1. Department of Molecular Biology & Center for Integrative Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
2. Department of Chemistry & Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
3. Skaggs School of Pharmacy & Pharmaceutical Sciences, University of California, San Diego, 9500 Gilman Drive, MC 0657, La Jolla, CA 92093-0657, USA
4. Department of Biomedical Engineering, Case Western Reserve University, 11100 Euclid Avenue, Cleveland, OH 44106, USA