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1.
Eu(III) and every newly synthesized ligand can form a binuclear Eu(III) complex with a 1:1 metal to ligand stoichiometry and nine-coordinate at Eu(III) center. Every ligand acts as a dibasic tetradentate ligand, binding to Eu(III) through the phenolate oxygen atom, nitrogen atom of quinolinato unit, the CN group (methylene) and −O-CN- group (enolized and deprotonated from OC-NH- group) of the aroylhydrazine side chain. One DMF (N,N-dimethylformamide) molecule is binding orthogonally to the ligand-plane from one side to the metal ion, while another DMF and a nitrate anion (bidentate) are binding from the other. Dimerization of the monomeric unit occurs through the phenolate oxygen atoms leading to a central planar four-membered (EuO)2 ring. On the other hand, all the ligands and Eu(III) complexes may be used as potential anticancer drugs, binding to Calf thymus DNA through intercalations at the order of magnitude 105-107 M−1. All the ligands and Eu(III) complexes are strong scavengers of hydroxyl radicals and superoxide radicals, but Eu(III) complex containing active phenolic hydroxyl group shows stronger scavenging effects for hydroxyl radicals than others, and Eu(III) complex containing N-heteroaromatic substituent shows stronger scavenging effects for superoxide radicals than others. 相似文献
2.
Nirali Pandya Noor‐ul H. Khan K. Jeya Prathap Rukhsana I. Kureshy Sayed H. R. Abdi Sandhya Mishra Hari C. Bajaj 《Chirality》2012,24(12):1063-1073
We are reporting the synthesis, characterization, and calf thymus DNA binding studies of novel chiral macrocyclic Mn(III) salen complexes S‐1 , R‐1 , S‐2 , and R‐2 . These chiral complexes showed ability to bind with DNA, where complex S‐1 exhibits the highest DNA binding constant 1.20 × 106 M?1. All the compounds were screened for superoxide and hydroxyl radical scavenging activities; among them, complex S‐1 exhibited significant activity with IC50 1.36 and 2.37 μM, respectively. Further, comet assay was used to evaluate the DNA damage protection in white blood cells against the reactive oxygen species wherein complex S‐1 was found effective in protecting the hydroxyl radicals mediated plasmid and white blood cells DNA damage. Chirality 24:1063–1073, 2012.© 2012 Wiley Periodicals, Inc. 相似文献
3.
Pankaj Kumar Sumit Kumar Chaturvedi Debasis Manna Biplab Mondal 《Inorganica chimica acta》2011,376(1):264-270
Two copper(II) complexes, 1 and 2 with L1 and L2 [L1 = 2-hydroxybenzyl(2-(pyridin-2-yl)ethylamine); L2 = 2-hydroxybenzyl(2-(pyridin-2-yl)methylamine)] ligands, respectively, have been synthesized and characterized. The interaction of both the complexes with DNA has been studied to explore their potential biological activity. The DNA binding properties of the complexes with calf thymus (CT) DNA were studied by spectroscopic titration. The complexes show binding affinity to CT DNA with binding constant (Kb) values in the order of 105 M−1. Thermal denaturation and circular dichroism studies suggest groove binding of the complexes to CT DNA. Complexes also exhibit strong DNA cleavage activity in presence of reducing agents like 3-mercaptopropionic acid and β-mercaptoethanol. Mechanistic studies reveal the involvement of reactive hydroxyl radicals for their DNA cleavage activity. 相似文献
4.
Feng Gao Hui Chao Jin-Quan Wang Yi-Xian Yuan Bin Sun Yuan-Fang Wei Bin Peng Liang-Nian Ji 《Journal of biological inorganic chemistry》2007,12(7):1015-1027
Many antitumor drugs act as topoisomerase inhibitors, and the inhibitions are usually related to DNA binding. Here we designed
and synthesized DNA-intercalating Ru(II) polypyridyl complexes Δ--[Ru(bpy)2(uip)]2+ and Λ-[Ru(bpy)2(uip)]2+ (bpy is 2,2′-bipyridyl, uip is 2-(5-uracil)-1H-imidazo[4,5-f][1,10]phenanthroline). The DNA binding, photocleavage, topoisomerase inhibition, and cytotoxicity of the complexes were studied.
