丹酚酸B与牛血清白蛋白相互作用的电化学研究

在0.01 mol.L-1磷酸盐缓冲溶液(pH 7.4)中,用循环伏安法和方波伏安法研究了丹酚酸B与牛血清白蛋白相互作用前后在DNA修饰玻碳电极上的电化学行为。实验表明,丹酚酸B在此修饰电极上于0.100 V处产生良好的氧化峰,加入牛血清白蛋白后,丹酚酸B的电子转移系数α和表观电子传递速率常数ks均发生了变化,氧化峰电位正移,峰电流减小。根据氧化电流的变化求得丹酚酸B和牛血清白蛋白相互作用的结合常数β=1.00×108L.mol-1,结合数m=1.71,表明丹酚酸B与牛血清白蛋白生成了结合比约为2∶1的非电活性复合物。该结果与荧光光谱法的研究结果一致。     

青蒿素与DNA作用的电化学机理

在体积分数为20%乙醇的Britton-Robinson缓冲溶液(pH=7.4)中,利用循环伏安法和紫外可见吸收光谱法研究了青蒿素与DNA的相互作用。电化学研究表明,DNA的存在能导致青蒿素在银电极上-0.672 V处的还原峰电流下降,峰电位正移。通过对比双链DNA(dsDNA)和单链(ssDNA)与青蒿素作用,得出青蒿素可嵌插到DNA分子中,形成非电活性的复合物。电化学方法可计算出DNA与青蒿素的结合比为1∶4,结合常数为3.6×104。电极过程的电化学参数表明,DNA作用前后,α、β值变化不明显,进一步证实了该复合物是非电活性;Ks值变小,表明二者作用后受扩散控制。紫外可见吸收光谱法研究表明,青蒿素对DNA分子发生嵌插作用。通过光谱滴定法可计算二者的结合比和结合常数,同样获得1个DNA结合4个青蒿素分子,结合常数为4.0×104,与电化学方法测定结果相吻合。实验数据显示,青蒿素进入细胞内有可能与细胞核中DNA结合,诱导细胞凋亡。     

银掺杂L-脯氨酸修饰电极用于研究肾上腺素与DNA的相互作用

采用循环伏安方法将Ag~+与L-脯氨酸单体共聚合在玻碳电极表面制得银掺杂聚L-脯氨酸修饰电极,并应用该修饰电极研究了肾上腺素(EP)与双链DNA(dsDNA)之间的相互作用。试验发现:在pH 7.0磷酸盐缓冲溶液中,EP在修饰电板上有一个明显的氧化峰;当加入一定量的dsDNA后,EP的氧化峰电流明显下降。EP氧化峰电流的下降值(△i)与dsDNA的质量浓度在一定范围呈线性关系;dsDNA与EP相互作用形成了分子比为1比2的复合物,两者的结合常数为4.56×10~4。     

6-糠氨基嘌呤的电化学行为及与DNA的相互作用

应用循环伏安法、微分脉冲伏安法和紫外光谱法研究了6-糠氨基嘌呤(6-KT)在汞电极上的电化学行为及与小牛胸腺DNA的相互作用.结果发现,6-KT的循环伏安曲线显示两对表征为扩散控制和吸附控制的氧化还原波.扩散控制波的氧化峰电流随6-KT浓度在1.00×10-4～5.00×10-2mmol·L-1范围内呈现良好的线性关系.依据预吸附时间和溶液pH值对吸附控制波的还原峰电位和峰电流的影响,讨论了6-KT在汞电极上的吸附机理.另外,6-KT的扩散控制波的还原峰电流随DNA浓度的增加而减小,峰电位正移,紫外吸收峰出现明显的减色效应,认为6-KT乃通过部分插入作用与DNA结合,结合常数为2.60×103 L·mol-1.     

粉防己碱在玻碳电极上的电化学行为及其与DNA的相互作用

应用循环伏安法、差分脉冲伏安法、控制电位电解法等电化学方法和紫外光谱法研究了粉防己碱在玻碳电极上的电化学行为及其与DNA的相互作用,并对相关电化学动力学参数进行考察。结果表明,粉防己碱在玻碳电极上发生了受扩散控制的不可逆氧化反应,其在玻碳电极上的电子转移数为2、质子转移数为2、电荷转移系数为0.62。粉防己碱的峰电流随着DNA的加入而降低,且峰电位发生正移,表明粉防己碱与DNA通过嵌插方式相互作用生成复合物,同时计算了两者反应的结合数以及结合常数,结果显示粉防己碱和DNA以1∶1结合形成粉防己碱-DNA复合物,结合常数为4.27×103。     

