Synthesis of 8-halogenated-7-deaza-2′-deoxyguanosine as an 8-oxo-2′-deoxyguanosine analogue and evaluation of its base pairing properties

8-Halogenated-7-deaza-2′-deoxyguanosines (8-halo-7-deaza-dG) were designed to structurally mimic 8-oxo-2′-deoxyguanosine (8-oxo-dG), which is representative of an oxidized nucleoside. It has been shown by NMR that the conformation around the N-glycosidic bond of (8-halo-7-deaza-dG) is preferably syn, similar to 8-oxo-dG. The base pairing properties of 8-halo-7-deaza-dG were studied by measuring the thermal denaturation temperature of the duplexes, showing that their base pair with dC is destabilized compared with natural dG. These results also support their preference for syn conformation. Unlike 8-oxo-dG, 8-halo-7-deaza-dG did not form a stable base pair with dA, most likely due to the lack of N7-H hydrogen bonding with dA. In conclusion, the newly-designed 8-halo-7-deaza-dG analogs resemble 8-oxo-dG in its shape and preference for syn conformation, but they do not form Hoogsteen base pair with the opposing dA.     

二氧化铈纳米微粒过氧化物酶活性及其在葡萄糖检测中的应用

合成了一种稳定和水溶性的聚丙烯酸修饰CeO2 NPs,利用动态光散射(DLS)、傅里叶变换红外光谱(FT-IR)和X射线光电子能谱(XPS)进行表征.结果表明,CeO2 NPs能够催化H2O2氧化3,3′,5,5′-四甲基联苯胺(TMB)发生显色反应,表现出过氧化物模拟酶催化活性.利用Raman和顺磁共振(EPR)光谱技术研究了其催化机理.基于CeO2 NPs催化TMB变色反应对H2O2浓度的依赖性和葡萄糖氧化酶能够催化溶解氧氧化葡萄糖产生H2O2的原理,构建了一种简单、灵敏、选择性高的测定血清中葡萄糖的检测方法.在优化条件下,测定葡萄糖的线性范围为0.5~10 mmol/L,检出限(3σ)为0.1 mmol/L.对1.0 mmol/L葡萄糖进行11次平行测定,其相对标准偏差为2.4%.该方法已成功用于血清样品中葡萄糖的测定.     

基于电活性铁氰化镍和金属模拟酶协同催化的蛋白质电化学检测

该文设计了一种基于金属纳米模拟酶协同催化产生不溶性沉淀的“signal-off”型电化学免疫传感器用于超灵敏检测甲胎蛋白(AFP）。通过夹心免疫法将具有辣根过氧化物活性的二抗耦合物空心纳米金-铂钯纳米颗粒(HAuNPs-PtPdNPs-Ab2）固载在电活性物质铁氰化镍纳米颗粒修饰的电极上。在H2O2存在下,以AFP捕获的二抗耦合物中的HAuNPs和PtPdNPs作为辣根过氧化物模拟酶催化4-氯-1-萘酚(4-CN）,并在电极界面生成不溶且不导电的沉淀物苯并-4-氯己二烯酮(4-CD）,有效阻碍了电子传递,电化学信号显著降低,可用于AFP的定量检测。实验表明,该传感器对0.1 pg/mL~200 ng/mL AFP表现出良好的检测线性,检出限(S/N=3）为33 fg/mL。该传感策略具有协同催化作用,可提供一种新的多重信号放大方法用于改善传感器的灵敏度。     

Studies on p-Nitrophenyl Picolinate Cleavage by Unsymmetrical Bis-Schiff Base Manganese(III) and Cobalt(II) Complexes in CTAB Surfactant Micellar Solution

The unsymmetrical bis-Schiff base manganese(III) and cobalt(II) complexes with either benzo-10-aza-crown ether pendants (MnL¹Cl, MnL²Cl) or morpholino pendant (MnL³Cl, CoL³) have been employed as models for hydrolase by studying the kinetics of their hydrolysis reactions with p-nitrophenyl picolinate (PNPP) in the buffered CTAB micellar solution. A kinetic model of PNPP cleavage catalyzed by these complexes is proposed. The effects of complex structures and reaction temperature on the rate of PNPP hydrolysis have been examined. All four complexes exhibit higher catalytic activity in the buffered CTAB micellar solution and the rate increases with pH of the buffered CTAB micellar solution under 25°C. The complexes containing a crown ether group exhibit higher catalytic activities than the free-crown analogues. The catalytic activity of manganese(III) complex is superiority over cobalt(II) complex in catalyzing hydrolysis of PNPP under the same ligand.     

