电化学方法研究多粘菌素B与磷脂酰胆碱的相互作用

采用电化学方法研究了一种多肽类抗生素多粘菌素B(PMB)与模拟生物膜硫醇-磷脂酰胆碱杂化双层膜之间的相互作用。PMB可与磷脂酰胆碱发生强相互作用,破坏双层膜结构,从而使膜的通透性升高。PMB的浓度、酸度、与膜的作用时间及膜中胆固醇的存在均影响二者的作用程度。另外,膜的自修复实验表明,被PMB破坏的双层膜电极在一定程度上可以在KCl溶液中重新自组装,且自修复的程度和修复时间及与之相互作用的PMB的浓度有关。     

金(111)电极表面浮动磷脂双层膜的原位偏振红外反射光谱研究(英文)

应用电化学原位偏振红外反射光谱法研究了构建于金(111)电极表面的浮动磷脂双层膜.金电极表面先自组装一层巯基葡萄糖单层来增加表面的亲水性,浮动磷脂双层膜通过LB-LS技术构建在巯基葡萄糖单层上.双层膜由双肉豆蔻磷脂酰胆碱(DMPC)、胆固醇和神经节苷脂GM1构成.GM1分子中的糖链可以物理吸附在巯基葡萄糖表面,在双层膜和基底间形成一个富含水的隔层.红外光谱表明浮动双层膜中的DMPC分子比传统的支撑双层膜中的DMPC分子有更强的水合作用,证实了双层膜和基底间水层的存在.该浮动双层膜更接近于实际的生物膜体系,并且在金电极表面有宽的电位区间,非常适于进一步的离子通道蛋白质研究.     

杂多酸K7Fe^3^+P2W17O62H2对硫醇-磷脂杂化双层膜通透性的影响

利用涂抹冷冻法制备了硫醇-磷脂杂化双层膜,采用循环伏安和交流阻抗方法,研究了硫醇-磷脂杂化双层膜与杂多酸K7Fe^3^+P2W17O62H2作用前后通透性的变化,发现该种杂多酸能够诱导硫醇-磷脂杂化双层膜产生一些孔洞,降低了膜电阻,增加了膜电容,也增加了探针Fe(CN)^3-/4-~6与电极的电子传递。同时对产生该现象的机理进行了初步的探讨。     

聚电解质多层有序膜电极的生成及其电化学特性

研究了在金电极表面硫醇自组装膜上聚电解质多层有序膜的形成过程及其电化学特性。用紫外光谱和电化学方法对多层有序膜进行了表征。结果表明，有序膜影响着离子在膜中的穿透性，离子型电活性物质如铁氰根离子和亚甲蓝等可嵌入有序膜中，研究了多层有序膜电极的电化学特性及膜中铁氰根离子的电化学行为。     

短杆菌肽在十八烷基硫醇自组装单层膜上的通道行为

短杆菌肽是短杆芽孢菌在芽孢形成过程中合成的一组憎水十五肽,它能在脂双层膜上形成一价阳离子通道,允许一些一价阳离子通过．短杆菌肽离子通道研究在天然双层膜以及人工双层膜,如类脂双层膜（BLM）、脂质体上开展的较多,而基于支撑膜的研究则极少［1-4]．本文在金电极上制备硫醇自组装单层膜,研究了短杆菌肽的离子通道行为,并提出了可能的机理．     

电化学法研究多粘菌素B与磷脂酰丝氨酸的相互作用及与其他磷脂的比较

采用头基修饰的磷脂在金电极表面构建了稳定的磷脂双层膜,并使用该膜模拟生物膜对多肽类抗生素多粘菌素B(PMB)和磷脂酰丝氨酸的相互作用进行了研究.PMB可与磷脂酰丝氨酸发生相互作用,破坏双层膜结构,从而使膜的通透性升高.PMB的浓度、作用时间以及膜中胆固醇的存在均影响二者的作用程度.被PMB破坏的双层膜电极在一定程度上可在KC1溶液中重新自组装,且自修复的程度与修复时间和PMB的浓度有关.此外,比较了PMB和多种磷脂之间的作用程度,磷脂的头基、烃链的长度以及不饱和度均会影响二者间的相互作用.     

