异丙酚与支撑双层类脂膜作用的电化学研究

以支撑双层类脂膜(s-BLM)作为生物膜模型,采用循环伏安法和交流阻抗技术研究了异丙酚与双层类脂膜的相互作用.结果表明,异丙酚能降低磷脂分子的有序性, 诱发s-BLM 上形成孔洞或缺陷, 且这种相互作用对作用时间、异丙酚浓度以及胆固醇的存在与否具有依赖性.     

插入式超声对酵母细胞膜通透性影响的研究

本论文选择生产1,6-二磷酸果糖(FDP)的酵母细胞为研究对象,采用紫外分光光度计测定超声处理后酵母细胞内核酸和蛋白质透出细胞膜的情况,使用次甲基蓝对超声处理后的细胞进行染色,用血球计数,测试经超声处理后细胞的生存能力,及通过测定胞外FDP的浓度变化,反映细胞膜通透性的变化。结果表明,插入式超声对细胞的通透性及细胞的存活率都有很大影响,而脉冲超声的间隙时间对核酸、蛋白质及细胞活性影响不是很大,但对FDP的渗出率有较大影响。     

Mathematical Modeling of Monovalent Permselectivity of a Bilayer Ion-Exchange Membrane as a Function of Current Density

Modification of an ion-exchange membrane with a thin layer, the charge of which is opposite to the charge of the substrate membrane, has proven to be an effective approach to obtaining a composite membrane with permselectivity towards monovalent ions. However, the mechanism of permselectivity is not clear enough. We report a 1D model based on the Nernst–Planck–Poisson equation system. Unlike other similar models, we introduce activity coefficients, which change when passing from one layer of the membrane to another. This makes it possible to accurately take into account the fact that the substrate membranes usually selectively sorb multiply charged counterions. We show that the main cause for the change in the permselectivity coefficient, P_1/2, with increasing current density, j, is the change in the membrane/solution layer, which controls the fluxes of the competing mono- and divalent ions. At low current densities, counterion fluxes are controlled by transfer through the substrate membrane, which causes selective divalent ion transfer. When the current increases, the kinetic control goes first to the modification layer (which leads to the predominant transfer of monovalent ions) and then, at currents close to the limiting current, to the depleted diffusion layer (which results in a complete loss of the permselectivity). Thus, the dependence P_1/2 − j passes through a maximum. An analytical solution is obtained for approximate assessment of the maximum value of P_1/2 and the corresponding fluxes of the competing ions. The maximum P_1/2 values, plotted as a function of the Na⁺ ion current density at which this maximum is reached, gives the theoretical trade-off curve between the membrane permselectivity and permeability of the bilayer monovalent selective ion-exchange membrane under consideration.     

Insight into the Impact of Oxidative Stress on the Barrier Properties of Lipid Bilayer Models

As a new field of oxidative stress-based therapy, cold physical plasma is a promising tool for several biomedical applications due to its potential to create a broad diversity of reactive oxygen and nitrogen species (RONS). Although proposed, the impact of plasma-derived RONS on the cell membrane lipids and properties is not fully understood. For this purpose, the changes in the lipid bilayer functionality under oxidative stress generated by an argon plasma jet (kINPen) were investigated by electrochemical techniques. In addition, liquid chromatography-tandem mass spectrometry was employed to analyze the plasma-induced modifications on the model lipids. Various asymmetric bilayers mimicking the structure and properties of the erythrocyte cell membrane were transferred onto a gold electrode surface by Langmuir-Blodgett/Langmuir-Schaefer deposition techniques. A strong impact of cholesterol on membrane permeabilization by plasma-derived species was revealed. Moreover, the maintenance of the barrier properties is influenced by the chemical composition of the head group. Mainly the head group size and its hydrogen bonding capacities are relevant, and phosphatidylcholines are significantly more susceptible than phosphatidylserines and other lipid classes, underlining the high relevance of this lipid class in membrane dynamics and cell physiology.     

