放线菌素D光敏产生活性氧的EPR研究

放线菌素D是一种和双链DNA和单链DNA都能发生选择性结合的抗生素, 而这种结合作用大大增加了DNA的光敏性. 利用电子顺磁共振(EPR)和自旋捕捉技术, 对放线菌素D光动力作用过程中产生的活性氧进行了系统研究, 发现无论是在溶液中还是在与DNA形成复合物以后, ¹O₂和O₂^—. 都是重要的活性产物, 而且两者的产额存在竞争关系. 实验结果说明, 放线菌素D的光敏作用是通过能量转移(Ⅱ型机制)和电子转移(Ⅰ型机制)两种反应途径进行的. 当在溶液中氧自由存在时, 以能量转移形成¹O₂为主; 而当和DNA形成复合物时, 放线菌素D的激发态与DNA之间的电子转移反应成为主要的反应途径.     

原位脱羧制备的配合物(HP2W18O62)(C6H6NO2)5·2H2O:结构、光谱及电化学性能

采用水热法将钨酸钠和浓磷酸与有机配体吡啶-2,6-二羧酸通过原位脱羧制得配合物(HP2W18O62)(C6H6NO2)5.2H2O(1),并用红外光谱、紫外光谱、循环伏安(CV)和X射线单晶衍射等方法进行了表征。分子中的2-吡啶甲酸来源于吡啶-2,6-二羧酸的脱羧反应。化合物1属于单斜晶系,空间群P21/n,晶胞参数分别为:a=1.553 3(2)nm,b=2.006 3(3)nm,c=2.759 9(4)nm,β=103.981(2)°,Z=4,F(000)=8 816。分子间氢键和2-吡啶甲酸与杂多化合物间的弱相互作用使该化合物具有3D超分子结构。CV结果表明,化合物1有四步氧化还原反应。     

抗癌药物cis-[Pt(NH3)(2-picoline)]2+与DNA加合物的结构和成键特征

利用分子力学、分子动力学、分子力学与量子化学相结合(Oniom)以及量子化学等多种方法研究了抗癌药物cis-[Pt(NH₃)(2-picoline)]²⁺与DNA片段d(ATACATG^*-G^*TACATA)·d(TATGTACCATGTAT)的加合物的几何构型和电子结构. 结果表明Oniom方法优化得到的构型与NMR实验测定的结构最为接近, Pt配合物与DNA中相邻的两个鸟嘌呤的N7原子形成较强化学键, 从而导致DNA的构型发生较大的变化. 同时, 配合物中NH₃的一个H与其邻近的鸟嘌呤的O6间形成的氢键也是影响Pt配合物与DNA加合物几何构型的重要因素. 上述化学键、氢键以及药物与碱基的甲基间的相互作用是药物分子能够对DNA进行识别的重要基础.     

0D/2D碳氮量子点(CNQDs)/BiOBr复合的S型异质结高效光催化降解和产H2O2(英文)

光生载流子的快速复合制约着BiOBr的光催化性能，通过构建界面紧密结合的异质结可以有效地解决这个问题。在本研究中，通过采用简单的高温高压水热法，首次在二维(2D)BiOBr表面上成功复合了零维(0D)的g-C3N4量子点(CNQDs)，并形成了具有紧密接触界面的0D/2D CNQDs/BiOBr S型异质结，主要原因是CNQDs杂环中的π电子与BiOBr产生了相互作用。CNQDs/BiOBr-1.50%复合材料在光照下降解四环素(TC)、环丙沙星(CIP)和产H₂O₂的表观反应速率常数k值分别是BiOBr的2.02、2.91和1.54倍。在循环测试中，CNQDs/BiOBr-1.50%显示出相对较高的光催化活性和结构稳定性。通过X射线光电子能谱(XPS)分析，明确CNQDs中的π电子与BiOBr具有相互作用，确认了异质结中光生电子的转移方向。CNQDs/BiOBrS型异质结的成功构建使其具有非凡的光催化稳定性和活性。更多活性物质的产生和稳定的催化活性归因于电子和空穴的独特转移机制。CNQDs/BiOBrS型异质结的特殊的电子-空穴转移机理实现...     

