such small size and force changes respectively.

I will describe efforts to establish and apply microscale tools to study the function of diverse protein complexes. First, I will discuss the design of single-cell EP cytometry fractionation of actin complexes from monomers. The microscale device geometry achieves rapid, arrayed on-chip sample preparation and EP fractionation without perturbing complexes. Second, I will share how magnetic tweezers reveal that tension in Rad51-DNA protein complexes drives accurate DNA damage repair processes. Finally, we will explore the future of microscale biophysical and biochemical analysis of complexes, with a focus on chaperone protein complexes responsible for protein folding, which goes awry in Alzheimer’s disease. 

4:00| PLSB 403
Thursday, March 22, 2018
Julea Vlassakis
Fellow, Herr Lab| University of California, Berkeley
Professor James Landers