As we expected, the synthesized Ru(II) complexes can intercalate into DNA base pairs and cleave the pBR322 DNA with high activity
upon irradiation. The mechanism studies reveal that singlet oxygen (1O2) and superoxide anion radical (O2•−) may play an important role in the photocleavage. The inhibition of topoisomerases I and II by the Ru(II) complexes has been
studied. The results suggest that both complexes are efficient inhibitors towards topoisomerase II by interference with the
DNA religation and direct topoisomerase II binding. Both complexes show antitumor activity towards HELA, hepG2, BEL-7402,
and CNE-1 tumor cells.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
5.
Parisa R. Jamaat Nasser Safari Mina Ghiasi S. Shahab-al-din Naghavi Mansour Zahedi 《Journal of biological inorganic chemistry》2008,13(1):121-132
Conversion of iron(II) verdoheme to iron(II) biliverdin in the presence of hydroxyl ion as a nucleophile and imidazole, pyridine,
water, hydroxyl, cyanide, phenolate, chloride, thiolate and imidazolate as axial ligands was investigated using the B3LYP
method and the 6-31G basis set. In the five-coordinated pathway the reactants and products are in the ground triplet state.
In this path, hydroxyl ion directly attacks the macrocycle. The exothermic energy for addition of hydroxyl ion to iron(II)
verdoheme with various ligands is 169.55, 166.34 and 164 kcal mol−1 for water, pyridine and imidazole, energies which are around 30–60 kcal mol−1 more exothermic than those for the other axial ligands used in this study. Therefore, imidazole, water and pyridine axial
ligands can facilitate hydrolytic cleavage of iron(II) verdoheme to form open-chained helical iron(II) biliverdin complexes.
The activation barrier for the conversion of iron(II) verdoheme hydroxyl species to the iron(II) biliverdin complex is estimated
to be 5.2, 4.2, 4.35, 13.76 and 14.05 kcal mol−1 for imidazole, water, cyanide, thiolate and imidazolate, respectively.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
6.
Dimiza F Papadopoulos AN Tangoulis V Psycharis V Raptopoulou CP Kessissoglou DP Psomas G 《Journal of inorganic biochemistry》2012,107(1):54-64
Cobalt(II) complexes with the non-steroidal anti-inflammatory drug naproxen in the presence or absence of nitrogen-donor heterocyclic ligands (pyridine, 2,2′-bipyridine or 1,10-phenanthroline) have been synthesized and characterized with physicochemical and spectroscopic techniques. The deprotonated naproxen acts as monodentate ligand coordinated to Co(II) ion through a carboxylato oxygen. The crystal structure of [bis(aqua)bis(naproxenato)bis(pyridine)cobalt(II)], 2 has been determined by X-ray crystallography. The EPR spectrum of complex 2 in frozen solution reveals that it retains its structure. UV study of the interaction of the complexes with calf-thymus DNA (CT DNA) has shown that the complexes can bind to CT DNA and [(2,2′-bipyridine)bis(methanol)bis(naproxenato)cobalt(II)] exhibits the highest binding constant to CT DNA. The cyclic voltammograms of the complexes recorded in DMSO solution and in the presence of CT DNA in 1/2 DMSO/buffer (containing 150 mM NaCl and 15 mM trisodium citrate at pH 7.0) solution have shown that they can bind to CT DNA by the intercalative binding mode which has also been verified by DNA solution viscosity measurements. Competitive study with ethidium bromide (EB) has shown that the complexes can displace the DNA-bound EB indicating that they bind to DNA in strong competition with EB. Naproxen and its cobalt(II) complexes exhibit good binding propensity to human or bovine serum albumin proteins having relatively high binding constant values. The antioxidant activity of the compounds has been evaluated indicating their high scavenging activity against hydroxyl free radicals and superoxide radicals. 相似文献
7.
Rachmilovich-Calis S Masarwa A Meyerstein N Meyerstein D 《Journal of inorganic biochemistry》2011,105(5):669-674
It has been recently reported that pyrophosphate, tri-polyphosphate, ATP and analogous ligands considerably decrease the yield of hydroxyl radicals by the Fenton reaction under conditions where [H2O2] > > [Fe(II)Ln]. It was suggested that this effect is due to the slowing down of the Fenton reaction by these ligands. This suggestion seemed surprising as polyphosphate ligands stabilize Fe(III). Indeed, a kinetic study points out that these ligands accelerate the rate of the Fenton reaction by several orders of magnitude. Thus it is suggested that the effect of the ligands on the yield of the hydroxyl radicals is due to the stabilization of the Fe(III) complexes which slows down, or inhibits, their reduction by the radicals formed in the system and thus decreases the overall yield of hydroxyl radicals. 相似文献
8.