Hydrolysis of BNPP Catalyzed by the Crowned Schiff Base Co(II) Complexes in Micellar Solution

Two symmetrical double aza‐crowned Schiff base cobalt(II) complexes were synthesized and characterized, and the metallomicelle made up of the cobalt(II) complexes and surfactant, as mimic hydrolytic metalloenzyme, was used in catalytic hydrolysis of bis(4‐nitrophenyl) phosphate (BNPP). The analysis of specific absorption spectrums of the hydrolytic reaction systems indicated that key intermediates made up of BNPP and Co(II) complexes are formed in reaction processes of the BNPP catalytic hydrolysis. In this article, the mechanism of BNPP catalytic hydrolysis has been proposed based on the analytic result of specific absorption spectrum. A kinetic mathematical model, for the calculation of the kinetic parameter of BNPP catalytic hydrolysis has been established based on the mechanism proposed. The acid effect of reaction system, the structural effect of the complexes, the effect of surfactant micelles and the effect of temperature on the rate of BNPP hydrolysis catalyzed by the complexes have been discussed.     

Oxidation Reaction of Phenol with H2O2 Catalyzed by Metallomicelles Made of Co(II) and Cu(II) Complexes of Imidazole Groups and Micelle as Mimic Peroxidase

The imidazole derivatives (N,N‐bis(2‐ethyl‐5‐methyl‐imidazole‐4‐ylmethyl) amino‐propane (biap)) and its complexes containing cobalt or copper ion were synthesized in this study. The oxidation reaction of phenol with oxidant H₂O₂ catalyzed by the metallomicelle made of the complexes of imidazole groups and micelle (CTAB, Brij35, LSS) as the mimetic peroxidase was studied. The results show that the reaction rate for the catalytic oxidation of phenol increases by a factor of approximately 1×10⁵ in the metallomicelle over that in the simple micelles or the pure buffer solution at pH=6.9 and 25°C. The catalytic effects changed with H₂O₂, temperature, pH, and surfactant kind in the catalytic reactive process are discussed. A kinetic mathematic model of the phenol oxidation catalyzed by the metallomicelle is proposed.     

模拟酶微型反应器中糠醛催化氧化为糠酸

在水与有机试剂组成的非均相体系中，用β－环糊精（β-cyclodextrin,缩写：β－CD）衍生物模拟生物酶，以强力搅拌下分散在有机溶剂中的小水珠作为微型反应器进行糠醛催化氧化为糠酸的反应，停止搅拌后体系立即分层，产物在有机相，残留的原料和模拟酶在水相。本合成方法简单，溶剂和模拟酶能回收，不产生污染，催化效率较均相高，为绿色合成化学制备医药、化工产品提供了一种新合成体系。     

Evaluation of the oxidase like activity of nanoceria and its application in colorimetric assays

Nanomaterial-based enzyme mimics have attracted considerable interest in chemical analysis as alternative catalysts to natural enzymes. However, the conditions in which such particles can replace biological catalysts and their selectivity and reactivity profiles are not well defined. This work explored the oxidase like properties of nanoceria particles in the development of colorimetric assays for the detection of dopamine and catechol. Selectivity of the system with respect to several phenolic compounds, the effect of interferences and real sample analysis are discussed. The conditions of use such as buffer composition, selectivity, pH, reaction time and particle type are defined. Detection limits of 1.5 and 0.2 μM were obtained with nanoceria for dopamine and catechol. The same assay could be used as a general sensing platform for the detection of other phenolics. However, the sensitivity of the method varies significantly with the particle type, buffer composition, pH and with the structure of the phenolic compound. The results demonstrate that nanoceria particles can be used for the development of cost effective and sensitive methods for the detection of these compounds. However, the selection of the particle system and experimental conditions is critical for achieving high sensitivity. Recommendations are provided on the selection of the particle system and reaction conditions to maximize the oxidase like activity of nanoceria.     

Imprinted Human Serum Albumin with Antioxidant Activity

In order to create a new mimic of glutathione peroxidase(GPx), bioimprinting was used to generate gluta-thione(GSH) binding site and chemical modification was used to incorporate catalytic group selenocystine(Sec). Human serum albumin(HSA) and S-substituted dinitrophenyl glutathione(GSH-S-DNP) were chosen as the imprinted matrix and imprinting template, respectively, to generate a GSH-imprinted protein(GSH-HSA) by bioimprinting. Sec was incorporated into the GSH-HSA by chemical modification to give a new GP...