小鼠受100rad照射后组织荧光产物含量和硒谷胱甘肽过氧酶活性的变化

本文中实验测定了100rad受照小鼠肝、脾和睾丸组织的荧光产物含量以及肝和脾组织的Se-GSHPX活性。与对照组相比,在照后的15天内肝荧光产物的含量无明显变化;在照后7天至15天脾荧光产物含量明显增加(P<0.01);睾丸除照后3天降低外(P<0.05),在观察的7天内无明显变化。从照后1天至5天肝SeGSHPx活性增高(P<0.05),到照后7天有恢复趋势;脾Se-GSHPx活性在照后3天明显升高(P<0.01),照后5天和7天转为降低(P<0.05)。     

DyP-Type Peroxidases: Recent Advances and Perspectives

In this review, we chart the major milestones in the research progress on the DyP-type peroxidase family over the past decade. Though mainly distributed among bacteria and fungi, this family actually exhibits more widespread diversity. Advanced tertiary structural analyses have revealed common and different features among members of this family. Notably, the catalytic cycle for the peroxidase activity of DyP-type peroxidases appears to be different from that of other ubiquitous heme peroxidases. DyP-type peroxidases have also been reported to possess activities in addition to peroxidase function, including hydrolase or oxidase activity. They also show various cellular distributions, functioning not only inside cells but also outside of cells. Some are also cargo proteins of encapsulin. Unique, noteworthy functions include a key role in life-cycle switching in Streptomyces and the operation of an iron transport system in Staphylococcus aureus, Bacillus subtilis and Escherichia coli. We also present several probable physiological roles of DyP-type peroxidases that reflect the widespread distribution and function of these enzymes. Lignin degradation is the most common function attributed to DyP-type peroxidases, but their activity is not high compared with that of standard lignin-degrading enzymes. From an environmental standpoint, degradation of natural antifungal anthraquinone compounds is a specific focus of DyP-type peroxidase research. Considered in its totality, the DyP-type peroxidase family offers a rich source of diverse and attractive materials for research scientists.     

Ascorbate Peroxidase and Catalase Activities and Their Genetic Regulation in Plants Subjected to Drought and Salinity Stresses

Hydrogen peroxide (H₂O₂), an important relatively stable non-radical reactive oxygen species (ROS) is produced by normal aerobic metabolism in plants. At low concentrations, H₂O₂ acts as a signal molecule involved in the regulation of specific biological/physiological processes (photosynthetic functions, cell cycle, growth and development, plant responses to biotic and abiotic stresses). Oxidative stress and eventual cell death in plants can be caused by excess H₂O₂ accumulation. Since stress factors provoke enhanced production of H₂O₂ in plants, severe damage to biomolecules can be possible due to elevated and non-metabolized cellular H₂O₂. Plants are endowed with H₂O₂-metabolizing enzymes such as catalases (CAT), ascorbate peroxidases (APX), some peroxiredoxins, glutathione/thioredoxin peroxidases, and glutathione sulfo-transferases. However, the most notably distinguished enzymes are CAT and APX since the former mainly occurs in peroxisomes and does not require a reductant for catalyzing a dismutation reaction. In particular, APX has a higher affinity for H₂O₂ and reduces it to H₂O in chloroplasts, cytosol, mitochondria and peroxisomes, as well as in the apoplastic space, utilizing ascorbate as specific electron donor. Based on recent reports, this review highlights the role of H₂O₂ in plants experiencing water deficit and salinity and synthesizes major outcomes of studies on CAT and APX activity and genetic regulation in drought- and salt-stressed plants.     

A novel hydrogen peroxide biosensor based on Au-graphene-HRP-chitosan biocomposites

Graphene was prepared successfully by introducing -SO₃⁻ to separate the individual sheets. TEM, EDS and Raman spectroscopy were utilized to characterize the morphology and composition of graphene oxide and graphene. To construct the H₂O₂ biosensor, graphene and horseradish peroxidase (HRP) were co-immobilized into biocompatible polymer chitosan (CS), then a glassy carbon electrode (GCE) was modified by the biocomposite, followed by electrodeposition of Au nanoparticles on the surface to fabricate Au/graphene/HRP/CS/GCE. Cyclic voltammetry demonstrated that the direct electron transfer of HRP was realized, and the biosensor had an excellent performance in terms of electrocatalytic reduction towards H₂O₂. The biosensor showed high sensitivity and fast response upon the addition of H₂O₂, under the conditions of pH 6.5, potential −0.3 V. The time to reach the stable-state current was less than 3 s, and the linear range to H₂O₂ was from 5 × 10⁻⁶ M to 5.13 × 10⁻³ M with a detection limit of 1.7 × 10⁻⁶ M (S/N = 3). Moreover, the biosensor exhibited good reproducibility and long-term stability.     