In this study, three alginate fractions with different molecular weights and ratios of mannuronic acid (M) to guluronic acid
(G) were prepared by enzymatic hydrolysis and ultrafiltration to assess the antioxidant property of alginates from Laminaria japonica with molecular weight below 10 kDa. The antioxidant properties of different molecular weight alginates were evaluated by
determining the scavenging abilities on superoxide, hydroxyl, and hypochlorous acid and inhibitory effect on Fe2+-induced lipid peroxidation in yolk homogenate. The results showed that low molecular weight alginates exhibited high scavenging
capacities on superoxide, hydroxyl, and hypochlorous acid radicals and good inhibition of Fe2+-induced lipid peroxidation in yolk. By comparison, alginate A1 with molecular weight below 1 kDa and M/G of 1.84 had better
scavenging activity on superoxide, hydroxyl, and hypochlorous acid radicals in vitro than A2 (1–6 kDa), A3 (6–10 kDa), ascorbic
acid, and carnosine. With similar M/G ratio, A2 exhibited better antioxidant activity on superoxide and hypochlorous acid
radicals than A3. However, fraction A3 with molecular weight of 6–10 kDa exhibited higher inhibitory ability on lipid peroxidation
in yolk in vitro than A1 and A2. The results indicated that molecular weight played a more important role than M/G ratio on
alginate to determine the antioxidant ability. By comparison, low molecular weight alginates composed of guluronic acid and
mannuronic acid exhibited better antioxidant ability on oxygen free radicals than sulfated polysaccharides from L. japonica in our previous study and represent a good source of marine polysaccharide with potential application as natural antioxidant. 相似文献
9.
Two zinc(II) terpyridine complexes Zn(atpy)2(PF6)2 (1) (atpy = 4′-p-N9′-adeninylmethylphenyl-2,2′:6,2′′-terpyridine) and Zn(ttpy)2(PF6)2 (2) (ttpy = 4′-p-tolyl-2,2′:6,2′′-terpyridine) have been synthesized and characterized by elemental analysis, 1H NMR and electrospray mass spectroscopy. The structure of complex 2 was also determined by X-ray crystallography, which revealed a ZnN6 coordination in an octahedral geometry with two terpyridine acting as equatorial ligands. The circular dichroism data showed
that complex 1 exhibited an ICD signal at around 300 nm and induced more evident disturbances on DNA base stacking than complex 2, reflecting the impact of the adenine moiety on DNA binding modes. Complex 1 exhibited higher cleavage activity to supercoiled pUC 19 DNA than complex 2 under aerobic conditions, suggesting a promotional effect of adenine moiety in DNA nuclease ability. Interestingly, both
complexes demonstrated potent in vitro cytotoxicity against a series human tumor cell lines such as human cervix carcinoma
cell line (HeLa), human liver carcinoma cell line (HepG2), human galactophore carcinoma cell line (MCF-7) and human prostate
carcinoma cell line (pc-3). The cytotoxicity is averagely 10 times more active than the anticancer drug cisplatin.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
10.
Ruth Bieda Igor Kitanovic Hamed Alborzinia Andreas Meyer Ingo Ott Stefan Wölfl William S. Sheldrick 《Biometals》2011,24(4):645-661
The cytostatic properties of novel rhodium(III) thiacrown ether complexes [RhCl(LL)([9]aneS3)]n+ with either aromatic κ2
N ligands (n = 2) or anionic chelate ligands (n = 1) have been investigated for the human cancer cell lines HT-29 and MCF-7 and for immortalized HEK-293 cells. Taken together
with literature IC50 values for analogous complexes with polypyridyl ligands or 1,4-dithiane, the in vitro assays indicate that dicationic complexes
with soft κ2
N (imino) or κ2
S (thiaether) ligands exhibit significantly higher antiproliferative effects than those with hard κ2
N (amino) ligands. Dicationic complexes are more active than monocationic complexes with similar ligands. Pronounced apoptosis-inducing
properties towards Jurkat cells were established for complexes with LL = bpm, dpq, and 1,4-dithiane. The order of activity
(bpm > 1,4-dithiane > dpq > bpy) contrasts to that observed for adhesive cancer cells (bpm > bpy, 1,4-dithiane > dpq). Necrosis
is insignificant in all cases. The percentage of Jurkat cells exhibiting apoptosis after 24 or 48 h incubation periods is
directly correlated to the percentage of cells exhibiting high levels of reactive oxygen species. As established by online
monitoring with a sensor chip system, treatment of MCF-7 cells with the bpm and 1,4-dithiane complexes leads to a significant
and permanent concentration-dependent decrease in oxygen consumption and cellular adhesion. 相似文献
11.
