氧化铈纳米酶的结构调控及POD酶活性研究

为探究CeO₂纳米粒子表面Ce³⁺/Ce⁴⁺比例变化对过氧化物酶（POD）活性的影响,以实现对POD催化反应的可控调节,本研究使用简易水热法合成CeO₂纳米粒子,并通过不同的气氛热处理来调控CeO₂纳米粒子表面Ce³⁺/Ce⁴⁺的比例来展开相关探索。     

兼具SOD和GPX活力的双功能酶的制备及性质研究

用苯甲基磺酰氟（ＰＭＳＦ）和Ｈ２Ｓｅ相继处理铜锌超氧化物歧化酶（Ｃｕ,Ｚｎ－ＳＯＤ）,将酶分子中的丝氨酸（Ｓｅｒ）转化为硒代半胱氨酸（ＳｅＣｙｓ）,从而引入了谷胱甘肽过氧化物酶（ＧＰＸ）的催化基因,使其在ＳＯＤ酶活性大部分保留的情况下,具有ＧＰＸ活性,其ＧＰＸ活力是ＰＺ５１活力的３０倍,研究了双功能酶的最佳制备条件,包括ＰＭＳＦ的剂量、反应最适温度及Ｈ２Ｓｅ处理时间等,并用电子能谱、ＤＴＮＢ等方法     

兼具SOD和GPX活力的双功能酶的制备及性质研究

用苯甲基磺酰氟（ＰＭＳＦ）和Ｈ_２Ｓｅ相继处理铜锌超氧化物岐化酶（Ｃｕ,Ｚｎ－ＳＯＤ）,将酶分子中的丝氨酸（Ｓｅｒ）转化为硒代半胱氨酸（ＳｅＣｙｓ）,从而引入了谷胱甘肽过氧化物酶（ＧＰＸ）的催化基团,使其在ＳＯＤ酶活性大部分保留的情况下,具有ＧＰＸ活性,其ＧＰＸ活力是ＰＺ５１活力的３０倍。研究了双功能酶的最佳制备条件,包括ＰＭＳＦ的剂量、反应最适温度及Ｈ_２Ｓｅ处理时间等,并用电子能谱、ＤＴＮＢ等方法测定了双功能酶的硒含量;测定了双功能酶对不同底物的米氏常数及双功能酶的荧光光谱、紫外吸收光谱及稳定性。     

基于纳米酶的脊髓损伤治疗

创伤性脊髓损伤是由外部冲击引起的椎管内神经结构损害,其发病率及致残率较高。目前临床治疗主要采用手术、激素冲击等方法,由于缺乏针对性治疗药物,无法实现实质性的功能恢复。针对脊髓损伤病理进程中氧化应激及神经炎症等特点,开发可持续降解自由基、抑制氧化应激、调节神经炎症的疗法成为研究热点。纳米酶具有与天然酶类似的催化活性,且在生理条件下稳定,可以持续抑制氧化应激和神经炎症,对脊髓损伤治疗具有重要意义。本文聚焦基于纳米酶的脊髓损伤治疗,介绍了脊髓损伤的病理生理学特点,纳米酶的分类、性质及纳米酶治疗脊髓损伤的研究进展,阐述了纳米酶对脊髓损伤治疗的推动作用,尤其使脊髓损伤治疗从单纯缓解症状的姑息治疗向神经再生的转变,展现了纳米酶作为脊髓损伤治疗平台的多功能性和潜在应用前景。     

脱氧核糖核酸对机体内超氧化物岐化酶和过氧化物酶活性影响初步研究

超氧化物岐化酶（SOD）和过氧化物酶（POD）是机体内重要的抗氧化酶系之一,其作用在于消除体内的自由基,防止自由基对细胞结构的损伤。它们的活性随增龄而下降,因此自由基不断损伤细胞结构,累积最终导致细胞衰亡和动物机体衰老,老龄小鼠服用DNA一段时间后,其体内SOD和POD的活性均显著提高,因而其衰老速度可能得到一定程度的延缓。     

萝卜过氧化物酶对小鼠机体抗氧化作用的研究

目的 探索新的抗氧化剂.方法 研究萝卜过氧化物酶(POD)对小鼠肝、脾和肾脏超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)、丙二醛(MDA)的影响.结果 用不同剂量的POD处理后,可以提高肝、脾和肾的SOD、GSH-Px的活性,减低丙二醛的含量.结论 萝卜过氧化物酶可以提高机体的抗氧化能力.     

