Quantitative pH assessment of small-volume samples using a universal pH indicator

We developed a hue-based pH determination method to analyze digital images of samples in a 384-well plate after the addition of a universal pH indicator. The standard error of calibration for 69 pH standards was 0.078 pH units, and no sample gave an error greater than 0.23 units. We then used in-solution isoelectric focusing to determine the isoelectric point of Wnt3A protein in conditioned medium and after purification and applied the described method to assess the pH of these small-volume samples. End users may access our standard to assay the pH of their own samples with no additional calibration.     

Computer model of unstirred layer and intracellular pH changes. Determinants of unstirred layer pH

Transmembrane acid–base fluxes affect the intracellular pH and unstirred layer pH around a superfused biological preparation. In this paper the factors influencing the unstirred layer pH and its gradient are studied. An analytical expression of the unstirred layer pH gradient in steady state is derived as a function of simultaneous transmembrane fluxes of (weak) acids and bases with the dehydration reaction of carbonic acid in equilibrium. Also a multicompartment computer model is described consisting of the extracellular bulk compartment, different unstirred layer compartments and the intracellular compartment. With this model also transient changes and the influence of carbonic anhydrase (CA) can be studied. The analytical expression and simulations with the multicompartment model demonstrate that in steady state the unstirred layer pH and its gradient are influenced by the size and type of transmembrane flux of acids and bases, their dissociation constant and diffusion coefficient, the concentration, diffusion coefficient and type of mobile buffers and the activity and location of CA. Similar principles contribute to the amplitude of the unstirred layer pH transients. According to these models an immobile buffer does not influence the steady-state pH, but reduces the amplitude of pH transients especially when these are fast. The unstirred layer pH provides useful information about transmembrane acid–base fluxes. This paper gives more insight how the unstirred layer pH and its transients can be interpreted. Methodological issues are discussed.     

pH Feedback control of enzyme membranes

pH feedback on immobilized enzymes is theoretically examined with respect to substrate and pH levels, strength of acids produced by the reaction, buffering and asymmetry of the system. All the productions of proton by the different reactions are taken into account by using a ‘symbolic species’ H^*. The system of differential diffusion-reaction equations is then integrated using numerical methods. The local ‘effective enzyme activity’ modulated by an acidity factor enables us to predict and quantify evolutions of the systems: NonMichacIian behavior of an immobilized MichaeIis-Mentcn-type enzyme is shown, even when pH back-actions are excluded: the analysis of intramembranc pH profiles shows that the shift of the optimal pH is a complex function of the substrate and pH levels, the intrinsic pH dependence of the enzyme, and the membrane characteristics. This study may easily be transposed to other types of effector such as divalent cations and used in examining self-regulations of multienzyme systems where pH-active reactions are involved.     

pH对游离L-脯氨酸羟化为L-羟脯氨酸的影响

通过用从动物组织中抽提出的原胶原脯氨酸羟基化酶,在Fe^2 、α-酮戊二酸和还原剂如抗坏血酸盐等物质存在的条件下,根据试验结果,不能排除其可把水溶液中游离的脯氨酸羟化为羟脯氨酸的可能性。并且反应体系的pH对反应有很大的影响,试验找出最适的反应pH,反应液的为3.52;抽提液的为6.95,与文献中原胶原脯氨酸羟基化酶羟化原胶原中脯氨酸的有很大差别。     

Short-term pH regulation in plants

Cellular pH regulation consists of two features: (i) Long-term pH homeostasis, which ensures that all H⁺ or OH⁻ produced in excess is ultimately removed from the cell and which requires metabolic energy; (ii) short-term reactions of the cell(s) to sudden shifts in intracellular pH, in order to prevent acute disturbances of metabolism. Recent progress in measuring and understanding of mainly short-term cellular regulation is summarized, including cellular responses to pH loads that arise from different sources such as external pH, weak acids/bases, protonophores, metabolic inhibitors, H⁺/cotransport, light and phytohormones. Whereas the plasma membrane H⁺ pump and metabolic adjustments may serve both long- and short-term pH control, physico-chemical buffering and the translocation of H⁺ from and to cellular compartments render only time-limited capacity for the neutralization of pH loads and seem exhausted within minutes. In spite of the widespread opinion that, because of tight regulation, intracellular pH does not vary with time, there is good evidence for long-lasting pH changes in plant cells, i.e. after hormonal stimulation, light/dark changes or carboxylation during crassulacean acid metabolism (CAM). This emphasizes that cytoplasmic pH, besides being well regulated, is essential not only for the regulation of membrane transport but also as a cellular messenger.     

New technology for the detection of pH

The measurement of pH is the most widely employed test for (bio-)chemical lab. Since the first use of glass electrode to detect pH, new techniques and methods have broaden the scope of pH detection. Metal/metal oxide, ion sensitive field-effect transistors (ISFET), fibre-optical techniques, nanotechniques, and conducting polymer techniques have been extensively developed. This review covers the various methods for pH detection. New development trends were discussed.     

受体介导内吞对巨噬细胞膜电位、胞浆和溶酶体pH的影响

本文利用荧光标记方法测定了刀豆素Ａ、麦芽凝集素、酵母多糖刺激引起的巨噬细胞膜电位、胞浆ｐＨ溶酶体ｐＨ的变化。结果显示三种配体均导致细胞膜电位超极化,胞浆ｐＨ降低、溶酶体ｐＨ或高,三个生理参量趋于稳定时间稍有不同。胞浆ｐＨ的降低可能有抑制内吞的作用,溶酶体ｐＨ上升是触发溶酶体内容物外排的基本因素。内吞引起的这些变化是细胞代谢过程中自我调节和保护的表现。     

环境pH诱导出芽短梗霉细胞多形化

出芽短梗霉具有酵母状细胞、膨大细胞、菌丝、厚垣孢子、念珠状菌丝和分生组织状结构。在最适pH条件下,出芽短梗霉生长繁殖以酵母状细胞（CBS100225等4菌株）或膨大细胞（CBS249.65等4菌株）为主。pH 2.2或pH 7.0诱导全部8株出芽短梗霉形成分生组织状结构。酵母状细胞转变成膨大细胞受低pH值诱导的占75%,还受高pH诱导的占50%。膨大细胞是多形性细胞转变的中心环节,可以转变成菌丝、厚垣孢子或分生组织状结构。     

日本沼虾幼虾对碱度和pH的适应性

采用急性毒性实验法,研究日本沼虾（Macrobrachium nipponense）对碱度和DH的适应能力,探讨内陆盐碱水域养殖的可能性。结果表明,pH对幼虾的24、48、72、96h半数致死值分别为10．13、9．72、9．67和9．51,安全与适应范围分别为5．26～8．67、5．10～8．84。碱度对幼虾的24h半数有效浓度为17．96mmol／L,95％置信限14．60—22．53mmol／L;24、48、96h半数致死浓度分别为48．95、45．15和44．96mmol／L,95％置信限分别为45．72～50．60、39．46～51．67及34．34～55．38mmol／L,安全碱度11．52mmol／L。结果表明,在pH≤9．0、碱度≤20．0mmol／L的内陆盐碱水域,可以养殖日本沼虾。