Co(phen)33+与6-巯基嘌呤及DNA间相互作用的研究

自1969年首次报道顺铂(cis-[Pt(NH 3 ) 2 Cl 2 ])对肿瘤有强烈抑制作用以来,金属配合物抗肿瘤药物的研究倍受重视 [1,2] ?很多抗肿瘤药物治疗恶性肿瘤疾病都是通过切割人体肿瘤细胞的DNA来实现的?DNA与外源性分子相互作用的研究构成肿瘤形成的机理和一些抗肿瘤药物作用机理的基     

Mg2NiH4对高氯酸铵热分解过程的影响

采用置换-扩散法制备了储氢材料Mg2NiH4, 用XRD, ICP和DSC-TG方法对其结构进行了表征. 用热分析法(DSC)研究了Mg2NiH4对高氯酸铵(AP)热分解过程的影响. 研究结果表明, Mg2NiH4对AP热分解过程有较大影响. Mg2NiH4可以显著促进AP的低温热分解过程, 降低高温热分解温度, 使DSC表观分解热明显增大. 随着加入量的增加, Mg2NiH4对AP热分解的催化促进作用增强, 当Mg2NiH4加入的质量分数为30％时, DSC表观分解热最大. 吸氢量越大, 储氢材料对AP的催化促进作用越强. Mg2NiH4催化促进AP分解过程的作用机理为: Mg2NiH4分解释放的H2及Mg和Ni与AP分解产物发生反应.     

具有纳米孔结构的配位聚合物[Co2(HO-BDC)2(bpe)2(H2O)2]n·n(py)·nH2O的合成、晶体结构与热稳定性

在水-吡啶混合体系中, 以5-羟基-1,3-苯二甲酸(简作HO-H2BDC )、1,2-二(4-吡啶)乙烷(简作bpe)为配体与Co(NO3)2·6H2O反应, 培养出[Co2(HO-BDC)2(bpe)2(H2O)2]n·n(py)·nH2O(py=pyridine)的紫色单晶, 该晶体属三斜晶系, P1空间群, 晶胞参数a=1.0245(3) nm, b=1.1467(3) nm, c=1.2430(4) nm, α=68.915(5)°, β=67.163(4)°, γ=71.373(4)°, V=1.2279(6) nm3, Z=1, Mr=979.70, Dc=1.325 Mg/m3, F(000)=506, μ=0.740 mm-1, R1=0.0515, wR2=0.1058. 该配位聚合物中在ac平面上具有规则平行四边形纳米尺寸的孔, 其孔径大小约为1.025 nm×1.354 nm, 而且通过氢键相互作用连成具有双层结构的2D网络结构. TGA曲线表明, 配位聚合物的失重发生在110~150 ℃之间, 总失重约为80.1%, 最终产物为Co2O3.     

方波伏安法研究[Ru（bpy）2dppz]2+与DNA的相互作用

合成了含有嵌入配体二吡啶并[3,2-a:2′,3′-c]-吩嗪(dppz)的钌配合物二联吡啶二吡啶并[3,2-a;2′,3′-c]吩嗪钌([Ru(bpy)2dppz]2+),并对其结构和物理化学性质进行了表征。采用方波伏安法研究了[Ru(bpy)2dppz]2+与天然双链小牛胸腺DNA的相互作用,实验结果表明,[Ru(bpy)2dppz]2+配合物的嵌入配体会嵌入DNA的碱基对中,与DNA结合形成体积较大的"金属配合物-DNA"联合体,该联合体在电解质溶液中扩散速度较慢,导致溶液中游离的钌配合物分子减少,峰电流信号降低。计算得到[Ru(bpy)2dppz]2+与DNA的结合常数Ka=1.7×105 L/mol,结合位点n=0.84。     

