壳寡糖铕、铽配合物的合成、表征及抗·O-2活性

用壳寡糖分别与硝酸铕和硝酸铽反应, 制备了壳寡糖-铕、壳寡糖-铽两种配合物. 用红外光谱、紫外光谱、 荧光和X射线光电子能谱(XPS)等分析测试手段对配合物进行了表征. 以吩嗪硫酸甲酯(PMS)-还原型辅酶Ⅰ烟酰胺腺嘌呤二核苷酸(NADH)-硝基四氮唑蓝(NBT)产生超氧阴离子自由基(·O-2)来研究壳寡糖和壳寡糖稀土金属配合物对·O-2自由基的清除作用. 结果表明: 壳寡糖与Eu3 或Tb3 形成了配合物, 壳寡糖-铕、壳寡糖-铽配合物中不仅壳寡糖氨基上的N原子参与了配位, 同时仲羟基的O原子也参与了配位. 壳寡糖和壳寡糖稀土金属配合物对·O-2均具有明显的清除作用, 配合物与壳寡糖相比对·O-2具有更高的清除活性.     

壳寡糖铕、铽配合物的合成、表征及抗·O2^-活性

用壳寡糖分别与硝酸铕和硝酸铽反应,制备了壳寡糖-铕、壳寡糖-铽两种配合物。用红外光谱、紫外光谱、荧光和X射线光电子能谱（XPS）等分析测试手段对配合物进行了表征。以吩嗪硫酸甲酯（PMS）-还原型辅酶Ⅰ烟酰胺腺嘌呤二核苷酸（NADH）-硝基四氮唑蓝（NBT）产生超氧阴离子自由基（·O2^-）来研究壳寡糖和壳寡糖稀土金属配合物对·O2^-自由基的清除作用。结果表明：壳寡糖与Eu^3＋或Tb^3＋形成了配合物,壳寡糖-铕、壳寡糖-铽配合物中不仅壳寡糖氨基上的N原子参与了配位,同时仲羟基的O原子也参与了配位。壳寡糖和壳寡糖稀土金属配合物对·O2^-均具有明显的清除作用,配合物与壳寡糖相比对·O2^-具有更高的清除活性。     

壳寡糖与硝酸钕配合物的合成和配位机理研究

用壳寡糖与硝酸钕反应,制备了壳寡糖-钕配合物。用红外光谱和X射线光电子能谱等分析测试手段对配合物进行了表征。从IR和XPS的测试结果可知,Nd^3＋与壳寡糖上的氨基N和仲羟基O配位,形成壳寡糖-钕配位聚合物。通过电导率研究其配位数,发现Nd^3＋可与壳寡糖的4个链节单元配位.根据以上的实验可推定中心离子Nd^3＋与壳寡糖4个链节单元上的氨基N和仲羟基O结合,形成八配位的壳寡糖-钕配位聚合物。     

羧甲基壳寡糖与钆配合物的制备

用羧甲基壳寡糖(CM-COS)与硝酸钆反应,制备了羧甲基壳寡糖与钆的配合物(CM-COS-Gd).用红外光谱、热重分析等测试手段对配合物进行了表征.讨论了溶液的酸碱度、反应时间和物料比对配合物形成的影响,对CM-COS-Gd的配位机理进行了初步研究.结果表明,不仅CM-COS中的羧基参与了配位,氨基上的氮原子和羟基氧原子也参与了配位.CM-COS-Gd和CM-COS相比,热稳定性有所增加.     

壳寡糖锌(Ⅱ)配合物的合成与结构表征

以壳寡糖(COS)为配位体,锌(Ⅱ)离子为配位离子,在均相反应条件下合成了壳寡糖锌(Ⅱ)配合物(COS-Zn),并优化了配合物的合成条件.利用红外光谱法(FT-IR)、差热分析法(DTA)和元素分析(EA)进行结构表征,并对配位机理进行了初步探讨.     

