DNA-binding and cleavage studies of a novel porphyrin ruthenium mixed complex [MPyTPP—Ru(pip)2Cl]+

A novel porphyrin ruthenium mixed complex, [MPyTPP—Ru(pip)₂Cl]⁺, has been prepared and characterized by elemental analyses, ES-MS, u.v.–vis. and electrochemistry. The DNA binding properties of this complex have been investigated by absorption spectroscopy, fluorescence spectroscopy and by viscosity measurements. The results indicate that the complex may bind with DNA in a groove-binding mode. Upon irradiation with u.v. light, this complex has been found to promote cleavage of plasmid pBR 322 DNA from the supercoiled form I to the open circular form II.     

Efficient photoinduced DNA damage by coralyne

The photoinduced DNA damage by the berberine derivative coralyne is presented. The irradiation of coralyne in the presence of plasmid DNA namely, pBR322, leads to remarkably fast DNA damage by single-strand cleavage, as determined by agarose-gel electrophoresis. Even upon exposure to sunlight, almost all of the supercoiled plasmid is converted to the open circular form in less than a minute [c(pBR322) = 3.5 x 10(-9) M; c(coralyne) = 4.3 x 10(-5) M]. The efficiency of the DNA strand cleavage is not decreased in the presence of radical-trapping reagents such as tert-butanol or DMSO. Moreover, the extent of the DNA damage is the same under aerobic conditions and at reduced oxygen concentration. Thus, the formation of reactive intermediates such as hydroxyl radicals or singlet oxygen is excluded. These results show that the exposure of coralyne and derivatives thereof to light, even with moderate light intensity, needs to be avoided during experiments in which their biological activity is assessed by plasmid unwinding assays.     

Photochemistry of N-isopropoxy-substituted 2(1H)-pyridone and 4-p-tolylthiazole-2(3H)-thione: alkoxyl-radical release (spin-trapping,EPR, and transient spectroscopy) and its significance in the photooxidative induction of DNA strand breaks

UVA-irradiation of the photo-Fenton reagents N-isopropoxypyridone 2b and N-isopropoxythiazole-2(3H)-thione 3b releases radicals which induce strand breaks. Transient spectroscopy establishes N-O bond scission [Phi(N)(-)(O) = (75 +/- 8)% for 2b and (65 +/- 7)% 3b] as the dominating primary photochemical process to afford the DNA-damaging radicals. Product studies and laser-flash experiments reveal that the thiazolethione 3b leads primarily to the disulfide 5, from which through C-S bond breakage, the bithiazyl 6, the thiazole 7, and the isothiocyanate 8 are derived. Upon irradiation of pyridone 2b (300 nm) in aqueous media, a mixture of isopropoxyl and 2-hydroxyprop-2-yl radicals is formed, as confirmed by trapping with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) and EPR spectroscopy. In contrast, the photolysis of the thiazolethione 3b (350 nm) affords exclusively the DMPO adducts of the isopropoxyl radicals. Control experiments disclose that the thiazolethione-derived photoproduct disulfide 5, or the intermediary thiyl radicals B, scavenge the carbon-centered 2-hydroxyprop-2-yl radicals, which are generated from the isopropoxyl radicals by hydrogen shift. With supercoiled pBR 322 DNA in a 60:40 mixture of H(2)O-MeCN, the pyridone 2b and the thiazolethione 3b display moderate strand-break activity (17% open-circular DNA for 2b and 12% for 3b). In pure water, however, the pyridone 2b photoinduces substantially more DNA cleavage (32% open-circular DNA), which is attributed to the peroxyl radicals generated from the 2-hydroxyprop-2-yl radicals by oxygen trapping. The lower strand-break activity of the thiazolethione 3b derives presumably from isopropoxyl radicals, because only these are detected in the photolysis of this photo-Fenton reagent.     

Ferric-ion-photosensitized damage to DNA by hydroxyl and non-hydroxyl radical mechanisms.

