1. Basic Research Program, Frederick National Laboratory for Cancer Research, Argonne, Illinois 60439, United States
2. Shemyakin−Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow 117997, Russian Federation
3. Department of Chemistry, Center for Structural Biology, Vanderbilt University, Nashville, Tennessee 37235, United States
4. Institute for Drug Discovery, Leipzig University, Leipzig, SAC 04103, Germany