La-O小团簇上超氧物种与过氧物种间的连接途径

采用密度泛函理论方法考察了La-O团簇上超氧物种与过氧物种间转化的连接途径. 单重态下, 团簇上单个超氧物种可通过一系列臭氧物种转化为过氧物种, 且转化能垒较高;三重态下, 单个超氧物种则并无与过氧物种间连接的途径. 然而, La-O团簇上两超氧物种间的相互作用及其转化也具单重态和三重态两条途径. 三重态下, 超氧物种可很容易地转化为过氧物种(O₂^- + O₂^-↔O₂^2- + O₂), 超氧物种与过氧物种处于快速的交换状态之中;单重态下, 超氧物种转化为过氧物种则需较高的活化能垒, 表明在单重态下这些氧物种具有较高的稳定性.     

Cytochrome c‐Based Amperometric Sensors for Superoxide Detection: Where Their Signal Comes From?

In a popular amperometric superoxide sensor, cytochrome c (Cyt c) is covalently immobilized onto a gold electrode previously covered with a self‐assembled monolayer (SAM) of carboxyl‐terminated alkanethiols. Therefore, a study was carried out to reveal the origins of the current response of such sensors. SAMs made of either 3,3′‐dithiodipropionic acid or 11‐mercaptoundecanoic acid and 11‐mercaptoundecanol were used to immobilize either Cyt c or an inert protein onto gold electrodes. The resulting modified electrodes were comparatively investigated by cyclic voltammetry and calibrated for superoxide detection. The obtained results bring evidence that significant part (>70 %) of the current response of the Cyt c‐modified electrodes to superoxide comes from direct oxidation of superoxide on gold (i.e. does not involve Cyt c).     

Synthesis and structural characterization of an anti-inflammatory principle purified from Lindera aggregata

Linderaggrine A (1) was characterized from the roots of Lindera aggregata and its chemical structure was established by the spectral analysis and chemical transformation. The chemical preparation of 1 and its isomer 2 provide unambiguous evidences for the structural determination of the naturally isolated compound. In addition, the inhibition of superoxide anion generation and elastase release by human neutrophils in response to FMLP/cytochalasin B of these synthetic products had been examined and among the tested compounds, linderaggrine A (1) displayed significant potential against the superoxide anion generation.     

Fabrication of Superoxide Dismutase (SOD) Imprinted Poly(ionic liquid)s via eATRP and its Application in Electrochemical Sensor

Superoxide dismutase (SOD) plays an important role in nearly all living cells. In this study, SOD imprinted poly(ionic liquid)s (SIPILs) were prepared on the surface of the bare Au electrode modified with nano‐palladium and nano‐gold (Au/nPd/nAu/SIPILs). SIPILs was synthesized with 1‐vinyl‐3‐propyl imidazole sulfonate ionic liquids as functional monomers via electrochemically mediated atom transfer radical polymerization (eATRP) catalyzed by SOD. The Au/nPd/nAu/SIPILs was examined by cyclic voltammetry (CV), scanning electron microscope (SEM), energy‐dispersive spectrometer (EDS) and X‐ray photoelectron spectroscopy (XPS). The Au/nPd/nAu/SIPILs was also used as an electrochemical sensor to determine SOD by differential pulse voltammetry (DPV). Under the optimal conditions, the detection range of SOD was from 1.0×10^?8 to 1.0×10² mg L^?1 with a limit of detection of 8.90×10^?9 mg L^?1 (S/N=3). Compared with other methods, the sensor based on SIPILs had the broader linear range and lower detection limit.     

Effect of hydrostatic pressure on the fluorescence of indole derivatives

Effects of hydrostatic pressure on the fluorescence emission of L-tryptophan, N-acetyl-L-trytophanamide and indole were investigated. An increase in pressure ranging from 1 bar to 2.4 kbar results in reversible red-shifts of the emission of the three fluorophores. The pressure-induced redshift amounts to about 170 cm^–1 at 2.4 kbar, and appears related to changes in Stokes shift of the fluorophores caused by pressure effects on the dielectric constant and/or refractive index of the medium. As the pressure range investigated here is the range commonly used in studies of protein subunit association and/or folding, these observations raise the need for caution in interpreting pressure-induced spectral shifts. The significance of these observations to pressure studies of proteins is illustrated by investigation of pressure effects on human Cu,Zn Superoxide dismutase (SOD) and azurin fromPseudomonas aeruginosa. A reversible 170 cm^–1 red-shift of the emission of SOD was observed upon pressurization to 2.4 kbar. This might be interpreted as pressure-induced conformational changes of the protein. However, further studies using SOD that had been fully unfolded by guanidine hydrochloride, and fluorescence anisotropy measurements indicated that the observed red-shift was likely due to a direct effect of pressure on the fluorescence of the single tryptophan residue of SOD. Similar pressure-induced red-shifts were also observed for the buried tryptophan residue of azurin or for azurin that had been previously denatured by guanidine hydrochloride. These observations further suggest that the effective dielectric constant of the protein matrix is affected by pressure similarly to water.     

