离心超滤质谱法筛选中药复方二妙丸中黄嘌呤氧化酶抑制剂

采用离心超滤质谱分析技术(UF-UPLC/Q-TOF/MS), 结合体外酶活性实验方法, 对中药复方二妙丸提取物中的黄嘌呤氧化酶抑制剂进行了筛选. 体外酶活性实验测得二妙丸水提液对黄嘌呤氧化酶的半数抑制浓度(IC₅₀)为(0.218±0.0034) mg/mL, 表明二妙丸具有较强的黄嘌呤氧化酶抑制活性. 进一步采用离心超滤质谱技术对二妙丸水提物中潜在的黄嘌呤氧化酶抑制剂进行筛选, 从中筛选并鉴定了9种具有潜在黄嘌呤氧化酶抑制活性的化合物, 为开发黄嘌呤氧化酶抑制剂及阐明二妙丸治疗痛风和高尿酸血症的作用机制提供了一定的依据.     

荧光动力学法测定超氧化物歧化酶的活性

超氧化物歧化酶的活力可以反映机体清除氧自由基的能力,在抗衰老研究中经常需对其进行准确测定。邻苯三酚自氧化可产生强荧光的醌,超氧化物歧化酶通过清除该反应过程中产生的超氧阴离子自由基使醌减少,据此建立了测定超氧化物歧化酶活力的荧光动力学方法。探讨了缓冲液的浓度、pH值、邻苯三酚浓度和温度对测定的影响。在Tris-HAC缓冲液浓度为0.1mol/L、pH8.2、邻苯三酚浓度为0.385mmol/L、温度为25℃的最佳条件下,得到SOD的线性响应范围为0.31~1.58mg/L;血清样品测定的RSD为1.12%(n=5);加标回收率在94.3%~103.49%之间。本法与黄嘌呤-黄嘌呤氧化酶法的测定结果一致,可用于动物样品中超氧化物歧化酶活力的测定。     

辣根过氧化物酶对心肌线粒体过氧化损伤的保护作用

以黄嘌呤氧化酶／次黄嘌呤自由基诱生系统建立了稳定的离体心肌线粒体的损伤模型，并应用此模型研究辣根过氧化物酶对心肌线粒体自由基氧化损伤的保护作用，结果表明，辣根过氧化物酶能抑制心肌线粒体中氧自由基的形成，降低膜脂的过氧水平，保护了线粒体膜酶活性，有效地防止自由基对线粒体结构和功能的损伤。     

荧烷染料/二芳基碘鎓盐同步光生色和光聚合体系

荧烷染料(FR)和二芳基碘盐(On⁺X^-)组成的体系,在光作用下,通过激发态的荧烷染料与碘盐之间发生电子转移反应,生成开环结构的荧烷染料有色体,伴随发生盐的光解反应,生成活性引发自由基碎片。该体系不仅可有效地引发烯类单体的聚合反应,也可同步发生光生色作用,产生较高的色密度。进一步研究了二芳基碘盐的取代基不同碳链长度和不同对离子及浓度诸因素,在光固化体系中对生色反应的影响。同时FR/On⁺X^-体系引发光交联形成的有色薄膜具有良好的色稳定性。     

罗丹明6G-I~-作荧光探针研究吲哚乙酸-辣根过氧化酶催化体系中活性氧的产生机理

以罗丹明6G-I-为荧光探针,探讨了辣根过氧化酶催化吲哚乙酸体系中活性氧物种的生成,发现在此体系中可产生单线态氧、超氧、羟基自由基和过氧化氢等活性氧物种.利用活性氧氧化I-成I3-后与罗丹明6G形成离子缔合物将导致其荧光猝灭的现象,可实现活性氧物种总量的测定.相应吲哚乙酸浓度在0.21～262.8μg/mL范围内催化产生的活性氧的总量与荧光猝灭强度△F呈良好的线性关系.反应动力学研究表明,辣根过氧化酶催化吲哚乙酸产生活性氧的反应是一级反应.     

