DNA Emission Research Articles

Synthesis, characterization and DNA-binding characteristics of Ru(II) molecular light switch complexes

A series of four polypyridyl Ru(II) complexes such as [Ru(L)4(PIP)]2+ and [Ru(L)4PPIP]2+ where L is 4-amino pyridine and Pyridine (PIP = 2-phenylimidazo[4,5-f] [1, 10] phenanthroline), (PPIP = 2-(4′-phenoxy-phenyl) imidazo[4,5-][1, 10]phenanthroline) have been synthesized and characterized by elemental analysis, physicochemical methods such as UV–vis, IR and NMR spectroscopic techniques. The DNA-binding behavior of these complexes was investigated by electronic absorption titrations, fluorescence spectroscopy, viscosity measurements and salt-dependent studies. The experimental results indicate that all these complexes can bind to DNA through an intercalation mode, the DNA-binding affinities of these complexes follow the order [Ru(4-APy)4(PPIP)]2+(1) > [Ru(Py)4PPIP]2+(2) > [Ru(4-APy)4(PIP)]2+(3) > [Ru(Py)4PIP]2+(4). Noticeably, these complexes have been found to be efficient photosensitisers for strand scissions in plasmid DNA. Further, all four complexes screened for their antimicrobial activity indicate that the complexes show appreciable activity against Escherichia coli and Neurospora Crassa. In addition, in the presence of Co2+, the emission of DNA-[Ru(L4)PPIP/PIP]2+ can be quenched and recovered by the addition of EDTA, which exhibited the DNA “light switch” properties.

Synthesis, DNA-binding and photocleavage of “light switch” complexes [Ru(bpy) 2(pyip)] 2+ and [Ru(phen) 2(pyip)] 2+

Two novel Ru(II) complexes [Ru(bpy) 2(pyip)] 2+ 1 and [Ru(phen) 2(pyip)] 2+ 2 (bpy = 2,2′-bipyridine; phen = 1,10-phenanthroline; pyip = 2-(pyridine-2-yl)imidazo-[4,5- f][1,10]-phenanthroline), have been synthesized and characterized by elemental analysis, ES-MS, 1H NMR, UV–Vis. The DNA-binding behaviors of both complexes were studied by spectroscopic methods and viscosity measurements. The results indicate that the two complexes can bind to CT-DNA in an intercalative mode, and also show that these two Ru(II) complexes can promote the photocleavage of pBR322 DNA. In addition, In the presence of Co 2+, the emission of DNA-[Ru(L) 2pyip] 2+ can be quenched, which exhibited the DNA “light switch” properties.

A novel DNA light switch [Ru(bpy)2pzip]2+ activated by cobalt(II) ion

A novel ruthenium(II) complex, [Ru(bpy) 2 pzip] 2+ has been synthesized and characterized. In the presence of Co 2+ or EDTA, [Ru(bpy) 2 pzip] 2+ exhibited the “on–off–on” properties of molecular “light switch”. A novel ruthenium(II) complex, [Ru(bpy) 2 pzip] 2+ has been synthesized and characterized. The DNA-binding properties of this complex have been studied by spectroscopic and viscosity measurements. The results indicated that the complex [Ru(bpy) 2 pzip] 2+ bound to double-stranded DNA in an intercalation mode. In the presence of Co 2+ , the emission of DNA–[Ru(bpy) 2 pzip] 2+ can be quenched. And when EDTA was added, the emission was recovered. The experiment results show that [Ru(bpy) 2 pzip] 2+ exhibited the “on–off–on” properties of molecular “light switch”.

Selection of viable cells with known DNA content.

Cells doubly stained with Hoechst 33342 (H-33342) for DNA content and fluorescein diacetate for viability can be selected on the basis of both criteria using a single UV laser flow sorter. The selection is made possible due to resonance energy transfer occurring between the H-33342 and fluorescein fluorophores. Both a static fluorescence microscope and a dual laser flow sorter were used to demonstrate that energy transfer occurs in the doubly stained cells and that the sensitized emission in conjunction with the DNA emission can be used to select populations of cells with known DNA content and viability. The results indicate that fluorescein liberated by cellular esterases is freely accessible to the nucleus.