壳寡糖与镧、铈配合物的合成、表征及应用

合成了壳寡糖，镧和壳寡糖，铈配合物，用红外光谱和紫外光谱进行了表征，并证实了氮，金属(N-M)键的形成，元素分析证实配合物中各元素C：H：N：La或Ce的原子个数比分别接近于24：44：4：1，即相当于配位数为4。壳寡糖一镧和壳寡糖一铈较未配位的镧或铈具有更强的催化氧化能力。配合物除去废液中磷[(PO)^3-4]的效果比未配位的镧和铈提高10％。配合物可提高蔬菜、水稻种子的发芽率，促进作物的营养生长，提高水稻产量3，3％，提高黄瓜产量12％～15％，对十字花科蔬菜的病毒有一定的抑制作用。     

壳寡糖和磷酸化壳寡糖对Cu(Ⅱ)的络合和缓释性能

以壳寡糖(COS)和磷酸化壳寡糖(PCOS)为原料与铜离子反应,制备了壳寡糖铜(Ⅱ)络合物(COS-Cu)和磷酸化壳寡糖铜(Ⅱ)络合物(PCOS-Cu),讨论了pH、时间、温度和PCOS取代度对络合物吸附量的影响.释放性能表明COS-Cu(Ⅱ)和PCOS-Cu(Ⅱ)均具有缓释性能,且PCOS-Cu(Ⅱ)具有更加均匀的释放速率.     

位点可控的二乙氧磷酰化壳寡糖的合成

以壳寡糖(COS)为原料, 二乙基亚磷酸酯(DEPH)为磷酰化试剂, 通过改变反应体系中三乙胺(TEA)的用量控制二乙基磷酰基的进攻位点, 实现了2-N和3,6-O位点二乙基亚磷酰化壳寡糖衍生物的合成, 制备了N-二乙氧磷酰化壳寡糖及N,O,O-二乙氧磷酰化壳寡糖, 并采用单一变量法对合成条件进行了优化, 用³¹P NMR对产物进行了跟踪分析. 合成N-二乙氧磷酰化壳寡糖的最优反应条件为2 g COS, n_COS∶n_TEA=1∶6, n_COS∶n_DEPH=1∶3, 滴加DEPH和CCl₄的时间为2 h, 低温反应2 h, 在该优化条件下产物的磷含量为1.50%(质量分数). 合成N,O,O-二乙氧磷酰化壳寡糖的最优反应条件为2 g COS, n_COS∶n_TEA=1∶6, n_COS∶n_DEPH=1∶5, 滴加DEPH和CCl₄ 的时间2 h, 低温反应4 h, 常温反应8 h, 在该优化条件下产物的磷含量为3.42%. 对合成反应的可能机理进行了推测.     

壳寡糖及酰化壳寡糖与钕(Ⅲ)配合物的合成及其与牛血清白蛋白相互作用的对比研究

用壳寡糖及酰化壳寡糖与氯化钕反应,合成了壳寡糖-钕和酰化壳寡糖-钕配合物,利用红外光谱(IR)、紫外光谱(UV)手段对其结构进行了表征。在模拟生理条件下,本文采用紫外光谱和荧光光谱研究了两种配合物与牛血清白蛋白(BSA)的相互作用,计算了配合物与BSA的结合常数、结合位点数。荧光光谱结果表明,配合物均可有规律地猝灭BSA的内源荧光,猝灭方式为静态猝灭,壳寡糖-钕和酰化壳寡糖-钕分别与BSA的结合常数为1.33×104L·mol-1和6.95×104L·mol-1,结合位点数为1.05和1.3,说明配合物与BSA均具有较强的结合作用,能够被BSA储存和运输,并且酰化壳寡糖-钕与BSA的结合能力强于壳寡糖-钕。最后采用紫外光谱法对其作用机理进一步确认。因此,酰化壳寡糖-钕可以被BSA存储和运输,有望成为蛋白质荧光探针。     

具有肿瘤荧光成像性能的核壳纳米过氧化氢酶模拟物

运用微波法在硅核壳荧光材料的表面修饰了2-(二吡啶甲胺基)丙酸的锰配合物,获得具有荧光性能的锰-硅核壳纳米结构复合物,运用IR,UV,TEM等方法表征了纳米复合物的结构。H2O2岐化实验显示锰-硅核壳纳米复合物具有较好的过氧化氢酶模拟特性,是一种新的纳米过氧化氢酶模拟物。体外细胞荧光成像研究表明2-(二吡啶甲胺基)丙酸修饰的纳米球不能进入肿瘤细胞内,而锰-硅核壳纳米复合物能进入肿瘤细胞内,具备良好的肿瘤靶向性,显著提高肿瘤荧光成像效果,可作为新型的肿瘤成像剂。     

DNA hydrolytic cleavage by the diiron(III) complex Fe(2)(DTPB)(mu-O)(mu-Ac)Cl(BF(4))(2): comparison with other binuclear transition metal complexes

