A Large Conformational Change of a Bridged β-Cyclodextrin Dimer in Aqueous Solution

A novel bridged β-CD dimer in which two β-cyclodextrins were linked by a naphthalene at positions 2 and 7 has been synthesized. 1H and 13CNMR measurements showed that a large change in the conformation of the dimer occurred in aqueous solution. The dimer interacted with methyl and ethyl orange to form stable inclusion complexes via "induced fit" mechanism.     

Interpretation of the cytostatic properties of sodium morpholyldithiocarbamate,a chelating agent

Summary The antioxidant properties of sodium morpholyldithiocarbamate (MorDTC) were studied in order to contribute to the interpretation of its antitumor activity and synergetic effect overcis-platinum.MorDTC inhibits pyrogallol autooxidation better than vitamin C but does not dismutate the superoxide radical generated by the xanthine — xanthine oxidase system. Nevertheless, the complexes formedin situ betweenMorDTC and Mn(II), Co(II), Ni(II), and Cu(II) do dismutate the superoxide radical with a SOD-like activity (SOD=superoxide dismutase), expressed in terms of IC₅₀ values within the range of 3.2 to 62 µM. The highest activity corresponds to Mn(II) and Cu(II) complexes. The possible inhibitory action ofMorDTC on erythrocyte SOD was also studiedin vitro; however, the results were negative. Therefore,MorDTC should dismulate the superoxide radical after chelating metals without inhibiting SOD, the enzyme playing this rolein vivo.

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Interpretation der cytostatischen Eigenschaften von Natriummorpholyldithiocarbamat, einem komplexbildenden Reagens

Zusammenfassung Die antioxidativen Eigenschaften von Natriummorpholyldithiocarbamat (MorDTC) wurden im Hinblick auf seine Wirkung gegen Tumore und seinem synergistischen Effekt im Zusammenhang mitcis-Platin untersucht.MorDTC hemmt die Autoxidation von Pyrogallol besser als Vitamin C, greift aber das vom System Xanthin-Xanthinoxidase gebildete Superoxidradikal nicht an. Dieses wird jedoch von demin situ ausMorDTC und Mn(II), Co(II), Ni(II) und Cu(II) gebildeten Komplexen mit einer SOD-vergleichbaren Aktivität umgesetzt (SOD=Superoxiddismutase; IC₅₀ im Bereich von 3.2 bis 62 µM). Die höchste Aktivität wurde für Mn(II)- und Cu(II)-Komplexe gefunden. Die hemmende Wirkung vonMorDTC auf erythrocytische SOD wurdein vitro untersucht. Die Ergebnisse waren negativ.MorDTC ist daher nach der Komplexierung mit Metallen in der Lage, das Superoxidradikal anzugreifen, ohne SOD, das Enzym, das Enzym, das diese Aufgabein vivo übernimmt, zu hemmen.

     

The Enzyme Source Effect on the Performance of a Catalase Organic Phase Enzyme Electrode

Summary. The role of the enzyme source was studied in the reaction of hydrogen peroxide decomposition by immobilised catalase in acetonitrile. Enzymes isolated from bacterial and mammalian sources were conveniently immobilised on a spectroscopic graphite to obtain an organic-phase enzyme electrode (OPEE). Amperometry at constant potential was employed as basic analytical approach in this study.     

基于羧基化聚吡咯-氯化血红素和点触发链置换反应信号放大的电化学生物传感器检测转基因作物中CaMV35S序列

为适应快速增长的转基因生物(GMOs)安全评价与管理的需求,高效、可靠的转基因检测技术研究与应用的重要性日益凸显。该文采用一步法合成了羧基化聚吡咯(cPPy)与氯化血红素(Hemin)的纳米复合物(cPPy-hemin),并以其为信号标签合成了一种DNA双链结构功能化的纳米信标(DNA-cPPy-hemin)。利用cPPy-hemin增强的模拟酶催化活性,结合点触发链置换反应(TSDR)信号放大策略,制备了一种新型电化学基因传感器用于转基因成分的灵敏检测。通过信号探针(Ps)与模板链(Ts)、辅助链(As)结合形成DNA双链体结构中的-NH2功能化cPPy-hemin,制备Ts/As/Ps-cPPy-hemin双链DNA结构的纳米信标。在目标花椰菜花叶病毒35S启动子(CaMV35S)序列和燃料链(Fs)存在下,TSDR过程释放出的Ps-cPPy-hemin与固定在电化学沉积金纳米粒子修饰GCE表面上巯基化的DNA捕获探针(Cs)相结合,利用cPPy-hemin对H₂O₂的模拟酶催化产生的电信号,可实现对CaMV35S的定量检测。在最优条件下...     