Yun-Jun Liu Zhen-Hua Liang Zheng-Zheng Li Cheng-Hui Zeng Jun-Hua Yao Hong-Liang Huang Fu-Hai Wu 《Biometals》2010,23(4):739-752
A new ligand DBHIP and its two ruthenium(II) complexes [Ru(dmb)2(DBHIP)](ClO4)2 (1) and [Ru(dmp)2(DBHIP)](ClO4)2 (2) have been synthesized and characterized. The cytotoxicity of DBHIP and complexes 1 and 2 has been assessed by MTT assay. The apoptosis studies were carried out with acridine orange/ethidium bromide (AO/EB) staining
methods. The binding behaviors of these complexes to calf thymus DNA (CT-DNA) were studied by absorption titration, viscosity
measurements, thermal denaturation and photoactivated cleavage. The DNA-binding constants of complexes 1 and 2 were determined to be 8.64 ± 0.16 × 104 (s = 1.34) and 2.79 ± 0.21 × 104 (s = 2.17) M−1. The results suggest that these complexes interact with DNA through intercalative mode. The studies on the mechanism of photocleavage
demonstrate that superoxide anion radical (O2
•–) and singlet oxygen (1O2) may play an important role in the DNA cleavage. The experiments on antioxidant activity show that these compounds also exhibit
good antioxidant activity against hydroxyl radical (OH•). 相似文献
12.
Mildred M. Rodriguez-Ramos Jonathan J. Wilker 《Journal of biological inorganic chemistry》2010,15(5):629-639
Modified oligonucleotides are showing potential for multiple applications, including drug design, nanoscale building blocks,
and biosensors. In an effort to expand the functionality available to DNA, we have placed chelating ligands directly into
the backbone of DNA. Between one and three nucleosides were replaced with 2,2′-bipyridine phosphates in 23-mer duplexes of
DNA. An array of metal ions were added (Fe2+, Co2+, Ni2+, Cu2+, Zn2+, and Pt2+) and the influences on duplex stability were examined by melting temperature studies. Titrations and UV–vis absorption spectroscopy
were used to provide insights into the nature of the metal complexes formed. We found that Ni2+ binding to 2,2′-bipyridine typically provided the greatest increase in duplex stability relative to the other metal ions
examined. For example, addition of Ni2+ to one 2,2′-bipyridine–DNA duplex increased the melting temperature by 13 °C, from 65.0 ± 0.3 to 78.4 ± 0.9 °C. These studies
show that metal ions and backbone ligands can be used to regulate DNA structure and stability. 相似文献
13.
Asieh Moodi Meissam Noroozifar Sona Niroomand 《Journal of biomolecular structure & dynamics》2013,31(8):937-950
To evaluate the biological preference of [Yb(phen)2(OH2)Cl3](H2O)2 (phen is 1,10-phenanthroline) for DNA, interaction of Yb(III) complex with DNA in Tris–HCl buffer is studied by various biophysical and spectroscopic techniques which reveal that the complex binds to DNA. The results of fluorescence titration reveal that [Yb(phen)2(OH2)Cl3](H2O)2 has strongly quenched in the presence of DNA. The binding site number n, apparent binding constant K b, and the Stern–Volmer quenching constant K SV are determined. ΔH 0, ΔS 0, and ΔG 0 are obtained based on the quenching constants and thermodynamic theory (ΔH 0?>?0, ΔS 0?>?0, and ΔG 0?<?0). The experimental results show that the Yb(III) complex binds to DNA by non-intercalative mode. Groove binding is the preferred mode of interaction for [Yb(phen)2(OH2)Cl3](H2O)2 to DNA. The DNA cleavage results show that in the absence of any reducing agent, Yb(III) complex can cleave DNA. The antimicrobial screening tests are also recorded and give good results in the presence of Yb(III) complex. 相似文献
14.
