1. Department of Chemistry and Biochemistry; University of California, San Diego; La Jolla California USA
2. Now at Department of Chemistry; University of Toronto; Toronto Ontario Canada
3. Department of Chemistry; University of Wisconsin-Madison; Madison Wisconsin USA
4. Now at Department of Environmental Health Science; University of Michigan; Ann Arbor Michigan USA
5. Scripps Institution of Oceanography; University of California, San Diego; La Jolla California USA