电化学活性的二茂铁-肽的合成及其对β-淀粉样肽聚集的抑制作用

以二茂铁甲酸、甘氨酸、苯丙氨酸、亮氨酸、缬氨酸和赖氨酸为原料,苯并三唑-1-四甲基六氟磷酸酯(HBTU)及1-羟基苯并三唑(HOBt)为缩合剂,采用固相合成法,合成了Fc-Gly-Lys-Leu-Val-Phe-Phe-Gly-Lys-OH(简称Fc-GKLVFFGK,其中Fc:ferrocenoyl,二茂铁).用HPLC分离纯化得到目标化合物,并对目标化合物进行红外、紫外、核磁和质谱表征确证其结构.Fc-GKLVFFGK的循环伏安扫描结果表明,在0.2～0.7V范围内出现了一对可逆的氧化还原峰,氧化峰和还原峰电位分别为0.464和0.396V;峰电位之差?Ep为58mV,峰电流密度之比Ipa/Ipc=1.07.采用ThT荧光探针法检测了Fc-GKLVFFGK对β-淀粉样肽(Aβ)聚集的抑制作用.实验结果表明,Fc-GKLVFFGK能有效地抑制Aβ1-42聚集,并且能有效地分解已形成的Aβ1-42纤维.     

二茂铁-肽Fc-Gly-Pro-Arg(NO_2)-OMe的合成及其与Cu(Ⅱ)作用

以二茂铁甲酸、甘氨酸(H-Gly-OMe)、脯氨酸(Boc-Pro-OH)、精氨酸(H-Arg(NO2)-OMe)等为原料,苯并三唑-1-四甲基六磷酸酯(HBTU)和1-羟基苯并三唑(HOBT)为缩合剂,采用液相法合成了二茂铁-肽Fc-Gly-Pro-Arg(NO2)-OMe(简称Fc-GPR),其总收率为48.1%.并对目标产物进行了红外(IR)光谱、核磁共振氢谱(1H-NMR)、质谱(ESI-MS)等表征.通过电化学方法研究了目标产物与Cu(Ⅱ)之间的相互作用.结果表明:目标产物在溶液中的电化学行为表现为可逆氧化还原反应,氧化和还原峰电位分别为0.624和0.552V(vsAg/AgCl),氧化和还原峰电流之比Ipa/Ipc为1.13,电极反应过程为扩散控制.目标产物与Cu(Ⅱ)形成配位比为2∶1的配合物.Fc-GPR与Cu(Ⅱ)的电极反应过程符合电化学-化学-电化学(ECE)历程.     

芦荟苷的循环伏安测定及其在玻碳电极上的电化学行为

用循环伏安法在pH 1.7的氯化钾-盐酸的底液中,得到了芦荟苷良好的氧化峰和还原峰,氧化峰电位(Epc)为-0.386 V,还原峰电位(Epa)为-0.441 V。峰电流(ipa)与芦荟苷浓度在1.195×10-6~2.152×10-4mol.L-1范围内呈线性关系。检出限(3S/N)为4.78×10-7mol.L-1。据此提出了循环伏安法测定芦荟中芦荟苷的含量。还研究了芦荟苷在玻碳电极上的电化学行为,结果表明芦荟苷的电极过程具有吸附性和不可逆性。     

趋磁细菌的电化学活性研究

采用循环伏安和计时电流等电化学手段研究了趋磁细菌(Magnetospirillum magneticum AMB-1)的电化学活性.通过对比不同培养条件下的循环伏安曲线可知,培养3 d时的菌体具有较强的电化学活性,其氧化峰出现在0.1 V处,还原峰出现在-0.2 V处;溶解氧能够改变氧化峰的峰电位(0 V),并形成新的还原峰(-0.3 V);磁小体的生成则严重抑制趋磁细菌的胞外电子传递过程.实验结果表明,磁小体的形成与趋磁细菌的胞外电子传递有关.     

含铕硅钼钨多金属氧酸盐水溶液的电化学性质

采用循环伏安法,研究双-Keggin型含铕硅钼钨多金属氧酸盐(Eu(SiMo4W7)213-)水溶液的电化学性质,结果表明,在0.7~-0.45V的电位区间内,Eu(SiMo4W7)213-呈现了两对准可逆的单电子氧化还原峰,峰电位随着溶液pH值的升高而线性负移,催化活性实验显示,在酸性溶液中该化合物对NaNO2和H2O2的还原反应具有良好的催化作用.     

