1. Contribution from the Department of Biology, Brookhaven National Laboratory, Upton, New York 11973, OttawaCarleton Chemistry Institute, Department of Chemistry, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada, K1S 5B6, and Research Services Division, Health Products and Food Branch, Health Canada, Tunney's Pasture, Ottawa, Ontario, Canada, K1A 0L2