Sonochemistry of cytochrome c. Evidence for superoxide formation by ultrasound in argon-saturated aqueous solution

Formation of superoxide anion radicals (O₂^·−) induced by 50 kHz ultrasound in argon (Ar)-saturated aqueous solution was studied. Although EPR-spin trapping study with 5,5-dimethyl-1-pyrroline N-oxide (DMPO;100 mM) revealed the formation of DMPO-adducts of hydroxyl radicals (^·OH) and hydroperoxy radicals (HO₂^·; acid form of O2^·−) in O₂-saturated solution after sonication, no evidence of HO₂^· was found in Ar-saturated solution. When ferricytochrome c (cytochrome c) in Ar-saturated aqueous solution was sonicated, the reduced form of cytochrome c was observed and 80% of its formation was inhibited by the addition of superoxide dismutase (SOD). Sodium formate enhanced the production of the reduced form of cytochrome c. The % inhibition by SOD for the reduction increased in the order of Xe > Ar > He in accord with the higher temperatures of the cavitation bubbles. These results indicate that the O₂^·− is formed by directly by the sonolysis of water in the absence of O₂ when the temperature of cavitation bubble collapse is sufficiently high.     

稳定直线型硝酮-O_2~(-·)加合物的构型因素解析

对生命体系中的氧自由基,Spin trapping-ESR方法是公认的特征分析手段[1].然而,对超氧阴离子自由基(O2-·)而言,其自由基加合物稳定性差.对此,人们通过改变硝酮的取代基团,设计出更为有效的O2-·捕获探针[2,3].另外,Zweier研究组[4,5]还应用密度泛函理论研究了影响五元环状硝酮     

New briaranes from the octocorals Briareum excavatum (Briareidae) and Junceella fragilis (Ellisellidae)

Six 12-hydroxybriaranes, including four new diterpenoids, briaexcavatins I-L (1-4), and two known metabolites, excavatolides C (5) and E (6), have been isolated from the cultured scleraxonia Briareum excavatum. In addition, the gorgonian coral Junceella fragilis yielded a new chlorinated briarane, fragilide C (10). The structures of above compounds were determined by spectroscopic methods and the structures of 5 and 6 were further confirmed by X-ray data analysis for the first time. The absolute configuration of 6 was elucidated by chemical conversion. Some of these briaranes have displayed inhibitory effects on superoxide anion generation by human neutrophils.     

Guaiacol as an Organic Superoxide Dismutase Mimics for Anti-ageing a Ru-based Li-rich Layered Oxide Cathode

High-capacity Li-rich layered oxides using oxygen redox as well as transition metal redox suffer from its structural instability due to lattice oxygen escaped from its structure during oxygen redox and the following electrolyte decomposition by the reactive oxygen species. Herein, we rescued a Li-rich layered oxide based on 4d transition metal by employing an organic superoxide dismutase mimics as a homogeneous electrolyte additive. Guaiacol scavenged superoxide radicals via dismutation or disproportionation to convert two superoxide molecules to peroxide and dioxygen after absorbing lithium superoxide on its partially negative oxygen of methoxy and hydroxyl groups. Additionally, guaiacol was decomposed to form a thin and stable cathode-electrolyte interphase (CEI) layer, endowing the cathode with the interfacial stability.     

基于高分辨质谱技术的农药与生物大分子相互作用的分析方法

建立了检测农药小分子与生物大分子(BSA蛋白,SOD酶)相互作用的高分辨质谱分析方法.对相应结合产物进行质谱检测,结果表明,BSA蛋白与甲基对硫磷分子在开始相互作用30 min后达到饱和,且每个蛋白分子最多与5个甲基对硫磷分子结合;BSA蛋白与甲维盐不存在相互作用.通过对SOD酶与敌敌畏,阿维菌素及噻呋酰胺结合产物的质谱检测发现每个SOD酶最多结合2个敌敌畏分子,1个阿维菌素分子,且不与噻呋酰胺相互作用.此外,实验表明,SOD酶与阿维菌素分子作用30 min后达到平衡,与敌敌畏分子作用20 min后达到平衡.通过对两种蛋白结合农药小分子过程的时间分辨分析发现,两种生物大分子结合农药小分子的机理过程存在差异.本方法与相关标准方法(荧光光谱法,NBT试剂盒法)及分子模拟对接结果比对说明,本方法切实可靠.本方法具有耗样量少、检测速度快、可提供多方面信息等优点,在新农药的研发及其安全性评价方面具有实用价值.