Rapid quantitative analysis of individual anthocyanin content based on high‐performance liquid chromatography with diode array detection with the pH differential method

A new quantitative technique for the simultaneous quantification of the individual anthocyanins based on the pH differential method and high‐performance liquid chromatography with diode array detection is proposed in this paper. The six individual anthocyanins (cyanidin 3‐glucoside, cyanidin 3‐rutinoside, petunidin 3‐glucoside, petunidin 3‐rutinoside, and malvidin 3‐rutinoside) from mulberry (Morus rubra) and Liriope platyphylla were used for demonstration and validation. The elution of anthocyanins was performed using a C₁₈ column with stepwise gradient elution and individual anthocyanins were identified by high‐performance liquid chromatography with tandem mass spectrometry. Based on the pH differential method, the high‐performance liquid chromatography peak areas of maximum and reference absorption wavelengths of anthocyanin extracts were conducted to quantify individual anthocyanins. The calibration curves for these anthocyanins were linear within the range of 10–5500 mg/L. The correlation coefficients (r²) all exceeded 0.9972, and the limits of detection were in the range of 1–4 mg/L at a signal‐to‐noise ratio ≥5 for these anthocyanins. The proposed quantitative analysis was reproducible with good accuracy of all individual anthocyanins ranging from 96.3 to 104.2% and relative recoveries were in the range 98.4–103.2%. The proposed technique is performed without anthocyanin standards and is a simple, rapid, accurate, and economical method to determine individual anthocyanin contents.     

Effect of pH value on the growth morphology of KH2PO4 crystal grown in defined crystallographic direction

KH₂PO₄ single crystals were grown in aqueous solution at different pH values by using “point seeds” with a defined crystallographic direction at 59 degree to the Z axis. Atomic Force Microscope (AFM) was applied to observe the surface morphology of (100) face. It was found that at the same supersaturation, the larger steps appeared at the lower pH value before appearance of 2D nucleus. We found that 2D nucleus was occurred at σ ≤ 0.04 when pH value is <2.8. The occurrence of 2D nucleus was caused by the decreasing step‐edge free energy with the decreasing of pH value in the growth solution. In this paper, we observed the morphologies of (100) faces of KDP crystals which grew in solutions with different pH values. 2D nucleuses appeared on the terrace of growth steps when pH value down to 2.8 and 3.2 at supersaturation of 0.04, while pH value down to 2.4, only 2D nucleation control the growth. Therefore, the pH value can change the growth mechanism of KDP crystals.     

Effects of Cations on HPTS Fluorescence and Quantification of Free Gadolinium Ions in Solution; Assessment of Intracellular Release of Gd3+ from Gd-Based MRI Contrast Agents

8-Hydroxypyrene-1,3,6-trisulfonate (HPTS) is a small, hydrophilic fluorescent molecule. Since the pKa of the hydroxyl group is close to neutrality and quickly responds to pH changes, it is widely used as a pH-reporter in cell biology for measurements of intracellular pH. HPTS fluorescence (both excitation and emission spectra) at variable pH was measured in pure water in the presence of NaCl solution or in the presence of different buffers (PBS or hepes in the presence or not of NaCl) and in a solution containing BSA. pKa values have been obtained from the sigmoidal curves. Herein, we investigated the effect of mono-, di-, and trivalent cations (Na⁺, Ca²⁺, La³⁺, Gd³⁺) on fluorescence changes and proposed its use for the quantification of trivalent cations (e.g., gadolinium ions) present in solution as acqua-ions. Starting from the linear regression, the LoD value of 6.32 µM for the Gd³⁺ detection was calculated. The effects on the emission were also analyzed in the presence of a combination of Gd³⁺ at two different concentrations and the previously indicated mono and di-valent ions. The study demonstrated the feasibility of a qualitative method to investigate the intracellular Gd³⁺ release upon the administration of Gd-based contrast agents in murine macrophages.     

pH对玫瑰红色素紫外和荧光光谱的影响

玫瑰是蔷薇科蔷薇属落叶丛生灌木,品种繁多,其花色、香、形具美,有极高的观赏和经济价值,我国玫瑰资源丰富,古代人们就将玫瑰用于染色、食品和药用等领域,现在玫瑰主要用于商品花卉和提取玫瑰精油.     

