Application of aluminium(III) complex with salicylidene-o-aminophenol to the fluorometric determination of nucleic acids.

In buffer medium of hexamethylene tetraamine-HCl at pH 5.9 the aluminium(III) complex with salicylidene-o-aminophenol (SAP) has a fluorescence peak at 508 nm with excitation at 410 nm. When nucleic acid coexists, it reacts with the complex within 8 min at room temperature to produce a non-fluorescent product, resulting in the decrease of fluorescence intensity of the aluminium complex. On basis of this, a new fluorometric method for nucleic acids determination is proposed. The calibration graphs for calf thymus DNA, fish sperm DNA and yeast RNA are linear up to 5.0, 4.0 and 3.0 microg ml(-1), respectively, and corresponding detection limits are 49, 52 and 62 ng ml(-1). The synthetic samples are analyzed with relative standard deviation of five measurements of 3.9-6.0%. DNA in an extraction product from human blood is determined using the calibration graph for calf thymus DNA, and the result is very close to that by the ethidium bromide assay. Compared with some established fluorometric methods, this procedure is sensitive, selective, reliable, reproducible and practical. The association constant of calf thymus DNA with the complex is estimated by two graphic methods. It is suggested that the binding reaction between nucleic acids with the complex proceeds in an intercalation way.