About the Authors
Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California Los Angeles, Los Angeles, California, United States of America
The authors have declared that no competing interests exist.
Conceived and designed the experiments: PVC SK BDY SGC. Performed the experiments: PVC BDY. Analyzed the data: PVC SK BDY SGC. Wrote the paper: PVC SK BDY SGC.