N—（1—萘乙酰基）—N′—（4—氨替吡啉基）硫脲对萝卜中可溶性蛋白含量、过氧化物酶和超氧化物歧化酶活性的影响（简报）

萝卜苗期喷洒不同浓度(1、10、50 mg@L-1)的N-(1-萘乙酰基)-N′-(4-氨替吡啉基)硫脲(NAT)后,萝卜肉质根中可溶性蛋白含量及超氧化物歧化酶活性增加,过氧化物酶活性下降.     

基于纳米酶的无抗生素抗菌策略

抗生素是抵抗细菌感染的有力武器,然而抗生素的过量使用和滥用加速了细菌耐药性的发展,严重威胁人类健康。开发高效和广谱的无抗生素抗菌策略迫在眉睫。以过氧化氢(H₂O₂)为代表的活性氧(reactive oxygen species, ROS)能氧化多种生物分子,使其结构和活性改变而发挥广谱抗菌作用,是无抗生素抗菌策略之一。然而,临床常用的H₂O₂浓度较高(0.5%～3%),会刺激皮肤和延缓伤口愈合。利用过氧化物酶催化H₂O₂生成氧化性更强的羟自由基(·OH),可大幅提高ROS抗菌策略的性能。然而,天然酶生产成本高、稳定性低等缺点限制了该策略的推广。纳米酶是具有类似天然酶催化活性的纳米材料的统称。与天然酶相比,纳米酶具有制备简单、成本低和易储存等优势,是开发基于ROS的无抗生素抗菌策略的良好选择。贵金属、金属氧化物、金属硫化物、金属有机框架、碳基纳米材料等多种纳米材料具有过氧化物酶、氧化酶等的模拟催化活性,基于这些材料的纳米酶抗菌研究层出不穷,本文将对这些研究进...     

锌胁迫对小球藻抗氧化酶和类金属硫蛋白的影响

通过对抗氧化酶活性和类金属硫蛋白的测定,考察在0、5、10、20、50和100 μmol/L Zn²⁺(氯化锌)胁迫下锌对普通海洋小球藻的生物学影响。结果表明:不同浓度Zn²⁺均能抑制小球藻的生长,当Zn²⁺浓度大于10 μmol/L时,小球藻生物量随培养时间延长而迅速下降;过氧化物歧化酶 (SOD)活性随Zn²⁺胁迫浓度的增加而增加,当Zn²⁺浓度为50 μmol/L时SOD活性达到最大,但继续增加Zn²⁺胁迫浓度反而导致SOD活性下降;而过氧化物酶 (POD)活性则随着Zn²⁺胁迫浓度的增加而降低。同时,实验发现藻细胞内有两种主要的锌结合形态,其中Zn结合类金属硫蛋白(Zn-MT-like)与兔肝金属硫蛋白(MT)的分子量相近,且随着Zn²⁺胁迫浓度的增加而出现规律性地增多。因此,藻细胞内Zn-MT-like蛋白的诱导量可作为小球藻受Zn²⁺胁迫的响应指标。     

纳米酶的抗菌作用及其机制研究进展

抗生素类药物的发现和使用给人类提供了抗击细菌感染的强大武器。但是,抗生素长期使用导致的细菌耐药问题限制了其在临床上的应用。开发新型的基于纳米酶(Nano-Enzyme)的新型抗菌剂为解决上述问题提供了新思路。将纳米酶可以归为两大类:一类是酶和纳米材料的复合材料;另一类是纳米材料本身具有类酶活性。因为银(Ag)纳米粒子是历史最悠久且研究最广泛的纳米抗菌剂,而且其抗菌机制多样化,因此将Ag纳米粒子的抗菌机制和最新进展单独论述。纳米抗菌剂可以组合多种抗菌机制协同抗菌,从而提高其抗菌性能。因此,在这篇综述中系统介绍了Ag纳米粒子和上述2种类型纳米抗菌剂的最新研究进展和抗菌机制,重点介绍了纳米材料的物理性质对抗菌活性和生物安全性的影响。最后,该综述还强调了该领域目前面临的问题和挑战,并对该领域的发展前景进行了展望。     

The Superoxide Dismutase-Like Activity of Some Copper (II) Complexes Derived from Tridentate Schiff Bases

