Green-light transilluminator for the detection without photodamage of proteins and DNA labeled with different fluorescent dyes

The excitation spectra of Nile red and SYPRO red, two currently used dyes f or the fluorescent staining of protein bands in sodium dodecyl sulfate (SDS )-polyacrylamide gels, show an excitation peak in the UV region and another in the visible region (maximum at about 550 nm). Ethidium bromide and othe r intercalating dyes, e.g. propidium iodide, ethidium dimers, and benzoxazo lium-4-quinolinium dimer-3 (YOYO), used for the fluorescent staining of DNA bands in agarose gels also show an excitation peak in the same region of t he visible spectrum. We have designed and constructed a green-light transil luminator with an emission maximum at 542 nm. This visible transilluminator allows the detection of protein bands stained with Nile red and SYPRO red with the same sensitivity obtained with a 300 nm UV transilluminator. The g reen-light transilluminator also allows the detection of about 2 ng of DNA per band in gels stained with ethidium bromide and the other intercalating dyes indicated above. In contrast to the UV transilluminators, the green-li ght transilluminator does not produce photodamage of DNA even after long ex posures (10 min). This makes this transilluminator very useful for preparat ive work. Furthermore, the green-light transilluminator does not require UV safety equipment and, consequently, it can be very convenient for teaching laboratories.