[1] Univ Washington, Dept Med, UW Med Lake Union, Seattle, WA 98109 USA
[2] Univ Washington, Mol & Cellular Biol Program, Seattle, WA 98109 USA
[3] Univ Washington, Dept Bioengn & Chem Engn, Natl ESCA & Surface Anal Ctr, Biomed Program, Seattle, WA 98195 USA