Hugh Wilson (Haw Yang and Quan Yang labs): Observing unconstrained biomolecular dynamics with high-precision single-molecule FRET in the ABEL Trap
A comprehensive understanding of biomolecules calls for the ability to observe single-molecule dynamics at the nanometer scale without perturbation or constraints. Single-molecule Förster resonance energy transfer (smFRET) is a powerful tool for probing nanoscale dynamics, but existing modalities have limitations. Solution based confocal measurements, in which labeled molecules diffuse through a stationary focused laser spot, are restricted by the short (~1ms) observation time. Tethering the labeled molecule to a surface can extend the observation time, but at the expense of restricting the molecule’s translational and rotational degrees of freedom. Moreover tethering the molecule may call for additional controls to check for perturbation to biological function. We overcome these limitations by combining smFRET optics with the capability to isolate individual molecules in solution using an Anti-Brownian ELectrokinetic (ABEL) trap. Our new platform, ABEL-FRET, enables photon-by-photon recording of smFRET trajectories over many seconds in solution, without tethering the molecule to a surface. We first demonstrate ABEL-FRET using short (10-15bp) DNA rulers and achieve precision that approaches the fundamental limit and is able to clearly resolve single basepair differences (~0.34nm). We also demonstrate the capability to observe dynamic smFRET transitions using Holliday junctions and to make simultaneous measurements of donor fluorescence lifetime and smFRET. We envision ABEL-FRET will fill a critical gap in the modern single-molecule toolkit.
Katherine Copenhagen (Center for the Physics of Biological Function): Myxococcus Xanthus Swarms as an Active Material
Thermodynamics and statistical mechanics are important tools for understanding how the properties of individual molecules lead to the bulk properties of passive materials. However, when a material is taken out of equilibrium by giving it’s molecules the ability to self propel, (as seen in bird flocks, fish schools, swarms of bacteria, and many other biological systems), they no longer follow the same laws as their equilibrium counterparts. We study Myxococcus Xanthus as a model system for active materials, and expand on ideas from soft-matter and liquid crystal science to understand the connection between active molecules and the bulk properties of materials.