WMELCHIOR@NTDOC.NCTNET.GOV (05/30/91)
In reply to Benedik's message regarding fluorescence DNA assays in microtiter plates: It is not necessary to excite in the UV. I have been doing similar assays with ethidium: excitation at 545 nm and emission at 575 nm. These wavelengths are not optimal but aren't too bad; fluorescent-activated cell sorters use excitation in the visible for a variety of dyes. I use a Pandex Fluorescence Concentration Analyzer (FCA; Pandex Division, Travenol Labs). My machine uses special plates that must be sealed before use (contact me for details), but newer instruments supposedly can use regular plates. I have also seen ads for machines from Millipore, Flow Laboratories, and Perkin Elmer. In my system, this assay allows measurement of much less than 100 ng DNA in a few microliters. Also, the DNA can be recovered in high yield from the hydrophobic wells of the plate, after the measurement. Bill Melchior National Center for Toxicological Research Jefferson, AR 72079 wmelchior@ntdoc.nctnet.gov