[1] Univ Chicago, Biophys Grad Program, Inst Biophys Dynam, Chicago, IL 60637 USA
[2] Univ Chicago, James Franck Inst, Inst Biophys Dynam, Chicago, IL 60637 USA
[3] Univ Chicago, Dept Phys, Chicago, IL 60637 USA
[4] Univ Chicago, Dept Mol Genet & Cell Biol, Dept Biochem & Mol Biol, Chicago, IL 60637 USA