[1] Univ Calif Berkeley, Dept Chem & Biomol Engn, Berkeley, CA 94720 USA
[2] Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA
[3] Univ Calif Berkeley, Dept Bioengn, Berkeley, CA 94720 USA
[4] Univ Calif Berkeley, Helen Wills Neurosci Inst, Berkeley, CA 94720 USA