化学发光法测定SOD活性的干扰因素及消除方法

采用黄嘌呤 -黄嘌呤氧化酶及邻苯三酚自氧化作为酶和非酶超氧阴离子自由基发生体系 ,以鲁米诺为发光剂 ,通过 SOD对发光的抑制率以测定 SOD活性。采用加热样品使 SOD失活 ,测得样品发光抑制率本底值 ,扣除本底值以消除干扰。在两种体系中测得结果有高度一致性 ,样品中 SOD活性分别为 1 70± 9.3U/m L和 1 65±2 .0 U/m L。本法用于测定生物制剂中 SOD活性 ,不需有机溶剂萃取 ,可有效地消除干扰 ,是一种实用、可靠测定 SOD活性的方法     

掺杂固定化酶柱的次黄嘌呤液滴光化学传感器研究

研制了一种基于掺杂的溶胶-凝胶固定化酶柱的次黄嘌呤液滴光化学传感器。在凝胶形成过程中添加肌氨酸和山梨醇,由于两种添加剂的模板作用,可形成大而有序的凝胶网格,使得酶与底物能充分接触,从而达到提高传感器响应速度和灵敏度的目的。基于这一方法固定了黄嘌呤氧化酶,并结合液滴光化学传感装置,用于次黄嘌呤的测定。在pH值为8.74的Tris-HC l缓冲液中,该传感器对2.0×10-7~8.0×10-6mol/L的次黄嘌呤呈线性响应,检出限为5.0×10-8mol/L。本实验固定化黄嘌呤氧化酶的催化效率是普通溶胶-凝胶法固定化酶的2.54倍。     

碳纳米管复合物极的构筑及其对嘌呤衍生物的同时测定

以嵌入式超薄碳糊(IUCP)前驱膜为基体,构建了单壁碳纳米管复合聚天青Ⅰ修饰电极(SWNTs/AZ/IUCP/CME).以扫描电镜表征其表面形貌,循环伏安法和微分伏安法考察其在黄嘌呤(XA)和次黄嘌呤(HXA)中的响应情况.实验表明,电极对XA和HXA的电化学反应表现出良好的增敏作用,采用微分伏安法测得XA和HXA的氧...     

聚苯胺黄嘌呤氧化酶电极的生物电化学活性

用电化学方法将黄嘌呤氧化酶固定在聚苯胺中以制成聚苯胺黄嘌呤氧化酶电极。该电极呈现典型的酶催化反应动力学特性。且具有快速的生物电化学响应。固定化黄嘌呤氧化酶的表观米氏常数为21×10^-^6mol.dm^-^3, 最适pH为8.4,酶催化反应的活化能为85.1kJ.mol^-^1。酶电极具有较高的稳定性。使用聚苯胺黄嘌呤氧化酶电极能可靠地测定较低的底物浓度, 如2×10^-^6mol.dm^-^3黄嘌呤。     

自由活动大鼠脑内次黄嘌呤的活体在线电化学分析方法研究

本文通过联用选择性的电化学传感器和活体微透析采样技术,提出并建立了自由活体大鼠脑内次黄嘌呤的在线电化学分析新方法.本研究中,次黄嘌呤被黄嘌呤氧化酶（XOD）催化氧化,同时产生H2O2.利用普鲁士蓝（PB）作为H2O2电化学还原的催化剂,通过测定H2O2,从而实现了次黄嘌呤的在线电化学分析.实验结果表明,所建立的方法具有很好的选择性、稳定性和重现性,可以应用于自由活动大鼠脑内次黄嘌呤的连续测定.本文的研究为与次黄嘌呤相关生理和病理过程分子机制的研究奠定基础.     

化学镀镍体系次亚磷酸钠氧化中间产物的ESR研究

化学镀镍是借助 Na H2 PO2 在具有催化活性金属表面的阳极氧化将溶液中的镍离子还原成金属镍 .伴随镍的沉积 ,表面同时有氢气析出 .同位素研究表明 [1,2 ] ,析出的氢气一部分为溶液中 H+或 H2 O的阴极还原 ,另一部分来自 Na H2 PO2 的阳极氧化过程 .Meerakker等[3～ 5 ] 认为 ,Na H2 PO2 的氧化经历了H2 PO-2 H+ HPO-.2 异相前置转化步骤 ,HPO-.2 阴离子自由基发生阳极氧化的同时伴有 H复合生成氢气过程 .而另一些研究者 [6～ 8] 认为 ,Na H2 PO2 的氧化过程为 H2 PO-2 + H2 O H2 PO-3 + 2 H,仅有 H自由基生成 ,并不产生 H…     

Kinetics of radiolytic oxidation of ferrous ions in some aqueous aerated systems

The oxidation of ferrous ions by organic peroxy radicals at different doses is non-linear, however, the plots of inverse of ferric ion concentration against inverse of dose are linear. This behavior is explained by a set of three general reactions. Some of the organic free radicals produced in these systems either react with O₂ forming peroxy radicals or they get oxidized by ferric ions. Other organic free radicals do not involve in the above competition and react with O₂ only.     

