Chemiluminescence investigation of the interaction of metalloporphyrins with nucleic acids

Abstract

The interaction of water-soluble cationic porphyrin meso-tetrakis(4- N-methylpyridinyl)porphyrin (TMPyP) manganese derivatives with DNA was demonstrated by their catalytic activity on the luminolH 2O 2 chemiluminescence (CL) system. The catalytic activity of Mn-TMPyP on the CL reaction was markedly enhanced when the complex was bound to DNA. The native form of DNA and thermally denatured DNA show the same degrees of enhancement. Different degrees of enhancement were obtained when Mn-TMPyP interacted with RNA and polynucleotides, whereas the interaction of nucleotides and bases with Mn-TMPyP had no effect on its catalytic activity. To examine the effect of the peripheral group of the porphyrin on its bonding properties, the interaction of manganese tetrakis(4-aminophenyl)porphyrin (Mn-TPPA 4), manganese tetrakis(carboxylphenyl)porphyrin (Mn-TPPC 4), manganese tetrakis(sulphophenyl)porphyrin (Mn-TPPS 4) and manganese tetrakis(4-trimethylaminophenyl)porphyrin (Mn_TAPP) with DNA was tested. Only the Mn-TPPA 4-catalysed CL reaction was significantly enhanced. The effects of the native form of DNA and thermally denatured DNA on the Mn-TPPA 4-catalysed CL reaction were very different to that on the Mn-TMPyP-catalysed CL reaction. With a fixed concentration of Mn-TMPyP there was a saturated concentration of DNA with respect to the metalloporphyrin (M-P). The binding number of M-P to DNA was estimated. Optimum conditions of the M-PDNA complex-catalysed luminol CL reaction were evaluated by using a flow-injection system. The use of the analytical parameters of the phenomenon as a means of determining DNA was examined. The detection limit (signal-to-noise ratio > 3) of DNA was 0.20 ng ml −1. The relative standard deviation ( n = 11) of the determination of 10 ng ml −1 DNA was 2.6%.