[1] Harvard Univ, Dept Chem & Chem Biol, Cambridge, MA 02138 USA
[2] UCB Biopharma SPRL, UCB NewMed, Global Chem, B-1420 Braine Lalleud, Belgium
[3] Univ Oxford, Chem Res Lab, 12 Mansfield Rd, Oxford OX1 3TA, England
[4] Massachusetts Gen Hosp, Div Nucl Med & Mol Imaging, Dept Radiol, Boston, MA 02114 USA
[5] Massachusetts Gen Hosp, Athinoula A Martinos Ctr Biomed Imaging, Charlestown, MA 02129 USA
[6] Harvard Med Sch, Charlestown, MA 02129 USA
[7] Max Planck Inst Kohlenforsch, Kaiser Wilhelm Pl 1, D-45470 Mulheim, Germany
[8] Barnard Coll, Dept Chem, 3009 Broadway, New York, NY 10027 USA