STUDY ON THE DIMER-MONOMER EQUILIBRIUM OF A FLUORESCENT DYE AND ITS APPLICATION IN NUCLEIC-ACIDS DETERMINATION

A novel spectrofluorimetric method has been proposed for the determina tion of nucleic acids based on shifting the dimer-monomer equilibrium of the fluorescent dye, acridine yellow (AY). Induced by the premicell ar aggregation of an anionic surfactant, sodium dodecyl sulphate (SDS) , AY formed a nonfluorescent homodimer (AYAY) which largely quenches t he fluorescence intensity of the dimer system. However, the fluorescen ce intensity of the system increased dramatically when nucleic acids w ere added to the solution. The fluorescence enhancement is probably ba sed on the DNA modulated shift of the dimer-monomer equilibrium of AY in the anionic surfactant solution. Intercalation of the monomer in DN A caused the dissociation of AYAY. and led a very high fluorescence en hancement. A linear dependence of fluorescence intensity on Calf thymu s (CT) DNA concentration over the rang of 0 similar to 40 mu g/ml CT D NA allowed sensitive quantification of CT DNA by a simple fluorescent method. The detection limit was 0.023 mu g/ml and the RSD was 1.5% for 2 mu g/ml CT DNA (n=7). Furthermore, calibration graphs for yeast RNA , polynucleotides, such as poly (A) and poly (I) were also obtained. ( C) 1998 Elsevier Science B.V.