[1] Univ Calif Berkeley, Calif Inst Quantitat Biosci QB3, Berkeley, CA 94720 USA
[2] Univ Calif Berkeley, Dept Mol & Cell Biol, Berkeley, CA 94720 USA
[3] Howard Hughes Med Inst, Chevy Chase, MD 20815 USA
[4] Univ Calif Berkeley, Dept Mech Engn, Berkeley, CA 94720 USA
[5] Lawrence Berkeley Natl Lab, Dept Biol Sci & Engn, Life Sci Div, Berkeley, CA 94720 USA