[1] Univ Calif Berkeley, MCB, Dept Mol & Cell Biol, Berkeley, CA 94720 USA
[2] Univ Calif Irvine, Dept Physiol & Biophys, Irvine, CA 92697 USA
[3] Univ Calif Berkeley, Lawrence Berkeley Lab, Div Mat Sci, Berkeley, CA 94720 USA
[4] Univ Calif Berkeley, Lawrence Berkeley Lab, Phys Biosci Div, Berkeley, CA 94720 USA