USE OF THIAZOLE ORANGE HOMODIMER AS AN ALTERNATIVE TO ETHIDIUM-BROMIDE FOR DNA DETECTION IN AGAROSE GELS

Detection of polymerase chain reaction-amplified DNA fragments is comm only accomplished by visualizing the products in electrophoretic agaro se beds with the use of ethidium bromide under ultraviolet light. Howe ver, ethidium bromide is mutagenic, and special handling and disposal precautions must be used. We report the use of a nonmutagenic dye, thi azole orange dimer (TOTO), which can be substituted for ethidium bromi de. The excitation maximum for TOTO under ultraviolet light is 488 nm, and the absorption maximum is 510 nm, necessitating photographic filt ers different from those used for ethidium bromide for optimal results . Of particular importance in TOTO's use is the quantity used for each gel lane, since excess TOTO will cause unacceptable product mobility retardation. TOTO is only slightly more expensive than ethidium bromid e. Overall, this stain provides very good visualization of polymerase chain reaction-amplified DNA bands in agarose gels. We believe the use of this safer reagent will become more widespread with increased regu lation of laboratory activities.