1. Chemical and Biosensors group, 805 Crosley, Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221, Physical Chemistry and Applied Spectroscopy (C-PCS), Los Alamos National Laboratory, P.O. Box 1663, MS J567, Los Alamos, New Mexico 87545, and Bioscience Division (B-7 and B-9), Los Alamos National Laboratory, PO Box 1663, MS E 529, Los Alamos, New Mexico 87545