Iron(III) and UVA (320-400 nm) light strongly diminished the transforming activity of Haemophilus influenzae DNA in the presence of oxygen. Iron(III) alone in the absence of light had no measurable effect on the transforming activity. The chelating agent ethylenediaminetetraacetic acid (EDTA) conferred virtually complete protection, but hydroxyl radical scavengers (mannitol, methanol, ethanol, isopropanol and dimethyl sulfoxide) inhibited only a small fraction of the inactivation. Treatment of plasmid DNA (pBR322) with iron(III) results in the conversion of the covalently closed circular form of the plasmid to open circles and ultimately to the linear form. Concomitant with the alteration in the conformation of the plasmid, the ability to transform Escherichia coli was reduced. In model systems, iron(III) photoreacted with the DNA backbone causing nicking and double-strand breakage. The results are consistent with a mechanism involving a preliminary complexation of iron(III) by DNA followed by the generation of reactive free radicals other than .OH. We suggest that bound iron, or other UV-absorbing transition metal complexes, may be chromophores capable of causing DNA damage in the long-wave near-UV region.     

Ternary iron(III) complex showing photocleavage of DNA in the photodynamic therapy window

A new ternary iron(III) complex [FeL(dpq)] containing dipyridoquinoxaline (dpq) and 2,2-bis(3,5-di-tert-butyl-2-hydroxybenzyl)aminoacetic acid (H3L) is prepared and structurally characterized by X-ray crystallography. The high-spin complex with a FeN3O3 core shows a quasi-reversible iron(III)/iron(II) redox couple at -0.62 V (vs SCE) in DMF/0.1 M TBAP and a broad visible band at 470 nm in DMF/Tris buffer. Laser photoexcitation of this phenolate (L)-to-iron(III) charge-transfer band at visible wavelengths including red light of >or=630 nm leads to cleavage of supercoiled pUC19 DNA to its nicked circular form via a photoredox pathway forming hydroxyl radicals.     

A Novel Photocleaver with Long Wavelength Absorption-Highly Efficient Antitumor Agent： 4- （2-Diethylamino-ethylamino） - 8-oxo-8H-acenaphtho- [ 1,2-b ] pyrrole-9-carbonitrile

IntroductionThe design of novel DNA photocleavers is of greatsignificance from the standpoints of chemistry,biology,and medicine[1].There have been many reports aboutDNA photocleavers.Usually,they bind to DNAviain-tercalation,electrostatic binding or self-stacking inter-actions[2,3],but under photoirradiation they can initiatesignificant damage to DNA without external chemicalinitiatorsviaa wide variety of ways,such as electrontransfer,the formation of radicals or singlet oxy-gen[4,5].It …     

Hydrolytic cleavage of DNA by quercetin manganese(II) complexes

Quercetin manganese(II) complexes were investigated focusing on its DNA hydrolytic activity. The complexes successfully promote the cleavage of plasmid DNA, producing single and double DNA strand breaks. The amount of conversion of supercoiled form (SC) of plasmid DNA to the nicked circular form (NC) depends on the concentration of the complex as well as the duration of incubation of the complexes with DNA. The maximum rate of conversion of the supercoiled form to the nicked circular form at pH 7.2 in the presence of 100 μM of the complexes is found to be 1.32 × 10⁻⁴ s⁻¹. The hydrolytic cleavage of DNA by the complexes was supported by the evidence from free radical quenching, thiobarbituric acid-reactive substances (TBARS) assay and T4 ligase ligation.     

DNA interaction studies of ruthenium(II) polypyridyl complex : [Ru(dmb)2(ITAP)](ClO4)2 (ITAP = isatino [1,2-b]-1,4,8,9-tetraazatriphenylene)

A new ligand ITAP and its complex [Ru(dmb)₂(ITAP)](ClO₄)₂ (ITAP = isatino [1,2-b]-1,4,8, 9-tetraazatriphenylene, dmb = 4,4′-dimethyl-2,2′-bipyridine) have been synthesized and characterized by elemental analysis, Fast atom bombardment mass spectra, Electrospray mass spectra, and ¹H NMR. Thermal denaturation and absorption titration experiments show the complex binds to calf thymus DNA (CT-DNA) with moderate affinities. Viscosity measurements and thermal denaturation indicate that the DNA-binding mode could be intercalative interaction. The Ru(II) complex in the presence of plasmid pBR322 DNA has been found to promote the cleavage of plasmid pBR322 DNA from the supercoiled Form I to the open circular Form II upon irradiation. Mechanisms for DNA cleavage by the complex were also investigated.     