水合作用与 pH 调控两性离子聚合物刷的相变行为

本文基于Flory-Huggins理论,建立理论模型研究水合作用与pH调控两性离子聚合物(ZP)刷的相变行为.理论模型考虑ZP的水合作用,以及ZP刷体系中的静电作用.研究发现,在不同pH条件下,ZP刷的体积分数随着水合作的减弱而的增加.随着pH的变化,ZP刷构象随着水合性转变行为明显改变,这是由于pH调控ZP链单体带有过多的净电荷(正电荷或负电荷),致使ZP链内出现静电排斥导致ZP刷溶胀.另外,当ZP链单体呈现过多的净电荷,会在很大程度上决定ZP刷体系静电势,影响ZP刷的相变行为.通过考察体系自由能,我们还发现,ZP刷体系自由能呈现了极大值,随着pH值的变化,自由能呈现的极大值随之改变,由此表明了体系的不稳定性,进而导致ZP刷体系发生相变.     

产电对微生物燃料电池参数的影响

测试了pH值和电导率的变化规律,分析了MFC开路电压的变化情况,为改善MFC的性能提供理论依据.采用驯化培养的菌种,MFC启动时间更短;在恒温、高温和高底物浓度条件下,开路电压更高、更稳.产物在阳极液中的积累会降低开路电压.阴极液和阳极液的pH值的差值与电流正相关.阳极液的电导率会减小,而阴极液的电导率会增大;阳极液中...     

Investigation on the conformational changes of bovine serum albumin in a wide pH range from 2 to 12

The conformation of bovine serum albumin largely depends on its microenvironment pH and affects its physical functions and applications. In this study, we investigated the effects of pH (wide range 2–12) on the conformation of bovine serum albumin based on spectroscopic signals by various spectroscopic means including fluorescence, synchronous fluorescence, resonance light scattering, UV-visible absorption, and circular dichroism. The changes in spectroscopic signals, such as peak position and intensity, showed that the structure of bovine serum albumin varied significantly with pH. The conformation of bovine serum albumin was compact at pH 6–7, as indicated by the largest peak position values and peak intensities in the fluorescence, synchronous fluorescence, and RLS spectra. The structure of bovine serum albumin became loose in the acidic or alkaline environment, as indicated by the decreased peak position values and peak intensities. The microenvironment of the amino acid residues of bovine serum albumin also varied with pH, as indicated by the changing peak position values. At pH 7, the hydrophobicity of the tyrosine and tryptophan residues was the weakest, as indicated by the minimum synchronous fluorescence signals. In addition, the secondary structure of bovine serum albumin, especially α-helix, varied with pH. The content of α-helix reached the maximum value of 68% at pH 6–8, whereas it decreased in the acidic or alkaline environment. The study provides valuable details for studying the physiological function and applications of serum albumins.     

Biomolecular Release Stimulated by Electrochemical Signals at a Very Small Potential Applied

DNA release electrochemically stimulated by applying ?10 mV on the modified electrode was studied. The release process was based on the local (interfacial) pH change produced upon H₂O₂ reduction electrocatalyzed by the immobilized microperoxidase‐11. SiO₂ nanoparticles attached to the electrode surface and functionalized with trigonelline and boronic acid species changed their electrical charge from positive to negative upon the interfacial pH change, thus allowing electrostatic adsorption of negatively charged DNA on the positive interface and then its repulsion/release from the negative interface. The loaded/released DNA molecules were labeled with a fluorescent dye to allow easy detection of the released DNA molecules. The important feature of the developed system is the controlled DNA release upon applying very small electrical potential on the modified electrode.     

Deep insights into the hydrolysis of N,N‐dialkylaminoethyl methacrylates in aqueous solution with 1H NMR spectroscopy

N,N‐dialkylaminoethyl methacrylate (DAEA) monomers are extensively used to prepare multi‐responsive polymers. However, these monomers face high risk of hydrolysis in their ester groups when being polymerized in water‐containing medias. Here, NMR spectroscopy was employed to continuously track the hydrolysis and solubility of four widely used DAEA monomers [CH₂CH₂R₁COO(CH₂)₂N(R₂)₂; R₁ = H or CH₃; R₂ = CH₃, CH₂CH₃ or CH(CH₃)₂] under typical polymerization conditions. With this technique, the hydrolysis reactivity and absolute hydrolysis amount of these monomers are separately examined, and then their kinetic correlations with solubility, molecular structure, pH, and temperature are established, so that the hydrolysis of DAEA monomers and even other esters with similar cyclic structure can be predicted. The present efforts are expected to provide a general understanding for the hydrolysis of all the DAEA monomers, benefitting to the optimization of polymerization toward well‐defined DAEA copolymers, as well as the design of smart soft matter for specific applications. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 914–923