The binuclear structure of Fe(2)(DTPB)(mu-O)(mu-Ac)Cl(BF(4))(2) (DTPB = 1,1,4,7,7-penta (2'-benzimidazol-2-ylmethyl)-triazaheptane, Ac = acetate) was characterized by UV-visible absorption and infrared spectra and NMR and ESR. The binding interaction of DNA with the diiron complex was examined spectroscopically. Supercoiled and linear DNA hydrolytic cleavage by the diiron complex is supported by the evidence from anaerobic reactions, free radical quenching, high performance liquid chromatography experiments, and enzymatic manipulation such as T4 ligase ligation, 5'-(32)P end-labeling, and footprinting analysis. The estimation of rate for the supercoiled DNA double strand cleavage shows one of the largest known rate enhancement factors, approximately 10(10) against DNA. Moreover, the DNA hydrolysis chemistry needs no coreactant such as hydrogen peroxide. The poor sequence-specific DNA cleavage indicated by the restriction analysis of the pBR322 DNA linearized by the diiron complex might be due to the diiron complex bound to DNA by a coordination of its two ferric ions to the DNA phosphate oxygens, as suggested by spectral characterizations. The hydrolysis chemistry for a variety of binuclear metal complexes including Fe(2)(DTPB)(mu-O)(mu-Ac)Cl(BF(4))(2) is compared. It is established that the dominant factors for the DNA hydrolysis activities of the binuclear metal complexes are the mu-oxo bridge, labile and anionic ligands, and open coordination site(s). Concerning the hydrolytic mechanisms, the diiron complex Fe(2)(DTPB)(mu-O)(mu-Ac)Cl(BF(4))(2) might share many points in common with the native purple acid phosphatases.     

Interaction between the Heme and a G-Quartet in a Heme-DNA Complex

The structure of a complex between heme(Fe(3+)) and a parallel G-quadruplex DNA formed from a single repeat sequence of the human telomere, d(TTAGGG), has been characterized by (1)H NMR. The study demonstrated that the heme(Fe(3+)) is sandwiched between the 3'-terminal G-quartets of the G-quadruplex DNA. Hence, the net +1 charge of the heme(Fe(3+)) in the complex is surrounded by the eight carbonyl oxygen atoms of the G-quartets. Interaction between the heme Fe(3+) and G-quartets in the complex was clearly manifested in the solvent (1)H/(2)H isotope effect on the NMR parameters of paramagnetically shifted heme methyl proton signals, and interaction of the heme Fe(3+) with the eight carbonyl oxygen atoms of the two G-quartets was shown to provide a strong and axially symmetric ligand field surrounding the heme Fe(3+), yielding a heme(Fe(3+)) low-spin species with a highly symmetric heme electronic structure. This finding provides new insights as to the design of the molecular architecture and functional properties of various heme-DNA complexes.     

Differential thermal analysis of the Al+20% (Fe-50%B) system

In the present study, aluminium and mechanically alloyed (36 h) Fe/B (50 wt%) are mixed. Al+20 (wt%) Fe/B mixture has been studied by differential thermal analysis to determine the aluminium quantity that is supposed to melt and afterwards does not solidify as it reacts with Fe/B powder. The different areas between endothermic reaction (melting peak) and exothermic reaction (solidification peak) allow in knowing the quantity of aluminium that reacts with Fe/B and the amount of intermetallic phases formed at high temperature. In order to follow the process, compacts were sintered at different temperatures (700, 800, 900, 1000 and 1200 °C), in N₂/10H₂/0.1CH₄ atmosphere. Microstructure was evaluated by image analysis and the results obtained by both techniques are compared.     

The flash-quench technique in protein-DNA electron transfer: reduction of the guanine radical by ferrocytochrome c