β-K4H3[SiW9O37(CpTi)3]·11H2O环戊二烯钛多酸衍生物与DNA作用研究

某些过渡金属配合物具有特异性催化DNA和RNA断裂的功能, 因而研究过渡金属配合物对DNA和RNA的断链反应对新型抗肿瘤、抗艾滋病化学药物的定向设计及其基因治疗和分子生物学中DNA和RNA的高度专一性定点断裂、 DNA定位诱变和构象识别具有重要意义和应用前景[1,2]. 我们对二茂钛多酸有机金属衍生物合成及抗肿瘤活性研究表明, 环戊二烯钛多氧金属酸盐衍生物具有很高的抗肿瘤活性和较好的水溶性及稳定性, 有潜在的抗肿瘤药用价值[3].     

The different behavior of rutile and anatase nanoparticles in forming oxy radicals upon illumination with visible light: an EPR study

Photoexcited TiO(2) has been found to generate reactive oxygen species, yet the precise mechanism and chemical nature of the generated oxy species especially regarding the different crystal phases remain to be elucidated. Visible light-induced reactions of a suspension of titanium dioxide (TiO(2)) in water were investigated using electron paramagnetic resonance (EPR) coupled with the spin-trapping technique. Increased levels of both hydroxyl (˙OH) and superoxide anion (˙O(2)(-)) radicals were detected in TiO(2) rutile and anatase nanoparticles (50 nm). The intensity of signals assigned to the ˙OH and ˙O(2)(-) radicals was larger for the anatase phase than that originating from rutile. Moreover, illumination with visible (nonUV) light enhanced ˙O(2)(-) formation in the rutile phase. Singlet oxygen was not detected in water suspension of TiO(2) neither in rutile nor in anatase nanoparticles, but irradiation of the rutile phase with visible light revealed a signal, which could be attributed to singlet oxygen formation. The blue part of visible spectrum (400-500 nm) was found to be responsible for the light-induced ROS in TiO(2) nanoparticles. The characterization of the mechanism of visible light-induced oxy radicals formation by TiO(2) nanoparticles could contribute to its use as a sterilization agent.     

CU(II) SENSITIZES pBR322 PLASMID DNA TO INACTIVATION BY UV-B(280–315 nm)

Abstract— Copper(II), in the presence of UV-B radiation(280–315 nm), can generate single-strand breaks in the sugar-phosphate backbone of pBR322 plasmid DNA. A low level of single-strand backbone breaks occurs in the presence of Cu(II) alone, but UV-B irradiation increases the rate by the more than 100-fold. Concomitant with the damage to the DNA backbone is a loss of transforming activity. Oxygen is required for generation of the single-strand breaks but not for the loss of transforming activity. A DNA glycosylase (Fpg), which participates in the repair of certain DNA nitrogenous base damage, does not repair plasmid DNA damaged by Cu(II). The hydroxyl radical scavenging compound DMSO is only somewhat effective at protecting the physical and biological properties of the DNA. These results with Cu(II) are compared to those obtained previously with pBR322 plasmid DNA in the presence of Fe(III) and UV-A.     

Resolution of circular, nicked circular and linear DNA, 4.4 kb in length, by electrophoresis in polyacrylamide solutions.

Circular DNA of more than 1,400 bp in size is known not to migrate into polyacrylamide gels. The migration of supercoiled plasmid pBR322 DNA (4,363 by) into uncrosslinked polyacrylamide (Mw 5 x 10(6)) solutions and its separation, on the basis of conformation, from its nicked form is demonstrated in this study. Migration of the supercoiled, nicked circular and linear forms of the plasmid DNA is retarded in proportion to the concentration of uncrosslinked polyacrylamide, the degree of retardation being highest for the nicked circular form. Decreasing the level of supercoiling of the covalently closed circular form by decreasing the concentration of the intercalating dye (ethidium homodimer) shows that the degree of retardation decreases in proportion to the superhelix density.     

手性钌(Ⅱ)配合物对DNA的立体选择性断裂

八面体钌(Ⅱ)多吡啶配合物与双螺旋DNA插入结合后具有较强的结合能力,并且含有一个具有氧化一还原活性的中心金属离子．它们对氧化剂相对比较稳定,但对光比较敏感,因此可利用光辐射使之产生单线态氧或羟基自由基等而使DNA裂解．此外,这些配合物具有左手∧-和右手△-两种构型,与同样具有手性的DNA作用时,存在着立体选择性结合．并且在对DNA的断裂反应中也存在一定的立体选择性,可作为不同构型DNA的结构探针．     

