泽泻原三萜、降三萜和倍半萜的分离及其抗炎活性研究＊

目的 对泽泻中原三萜、降三萜和倍半萜化学成分分离和鉴定及其抗炎活性进行研究；方法 采用硅胶柱色谱、凝胶柱色谱、高速逆流色谱、中压制备色谱和半制备色谱法对泽泻中各类化合物进行分离，利用¹H和¹³C NMR对分离化合物进行结构鉴定；通过测定各单体对LPS（1 μg·mL^-1）诱导Caco-2细胞中NO生成的抑制作用评价其抗炎活性。结果 从泽泻中分离得到19个化合物，包括8个原三萜类成分：alisol A 23 acetate （1），alisol G （2），16-oxo-11-anhydroalisol A （3），16-oxo-11-anhydroalisol A 24 acetate （4），alisoma A （5），alisoma B （6），alismanol J （7），alismanol B （8）；1个降三萜类成分：17-nor-protostane （9）；9个倍半萜类成分：orientalol L （10），orientalol M （11），orientalol N （12），orientalol O （13），orientalol P （14），alismanoid A （15），heyneanones D （16），leptocladol B （17），chabrolidione B （18）；1个木脂素类成分：pnoresinol （19）。原三萜类成分均具有显著的抑制活性，化合物1-8的IC₅₀分别为2.1、0.9、7.3、10.0、11.0、16.0、13.5和10.5 μmol·mL^-1，降三萜及倍半萜活性较弱，化合物10、11、13、15、16和17的IC₅₀分别为24.0、26.2、30.6、15.7、17.2和15.2 μmol·mL^-1。结论 化合物16、17、18和19为该植物首次分离得到。首次报道了倍半萜类成分对LPS诱导Caco-2细胞中NO生成的抑制作用，其中alisol A 23 acetate和alisol G的抑制活性最强。     

Coupling of diversification and pH adaptation during the evolution of terrestrial Thaumarchaeota

The Thaumarchaeota is an abundant and ubiquitous phylum of archaea that plays a major role in the global nitrogen cycle. Previous analyses of the ammonia monooxygenase gene amoA suggest that pH is an important driver of niche specialization in these organisms. Although the ecological distribution and ecophysiology of extant Thaumarchaeota have been studied extensively, the evolutionary rise of these prokaryotes to ecological dominance in many habitats remains poorly understood. To characterize processes leading to their diversification, we investigated coevolutionary relationships between amoA, a conserved marker gene for Thaumarchaeota, and soil characteristics, by using deep sequencing and comprehensive environmental data in Bayesian comparative phylogenetics. These analyses reveal a large and rapid increase in diversification rates during early thaumarchaeotal evolution; this finding was verified by independent analyses of 16S rRNA. Our findings suggest that the entire Thaumarchaeota diversification regime was strikingly coupled to pH adaptation but less clearly correlated with several other tested environmental factors. Interestingly, the early radiation event coincided with a period of pH adaptation that enabled the terrestrial Thaumarchaeota ancestor to initially move from neutral to more acidic and alkaline conditions. In contrast to classic evolutionary models, whereby niches become rapidly filled after adaptive radiation, global diversification rates have remained stably high in Thaumarchaeota during the past 400–700 million years, suggesting an ongoing high rate of niche formation or switching for these microbes. Our study highlights the enduring importance of environmental adaptation during thaumarchaeotal evolution and, to our knowledge, is the first to link evolutionary diversification to environmental adaptation in a prokaryotic phylum.Ammonia oxidation, the first and rate-limiting step in nitrification, is central to the global nitrogen cycle. Ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) perform this biochemical transformation, converting as much as 70% of the 100 Tg of nitrogen fertilizer applied annually (1) and generating significant nitrous oxide (2). Although only distantly related, AOA and AOB perform similar ecosystem functions by catalyzing the conversion of ammonia to nitrite (via hydroxylamine) by using ammonia monooxygenase, a multimeric enzyme comprising the subunits AmoA, AmoB, and AmoC (3). Although AOA were initially classified as Crenarchaeota, improvements in phylogenetic methods and genomic sampling of uncultured archaeal diversity led to their placement within a new archaeal phylum, the Thaumarchaeota (4, 5). These organisms are ubiquitous, with archaeal amoA genes frequently outnumbering those of AOB (6). Furthermore, AOA are the principal drivers of ammonia oxidation in many soils, particularly those with low pH (7, 8). Environmental pH is a major factor affecting the distribution of AOA in terrestrial ecosystems (3, 9), and most terrestrial Thaumarchaeota can be phylogenetically assigned to one of five pH-adapted lineages, two being acidophilic, two alkalinophilic, and one neutrophilic (9).Despite great progress in understanding of thaumarchaeotal ecology and physiology (10), little is known about the evolutionary mechanisms that have generated their great diversity in nature. In multicellular eukaryotes, the fossil record can provide insight into evolutionary processes over geological timescales, but such approaches are not possible for many prokaryotes because of the lack of an informative fossil record. In this context, recently developed probabilistic methods geared toward reconstructing the dynamics of species diversification and trait evolution using molecular phylogenies (11–13) have great potential. A recent Bayesian method that explicitly aims to characterize and quantify heterogeneity in evolutionary rates (13–15) holds particular promise for modeling prokaryotic evolution, whereby features such as massive population size, frequent lateral gene transfer (LGT), and fast growth all facilitate rapid increases in diversity, suggesting that complex evolutionary regimes may be the norm. Here, we apply these recently developed methods to test a key hypothesis about the ecological drivers of thaumarchaeotal diversification through deep evolutionary time. Based on the documented importance of soil pH in structuring modern AOA communities (9), we tested the hypothesis that adaptation to pH is an important driver of diversification in the Thaumarchaeota by comparing associations between pH and a range of other environmental factors with diversification in Thaumarchaeota.     