Chak Ming Sze George N. Khairallah Zhiguang Xiao Paul S. Donnelly Richard A. J. O’Hair Anthony G. Wedd 《Journal of biological inorganic chemistry》2009,14(2):163-165
The chaperone protein CopC from Pseudomonas syringae features high-affinity binding sites (K
D ~ 10−13 M) for both CuI (Met-rich) and CuII (His-rich). When presented with these sites in the apoprotein, electrospray ionisation mass spectrometry confirmed that cis-Pt(NH3)2Cl2 (cisplatin) and the fragments [PtIIL]2+ (L is 1,2-diaminoethane, 2,2′-bipyridine) occupied the CuI site specifically in the 1:1 Pt–CopC adducts (purified by cation-exchange chromatography). The cis-Pt(NH3)2 fragment was not present in these adducts (the dominant product for cisplatin was Pt–CopC in which all original ligands were
displaced), while bidentate ligands L were retained in LPt–CopC adducts. In the context of the Met-rich CuI pump Ctr1 as a significant entry point for cisplatin into mammalian cells, the present work confirms the ability of Met-rich
sites in proteins to remove all ligands from cisplatin. It focuses attention on the potential of proteins that are part of
the natural copper transport pathways to sequester the drug. These pathways are worthy of further study at the molecular level.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
15.
Selvan Nehru Renganathan Arun Kumpati Premkumar 《Journal of biomolecular structure & dynamics》2013,31(11):1876-1888
A new series of pendant-type polymer-cobalt(III) complexes, [Co(LL)2(BPEI)Cl]2+, (where BPEI?=?branched polyethyleneimine, LL?=?dipyrido[3,2-a:2′,3′-c](6,7,8,9-tetrahydro)phenazine (dpqc), dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq) and imidazo[4,5-f]1,10-phenanthroline (ip)) each with three different degrees of coordination have been synthesized and characterized. Studies to know the mode and strength of interaction between these polymer–metal complexes and calf thymus DNA have been performed by UV–Visible absorption and emission techniques. Among these series, each polymer metal complex having higher binding strength with DNA has been selected to test against human cancer/normal cell lines. On the basis of these spectral studies, it is proposed that our polymer–metal complexes bind with DNA mainly through intercalation along with some electrostatic binding. The order of binding strength for the complexes with ligand, dpqc?>?dpq?>?ip. The analysis of the results suggests that polymer–cobalt(III) complexes with higher degree of coordination effectively binds with DNA due to the presence of large number of positively charged cobalt(III) chelates in the polymer chain which cooperatively act to increase the overall binding strength. These polymer–cobalt(III) complexes with hydrophobic ligands around the cobalt(III) metal centre favour the base stacking interactions via intercalation. All the complexes show very good anticancer activities and increasing of binding strength results in higher inhibition value. The polymer–cobalt(III) complex with dpqc ligand possess two fold increased anticancer activity when compared to complexes with other ligands against MCF-7 cells. Besides, the complexes were insensitive towards the growth of normal cells (HEK-293) at the IC50 concentration. 相似文献
16.
The most aggressive product of water radiolysis, the hydroxyl (OH) radical, is responsible for the indirect effect of ionizing radiations on DNA in solution and aerobic conditions. According to radiolytic footprinting experiments, the resulting strand breaks and base modifications are inhomogeneously distributed along the DNA molecule irradiated free or bound to ligands (polyamines, thiols, proteins). A Monte-Carlo based model of simulation of the reaction of OH radicals with the macromolecules, called RADACK, allows calculating the relative probability of damage of each nucleotide of DNA irradiated alone or in complexes with proteins. RADACK calculations require the knowledge of the three dimensional structure of DNA and its complexes (determined by X-ray crystallography, NMR spectroscopy or molecular modeling). The confrontation of the calculated values with the results of the radiolytic footprinting experiments together with molecular modeling calculations show that: (1) the extent and location of the lesions are strongly dependent on the structure of DNA, which in turns is modulated by the base sequence and by the binding of proteins and (2) the regions in contact with the protein can be protected against the attack by the hydroxyl radicals via masking of the binding site and by scavenging of the radicals. 相似文献
17.
Novel 2-oxo-1,2-dihydroquinoline-3-carbaldehyde (4′-methylbenzoyl) hydrazone (H2L) (1) and its two copper(II) complexes have been synthesized. Single-crystal X-ray diffraction studies revealed that the structure
of the new copper(II) chloride complex, [Cu(H2L)Cl2]·2H2O (2), is square pyramidal and that of the copper(II) nitrate complex, [Cu(HL)NO3]·DMF (3), is square planar. In 2, the copper atom is coordinated by the ligand with ONO donor atoms, one chloride ion in the apical position, and the other
chloride in the basal plane. In 3, the ligand coordinates as a uninegative tridentate ONO− species and with one nitrate ion in the basal plane. DNA binding experiments indicated that the ligand and copper(II) complexes
can interact with DNA through intercalation. Bovine serum albumin binding studies revealed that the compounds strongly quench
the intrinsic fluorescence of bovine serum albumin through a static quenching process. Antioxidative activity tests showed
that 1 and its copper(II) complexes have significant radical scavenging activity against free radicals. Cytotoxic activities of
the ligand and copper(II) complexes showed that the two copper(II) complexes exhibited more effective cytotoxic activity against
HeLa and HEp-2 cells than the corresponding ligand. The entire biological activity results showed that the activity order
was 1 < 2 < 3. 相似文献
18.
