1. Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania 16802, Cancer Research UK Nucleic Acid Structure Research Group, University of Dundee, Dundee DD1 5EH, United Kingdom, and Department of Pediatrics and Communicable Diseases, University of Michigan, Ann Arbor, Michigan 48109