Self‐Assembled Graphene–Enzyme Hierarchical Nanostructures for Electrochemical Biosensing

The self‐assembly of sodium dodecyl benzene sulphonate (SDBS) functionalized graphene sheets (GSs) and horseradish peroxidase (HRP) by electrostatic attraction into novel hierarchical nanostructures in aqueous solution is reported. Data from scanning electron microscopy, high‐resolution transmission electron microscopy, and X‐ray diffraction demonstrate that the HRP–GSs bionanocomposites feature ordered hierarchical nanostructures with well‐dispersed HRP intercalated between the GSs. UV‐vis and infrared spectra indicate the native structure of HRP is maintained after the assembly, implying good biocompatibility of SDBS‐functionalized GSs. Furthermore, the HRP–GSs composites are utilized for the fabrication of enzyme electrodes (HRP–GSs electrodes). Electrochemical measurements reveal that the resulting HRP–GSs electrodes display high electrocatalytic activity to H₂O₂ with high sensitivity, wide linear range, low detection limit, and fast amperometric response. These desirable electrochemical performances are attributed to excellent biocompatibility and superb electron transport efficiency of GSs as well as high HRP loading and synergistic catalytic effect of the HRP–GSs bionanocomposites toward H₂O₂. As graphene can be readily non‐covalently functionalized by “designer” aromatic molecules with different electrostatic properties, the proposed self‐assembly strategy affords a facile and effective platform for the assembly of various biomolecules into hierarchically ordered bionanocomposites in biosensing and biocatalytic applications.     

茭白中过氧化物酶的部分纯化及其性质的初步研究

采用硫酸铵沉淀及DEAE-SepharoseFF离子交换色谱对茭白中过氧化物酶进行了初步纯化,得到了部分纯化的两种过氧化物酶(组分A和组分B),其中组分A为酸性过氧化物酶,而组分B为碱性过氧化物酶。两种过氧化物酶的最适pH分别为5.0(A)和5.5(B),同时两种酶的热稳定性有一定的差异。     

H2O2对家蝇蛹内部几种酶活性的影响

目的研究外源H2O2对家蝇蛹内与抗性相关的几种酶活性的影响。方法通过H2O2诱导,测定家蝇蛹内过氧化氢酶(CAT)、过氧化物酶(POD)、抗坏血酸过氧化物酶(AsA-POD)以及多酚氧化酶(PPO)的活性变化。结果H2O2处理后蛹内CAT和AsA-POD的活性变化规律与处理前差别不大;POD活性在H2O2处理后12h内出现活性高峰,约为对照组的2.5倍,此后稍高于对照组,最后基本与对照组持平;PPO活性在处理后12h内与对照组相当,此后活性骤然升高,处理后24h达到对照组的2.13倍,然后变化速度减慢,但一直维持在对照组的1.3倍左右,48h后活性开始下降。结论H2O2对CAT和AsA-POD的活性影响较小,对POD和PPO的活性有一定的影响。     

磁性纳米酶显色技术在食品安全检测中的应用

磁性纳米酶显色技术是指利用磁性纳米酶的类过氧化物酶性质,在显色底物的存在下,对目标物进行快速、灵敏、可视化检测的新型技术。与天然酶相比,磁性纳米酶易制备、易保存、易回收、成本低。本文简单介绍了磁性纳米酶的催化机理和活性调节,重点综述了磁性纳米酶显色技术在食品中农兽药和重金属残留、食源性致病菌及其它有害物质检测中的应用现状。目前,该技术仍存在酶活性较弱、检测应用范围较窄、选择性欠佳等问题。本文针对上述问题提出了相关建议,并对其未来发展方向进行了展望。     

饮料型马铃薯酸奶的研究

本文研究了马铃薯酸奶的加工工艺和最佳配方。实验结果表明：热烫时间为３ｍｉｎ，质后颗粒直径≤３μｍ；最佳发酵工艺为：接种量２－４％，发酵时间４ｈ，培养温度４１－４３℃；最佳配方条件为：马铃薯２０－３０％，牛乳１０－１５％，蔗糖１．５－２％，酸性ＣＭＣ０．２％，魔芋精粉０．２％。