1. Searle Research and Development, Pharmacia Company, St. Louis, Missouri 631981;
2. Agricultural Genomics, Monsanto Company, St. Louis, Missouri 631672;
3. Department of Microbiology and Immunology, Georgetown University, Washington, D.C. 200073;
4. Synergy Pharmaceuticals, Sommerset, New Jersey 088734; and
5. Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Layfayette, Indiana 47907-13335