An experimental comparison between the aqueous pH scale and the electron donicity scale

We have made an experimental comparison of the aqueous pH scale with the Lewis base donicity scale. This requires an indicator that can function in both kinds of system. We find that the zeta-potential zero charge point for certain oxide materials provides a suitable indicator. The materials are: SiO₂, Al₂O₃, TiO₂, and MgO. For each material, we measure the zeta potential in aqueous media as a function of pH. In each case, the zeta potential varies systematically with pH, and changes sign at some value of pH, that we refer to as the zero charge point. We then do similar measurements in a series of organic liquids having different donicities. In this case, the zeta potential varies systematically with the donicity and may change sign. In such cases, we determine the donicity that corresponds to the zero charge point. For a given oxide material, we can then relate a zero charge point on the pH scale to one on the donicity scale. This gives us a consistent experimental alignment of the pH and donicity scales, relative to one another. We compare our results with thermodynamic data, relating to the pH scale, and the hydrogen electrode, and find good agreement.     

由酸效应系数计算pH值的新方法

基于酸效应系数αL(H)与溶液酸度的关系,建立了一种由αL(H)手工计算pH值的新方法.该方法无需解高次方程,仅需对lgαL(H)及相关pKa作加减运算、复杂体系也只需增加少量以10为底的乘方运算及常用对数运算即可.因而方法简便,计算误差可预先设置,本文控制不超过5%.     

Acid‐Labile Thermoresponsive Copolymers That Combine Fast pH‐Triggered Hydrolysis and High Stability under Neutral Conditions

Biodegradable polymeric materials are intensively used in biomedical applications. Of particular interest for drug‐delivery applications are polymers that are stable at pH 7.4, that is, in the blood stream, but rapidly hydrolyze under acidic conditions, such as those encountered in the endo/lysosome or the tumor microenvironment. However, an increase in the acidic‐degradation rate of acid‐labile groups goes hand in hand with higher instability of the polymer at pH 7.4 or during storage, thus posing an intrinsic limitation on fast degradation under acidic conditions. Herein, we report that a combination of acid‐labile dimethyldioxolane side chains and hydroxyethyl side chains leads to acid‐degradable thermoresponsive polymers that are quickly hydrolyzed under slightly acidic conditions but stable at pH 7.4 or during storage. We ascribe these properties to high hydration of the hydroxy‐containing collapsed polymer globules in conjunction with autocatalytic acceleration of the hydrolysis reactions by the hydroxy groups.     

Kinetic Buffers

This paper proposes a new type of molecular device that is able to act as an inverse proton sponge to slowly decrease the pH inside a reaction vessel. This makes the automatic monitoring of the concentration of pH‐sensitive systems possible. The device is a composite formed of an alkyl chloride, which kinetically produces acidity, and a buffer that thermodynamically modulates the variation in pH value. Profiles of pH versus time (pH–t plots) have been generated under various experimental conditions by computer simulation, and the device has been tested by carrying out automatic spectrophotometric titrations, without using an autoburette. To underline the wide variety of possible applications, this new system has been used to realize and monitor HCl uptake by a di‐copper(II) bistren complex in a single run, in a completely automatic experiment.     

双刺激响应型纳米载药系统的构建及性能

采用聚乙二醇单甲醚(mPEG)为亲水段,聚赖氨酸(PzLL)为疏水段,通过二硫键和碳氮双键串联桥连合成了两嵌段共聚物(mPEG-CN-SS-PzLL),其中的二硫键具有还原敏感性,碳氮双键具有pH酸敏感性。通过红外光谱和核磁共振谱等手段测试分析了产物的化学结构。将聚合物通过透析法自组装制备得到双刺激响应型纳米载药粒子。结果表明:该纳米载药粒子的药物包封率较高,达到52%。该载药系统在还原环境或酸性环境下具有良好的体外释药性能。     

Microwire Chronoamperometric Determination of Concentration,Diffusivity, and Salinity for Simultaneous Oxygen and Proton Reduction

A microwire chronoamperometric method is reported employing a 25 µm diameter platinum microwire for multi‐parameter electroanalysis with digital simulation‐based evaluation (employing DigiElch 4.F). Concentration and diffusion coefficient data are obtained for the reduction of oxygen and for the reduction of protons individually and simultaneously in saline (0.1 M to 4.0 M NaCl) electrolyte media. The diffusion coefficient and concentration data for oxygen allows salinity levels to be estimated. The microwire chronoamperometry method offers versatility and precision due to (i) a slow approach to steady state (when compared to microdisc methods) and (ii) insignificant viscosity effects (when compared to hydrodynamic methods).     

Raman spectroscopic probing of plant material using SERS

We report surface‐enhanced Raman studies on intact plant material using onion layers as a biological target, and silver nanoaggregates and silver island films as enhancing plasmonic structures. Surface‐enhanced Raman scattering (SERS) enhancement allows the detection of strong Raman signatures of chemical constituents of the surface of the onion layer such as cellulose, proteins, and flavonols. Because of long‐time incubation, SERS sensors can access the extracellular space in the inner of the layer. The location of silver nanoparticles inside the onion layer has been monitored by the SERS images collected from chemicals present in the onion and/or reporter molecules attached to the nanoparticles. Our studies show a competitive adsorption of intrinsic bio molecules of the onion layer and reporter molecules. Different spectra from different places of the layer indicate the complex heterogeneous chemical structure of the plant material. The pH‐sensitive reporter molecule para mercapto benzoic acid attached to the nanoparticles allows us to infer pH values inside the extracellular matrix of the onion layer. Copyright © 2015 John Wiley & Sons, Ltd.     

Application of chromatography technology in the separation of active alkaloids from Hypecoum leptocarpum and their inhibitory effect on fatty acid synthase

A method that involved the combination of pH‐zone‐refining counter‐current chromatography and semipreparative reversed‐phase liquid chromatography has been established for the preparative separation of alkaloids from Hypecoum leptocarpum. From 1.2 g of crude sample, 31 mg N‐feruloyltyramine, 27 mg oxohydrastinine, 47 mg hydroprotopine, 25 mg leptopidine, and 18 mg hypecocarpine have been obtained. The structure of the new compound, hypecocarpine, is confirmed based on the analysis of spectroscopic data, including NMR, UV, and IR spectroscopy and positive electrospray ionization mass spectrometry. The known chemical structures were characterized on the basis of ¹H and ¹³C NMR spectroscopy. The purities of the five alkaloids are all over 92.7% as determined by high‐performance liquid chromatography. The alkaloids’ cytotoxicity in breast cancer cells is assessed by using a Cell Counting Kit assay and their inhibitory effect on fatty acid synthase expression is assessed by a Western blot assay. These results suggest that leptopidine could suppress growth and induce cytotoxicity in breast cancer cells and that the cytotoxicity of leptopidine may be related to its inhibitory effect on fatty acid synthase expression.