Living cells exert forces in order to move, divide, and fight off infections. Cellular forces are generated by the assembly and disassembly of biopolymers and the action of motor proteins. In the Biophysics Laboratory, directed by Prof. Upadhyaya, experiments are underway to study how these forces are generated and controlled in selected cells. These experiments examine how cells of the immune system utilize cellular forces to detect and fight off infections, how cells sense the mechanical properties of their environment, and how these forces drive cell movement.

A few projects that involve undergraduate researchers are:

• Measuring cellular viscoelasticity using magnetic tweezers: A specially designed magnetic tweezer system is used to apply a force on paramagnetic beads attached to cells. The applied force deforms the cells and the time-scales of the bead relaxation are measured. Different drugs are used to perturb cellular biopolymers, and their effect on cellular response to applied forces is studied.
• Single molecule imaging of biopolymer dynamics: Cells deposited on adhesive surfaces deform to adopt a characteristic shape that resembles a fried egg. Various parameters of the flow, such as velocity and spatial coherence, can be visualized by fluorescence microscopy of genetically-labeled actin molecules. Single-molecule imaging via a highly-sensitive camera is used to monitor the movement of small numbers of single actin molecules. Statistical characterization of the movement is used to determine how cellular proteins use the actin flow in order to move on the cell surface.