Lei Jia Peng Jiang Zhong-yan Hao Long-hai Chen Ning Tang Qin Wang 《Inorganica chimica acta》2010,363(5):855-6176
Three novel ternary copper(II) complexes, [Cu2(phen)2(l-PDIAla)(H2O)2](ClO4)2·2.5H2O (1), [Cu4(phen)6(d,l-PDIAla)(H2O)2](ClO4)6·3H2O (2) and [Cu2(phen)2(d,l-PDIAla)(H2O)](ClO4)2·0.5H2O (3) (phen = 1,10-phenanthroline, H2PDIAla = N,N’-(p-xylylene)di-alanine acid) have been synthesized and structurally characterized by single-crystal X-ray crystallography and other structural analysis. Spectrometric titrations, ethidium bromide displacement experiments, CD (circular dichroism) spectral analysis and viscosity measurements indicate that the three compounds, especially the complex 3, strongly bind to calf-thymus DNA (CT-DNA). The intrinsic binding constants of the ternary copper(II) complexes with CT-DNA are 0.89 × 105, 1.14 × 105 and 1.72 × 105 M−1, for 1, 2 and 3, respectively. Comparative cytotoxic activities of the copper(II) complexes are also determined by acid phosphatase assay. The results show that the ternary copper(II) complexes have significant cytotoxic activity against the HeLa (Cervical cancer), HepG2 (hepatocarcinoma), HL-60 cells (myeloid leukemia), A-549 cells (pulmonary carcinoma) and L02 (liver cells). Investigations of antioxidation properties show that all the copper(II) complexes have strong scavenging effects for hydroxyl radicals and superoxide radicals. 相似文献
19.
With a model system of pBR322 plasmid DNA solution in vitro, the dose effects of radiation- induced single- and double-strand
breaks (SSB and DSB) were measured and DSB was distinguished into α- and β-types. Under the condition of low scavenging capacity
existing in the irradiated DNA solution, SSB and αDSB were mainly induced by hydroxyl radicals (·OH). Moreover, a certain relationship was obtained between the SSB and αDSB yields and the DNA concentration. It was found
that when the DNA solution was irradiated in the presence of 2.5 mmol dm–3 mannitol, the reciprocals of G(SSB) and G(αDSB), respectively, were linearly related to the reciprocal of the DNA concentration,
i.e. the competition reactions of DNA and mannitol for ·OH radicals can be described by second-order kinetics. The rate coefficients and the efficiencies of the ·OH radical inducing SSB were deduced. Also, the reaction rate coefficients and the efficiencies for the induction of αDSB
from SSB by the ·OH radical transfer mechanism, were first derived from the competition kinetics.
Received: 27 October 1999 / Accepted: 15 March 2000 相似文献
20.
Jingli Liu Huili Sun Fang Dong Qinzhao Xue Gang Wang Song Qin Zhanyong Guo 《Carbohydrate polymers》2009,78(3):439-443
Various quaternized chitosans (QCSs) were synthesized according to previous method. Their reducing power and antioxidant potency against hydroxyl radicals (OH) and hydrogen peroxide (H2O2) were explored by the established systems in vitro. The QCSs exhibited markedly antioxidant activity, especially TCEDMCS, whose IC50 on hydroxyl radicals was 0.235 mg/mL. They showed 65–80% scavenging effect on hydrogen peroxide at a dose of 0.5 mg/mL. Generally, the antioxidant activity decreased in the order TCEDMCS > TBEDMCS > EDMCS > PDMCS > IBDMCS > Chitosan. Furthermore, the order of their OH and H2O2 scavenging activity was consistent with the electronegativity of different substituted groups in the QCSs. The QCSs showed much stronger antioxidant activity than that of chitosan may be due to the positive charge density of the nitrogen atoms in QCSs strengthened by the substituted groups. 相似文献