Electron transfer from a protein to oxidatively damaged DNA, specifically from ferrocytochrome c to the guanine radical, was examined using the flash-quench technique. Ru(phen)2dppz2+ (dppz = dipyridophenazine) was employed as the photosensitive intercalator, and ferricytochrome c (Fe3+ cyt c), as the oxidative quencher. Using transient absorption and time-resolved luminescence spectroscopies, we examined the electron-transfer reactions following photoexcitation of the ruthenium complex in the presence of poly(dA-dT) or poly(dG-dC). The luminescence-quenching titrations of excited Ru(phen)2dppz2+ by Fe3+ cyt c are nearly identical for the two DNA polymers. However, the spectral characteristics of the long-lived transient produced by the quenching depend strongly upon the DNA. For poly(dA-dT), the transient has a spectrum consistent with formation of a [Ru(phen)2dppz3+, Fe2+ cyt c] intermediate, indicating that the system regenerates itself via electron transfer from the protein to the Ru(III) metallointercalator for this polymer. For poly(dG-dC), however, the transient has the characteristics expected for an intermediate of Fe2+ cyt c and the neutral guanine radical. The characteristics of the transient formed with the GC polymer are consistent with rapid oxidation of guanine by the Ru(III) complex, followed by slow electron transfer from Fe2+ cyt c to the guanine radical. These experiments show that electron holes on DNA can be repaired by protein and demonstrate how the flash-quench technique can be used generally in studying electron transfer from proteins to guanine radicals in duplex DNA.     

DNA cleavage activity of Fe(II)N4Py under photo irradiation in the presence of 1,8-naphthalimide and 9-aminoacridine: unexpected effects of reactive oxygen species scavengers

The DNA cleavage activity of the iron(II) complex of the ligand N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine (N4Py) was investigated in the presence of the chromophores 1,8-naphthalimide (NI) and 9-aminoacridine (AA) under photo irradiation at 355 and 400.8 nm and compared to the activity of the complex without the chromophores. Whereas in most cases no synergistic effect of the added chromophores on DNA cleavage efficiency was observed, it was found that for Fe(II)N4Py, in combination with NI under irradiation at 355 nm, the DNA cleavage activity was increased. Surprisingly, it was found that the addition of reactive oxygen species (ROS) scavengers gave rise to significantly increased DNA cleavage efficiency, which is a highly counterintuitive observation since ROS are needed to achieve DNA cleavage. A hypothesis is put forward to explain, at least partly, these results. It is proposed that the addition of scavengers inhibits quenching of (3)NI*, thus making photo-induced electron transfer between (3)NI* and Fe(III)N4Py more efficient. This results in reduction of Fe(III)N4Py to Fe(II)N4Py, which can then react with ROS giving rise to DNA cleavage. Hence the role of the scavengers is to maintain a close to optimal concentration of ROS. The present study serves as an illustration of the care that needs to be exercised in interpreting the results of experiments using standard ROS scavengers, since especially in complex systems such as presented here they can give rise to unexpected phenomena. In the presence of 1,8-naphthalimide or 9-aminoacridine, ROS scavengers can increase the DNA cleavage efficiency of Fe(II)N4Py complex under photo irradiation.     

阿霉素─铁(Ⅲ)配合物的电化学特征及其与DNA结合作用研究

采用示波极谱法和循环伏安法研究了3公铁离子Fe(Ⅲ)与阿霉素(ADM)配合物的电化学特性.在生理pH条件下,Fe(Ⅲ)与ADM形成2：1的稳定配合物,Fe(Ⅲ)的配位使ADM在更负的电势下才能还原,这与其心脏毒性减轻密切相关.采用线性扫描、吸收光谱和凝胶电泳法研究了ADM－Fe(Ⅲ)配合物与DNA的结合作用,ADM－Fe(Ⅲ)配合物仍保留了ADM插入结合的特征,并形成一种稳定的DNA－Fe(Ⅲ)－ADM的三元结合物.     

