1. California NanoSystems Institute, University California Los Angeles, Los Angeles, CA 90095, USA.
2. Department of Microbiology, Immunology, & Molecular Genetics, University of California Los Angeles, Los Angeles, CA 90095, USA.
3. Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA 90095, USA.
4. David Geffen School of Medicine, University of California Los Angeles and Greater West Los Angeles Health Care System, Los Angeles, CA 90095, USA.