1. Mailman Research Center, McLean Hospital, Harvard Medical School, Belmont, Massachusetts 02478.
2. Center for Immunology and Microbial Disease, Albany Medical College, Albany, New York 12208.
3. Department of Chemistry, State University of New York at Albany, Albany, New York 12208.
4. Department of Biological Sciences, University of Rhode Island, Kingston, Rhode Island 02881.
5. Department of Chemistry and Chemical Engineering, University of Maribor, Maribor, Slovenia.