Attachment of gold nanoparticles to glassy carbon electrode and its application for the voltammetric resolution of ascorbic acid and dopamine

Gold nanoparticles have been attached on glassy carbon electrode surface through sulfhydryl-terminated monolayer and the gold nanoparticles-immobilized glassy carbon electrodes have been applied to the electrocatalytic oxidation of ascorbic acid, reducing the overpotential by about 200 mV with obviously increased current response. Due to its strong electrocatalytic activity towards ascorbic acid, the gold nanoparticles modified electrode can resolve the overlapped voltammetric waves of ascorbic acid and dopamine into two well-defined voltammetric peaks with peak-to-peak separation in potentials of about 300 mV. This can be used to allow the selective determination of ascorbic acid in the presence of dopamine. The catalytic current obtained from differential pulse voltammetry is linearly dependent on ascorbic acid concentration over the range of 6.5 × 10^?6 to 1.45 × 10^?4 M with correlation coefficient of 0.998 in the presence of dopamine. The detection limit (3σ) for AA was found to be 2.8 × 10^?6 M. The simultaneous determination of ascorbic acid and dopamine in their binary mixture has also been investigated. The modified electrode shows good selectivity, stability and anti-fouling properties. The proposed methods have been used for the selective determination of ascorbic acid in the presence of dopamine and for the simultaneous determination of both them in their mixtures with satisfactory results.     

On the adsorption and reduction of NO3− ions at Au and Pt electrodes studied by in situ FTIR spectroscopy

The adsorption of nitrate ions on gold and platinum electrodes in acid solution has been studied in acidic solution using in situ FURS. It is found that nitrate is adsorbed probably with a two-fold coordination on gold electrodes as suggested by the adsórbate potential-dependent spectral feature centered between 1440 and 1460 cm^?1. In addition, partial reduction of the nitrate ions at more negative potentials (ca. 0.05 V) generates nitrite ions in solution. These ions are co-adsorbed with nitrate ions in the double layer region of potentials. The nitrite ions seem to be adsorbed O-down with a one-fold or two-fold coordination. Platinum electrodes are found to be much more active catalytically to nitrate reduction than gold electrodes. The reduction of nitrate ions at potentials below 0.8 V generates an adsorbed product presenting a potential-dependent band at 1540 to 1580 cm^?1 which has been identified as adsorbed NO.     

Electrochemical properties of a tetrabromo-p-benzoquinone modified carbon paste electrode. Application to the simultaneous determination of ascorbic acid,dopamine and uric acid