Photochemistry of perfluoroacyl halides in the presence of O2 and CO

Photolyses of CF₃C(O)X and C₂F₅C(O)X (X=Cl, F) at 254 nm in the presence of O₂ yield the perfluorinated radicals C₂F₅O (C₂) and CF₃O (C₁), respectively. The C₂ radicals decompose to give CF₃ radicals:

C₂F₅O→CF₃+CF₂O

which, in turn, react with O₂ leading to the formation of C₁ radicals. When in addition to O₂, CO is present, the C₁ radicals react with it leading to its catalytic oxidation to CO₂. The trioxide CF₃OC(O)O₃C(O)OCF₃ was observed following the photolysis of all four halides in the presence of O₂ and CO.

The other radical partners coming from the initial step in the photolysis (XC(O)) as well as the products of their reaction with O₂ (XC(O)O_y, y=1, 2) do not react with CO but when X=F they lead to the formation of a new stable peroxy molecule with the formula CF₃OC(O)O₂C(O)F. Some of the properties of this new molecule, its stability and its IR features are presented in this work.     

Free radical inactivation of pepsin

Alkylperoxy radicals containing one, two or three chlorine atoms, CO^-₂, O₂ ^- were reacted with pepsin in aqueous solutions. It was found that only Cl₃COO and CO^-₂ inactive pepsin, attacking preferentially the disulfide bridge. Transient spectra obtained upon completion of the Cl₃COO + pepsin reaction at pH 5 indicate that 20% of initially produced Cl₃COO radicals oxidizes tryptophan residues, and 40% disulfide bridges. The inactivation induced by the Cl₃COO radical increases at lower pH, and the maximal inactivation, G_in = 5.8, was observed at pH 1.5. The inactivation of pepsin by CO^-₂ radicals depends on the absorbed dose. The maximal inactivation, G_in = 4.5, was determined in the dose range from 38 to 53 Gy.     

Ag_3PO_4/BiVO_4复合光催化剂的制备及可见光催化降解染料(英文)

结合回流法和原位沉淀法成功制备磷酸银/矾酸铋(Ag3PO4/BiVO4)复合光催化剂.通过X射线衍射(XRD)、场发射扫描电子显微镜(FESEM)、能量色散X射线光谱(EDS)、紫外-可见漫反射光谱(UV-Vis DRS)及光致发光(PL)光谱对制备样品进行表征.XRD和FESEM结果表明成功制备Ag3PO4/BiVO4复合光催化剂.采用节能发光二极管灯(LED)作为可见光光源,在低消耗光催化系统中评价制备样品可见光催化降解染料的活性.当Ag3PO4和BiVO4的组成摩尔比为1:3时,复合Ag3PO4/BiVO4光催化剂呈现出高于纯相Ag3PO4的催化活性,可减少Ag3PO4的使用量.Ag3PO4/BiVO4复合光催化剂在中性溶液中表现出高活性,同时证实其对阳离子染料的光催化降解效果强于阴离子染料.在Ag3PO4/BiVO4系统中,超氧自由基和空穴是主要的活性物种.经过三次循环利用,Ag3PO4/BiVO4复合催化剂的可见光催化活性表现出不同程度的降低,归因于降解过程中产生金属银.     

EPR study of the radicals formed upon UV irradiation of ceria-based photocatalysts