DNA-binding and photoactivated cleavage of enantiomeric ruthenium(II) complexes

A set of enantiomeric Ru^II complexes Δ- and Λ-[Ru(bpy)₂TAPTP](PF₆)₂(bpy=2,2’-bipyridine, TAPTP=4,5,9,18-tetraazaphenanthreno[9,10-b]triphenylene) have been synthesized and characterized. Binding of both enantiomers to calf thymus DNA has been studied by spectroscopic methods, viscosity, and equilibrium dialysis. The experimental results indicated that both enantiomers bind to DNA by intercalation. Upon irradiation at 302 nm, both enantiomers were found to promote the cleavage of plasmid pBR 322 DNA from supercoiled form I to a nicked form II, and obvious enantioselectively was observed on DNA cleavage, the Λ- enantiomer exhibiting higher cleaving efficiency. The mechanisms for DNA cleavage by the two enantiomers are also proposed.     

Separation of different physical forms of plasmid DNA using a combination of low electric field strength and flow in porous media: effect of different field gradients and porosity of the media

The retention of different physical forms of DNA by an electric field in a chromatography system was studied. We were able to effectively separate the supercoiled and the open circular forms of plasmid DNA using this type of electrochromatography system. Chromatography columns were packed with porous beads, and an axial electric field was applied so that convective buffer flow opposed the direction of electrophoresis of the DNA. A model system composed of approximately equal amounts of the super-coiled and open circular forms of the plasmid pBR 322 (4322 base pairs) was used to test the separation. Chromatography beads (agarose-based) with different porosities were used to determine the effect of the stationary phase on the separation. The porous media did not have a major effect on the separation, but the best separations were obtained using porous chromatography media made with the highest agarose concentration (10% agarose). Selective elution of plasmid DNA with different forms was obtained by either increasing the flow rates or decreasing the electric field strength (by steps or a gradient). In all the separations, the more compact supercoiled form of the plasmid was retained less strongly than either the open circular form (nicked) or the linear form. High molecular weight host genomic DNA was more strongly retained than the plasmid DNA. Increasing the ionic strength of the buffer improved resolution and capacity. The capacity of the separation was determined by injecting increasing amounts of plasmid DNA. Satisfactory separation was obtained at sample loading of up to 360 microg of total DNA on a column with dimensions of 2.5 by 11 cm (bed volume of 54 mL). The retention of DNA depends upon a counter-current flow of electrophoresis and convective flow and could be regarded as a type of field flow fractionation. The retention of the DNA by the electric field and flow is discussed in relation to the diffusion coefficients of the DNA.     

Rapid green and blue light‐induced CO release from bromazepam Mn(I) and Ru(II) carbonyls: synthesis,density functional theory and biological activity evaluation

Two new photoactivatable carbon monoxide‐releasing molecules (CORMs), fac ‐[Mn(CO)₃(BZM)Br] ( 1 ) and [RuCl₂(BZM)(CO)₂] ( 2 ), derived from the anti‐anxiety drug bromazepam (BZM) and capable of rapid release of CO upon the illumination with light‐emitting diode (LED) source light (470–525 nm) have been synthesized and characterized. The photo‐delivery of CO to myoglobin solution could be achieved via the illumination of 1 at 525 nm for 10 min or at 470 nm for 1 min. The addition of water to a dimethylsulfoxide (DMSO) solution of 1 increases its stability, but it decreases the rate of the CO‐releasing process. CORM 2 behaves as a good visible photoCORM, whereby its two CO molecules are released within 10 min upon exposure to LED light source at 470 nm in DMSO. The illumination profile of 2 was also examined using solution infrared spectroscopy. The cis /trans stereochemistry around the Ru(II) ion was determined using quantum chemical calculations. The formation of photoCORMs leads to an improvement in the toxicity of BZM against tested microbes.     

Synthesis, DNA-binding, and Photocleavage of 2,3-Di-2-pyridylquinoxaline-silver(Ⅰ) Complex

A new dinuclear complex, [Ag(L)(CH3CN)]2(C1O4)2·2H2O(L=2,3-di-2-pyridylquinoxaline), was prepared and characterized by elemental analyses,IR spectroscopy, and single-crystal X-ray diffraction analyses. The interaction of the complex with calf thymus DNA(CT-DNA) was investigated by absorption, fluorescence spectroscopies, and viscosity measurement. The results suggested that the complex was bound to DNA via an intercalative mode. The intrinsic binding constant value Kb was found to be approximately 1.48×103 L·mol-1. Moreover, the Ag(Ⅰ) complex could cleave the plasmid pUC19 DNA from the supercoiled Form I to the nicked Form Ⅱ under irradiation at 365 nm.     