Orientation of iron bleomycin and porphyrin complexes on DNA fibers

Bleomycin (Blm) is an antitumor agent that requires iron and oxygen for strand cleavage of DNA. In this study, ferric bleomycin, Fe(III)Blm, or the nitric oxide adduct of ferrous bleomycin, ON-Fe(II)Blm, were bound to one-dimensionally oriented DNA fibers. Reductive nitrosylation of Fe(III) complexes took place in situ on B-form DNA fibers. Electron paramagnetic resonance (EPR) spectra were obtained as a function of the angle phi between the magnetic field B and the fiber axis Zf. For comparison, EPR spectra were acquired for ON-Fe(II)TMpyP and ON-Fe(II)TMpyP-Im on oriented DNA fibers, where TMpyP is 5,10,15,20-tetrakis(1-methyl-4-pyridino)porphyrin and Im is imidazole. EPR spectra showed both low-spin Fe(III)Blm and ON-Fe(II)Blm bound to B-form DNA in two slightly different binding orientations in the ratio of 1:0.2. With A-form DNA, a fraction of bound Fe(III)Blm was high spin. Specifically, the angle beta between the fiber axis Zf and the g axis, gz, perpendicular to or nearly perpendicular to the equatorial plane of the iron complex was estimated as 20 degrees and 25 degrees for ON-Fe(II)Blm and 30 degrees and 25 degrees for Fe(III)Blm, respectively. The angle gamma that determines the orientation of gx and gy axes was estimated as 90 degrees for the two ON-Fe(II)Blm species and 10 degrees for the two Fe(III)Blm species, respectively. The NO was held rigidly in place as the temperature increased from 123 K to room temperature for ON-Fe(II)Blm but not for ON-Fe(II)TMpyP or ON-Fe(II)TMpyP-Im. It is hypothesized that the NO is structurally oriented by hydrogen bonding like the peroxide is held in HO2(-)-Co(III)Blm (Wu et al. J. Am. Chem. Soc. 1996, 118, 1281-1294). The EPR parameters are consistent with a six-coordinate complex for ON-Fe(II)Blm, although the superhyperfine structure from the trans nitrogen was not detected. The increase in g value anisotropy upon binding ON-Fe(II)Blm to DNA fiber may be caused by an increase in the overlap of d pi and 2p pi* orbitals induced by an interaction of NO with DNA and/or by a perturbation of d orbitals due to the pyrimidine-guanine interaction. It is concluded that the EPR parameters of ON-Fe(II)Blm and Fe(III)Blm bound to oriented DNA support the hypothesis that FeBlm species bind to DNA with adduct structures similar to those formed by related CoBlm species and DNA.     

Scanning electrochemical microscopy. 51. Studies of self-assembled monolayers of DNA in the absence and presence of metal ions

Scanning electrochemical microscopy was used to examine electron transfer across a self-assembled monolayer of thiol-modified DNA duplexes on a gold electrode. The apparent rate constant for heterogeneous ET from a solution redox probe, Fe(CN)6(3-/4-), to the gold surface through ds-DNA was 4.6 (+/-0.2) x 10(-7) cm/s. With the addition of Zn2+, which resulted in the formation of a metalated DNA (M-DNA) monolayer, the rate constant increased to 5.0 (+/-0.3) x 10(-6) cm/s. Upon treating M-DNA with EDTA, the zinc ions were released from the monolayer and the original rate constant for the DNA duplexes was restored. The enhanced ET rate was also observed at a DNA monolayer treated with Ca2+ or Mg2+, which does not complex by the DNA bases to form M-DNA. The binding of these cations facilitated the monolayer penetration by the probe mediator Fe(CN)6(3-/4-) and accordingly caused an increased redox signal of the mediator at the ds-DNA-modified electrode. Cationic or neutral mediators were not blocked by the ds-DNA monolayer. These results suggest that although the increased electron transport through M-DNA could partially be ascribed to the intrinsic enhancement of electric conductivity of M-DNA, which has been confirmed by photochemical studies, the change in the surface charge of DNA monolayers on the electrode caused by the binding of metal ions to DNA molecules may play a more important role in the enhancement of current with M-DNA.     

New method for simultaneous determination of Fe(II) and Fe(III) in water using flow injection technique

The method exploits the possibilities of flow injection gradient titration in a system of reversed flow with spectrophotometric detection. In the developed approach a small amount of titrant (EDTA) is injected into a stream of sample containing a mixture of indicators (sulfosalicylic acid and 1,10-phenanthroline). In acid environment sulfosalicylic acid forms a complex with Fe(III), whereas 1,10-phenanthroline forms a complex with Fe(II). Measurements are performed at wavelength λ = 530 nm when radiation is absorbed by both complexes. After injection EDTA replaces sulfosalicylic acid and forms with Fe(III) more stable colourless complex. As a result, a characteristic “cut off” peak is registered with a width corresponding to the Fe(III) concentration and with a height corresponding to the Fe(II) concentration. Calibration was performed by titration of four two-component standard solutions of the Fe(II)/Fe(III) concentrations established in accordance with 2² factorial plan. The method was tested with the use of synthetic samples and then it was applied to the analysis of water samples taken from artesian wells. Under optimized experimental conditions Fe(II) and Fe(III) were determined with precision less than 0.8 and 2.5% (RSD) and accuracy less than 3.2 and 5.1% (relative error) within the concentration ranges of 0.1-3.0 and 0.9-3.5 mg L⁻¹ of both analytes, respectively.