1. Center for Radiological Research, University of Missouri, Columbia, Missouri 65211, Division of Radiopharmacy, Paul Scherrer Institute, CH-5232 Villigen, Switzerland, Forschungszentrum Rossendorf, Institute of Radiochemistry, c/o Dresden University of Technology, D-01062 Dresden, Germany, and Institute of Inorganic Chemistry, Spitalstrasse 51, CH-4056 Basel, Switzerland