不同浓度Na2SO3处理对大花惠兰叶片内SOD、CAT活性的影响

用0.1%、0.4%、0.7%的Na2SO3溶液浸泡处理来研究模拟大气污染胁迫下大花惠兰(cymbidium grandiflorum)叶片内保护酶活性的变化,比较2、4、6、8 h后叶片内超氧化物岐化酶(SOD)、过氧化氢酶(CAT)活性的动态变化过程,结果发现,随着Na2SO3浓度的升高,SOD的活性均高于对照组,但幅度随时间延长而降低,CAT只有在0.10%的Na2SO3处理下高于对照组,其余呈缓慢下降趋势。说明高浓度Na2SO3处理后期,叶片内保护酶系统清除活性氧的能力下降,从而引起细胞膜损伤。     

铈对花生幼苗抗氧化酶活性影响的研究

采用花生(A rach is hypogaca l)幼苗为材料,通过叶面喷施C eC l3溶液,研究铈对花生生长初期超氧化物歧化酶及相关生理指标的影响。结果表明,20μg/L~80μg/L铈使叶片的超氧化物歧化酶(SOD)活性升高,100μg/L和200μg/L的铈使SOD活性下降,后者较前者更加显著;铈对过氧化物酶(POD)活性和叶片可溶性蛋白含量的影响较SOD而言相对平缓,但趋势相同。证实,铈对SOD的促进作用主要表现在锰型SOD上,体外实验表明M n-SOD酶蛋白能与C e3+结合。     

Rapid Diminution in the Level and Activity of DNA-Dependent Protein Kinase in Cancer Cells by a Reactive Nitro-Benzoxadiazole Compound

The expression and activity of DNA-dependent protein kinase (DNA-PK) is related to DNA repair status in the response of cells to exogenous and endogenous factors. Recent studies indicate that Epidermal Growth Factor Receptor (EGFR) is involved in modulating DNA-PK. It has been shown that a compound 4-nitro-7-[(1-oxidopyridin-2-yl)sulfanyl]-2,1,3-benzoxadiazole (NSC), bearing a nitro-benzoxadiazole (NBD) scaffold, enhances tyrosine phosphorylation of EGFR and triggers downstream signaling pathways. Here, we studied the behavior of DNA-PK and other DNA repair proteins in prostate cancer cells exposed to compound NSC. We showed that both the expression and activity of DNA-PKcs (catalytic subunit of DNA-PK) rapidly decreased upon exposure of cells to the compound. The decline in DNA-PKcs was associated with enhanced protein ubiquitination, indicating the activation of cellular proteasome. However, pretreatment of cells with thioglycerol abolished the action of compound NSC and restored the level of DNA-PKcs. Moreover, the decreased level of DNA-PKcs was associated with the production of intracellular hydrogen peroxide by stable dimeric forms of Cu/Zn SOD1 induced by NSC. Our findings indicate that reactive oxygen species and electrophilic intermediates, generated and accumulated during the redox transformation of NBD compounds, are primarily responsible for the rapid modulation of DNA-PKcs functions in cancer cells.     

多酚氧化酶及超氧化物歧化酶与花生霉变的关系

探讨多酚氧化酶(PPO)及超氧化物歧化酶(SOD)活力变化与花生霉变进程的关系,为食品质量检测及食品的储藏安全提供理论依据。分别采用邻苯二酚显色法和邻苯三酚自氧化法测定PPO及SOD的酶活力。结果表明,PPO及SOD酶活均随着花生霉变进程变化而变化,呈现出特定的规律性。安全可食阶段的花生PPO酶活最高,而SOD酶活则最低。当花生微量长霉时,PPO酶活减少率为38.42%,而SOD酶活增加率则超过500%。这些数据可以作为花生是否霉变的评判依据。     

Purification and characterization of superoxide dismutase from garlic

An efficient and easily scaled up method to isolate superoxide dismutase from garlic is proposed. The separation and purification procedure consists of phosphate buffer extraction, heat treatment and a two-stage ultrafiltration process. The enzyme was purified 139-fold with a specific activity of 2867 U/mg protein and a yield of 91%. The native molecular mass of superoxide dismutase estimated by fast protein liquid chromatography on a Superose 6 column was 28 kDa. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis showed a single band near 14 kDa, suggesting that native enzyme was homo-dimeric. The optimal pH for enzyme activity was found to be 7.0, and at this pH the enzyme exhibited maximum activity at 50 °C in 50 mM sodium phosphate buffer. Among various metal ions examined, Cu²⁺ and Zn²⁺ exerted a positive effect on superoxide dismutase activity, whereas Hg²⁺ was found to be a strong inhibitor. The final purified enzyme had an isoelectric point of 5.1-5.4 and a sheet content of 46%, consistent with the literature values. This shows that the purified SOD folded with a reasonable secondary structure.     

SODM、DTA-6和Cc对大豆生育中后期功能叶片生理特性的影响

在大田栽培条件下,以垦农4号为材料,通过叶面喷施植物生长调节剂SOD模拟物（SODM）、2-N,N-二乙氨基乙基己酸酯（DTA-6）、氯化胆碱（Cc）,研究其对大豆生育中后期功能叶片某些生理特性的影响。结果表明,喷施后5～20d,SODM、DTA-6、Cc处理提高了叶片的Chla、Chlb及Chl（a＋b）含量,降低了Chla／Chlb比值,其中SODM调控效果最佳。SODM、DTA-6提高了叶片可溶性蛋白质和可溶性糖含量。SODM、DTA-6、Cc处理在多数测定时期内均提高了叶片SOD和POD活性,其中DTA-6对SOD活性的调控作用最强,SODM次之;SODM对POD活性调控效果最佳,DTA-6次之。同时,DTA-6和SODM提高了叶片CAT活性,减缓了MDA含量的升高,而Cc对上述多项指标的调控作用均不明显。综合分析表明,叶面喷施DTA-6和SODM,调节了大豆生育后期功能叶片的生理代谢水平,延缓了大豆植株的衰老进程,提高了大豆产量。     

含锰的功能基包覆二氧化硅纳米颗粒的制备及SOD活性研究

采用Stber方法制备了二氧化硅纳米颗粒(硅球)。通过偶联反应将3-氯丙基三乙氧基硅烷(ACTES)与二乙烯三胺(DETA)的反应产物接枝在硅球上,形成含功能基的硅球,再和锰离子配位得到一种含锰及二乙烯三胺修饰的功能基二氧化硅纳米颗粒。用FTIR、TGA、SEM和EDS对其进行了表征,并用改进的四氮唑蓝法对其SOD活性进行了测定。结果表明,该纳米颗粒具有较高的SOD活性,其活性单位为IC50=0.026g·L-1。     

酸雨对黄棕壤的致酸作用与对小麦幼苗膜脂过氧化水平的影响

通过模拟酸雨淋洗土壤,造成了土壤酸化和盐基流失。将小麦幼苗栽培于由酸雨致酸的土壤上,导致小麦幼苗的膜脂过氧化水平提高。其中致酸土壤对根系膜脂过氧化水平的影响大于对叶片膜脂过氧化水平的影响。     

基于XML图的RBAC模型研究

针对传统XML描述的基于角色的访问控制(RBAC)模型在角色权限继承、约束方面支持的不足,提出了一种基于XML图的RBAC3模型。该模型通过属性引用的方式实现了多重继承并引入面向对象中私有继承的概念,使角色的私有权限得到保护。同时,通过引入互斥权限的概念简化了责任分离的实现。