新型铜配合物[Cu(PyPt)(NO3)2]合成、结构、表征及其与DNA相互作用

本文报道了新型铜配合物[Cu(PyPt)(NO3)2](HPyPt是N-2-吡啶基-N'-苯基硫脲)的合成、结构、波谱表征及其与DNA相互作用研究.该配合物属三斜品系P1空间群,其中a=0.761 52(15)nm,b=0.80957(16)nm,c=1.311 3(3)nm,α=76.01(3)°,β=89.59(3)°,γ=68.24(3)°,V=0.7255(2)nm3,Z=2.利用荧光光谱法、紫外光谱法和粘度法初步研究了[Cu(PyPt)(NO3)2]与小牛胸腺DNA的相互作用,计算其与DNA结合常数Kb为1.63×103 L·mol-1.     

双核钒席夫碱配合物[VO(μ2-O)(o-Vanillin-en)]2的合成、结构及与DNA相互作用

在甲醇体系中乙酰丙酮氧钒与邻香草醛缩牛磺酸钾席夫碱在乙二胺存在下反应得到一个双核钒配合物。通过红外光谱和X-射线单晶衍射对其进行了表征。晶体结构表明该化合物的晶体属于三斜晶系，P1空间群，晶胞参数为a=0.898 67(19)nm，b=1.159 3(3) nm，c=1.200 0(3) nm，α=106.872(3)°，β=102.718(4)°，γ=94.905(3)°，Z=2。通过紫外吸收光谱法和循环伏安法研究了钒配合物与小牛胸腺DNA间的相互作用。紫外吸收光谱法得到配合物与DNA的结合常数为1.77×10⁴ dm³·mol^-1。     

Examining the binding mechanism of 3,4-dihydro-3-(2-oxo-2-phenylethylidene)-quinoxalin-2(1H)-one and its fragments to Cu2+

The structure and stoichiometries of the complexes that could be formed between Cu²⁺ and 3,4-dihydro-3-(2-oxo-2-phenylethylidene)-quinoxalin-2(1H)-one (1) were investigated by various spectral techniques such as IR, fluorescence, UV–vis and electron paramagnetic resonance. The results suggest that initially 3?:?1 and 2?:?1 (1/Cu²⁺) complexes are formed at low Cu²⁺ concentration and upon adding more Cu²⁺, 1?:?1 (preferred) and 1?:?2 complexes are generated. Since 1 possesses two possible binding sites, further exploration was done by testing the binding ability of Cu²⁺ to fragments of 1, namely β-enaminoketone derivatives (2–3) and quinoxaline-2-one (4), and by executing calculations of thermodynamic parameters of the reaction between 1 and Cu²⁺ in ethanol, optimized geometries of the possible complexes, and estimation of stability constants at various stoichiometries. Consequently, a step-by-step binding mechanism is suggested for formation of various complexes between 1 and Cu²⁺.     

Oxidative DNA Damage in the Photolysis of Af-Hydroxy-2-Pyridone, a Specific Hydroxyl-Radical Source

Abstract The photooxidative DNA damage by iV-hydroxy-2-pyri-done (1) is caused by hydroxyl radicals, as confirmed by electron paramagnetic resonance studies with the spin trap 5,5-dimethylpyrroline JV-oxide. Irradiation of the pyridone 1 at 300 nm induced strand breaks in super-coiled pBR322 DNA, while in calf-thymus DNA and 2'-deoxyguanosine (dG), respectively, 8-oxoguanine and 8-oxo-7,8-dihydro-2'-deoxyguanosine were formed. Time-dependent control experiments disclosed that photoprod-ucts of pyridone 1, e.g. 2-pyridone (3), are not responsible for the modification of DNA. Also the photosensitization by the pyridine-2-one chromophore was excluded, because JV-methylpyridine-2-one (2), which cannot generate hydroxyl radicals, was ineffective in the photooxidation of DNA and dG. Thus, the photolysis of pyridone 1 serves as a specific source of hydroxyl radicals for DNA damage, both strand breaks and base modifications.     

