Intercalating Fluorescent Sensors For T·AT Triplex DNA Based On Naphthylquinoline

DNA triple-helix formation is of great potential including selective control of gene expression, site-directed mutagenesis, gene repair, in situ chromosome labelling and other molecular diagnostics, thus the antigene strategy based on triplex DNA offers new therapeutic applications. Triplex DNA tools on this basis are of great interest from the standpoint of chemistry, medicine and biology. In this dissertation, a serial of T-AT triplex DNA probes composed of triplex DNA intercalator, spacer and fluorophore were synthesized and evaluated. Some triplex DNA bis-intercalator ligands were also synthesized and evaluated.A serial of triplex DNA probes were synthesized. In the probe, N,N-bis-(3-aminopropyl)amine was used as spacer, danyl or 4-aminonaphthalimide was used as fluorophore. The fluorescence of the probe is weak because the distance between the intercalator and the fluorophore is very close in free state. Upon intercalating into a triplex DNA, however, the probe emits greater fluorescence due to the increase of the distance between the two moieties. We found that these probes were triplex selective because they could highly enhance the Tm of T-AT triplex, but hardly enhance the Tm of AT duplex. Most compounds had fluorescence enhancement to the T-AT triplex.Another serial of triplex DNA probes were synthesized, whose spacer was N,N'-bis-(3-aminopropyl)piperazine, fluorophore was danyl, 4-aminonaphthalimide and cy-7 dye respectively. This spacer is a little more rigid than N,N-bis-(3-aminopropyl)amine. The ATm was 26 — 30°C to T-AT triplex, but only about 2°C to AT duplex. Compared with N,N-bis-(3-aminopropyl)amine spacer, N,N'-bis-(3-amino propyl)piperazine spacer had bigger fluorescence enhancement. A fluorescence melting method was brought forward to measure the Tm of the complex of 2a and T-AT triplex. This method was a'dependable method proved by UV melting method. We further proved this method by measuring the Tm of the complex of 2a and AT duplex through a Smart Cycler apparatus. An explanation for the different fluorescence response to T-AT triplex between la and 2a was presented by using of semi-empirical calculation method-AM1.A novel triplex DNA fluorescent probe, which takes 4-aminonaphthalimide or danyl as reporting group, ethylene group as a spacer and a triplex-select intercalatoras recognizing group, was synthesized based on photoinduced electron transfer (PET). Fluorescence response of probes to different DNA was studied through fluorescent spectra. We found that probe 3a was very sensitive to T-AT triplex, the fluorescence response of 3a to pH also proved the PET mechanism.Some triplex DNA bis-intercalator ligands (N1-N8) and a mono-intercalator ligand (NO) were also synthesized. The Tm values were studied through the UV melting experiments. The experiments concerning the effects of different concentrations of N6 to T-AT triplex and AT duplex suggested that appropriately designed bis-intercalator ligands were better than mono-intercalator ligands in selectively enhancing the stability of T-AT triplex.