Simple and sensitive determination of nucleic acids using palladium(II) complex with 2-(2-thiazolylazo)-5-dimethylaminobenzoic acid

The paper describes the use of the palladium(II) complex with 2-(2-thiazolylazo)-5-dimethylamino-benzoic acid (TAMB) for the spectrophotometric determination of nucleic acids with the detection limit at ng levels. At pH 5.9, Pd(II), TAME and nucleic acids interact rapidly at room temperature to form a supermolecular complex, leading to absorbance decreases at 621 and 675 nm of the palladium(II)-TAMB complex. With 675 nm as the measurement wavelength, the calibration linearity for calf thymus DNA (ct DNA), fish sperm DNA (fs DNA), and yeast RNA extend up to 3.5, 3.5 and 2.0 mu g ml(-1), respectively, with corresponding 3 sigma detection of 22, 27 and 25 ng ml(-1). Relative standard deviations for the synthetic samples are within 2.8% (n = 5). DNA extracted from pig liver is determined with a calibration graph for ct DNA, the result being very close to obtained by ethidium bromide fluorimetry. Compared to other colorimetric nucleic acids assays, the outstanding aspects of the present method are its sensitivity, simplicity and practicality. By the Rosenthanl and Meehan graphical procedures, the binding number and association constant of ct DNA with the complex are estimated, and the binding reaction is considered to be an intercalation. (C) 2000 Elsevier Science B.V. All rights reserved.