Sensitive detection of a plant virus by electrochemical enzyme-linked immunoassay

The electrochemical enzyme-linked immunoassay increases the sensitivity of the detection of cucumber mosaic virus (CMV) by 5-fold compared with the spectrophotometric o-phenylenediamine (OPD) enzyme-linked immunosorbent assay (ELISA). The detection limit for the purified CMV is 1.0 ng/mL and the highest dilution ratio of the infected leaf sap is 1:5.0 x 10(4). The method is based on coupling the oxidation reaction of o-aminophenol (OAP)-H2O2 catalyzed by HRP-IgG conjugate with the electro-reduction of the enzymatic product. The enzymatic product 2-aminophenoxazine-3-one exhibits a sensitive second order derivative linear-sweep voltammetric response at the potential of -0.65 V (vs. Ag/AgCl) in pH 8.0 Britton-Robinson (B-R) buffer solution. So it can be applied to the detection of the plant virus with highly improved sensitivity.     

Ruthenium(II)(bpy)(2)L](2+), where L are imidazo[f]-1,10-phenanthrolines: synthesis, photophysics and binding with DNA

Three Ru(II) complexes of type as [Ru(II)(bpy)(2)L](2+) were synthesized, where L are l,10-phenanthroline derivatives of imidazole (1), having at position 2 alpha-naphthyl (2), 3-methoxy-4-hydroxy-phenyl (3). All complexes show intense MLCT transition both in acetonitrile and in water and also exhibit strong emission at room temperature, which is efficiently quenched by oxygen as well as, to some extent, by water. The binding of complexes 1-3 to calf thymus DNA was investigated by using electronic absorption, steady-state luminescence, luminescence quenching, excited-state lifetime and circular dichroism spectra. Hypochromic effect, luminescence enhancement, and quenching studies demonstrate the existence of intercalation mode. Circular dichroism spectra indicate the stereoselectivity of the binding. The binding of 1-3 with DNA is sensitive to the nature of ligands, such as planarity, pi-electron extension and hydrophobicity. Complex 3 exhibits the strongest binding with DNA, which can be attributed to hydrogen bonding.     

Synthesis and spectroscopic DNA binding studies of [Ru(phen)2(tbtc)]2+ and [Ru(2,9-dmp)2(tbtc)]2+

A new polypyridyl ligand tbtc (tbtc=4,5,9,14-tetraaza-benzo[b]triphenylene-11-carboxylic acid methyl ester) and its complexes [Ru(phen)2(tbtc)]2+ (1) (phen=1,10-phenanthroline) and [Ru(2,9-dmp)2(tbtc)]2+ (2) (2,9-dmp=2,9-dimethyl-1,10-phenanthroline) were synthesized and characterized by element analysis, MS, and 1H NMR. The DNA binding properties of both complexes to calf thymus DNA (CT-DNA) were investigated by different spectrophotometric methods and viscosity measurements. The results suggest that both complexes bind to DNA via an intercalative mode, and the DNA binding affinity of complex 1 is much greater than that of complex 2. This difference in binding affinity probably was caused by the different ancillary ligands. Also, when irradiated at 365 nm, complex 1 was found to be a more-effective DNA-cleaving agent than complex 2.     