复层固液分离膜的制备及性能研究

采用聚丙烯（PP）粉末在非织造布表面烧结的方式来制备多孔质复层固液分离膜,并通过粘合剂及烧结时间2个变量来控制分离膜的孔径、渗透率等性能。结果表明：随着粘合剂的增加,分离膜的渗透性能下降明显,孔径变小;同时热压时间的延长也会影响分离膜各项性能,但比粘合剂影响小。     

Solution‐NMR Characterization of Outer‐Membrane Protein A from E. coli in Lipid Bilayer Nanodiscs and Detergent Micelles

X‐ray crystallography and solution NMR of detergent‐reconstituted OmpA (outer membrane protein A from E. coli) had shown that this protein forms an eight‐stranded transmembrane β‐barrel, but only limited information was obtained for the extracellular loops. In NMR studies of OmpA in two different detergent micelles, “NMR‐invisible” amino acid residues in‐between the extracellular loops and the β‐barrel prevented complete structural characterization. Here, we show that this NMR‐invisible ring around the β‐barrel of OmpA is also present in lipid bilayer nanodiscs and in mixed micelles with a third detergent, thus suggesting that the implicated rate processes have a functional role rather than representing an artifact of the protein reconstitution. In addition to sequence‐specific NMR assignments for OmpA in the nanodiscs, the present results are based on a protocol of micro‐coil TROSY‐ and CRINEPT‐type NMR diffusion measurements for studying the hydrodynamic properties and the foldedness of [²H,¹⁵N]‐labeled membrane proteins in nanodiscs. This protocol can be applied under conditions closely similar to those used for NMR structure determinations or crystallization trials.     

Erythrocyte Membrane Nanomechanical Rigidity Is Decreased in Obese Patients

This work intends to describe the physical properties of red blood cell (RBC) membranes in obese adults. The hypothesis driving this research is that obesity, in addition to increasing the amount of body fat, will also modify the lipid composition of membranes in cells other than adipocytes. Forty-nine control volunteers (16 male, 33 female, BMI 21.8 ± 5.6 and 21.5 ± 4.2 kg/m², respectively) and 52 obese subjects (16 male and 36 female, BMI 38.2± 11.0 and 40.7 ± 8.7 kg/m², respectively) were examined. The two physical techniques applied were atomic force microscopy (AFM) in the force spectroscopy mode, which allows the micromechanical measurement of penetration forces, and fluorescence anisotropy of trimethylammonium diphenylhexatriene (TMA-DPH), which provides information on lipid order at the membrane polar–nonpolar interface. These techniques, in combination with lipidomic studies, revealed a decreased rigidity in the interfacial region of the RBC membranes of obese as compared to control patients, related to parallel changes in lipid composition. Lipidomic data show an increase in the cholesterol/phospholipid mole ratio and a decrease in sphingomyelin contents in obese membranes. ω-3 fatty acids (e.g., docosahexaenoic acid) appear to be less prevalent in obese patient RBCs, and this is the case for both the global fatty acid distribution and for the individual major lipids in the membrane phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylserine (PS). Moreover, some ω-6 fatty acids (e.g., arachidonic acid) are increased in obese patient RBCs. The switch from ω-3 to ω-6 lipids in obese subjects could be a major factor explaining the higher interfacial fluidity in obese patient RBC membranes.     

新型阻醇质子导电聚合物膜——PVA-Nafion共混膜的制备及性能研究

针对直接甲醇燃料电池(DMFC)中普遍使用NafionTM系列全氟磺酸膜而存在的甲醇穿透问题,鉴于质子、水和甲醇在传递中的相互关联,提出将目标膜视为优先透过质子的质子-甲醇分离膜,制备了在渗透蒸发醇-水分离领域有良好分离效果的聚乙烯醇(PVA)与全氟磺酸材料共混形成的PVA-Nafion共混膜并研究了膜的阻醇和质子导电性能。PVA的加入有效调节了膜内的亲、憎水平衡,使膜的阻醇效果较NafionTM商品膜提高,且共混后,膜的阻醇性能并非只是PVA和Nafion材料各自性能的简单加和平均,而是在一定配比(WNafion=60%)下出现了最优值。所制备的共混膜中有几种膜的透过系数P达到了10-8cm2穝-1,而电导率s 达10-4S穋m-1;如果以电导率和甲醇透过系数的比值(s / P)作为综合指标,共混膜的综合性能可较Nafion117商品膜高约2.5倍。     

无机膜处理乳化废水实验研究

为除去废水中的乳化油,以达到环保排放标准,采用无机陶瓷微滤膜对乳化废水进行中试实验研究。实验表明:乳化液废水经孔径为200nm的无机陶瓷膜处理后,透过液可达国家排放标准;在最佳操作压力0.16MPa下,系统可连续、稳定运行20h以上,平均膜通量为272L.m-2.h-1;化学清洗30min后,可使膜通量恢复至初始通量的95%。经初步经济分析,平均单位(m3)料液运行成本为4.49元,实验结果表明,用无机陶瓷膜处理乳化液废水是一种经济、技术可行的方法。     