The electrochemical study of a tetrabromo-p-benzoquinone modified carbon paste electrode (TBQ-MCPE), as well as its efficiency for electrocatalytic oxidation of ascorbic acid, dopamine and uric acid, is described. Cyclic voltammetry was used to investigate the redox properties of this modified electrode at various solution pH values and at various scan rates. Three linear segments were found with slope values of ?58.4 mV/pH, ?28.1 mV/pH and 0.0 mV/pH in the pH range 2.0–7.1, pH 7.1–9.0 and pH 9.0–11.0, respectively. The apparent charge transfer rate constant, k_s, and transfer coefficient, α, for electron transfer between TBQ and CPE were calculated as 3.79 ± 0.10 s^?1 and 0.55, respectively. The electrode was also employed to study the electrocatalytic oxidation of AA, using cyclic voltammetry, chronoamperometry and differential pulse voltammetry as diagnostic techniques. It has been found that the oxidation of AA at the surface of TBQ-MCPE occurs at a potential of about 430 mV less positive than that of an unmodified CPE. The diffusion coefficient of AA was also estimated using chronoamperometry. The kinetic parameters such as the electron transfer coefficient, α, and heterogeneous rate constant, $k_{\mathrm{h}}^{\prime }$, for oxidation of AA at the TBQ-MCPE surface was determined using cyclic voltammetry. Differential pulse voltammetry (DPV) exhibits two linear dynamic ranges and a detection limit of 0.62 μM for AA. In DPV, the TBQ-MCPE could separate the oxidation peak potentials of AA, DA and UA present in the same solution, though at the unmodified CPE the peak potentials were indistinguishable. This modified electrode was quite effective not only to detect AA, DA and UA, but also in simultaneous determination of each component concentration in the mixture.     

阳极氧化处理后的新型钛合金表面成骨细胞OPG、RANKL基因表达研究

目的:新型钛合金Ti-24Nb-4Zr-7.9Sn(TNZS)经过阳极氧化(anodic oxidation,AD)技术处理后,分析其表面的人成骨样MG63细胞骨保护素(osteoprotegerin,OPG)、细胞核因子-κB受体活化因子配体(RANKL)基因表达水平.方法:将人成骨样MG63细胞接种于Ti-6Al-4V、TNZS、AD-TNZS表面,采用半定量RT-PCR法检测OPG、RANKL mRNA的表达量.结果:人成骨样MG63细胞在AD-TNZS表面的OPGm RNA表达量有所提高,而RANKL mRNA的表达量3组材料间无明显差异.结论:阳极氧化处理的TNZS钛合金可能通过影响骨保护素、细胞核因子-κB受体活化因子配体调节成骨细胞、破骨细胞的平衡,从而促进种植体植入后的骨重建.     

Kinetic and mechanistic study of methanol oxidation on a Pt(100) surface in alkaline media1

A comparative study of methanol oxidation on a Pt(100) surface was carried out in bicarbonate, carbonate and different pH values of sodium hydroxide solutions. It was shown that Pt(100) adsorbs OH and `poisoning species'. The surface activity was directly correlated to the OH<sub>ad</sub> species coverage. The `poisoning species', produced in methanol oxidation, participate in the reaction at higher potentials, but block the surface partially at lower potentials. A dual path reaction mechanism, common to all the alkaline solutions used, was proposed based on the assumptions that HCO is a reactive intermediate and that a formate is a reaction product in the main path, while CO₂ is a product of `poisoning species' oxidation in a parallel reaction path.     

经微弧氧化钛铌锆锡合金的生物安全性评价

目的：评价低弹性模量钛铌锆锡合金（TNZS）表面应用微弧氧化技术进行改性后的生物安全性。方法：参照ISO7405-1997（E）/GB16886-1997最新标准,对该材料分别进行细胞毒性试验、溶血试验、口腔黏膜刺激试验、短期全身毒性试验。结果：体内外生物学试验结果表明：细胞毒性试验显示TNZS合金经微弧氧化处理后无细胞毒性;溶血率小于5%,有良好的血液相容性;口腔黏膜刺激试验未见异常组织学反应;短期全身毒性试验显示无明显短期全身毒性。结论：钛铌锆锡合金经微弧氧化技术改性后,显示了良好的生物安全性。     

成骨细胞在微弧氧化处理后纯钛表面的附着、增殖及ALP活性

目的 :对表面微弧氧化 (microarcoxidation ,MAO)处理后的纯钛材料进行成骨细胞生物相容性检测 ,评价改进的MAO工艺应用于钛植入材料表面处理的可能性。方法 :纯钛材料经过 2种MAO处理后 (MAO 1和MAO 2工艺 ) ,采用MC 3T3细胞系对不同时间点成骨细胞在材料表面的附着率、生长增殖情况以及ALP活性进行检测 ,以未经处理光滑纯钛表面作为对照 ,以SPSS对实验结果进行统计分析。结果 :早期 (0 .5h、1h)细胞附着率差异有统计学意义 ,MAO 1组 >MAO 2组 >纯钛组 ;2h后 ,MAO 1组与MAO 2组无差异 ,2组细胞附着率都显著高于纯钛组。细胞增殖及ALP活性测试中 ,MAO 1处理组在各时间点都显著高于另外 2组。结论 :MAO处理后的纯钛对成骨细胞的生物相容性优于未处理组 ,改进的MAO 1处理工艺较一般工艺可以更有效提高成骨细胞的早期粘附、增殖及ALP活性。