Regioselective alkylation of 2-alkyl-5,6,7,8-tetrahydro-3h-cycloheptimidazol-4-ones and 2-alkyl-3h-cycloheptimidazol-4-ones

Regioselective alkylation of 2-alkyl-5,6,7,8-tetrahydro-3H-cycloheptimidazol-4-one (1) and 2-alkyl-3H-cycloheptimidazol-4-one (2) was investigated. 3-[2'-(1-tert-Butyl-1H-tetrazol-5-yl)biphenyl-4-ylmethyl]-2-propyl-5,6,7,8-tetrahydro-1H-cycloheptimidazol-4-one (6) was preferentially obtained under the conditions by using NaH in DMF or THF. On the other hand, 3-[2'-(1-tert-butyl-1H-tetrazol-5-yl)biphenyl-4-ylmethyl]-2-propyl-5,6,7,8-tetrahydro-3H-cycloheptimidazol-4-one (5), the synthetic intermediate compound of Pratosartan, was obtained selectively in the presence of n-Bu(4)NBr in toluene by using aqueous sodium hydroxide as a base. In this reaction, it was found that the concentration of the alkaline solution influences its regioselectivity. This selectivity was observed even for aldehyde and ester derivatives.     

Sensitive detection of a plant virus by electrochemical enzyme-linked immunoassay

The electrochemical enzyme-linked immunoassay increases the sensitivity of the detection of cucumber mosaic virus (CMV) by 5-fold compared with the spectrophotometric o-phenylenediamine (OPD) enzyme-linked immunosorbent assay (ELISA). The detection limit for the purified CMV is 1.0 ng/mL and the highest dilution ratio of the infected leaf sap is 1?:?5.0 × 10⁴. The method is based on coupling the oxidation reaction of o-aminophenol (OAP)-H₂O₂ catalyzed by HRP-IgG conjugate with the electro-reduction of the enzymatic product. The enzymatic product 2-aminophenoxazine-3-one exhibits a sensitive second order derivative linear-sweep voltammetric response at the potential of –0.65 V (vs. Ag/AgCl) in pH 8.0 Britton-Robinson (B-R) buffer solution. So it can be applied to the detection of the plant virus with highly improved sensitivity.     

The resonance Rayleigh scattering of the interaction of copper(II)-bleomycinA2 with DNA and its analytical application

The forming of bleomycinA2-Cu(II) cationic chelate and the interaction of the chelate with DNA have been investigated by using resonance Rayleigh scattering (RRS), molecular absorption and fluorescence spectra. The result shows that in aqueous solution, bleomycinA2 (BLMA2) can react with Cu(II) to form 1:1 cationic chelate which contributes to the changes of the absorption spectra and the quenched fluorescence of BLMA2. When the cationic chelate further bound with DNA to form ternary ion-association complexes, the remarkable enhancement of the RRS intensity was observed. In this work, the optimum conditions for the coordination reaction of BLMA2 with Cu(II) and some influencing factors have been investigated. The reaction mechanism of BLMA2-Cu(II) binding with DNA was suggested and a binding model was proposed. In addition, the fluorescence quenching type of BLMA2 was investigated. A highly sensitive, simple and rapid new method for the determination of DNA by using BLMA2-Cu(II) as RRS probe has been developed. The detection limits (3σ) are 7.2 ng/mL for ctDNA, 7.1 ng/mL for sDNA and 18 ng/mL for hsDNA. The method can be applied to the determination of trace amounts of DNA.     

Synthesis and biological evaluation of 5’-phenyl-3’H-spiro-[indoline-3,2’-[1,3,4]oxadiazol]-2-one analogs

A series of 5'-phenyl-3'H-spiro[indoline-3,2'-[1,3,4]thiadiazol]-2-one analogs were synthesized and their Bcl-2 protein inhibitory activities were studied. The lead compound was originally identified using a fluorescence polarization-based competitive binding assay. Among the 10 compounds investigated, 1k showed good binding affinities to Bcl-xL and Mcl-1, with inhibition constants of 8.9 mmol/L and 3.4 μmol/L, respectively. While compound 1c achieved tight binding affinities to Bcl-xL (Ki = 0.16 μmol/L), has the potential to be a new lead compound.