[1] Acenta Discovery Inc, Tucson, AZ 85747 USA
[2] Georgetown Univ, Dept Biol, Washington, DC 20057 USA
[3] Johns Hopkins Univ, Dept Radiol, Baltimore, MD 21287 USA
[4] Univ Illinois, Coll Pharm, Dept Med Chem & Pharmacognosy, Drug Discovery Program, Chicago, IL 60612 USA