1. V. S.-Y. Lin, K. Motesharei, M. R. Ghadiri, Departments of Chemistry and Molecular Biology, and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
2. K.-P. S. Dancil and M. J. Sailor, Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093–0358, USA.