丹参酮ⅡA在碳糊电极上的伏安行为及其测定

研究了丹参酮ⅡA(TS)在碳糊电极(CPE)上的伏安行为,结果表明:在0.2 mol/L BR(pH 2.4)的乙醇/水(40∶60,V/V)中,TS的羰基发生单电子、单质子的氧化还原反应,该反应是一个有吸附特征的可逆过程;还原产物半醌自由基能稳定存在,这可能是由于CPE中疏水有机相阻止了该自由基的岐化反应。还原峰和氧化峰的峰电位分别为-0.31和-0.24 V(vs,SCE),二阶导数氧化峰峰电流与TS浓度在1.2×10-8~8.2×10-7mol/L范围内呈线性关系;检出限为4.1×10-9mol/L。本方法可用于复方丹参片中丹参酮总含量的测定。     

L-半胱胺尾式卟啉铜(Ⅱ)修饰金电极检测苯酚

将制备的L-半胱胺卟啉铜(Ⅱ) (CuL) 配合物自组装在Au电极表面,获得电化学苯酚传感器(CuL/Au).在pH 7.0的磷酸盐缓冲液(PBS)中于-0.4 V～0.5 V (vs. SCE)电位范围内有一对氧化还原峰,峰电位分别为Epa = 0.09 V和Epc = - 0.06 V.实验结果表明CuL能够催化氧化苯酚,通过产物在电位0.1 V下的电化学响应对苯酚进行测定.该电极对苯酚表现出快速的响应(响应时间＜10 s).传感器对苯酚的测定具有较宽的线性范围(5.0×10-7 mol·L-1～2.5×10-4 mol·L-1),检出限为2.0×10-7 mol·L-1.该电极用于地表水中苯酚含量检测,并与标准方法4-氨基安替比林分光光度法作了对照,结果满意.     

二茂铁修饰Aβ疏水段五肽的电化学性质及自组装研究

五肽Lys-Leu-Val-Phe-Phe(即KLVFF)是β-淀粉样肽(Aβ)疏水核心片段,其自组装方式对Aβ的聚集具有重要影响。在本文中,首先对二茂铁修饰的五肽,即Fc-Lys(Z)-Leu-Val-Phe-Phe-OMe(简称Fc-KLVFF)的电化学性质进行了研究,结果表明,在0.4~0.8 V范围内出现了一对可逆的氧化还原峰,氧化峰和还原峰电位分别为0.626和0.544 V,峰电位之差ΔEp为82 mV,峰电流密度之比Ipa/Ipc为1.08,扩散系数D0=1.784×10-6cm2.s-1。其次通过TEM观察到Fc-KLVFF在甲醇溶液中自组装成纳米管,傅里叶红外光谱分析表明纳米管的二级结构主要为β-折叠,紫外-可见和荧光光谱证实苯丙氨酸残基芳香环之间的π-π堆积作用在其自组装成纳米管时起着重要作用。最后提出了Fc-KLVFF的自组装机理模型。     

硒杂环化合物(4,5-苯并苤硒脑)在金表面上的自组装

为了寻求新的自组装单分子膜体系,构建新的功能膜,研究了具备平面型的大环共轭硒杂环化合物-- 4,5-苯并苤硒脑(苯并[c]硒二唑,简称苤硒脑)在金表面的自组装单分子膜.通过X射线光电子能谱(XPS)和电化学手段对其进行表征.XPS研究结果表明,自组装形成单分子膜后,苤硒脑分子中Se3d结合能从57.4 eV下降到57.1 eV;表明硒杂环化合物是通过金硒键固定在金表面上的;电化学循环伏安法实验表明,金电极表面上自组装该有机硒后, Fe(CN)63-/4-的氧化还原峰几乎完全消失;以四硼酸钠为底液,测得该化合物自组装在金表面上时,其还原电位在-0.66 V,与在溶液中用裸金电极测得的还原峰电位基本一致.     

纳米TiO2/聚苯胺复合膜电极的制备及其电化学性能

采用1mol·L-1硫酸作为介质,扫描速度为100mV*s-1,扫描电位为-0.2V～0.8V,用循环伏安法在纳米二氧化钛(Nano-TiO2)膜电极上实现了苯胺(Aniline)的电化学聚合,并对制得的Nano-TiO2/聚苯胺复合膜的电化学性质进行了研究.结果表明在峰电位(Ep)为0.28V处有一个明显的氧化峰,在Ep为 0.54V,0.08V,-0.06V处分别有一个还原峰,经长时间扫描,氧化峰电流可达到50mA·cm-2,具有工业应用价值.同时实验也表明,复合膜的生成、Ip的大小受溶液浓度、扫描速度以及扫描电位的影响.     

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.     

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.     

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.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

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.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

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.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

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.