Fluorescence lifetime for on-the-fly multiplex detection of DNA restriction fragments in capillary electrophoresis

This paper describes the first use of frequency-domain fluorescence lifetime for multiplex detection of DNA restriction fragments in capillary electrophoresis (CE). The fragments were labeled with monomeric intercalating dyes that can be excited by either the 488- or 514-nm line of an argon ion laser and have lifetimes in the range of 0.5-2.5 ns. We were able to achieve multiplex lifetime detection in the CE separation of a restriction fragment digest and a DNA size ladder in the same run, for fragments shorter than 700 bp. Different gel buffer systems, including a modified polyacrylamide gel and several tris-borate-EDTA/hydroxyethylcellulose (TBE/HEC) gels, were investigated for separation and detection of the dye-labeled DNA fragments. Best results for both electrophoretic resolution and lifetime detection were obtained using a gel containing 1% high molecular weight (90,000-105,000) HEC and 0.3% low molecular weight (24,000-27,000) HEC in TBE buffer.