Theoretical and Experimental Study of Joint Osmotic and Electroosmotic Water Transfer through a Cation-Exchange Membrane

Using the previously developed cell model of a charged membrane and the principles of linear thermodynamics of irreversible processes (the Onsager approach), exact and approximate (in the case of an ideally selective membrane) analytical formulae for calculating the osmotic and electroosmotic permeability of the membrane in aqueous solutions of 1:1 electrolyte at constant electric current density and concentration gradient were suggested. The formulae have been successfully verified by our own experimental data for the extrusion cation-exchange membrane MF−4SC p.29 in NaCl solution up to concentrations of 3 M. The contribution of electroosmotic and osmotic water fluxes to the total water transport through the mentioned individual perfluorinated ion-exchange membrane under conditions close to the process of electrodialysis concentrating was experimentally estimated. The cases of co- and counter-directed osmotic and electroosmotic water fluxes are studied. A good correspondence between theoretical and experimental results was obtained, which made it possible to determine the physicochemical parameters of the electromembrane system (the diffusion coefficients of individual ions and the coefficient of equilibrium distribution of electrolyte molecules in the membrane matrix, the characteristic exchange capacity of the cell model). The achieved results make it possible to fully characterize existing and promising types of ion-exchange membranes based on the developed cell model of a charged membrane.     

Influence of Water Compositions and Conditioning on Flux Enhancement in an Immersed Membrane System

Abstract

The objective was to quantify the importance of operational conditions, aeration, and physico‐chemical conditioning on membrane fouling intensity. The suspension filterability was also analysed by using frontal filtration and a cake filtration model. Results pointed out the moderated role of aeration to reduce compound accumulation on the membrane surface. It did not appear as a determining criterion to prevent membrane fouling. In contrast, the physico‐chemical conditioning appeared as a determining criterion to increase critical flux. According to the experimental conditions 200 l/m²/h/bar membrane permeability could be maintained transmembrane pressure (TMP) when filtering stored rainwater. This permeability value was 2–3 times higher than the values obtained without conditioning. Moreover, according to the low turbidity of such stored rainwater and because of the high selectivity of the membrane, the coagulation step, a very low amount of 10 mg/l FeCl₃, was sufficient to intensify the filtration step. This conditioning interest appeared less significant when filtering salted water in immersed membrane systems, but a 20 mg/l FeCl₃ addition appeared sufficient to double the value of critical flux. Nevertheless filtration in frontal mode pointed out the significant impact of physico‐chemical conditioning in reducing the cake deposit hydraulic resistance.     

纤维素/丝素复合膜的制备与性能

通过共混法制备了纤维素/丝素复合膜,复合膜的最佳配比为纤维素占共混膜的90%,丝素占10%。在此条件下形成的复合膜的力学性能、水溶液稳定性、水蒸汽透过系数较单一成分的膜有明显改善,纤维素与丝素之间存在着氢键等强烈的相互作用和良好的相容性。X射线衍射分析进一步验证了复合膜的结晶性能。     

明胶膜固定化脲酶的制备及性质

以明胶为载体,戊二醛为交联剂,采用包埋-交联联用法制备了明胶膜固定化脲酶,其酶活力为6 07U/g载体,酶活力收率为66 1%。最优固定化条件是包酶量为10mg酶/g明胶,ρ(明胶)=100g/L,φ(戊二醛)=0 5%。研究了固定化酶的性质,并与游离酶作了比较,游离酶的最适pH=7 0,固定化酶的最适pH=6 5;游离酶的最适温度为60℃,固定化酶的最适温度升至70℃;固定化酶与游离酶的米氏常数Km分别为11 7mM和12 4mM;固定化酶在80℃下180min仍保留初始活力的10%,而游离酶几乎完全失活。固定化酶重复使用20次其活力仅下降15%,4℃下贮存35d后仍保持初始活力的55%。     

聚合物电解质膜燃料电池用电催化剂非碳载体的研究进展

综述了近年来非碳载体材料(碳化物、氧化物、复合型氧化物、亚化学计量钛氧化物等)的研究动态,介绍了其特点和制备方法,重点评价了以其为载体的铂基催化剂的催化活性及稳定性,并与目前普遍采用的商业碳载铂(Pt/C)催化剂进行了比较. 最后,对非碳材料用作载体存在的问题进行了分析,并对此类载体材料的发展方向进行了展望,提出高比表面、高电导率、高稳定性非碳载体材料的合成及载体与贵金属之间强相互作用机理的研究是载体研究的主要方向.     