Oxygen free radicals are the final or intermediate products of many metabolic reactions. Of greatest significance to the organism are superoxide anion radical (O₂-), hydrogen peroxide (H₂O₂), hydroxyl radical (OH). singlet oxygen (^lO₂) etc. A proper ratio between both production and breakdown of oxy-radicals is essential for the maintenance of a dynamic equilibrium of vital processes. The superoxide dismutases protect cells against toxic influence of the superoxide. In addition, some square-pyramidally pentacoordinated copper(II) complexes, derived from tridentate Schiff bases of the N-salicylideneaminoal-canoate type, show remarkable SOD-like activity. A selected set of complexes of this type have been tested: potassium [aqua-(N-salicylideneglutamato) cuprate] (L-and D,L-form). potassium [(isothiocyanato)-(N-salicylideneglycinato) cuprate], potassium [(isothiocyanato)-(N-salicylidene-D,L-alaninato) cuprate]. potassium ((isothiocyanato)-(N-salicylidene-β-alaninato) cuprate] and potassium [(isocyanate)-(N-salicylideneglycinato) cuprate]. Our results suggest that the copper complexes are not only antioxidants, but may also possess anti-inflammatory, cytostatic and radioprotective properties.     

Divalent-metal-dependent nucleolytic activity of Cu, Zn superoxide dismutase

The known action of Cu, Zn superoxide dismutase (holo SOD) that converts O₂ ⁻ to O₂ and H₂O₂ plays a crucial role in protecting cells from toxicity of oxidative stress. However, the overproduction of holo SOD does not result in increased protection but rather creates a variety of unfavorable effects, suggesting that too much holo SOD may be injurious to the cells. In the in vitro study, we report a finding that the holo SOD from bovine erythrocytes and its apo form possess a divalent-metal-dependent nucleolytic activity, which was confirmed by UV–vis absorption titration of calf thymus DNA (ctDNA) with the holo SOD, quenching of holo SOD intrinsic fluorescence by ctDNA, and by gel electrophoresis monitoring conversion of DNA from the supercoiled DNA to nicked and linear forms, and fragmentation of a linear λDNA. Moreover, the DNA cleavage activity was examined in detail under certain reaction conditions. The steady-state study indicates that DNA cleavage supported by both forms of SOD obeys Michaelis–Menten kinetics. On the other hand, the assays with some other proteins indicate that this new function is specific to some proteins including the holo SOD. Therefore, this study reveals that the divalent-metal-dependent DNA cleavage activity is an intrinsic property of the holo SOD, which is independent of its natural metal (copper and zinc) sites, and may provide an alternative insight into the link between SOD enzymes and neurodegenerative disorders.     

前沿透视: 纳米酶具有类似生物酶的变性态？

纳米酶被认为在底物识别、催化机制、反应动力学等方面具有类似生物酶的特性,但纳米酶是否具有变性失活、并且在一定条件下恢复活性的特性,这是在纳米酶研究过程中需要关注的问题。     

褶纹冠蚌铜锌超氧化物歧化酶的可溶性表达及其活性分析

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Roles of exogenous divalent metals in the nucleolytic activity of Cu,Zn superoxide dismutase

It is well known that the wild type Cu,Zn superoxide dismutase (holo SOD) catalyzes the conversion of superoxide anion to peroxide hydrogen and dioxygen. However, a new function of holo SOD, i.e., nucleolytic activity has been found [W. Jiang, T. Shen, Y. Han, Q. Pan, C. Liu, J. Biol. Inorg. Chem. 11 (2006) 835-848], which is linked to the incorporation of exogenous divalent metals into the enzyme-DNA complex. In this study, the roles of exogenous divalent metals in the nucleolytic activity were explored in detail by a series of biochemical experiments. Based on a non-equivalent multi-site binding model, affinity of a divalent metal for the enzyme-DNA complex was determined by absorption titration, indicating that the complex can provide at least a high and a low affinity site for the metal ion. These mean that the holo SOD may use a "two exogenous metal ion pathway" as a mechanism in which both metal ions are directly involved in the catalytic process of DNA cleavage. In addition, the pH versus DNA cleavage rate profiles can be fitted to two ionizing-group models, indicating the presence of a general acid and a general base in catalysis. A model that requires histidine residues, metal-bound water molecules and two hydrated metal ions to operate in concert could be used to interpret the catalysis of DNA hydrolysis, supported by the dependences of loss of the nucleolytic activity on time and on the concentration of the specific chemical modifier to the histidine residues on the enzyme.