Synthesis,DNA-binding,and Photocleavage of 2,3-Di-2-pyridylquinoxaline-silver（I） Complex

A new dinuclear complex, [Ag（L）（CH3CN）]2（ClO4）2·2H2O（L=2,3-di-2-pyridylquinoxaline）, was prepared and characterized by elemental analyses, IR spectroscopy, and single-crystal X-ray diffraction analyses. The interaction of the complex with calf thymus DNA（CT-DNA） was investigated by absorption, fluorescence spectroscopies, and viscosity measurement. The results suggested that the complex was bound to DNA via an intercalative mode. The intrinsic binding constant value Kb was found to be approximately 1.48×10^3 L·mol^-1. Moreover, the Ag（I） complex could cleave the plasmid pUC19 DNA from the supercoiled Form Ⅰto the nicked FormⅡ under irradiation at 365 nm.     

N-hydroxy-4-(4-chlorophenyl)thiazole-2(3H)-thione as a photochemical hydroxyl-radical source: photochemistry and oxidative damage of DNA (strand breaks) and 2'-deoxyguanosine (8-oxodG formation)

On irradiation of N-hydroxythiazole-2(3H)-thione 3 at 300 nm, the photoproducts disulfide 4, bisthiazole 5 and thiazole 6 are formed. During this photolysis, hydroxyl radicals are released, which have been detected by spin trapping with 5,5-dimethyl-1-pyrroline N-oxide (DMPO), coupled with electron paramagnetic resonance spectroscopy. In the presence of supercoiled pBR322 DNA, irradiation of thiazolethione 3 induces strand breaks through the photogenerated hydroxyl-radicals, as confirmed by control experiment with the hydroxyl-radical scavenger isopropanol. Singlet oxygen appears not to be involved, as attested by the lack of a D2O isotope effect. During the photoreaction of thiazolethione 3 in the presence of 2'-deoxyguanosine (dG), the latter is photooxidized (ca 10% conversion after 2 h of irradiation) to the 7,8-dihydro-8-oxo-2'-deoxyguanosine as the main oxidation product. The dG conversion levels off after complete consumption of thiazolethione 3 and is suppressed by the addition of the hydroxyl-radical scavenger 2,6-di-tert-butylcresol or DMPO. Since the photoproducts 4-6 are ineffective as sensitizers for the photooxidation of dG and DNA, the hydroxyl radicals released in the photolysis of thiazolethione 3 are the oxidizing species of DNA and dG. These results suggest that the thiazolethione 3 may serve as a novel and effective photochemical hydroxyl-radical source for photobiological studies.     

Synthesis, structure and comparison of the DNA cleavage ability of metal complexes M(II)L with the N-(2-ethoxyethanol)-bis(2-picolyl)amine ligand L (M = Co, Ni, Cu and Zn)

Complexes of a N,N-bis(2-picolyl)amine (bpa) derivative with a pendant ethoxyethanol side chain (bpa(CH2)2O(CH2)2OH) (1) with late divalent transition metal ions Co(II), Ni(II), Cu(II) and Zn(II) have been studied. All complexes, [[bpa(CH2)2O(CH2)2OH]Co(NO3)](NO3) (1Co), [[bpa(CH2)2O(CH2)2OH]Ni(NO3)](NO3) (1Ni), [[bpa(CH2)2O(CH2)2OH]Cu(H2O)(NO3)](NO3) (1Cu) and [[bpa(CH2)2O(CH2)2OH]Zn(NO3)](NO3) (1Zn), were comprehensively characterized and their X-ray single crystal structures have been determined. The complexes show hexacoordinated geometries, in which 1 acts as a tetradentate (1Cu) or pentadentate (1Co, 1Ni and 1Zn) ligand. DNA cleavage experiments have been performed on supercoiled double stranded DNA plasmids in order to compare the cleavage efficiency of all four metals in the same ligand environment of 1. In this assay, 1Co and 1Cu showed the highest cleavage efficiency, whereas 1Ni and 1Zn were virtually inactive. Quantification of the gel electrophoresis bands showed that more than 80% of the plasmid has suffered at least one single strand cut in the case of 1Cu, and about 50% of the plasmid was nicked by 1Co. The differential cleavage activity is discussed in relation to the structural findings and a mechanism is proposed for 1Cu.