Role of C-Terminal Domain and Membrane Potential in the Mobility of Kv1.3 Channels in Immune Synapse Forming T Cells

Voltage-gated Kv1.3 potassium channels are essential for maintaining negative membrane potential during T-cell activation. They interact with membrane-associated guanylate kinases (MAGUK-s) via their C-terminus and with TCR/CD3, leading to enrichment at the immunological synapse (IS). Molecular interactions and mobility may impact each other and the function of these proteins. We aimed to identify molecular determinants of Kv1.3 mobility, applying fluorescence correlation spectroscopy on human Jurkat T-cells expressing WT, C-terminally truncated (ΔC), and non-conducting mutants of mGFP-Kv1.3. ΔC cannot interact with MAGUK-s and is not enriched at the IS, whereas cells expressing the non-conducting mutant are depolarized. Here, we found that in standalone cells, mobility of ΔC increased relative to the WT, likely due to abrogation of interactions, whereas mobility of the non-conducting mutant decreased, similar to our previous observations on other membrane proteins in depolarized cells. At the IS formed with Raji B-cells, mobility of WT and non-conducting channels, unlike ΔC, was lower than outside the IS. The Kv1.3 variants possessing an intact C-terminus had lower mobility in standalone cells than in IS-engaged cells. This may be related to the observed segregation of F-actin into a ring-like structure at the periphery of the IS, leaving much of the cell almost void of F-actin. Upon depolarizing treatment, mobility of WT and ΔC channels decreased both in standalone and IS-engaged cells, contrary to non-conducting channels, which themselves caused depolarization. Our results support that Kv1.3 is enriched at the IS via its C-terminal region regardless of conductivity, and that depolarization decreases channel mobility.     

The Effect of Hydrotalcite Content in Microporous Composite Membrane on Gas Permeability and Permselectivity

Microporous silica membrane containing hydrotalcite (HT) was prepared successfully without losing the former’s molecular sieving property. The microporous HT-silica membrane (200 nm in thickness) was formed on the surface of mesoporous γ-alumina layer (9 μm in thickness) and supported by macroporous α-alumina substrate (ca. 2 mm in thickness). The pore size of the microporous HT-silica membrane was 8.5Å, slightly larger than the pristine silica membrane (5Å). The composite membrane was found to enhance the permeability of gases and permselectivity of carbon dioxide from gas mixture comprising methane, hydrogen or nitrogen. Microporous HT-silica membrane with 15 vol.% HT displayed the highest permselectivities in the order of CO₂/CH₄ > CO₂/N₂ > CO₂/H₂ and the permselectivities decreased with increasing HT content.     

燃料电池用非氟复合质子交换膜的研究进展

介绍了几种非氟复合质子交换膜,包括有机-无机杂化材料质子交换膜(ORMOER)和基于聚苯并咪唑(PBI)、磺化聚醚醚酮(SPEEK)的复合质子交换膜,主要从制备方法出发分析了每种复合膜的优缺点以及在燃料电池(PEMFC)中的应用前景。     

Optimization of Chemical Cleaning for Improvement of Membrane Performance and Fouling Control in Drinking Water Treatment

A pilot-scale study using a ZeeWeed^® 1000 membrane pilot plant was conducted to optimize the use of sodium hypochlorite (NaClO) and citric acid for membrane permeability recovery and membrane fouling control in drinking water treatment. Backwash was the most effective strategy for permeability recovery and under the same NaClO dose, a lower concentration combined with a longer soak time achieved a higher permeability recovery. Organics were the major foulants responsible for permeability decrease. Inorganic foulants surprisingly increased after NaClO cleaning. Similarly, a lower pH was more effective in permeability recovery than a higher concentration of citric acid.     

燃料电池用碱性阴离子交换膜的研究进展

碱性阴离子交换膜(AAEM)是碱性阴离子交换膜燃料电池(AAEMFC)的核心部件,起到阻隔阴阳两极和传导OH-的双重作用,其性能好坏直接影响到AAEMFC的性能和使用寿命。从膜的结构和制备方法分类,综述了碱性阴离子交换膜燃料电池用有机-无机杂化膜、掺杂型膜及均相膜的特性和研究现状。