粉防己碱在玻碳电极上的电化学行为及其与DNA的相互作用

应用循环伏安法、差分脉冲伏安法、控制电位电解法等电化学方法和紫外光谱法研究了粉防己碱在玻碳电极上的电化学行为及其与DNA的相互作用,并对相关电化学动力学参数进行考察。结果表明,粉防己碱在玻碳电极上发生了受扩散控制的不可逆氧化反应,其在玻碳电极上的电子转移数为2、质子转移数为2、电荷转移系数为0.62。粉防己碱的峰电流随着DNA的加入而降低,且峰电位发生正移,表明粉防己碱与DNA通过嵌插方式相互作用生成复合物,同时计算了两者反应的结合数以及结合常数,结果显示粉防己碱和DNA以1∶1结合形成粉防己碱-DNA复合物,结合常数为4.27×103。     

6-苄氨基嘌呤的电化学行为及与DNA的相互作用

应用循环伏安法、微分脉冲伏安法和紫外光谱法研究了6-苄氨基嘌呤(6-BA)在汞电极上的电化学行为,及与小牛胸腺DNA的相互作用.结果发现,6-BA的循环伏安曲线显示三对扩散或吸附控制的氧化还原波.扩散波的氧化峰电流随6-BA浓度在0.1～50.0 μmol·L-1范围内呈现良好的线性关系.依据预吸附时间和溶液pH值对吸附波的还原峰电位和峰电流的影响,讨论了6-BA在汞电极上的咐附机理.另外,6-BA的还原峰电流随DNA浓度的增加而减小,峰电位正移,紫外吸收峰出现明显的减色效应,认为6-BA通过部分插入作用与DNA结合,结合常数为2.3×103L·mol-1.     

6-取代嘌呤的电化学行为及与DNA的相互作用

应用循环伏安法和微分脉冲伏安法研究了6-糠氨基嘌呤(6-KT)和6-巯基嘌呤(6-MP)在汞电极上的电化学行为及与小牛胸腺DNA的相互作用.结果发现,6-KT和6-MP的循环伏安曲线均显示两对分别表征为扩散控制和吸附控制的氧化还原波.扩散控制波的氧化峰电流随6-取代嘌呤浓度在0.1~50.0μmol.L-1范围内呈现良好的线性关系.依据预吸附时间和溶液pH值对吸附控制波的还原峰电位和峰电流的影响,讨论了6-KT和6-MP在汞电极上的吸附机理.作者认为,6-KT乃通过部分插入作用与DNA结合,而6-MP与DNA间的相互作用为静电模式.     

苯甲酸二聚铜配合物与DNA相互作用的电化学研究及应用

采用电化学法对自行合成的苯甲酸二聚铜配合物[Cu(R)2]与鲑鱼精DNA的相互作用进行了研究。配合物在0.197 V和0.162 V处有一对氧化还原峰。加入双链DNA(dsDNA)后,氧化还原峰电流明显降低且式量电位正移,说明苯甲酸二聚铜配合物与DNA以嵌入方式生成一种非电活性超分子复合物,导致苯甲酸二聚铜配合物的峰电流降低,峰电流在一定范围内与鲑鱼精dsDNA质量浓度呈线性关系,线性范围为3.0×10-2~4.5×10-3mg/L,检出限为3.5×10-4mg/L。同时,以[Cu(R)2]作杂交指示剂,把一种新型发夹结构锁核酸探针(LNA)固定在金电极表面制备了电化学生物传感器,将该修饰电极与人工合成的慢性粒细胞白血病BCR/ABL融合基因片段进行杂交,用差示伏安法进行检测,该铜配合物能够较好地区分探针序列、单碱基错配序列和互补链序列。     

纳米金修饰碳糊电极上甲氨蝶呤的电化学测定及其与鲱鱼精DNA相互作用的研究

制备了纳米金修饰碳糊电极,使用循环伏安法(CV)研究了甲氨蝶呤(MTX)在该修饰电极上的电化学特性,并建立了纳米金修饰碳糊电极电化学测定MTX的新方法.利用线性扫描伏安法(LSV)和方波伏安法(SWV)研究了MTX与鲱鱼精DNA的相互作用.实验发现,在pH 3.6 HAc-NaAc缓冲溶液中,MTX在0.86 V处有一灵敏的氧化峰,氧化峰电流Ipa与MTX的浓度在0.5 ～10.0 μmol·L-1范围内呈良好的线性关系,方法检出限(S/N=3)为0.2μmol·L-1.对3.0 μmol·L-1的MTX进行11次平行测定,其RSD为4.7％.该修饰电极可用于MTX样品的测定,结果满意.当不同浓度鲱鱼精DNA加入MTX溶液后,氧化峰电位正移,氧化峰电流降低,表明MTX与鲱鱼精DNA之间发生了相互作用,形成了非电活性化合物.电化学研究表明,MTX与鲱鱼精DNA之间的结合比为2∶1,结合常数为4.6×105 L·mol-1.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.