泰和乌骨鸡及其黑素对小鼠红细胞过氧化氢酶及血浆过氧化脂质的影响

以泰和乌骨鸡及其黑素为药物直接喂养小鼠,测定实验鼠红细胞过氧化氢酶的活性及血浆过氧化脂质的含量,以探讨乌骨鸡是否具有抗衰老作用。实验结果表明：１）泰和乌骨鸡及其黑素有提高小鼠红细胞过氧化氢酶活性的趋势,但其提高的幅度尚未达到显著水平;２）泰和乌骨鸡及其黑     

锰取代血红蛋白的制备及其类酶活性的研究

将Mn-原卟啉Ⅸ与脱辅基血红蛋白重组得到Mn取代Fe的重组血红蛋白，用紫外-可见光谱法和SDS-PAGE电泳法对Mn取代的血红蛋白进行了鉴定．检测了血红蛋白和Mn取代的血红蛋白的过氧化物酶活性和过氧化氢酶活性．研究发现，Mn取代的血红蛋白的过氧化物酶活性是血红蛋白的70％，过氧化氢酶活性约是血红蛋白的1．9倍．     

Phen-铜(II)-氨基酸配合物的合成、表征及其SOD活性

合成了3个新的SOD模拟配合物：[Cu(Phen)(L-Gln)(H₂O)]Cl·2H₂O (1)、[Cu(Phen)(L-Ala)(H₂O)]Cl·4H₂O (2)、[Cu(Phen)(L-Thr)(H₂O)]Cl·2H₂O (3) [Phen(1，10-邻菲咯啉)、L-Gln(谷氨酰胺)、L-Ala(丙氨酸)、L-Thr(苏氨酸)]。用元素分析、摩尔电导、红外光谱、紫外-可见光谱对配合物进行了表征。用X-射线衍射对配合物[Cu(Phen)(L-Gln)(H₂O)]Cl·2H₂O的晶体结构进行了测定。用氯化硝基四氮唑蓝(NBT)光还原法对这3个配合物催化歧化超氧阴离子自由基(O₂^{- ·})的能力进行了测定。结果表明：这些配合物具有较高的SOD活性， 催化速率常数K_Q分别为1.58 × 10⁷ mol^-1·L·s^-1、5.65 × 10⁷ mol^-1·L·s^-1、0.83 × 10⁷ mol^-1·L·s^-1。     

Covalent conjugation of tetrameric bovine liver catalase to liposome membranes for stabilization of the enzyme tertiary and quaternary structures

Tetrameric bovine liver catalase (BLC) is unstable because of its dissociation into subunits at low enzyme concentrations and the conformational change of the subunits at high temperatures. In this work, for stabilization of BLC, the enzyme was covalently conjugated with liposome membranes composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), cholesterol and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-glutaryl (NGPE). The NGPE, which was responsible for the BLC/membrane coupling, was altered from 0.05 to 0.2 in its liposomal mole fraction f_G. The catalase-conjugated liposome (CCL) with f_G of 0.15 showed the maximum number of the conjugated BLC molecules of 28 per liposome. The reactivity of CCLs to H₂O₂ was as high as that of free BLC at 25 °C in Tris–HCl buffer of pH 7.4. Among the CCLs, the catalyst with f_G of 0.15 was the most stable at 55 °C in its enzyme activity in the buffer because the appropriate number of BLC/liposome covalent bonding prevented the dissociation-induced enzyme deactivation. Furthermore, the CCL showed much higher stability at 55 °C than the free BLC/enzyme-free liposome mixture and free BLC at the low BLC concentration of 340 ng/mL. This was because BLC in the CCL was located in the vicinity of the host membrane regardless of the catalyst concentration, which could induce the effective stabilization effect of the membrane on the enzyme tertiary structure as indicated by the intrinsic tryptophan fluorescence analysis. The results obtained demonstrate the high structural stability of BLC in the CCL system, which was derived from the covalent bonding and interaction between BLC and liposomes.     

Synthesis and binding ability of bile acid-based receptors for recognition of flavin analogues

Novel cholaphanes 6a,b, based on lithocholic and deoxycholic acids, were synthesised through 3a,b by a sequence of reactions involving Cs-salt methodology of macrocyclisation. Cholaphanes 6a,b and acyclic steroidal receptors 3a,b bind flavin analogues via three hydrogen bonds in CHCl₃.     

聚酰胺类多肽二级结构模拟物的结构设计与性质分析

多肽与蛋白质具有结构支持、酶促催化、蛋白-蛋白相互作用等一系列功能。其中,二级结构作为少数氨基酸参与的相对局域性的结构,是一切高级结构的基础。为了模拟天然多肽的结构与功能,人们成功设计并合成了多种非天然的寡聚物结构。这些拟肽或类肽结构能有效地模拟以α-螺旋、转角为主体的多肽二级结构。二级结构模拟物具有重要的理论意义,并被进一步用于蛋白-蛋白相互作用的抑制剂研究与新药设计中。本文从分析多肽的二级结构特征入手,分类阐述了目前的各类多肽二级结构模拟物,并重点分析了最为主要的基于酰胺键型的模拟物的设计与结构多样性。同时,本文提出一系列形象化的命名手段进行分类,如χ肽、ζ/ξ-肽及ζ-ξ-肽等。