EPR measurements reveal remarkable differences on the type of radicals produced after UV illumination of TiO₂, CeO₂ and 0.8% CeO₂/TiO₂ photocatalysts. Photoactivation of the TiO₂ sample in vacuum results in the formation of Ti⁴⁺–O⁻ species and a small amount of Ti³⁺ centers. In the presence of adsorbed oxygen, irradiation of this material also generates Ti⁴⁺–O₃⁻ radicals. In the case of the CeO₂/TiO₂ catalyst, the ceria component is present in a highly dispersed state, as indicated by XRD and UV–Vis diffuse reflectance spectra (DRS) results. Accordingly, the only type of Ce⁴⁺–O₂⁻ adducts generated on the CeO₂/TiO₂ sample are indicative of the presence of two-dimensional patches of ceria on the anatase surface. On the other hand, photoactivation of the CeO₂/TiO₂ sample in the presence of oxygen also leads to the formation of some Ti⁴⁺–O⁻ and Ti³⁺ centers. In the case of the CeO₂ sample, superoxide radicals are observed upon irradiation in vacuum and subsequent oxygen adsorption. Further irradiation of this material in the presence of oxygen increases the amount of Ce⁴⁺–O₂⁻ radicals and simultaneously generates new species, which are tentatively assigned to Ce⁴⁺–O₂H radicals. Photocatalytic activity was tested for toluene oxidation, and the results obtained show that the photodegradation rate is slightly lower for CeO₂/TiO₂ than for the TiO₂ sample. However, the selectivity towards benzaldehyde (6–13%) is comparable for both materials. In the case of CeO₂, the photo-oxidation rate is an order of magnitude lower than for TiO₂, although mineralization of toluene is almost complete. Photoactivity results are discussed in connection with the characteristics of the radicals observed.     

直线型l-CnH(n=5,6)自由基与氧气反应机理的理论研究

为了探索更长的碳链自由基l-C_nH与O₂反应的机理, 在CCSD(T)/CC-PVTZ+ZPVE//B3LYP/6-311++G(d,p)的计算水平下, 讨论了当n=5,6时, l-C_nH+O₂的各个异构化反应通道. 当n=5时, 主要反应通道为碳迁移过程, 生成主要产物为P2(CO₂+C₄H); 当n=6时, 碳-氧交换[产物为P1(CO+HC₅O)]和氧迁移过程[产物为P3(³O+HC₆O)]均为主要通道, 并具有很高的竞争性. 将所得结构与l-C_nH(n≤4)+O₂的反应机理进行了对比.     

Rate coefficients for the reactions of cyclohexadienyl (c-C6H7) radicals with O2 and NO at room temperature

Rate coefficients for the reactions of cyclohexadienyl (c-C₆H₇) radicals with O₂ and NO were measured at 296 ± 2 K. The c-C₆H₇ radicals were detected selectively by laser-induced fluorescence. The rate coefficient for the reaction of c-C₆H₇ with O₂, (4.4 ± 0.5) × 10⁻¹⁴ cm³ molecule⁻¹ s⁻¹, was independent of the bath-gas (He) pressure (13–80 Torr). In the reaction of c-C₆H₇ with NO, thermal equilibrium among c-C₆H₇, NO, and C₆H₇NO was observed. The forward and reverse reactions were in the falloff region, and the equilibrium constant was (1.5 ± 0.6) × 10⁻¹⁵ cm³ molecule⁻¹.     

O2/CO2燃烧气氛对混煤灰中矿物质间反应影响研究

对蒙煤与平七煤两种单煤及其按照不同比例组成的混煤,分别在O₂/CO₂和O₂/N₂气氛下,采用管式炉燃烧制取灰样;对灰样进行灰熔点、XRD及同步热分析（TG/DSC）测试,并进行相关热力学计算,分析了O₂/CO₂燃烧方式对混煤灰中矿物质间反应的影响。结果表明,常规灰熔点测试方法测得的两种气氛下的混煤灰熔点没有明显差别。O₂/CO₂气氛促进了煤灰/混煤灰中钙的碳酸化,且明显抑制了高温下CaCO₃的分解。气氛的改变影响了含钙矿物的转化,进而影响了混煤中钙与莫来石反应生成低温共熔物;O₂/CO₂气氛下钙更易于与莫来石发生反应生成低温共熔物,从而会增加结渣倾向。当混煤中蒙煤比例达到或大于75%时,随着蒙煤比例的逐渐增加,莫来石含量减少,O₂/CO₂气氛对钙与莫来石之间的反应影响减弱,但对含铁矿物的影响更加明显,使其更易于生成含铁玻璃体,从而也会增加结渣倾向。     

乙酸钠、草酸钠、酒石酸钾在三氧化钨-水体系中光生自由基的研究

当分散在溶液中的TiO₂、znO、CdS、WO₃等多相体系受到光照时,固态的半导体物质吸收光子后会产生电子-空穴对,它们在半导体界面上与周围介质反应,可能以各种方式进行电荷转移而形成不同的活泼中间体,引起人们对发生在半导体粉末上的光化学过程的关注。