由烷基硫醇组成的三元混合膜结构与性质研究

本文采用共吸附法制备了由戊硫醇(PT),癸硫醇(DT)和十六烷基硫醇(HDT)组成的三元混合膜,通过循环伏安,X-射线光电子能谱,扫描隧道显微镜(STM)和导电原子力对其结构及性质进行了表征。研究表明硫醇分子通过Au-S键在金电极上形成了一层致密的单分子膜,组装膜表面组成与其在组装液中的摩尔浓度有关。混合膜中各组分形成独立的相区,具有不同的电子传递能力。该研究为未来纳米器件的开发提供更多样化的表面以及更加详实的理论依据。     

正、叔十二烷基硫醇在铜表面上自组装膜测试

研究了正、叔十二烷基硫醇在铜表面上的自组装及混合自组装成膜情况,并利用交流阻抗和极化曲线电化学方法测试了正、叔十二烷基硫醇在铜表面上自组装膜及混合自组装膜对铜的耐腐蚀性,考察了正十二烷基硫醇自组装膜质量与正十二烷基硫醇溶液的浓度及组装时间的关系。研究结果显示,混合自组装膜的质量及其对铜的耐腐蚀性比仅组装正或叔十二烷基硫醇均有很大的提高。     

硫醇自组装膜对金电极上吡咯电化学聚合的影响

用电化学聚合法在多种烷基硫醇自组装膜修饰金电极上制备了聚吡咯.通过计时安培法、循环伏安法和交流阻抗技术研究了自组装膜的烷基链长和端基功能团对吡咯聚合过程和性质的影响.当自组装膜较完美时,聚吡咯沉积在自组装膜表面;而当自组装膜有一定缺陷时,吡咯在针孔处成核,然后继续生长并完全覆盖在自组装膜表面.研究结果表明,烷基硫醇的链越短,吡咯聚合越容易;疏水的烷基硫醇自组装膜有利于聚吡咯在电极表面的生长.     

界面可控硫醇SAMs纳米金修饰金电极的电化学行为研究

在裸金电极上自组装不同比例的4,4’-二甲基联苯硫醇(MTP)和硫辛酸(TA)混合液,形成自组装膜(MTP+TA/Au SAMs),再修饰纳米金,制得纳米金混合巯基修饰金电极(AuNPs/MTP+TA/Au)。研究了纳米金混合巯基修饰金电极的电化学行为和阻抗行为,结果表明电极表面pH值的改变对电极表面的电子转移有重要影响。对葡萄糖传感器的制备条件、测定条件、抗干扰能力等进行了讨论,结果表明修饰电极的微结构和微环境有必要进一步研究。     

Ferrocene embedded in an electrode-supported hybrid lipid bilayer membrane: a model system for electrocatalysis in a biomimetic environment

An electrode-supported system in which ferrocene molecules are embedded in a hybrid bilayer membrane (HBM) has been prepared and characterized. The redox properties of the ferrocene molecules were studied by varying the lipid and alkanethiol building blocks of the HBM. The midpoint potential and electron transfer rate of the embedded ferrocene were found to be dependent on the hydrophobic nature of the electrolyte and the distance at which the ferrocene was positioned in the HBM relative to the electrode and the solution. Additionally, the ability of the lipid-embedded ferrocenium ions to oxidize solution phase ascorbic acid was evaluated and found to be dependent on the nature of the counterion.     

Characterization of micropatterned lipid membranes on a gold surface by surface plasmon resonance imaging and electrochemical signaling of a pore-forming protein

We report the fabrication and characterization of a micropatterned membrane electrode for electrochemical signaling of a bacterial pore-forming toxin, Streptolysin O (SLO) from S. pyogenes. Microcontact printing of an alkylthiol monolayer was used to fabricate an array template, onto which cholesterol-containing DMPC vesicles were fused to form lipid layer structures. The construction of the supported membranes, including pattern transfer and vesicle fusion, was characterized by in-situ surface plasmon resonance (SPR) imaging and electrochemistry. Quantitative analysis of the resulting membrane by using SPR angular shift measurements indicates that the membranes in the hydrophilic pockets have an average thickness of 8.2 +/- 0.4 nm. Together with fluorescence microscopy studies, the results suggest that this could be a mixed lipid assembly that may consist of a bilayer, vesicle fragments, and lipid junctions. The voltammetric response of the redox probe ferrocene carboxylic acid (FCA) was measured to quantify the toxin action on the supported membrane. The electrochemical measurements indicate that fusion of vesicles on the template blocked the access of FCA, whereas the injection of SLO toxin restored the redox response. The anodic peak current of FCA was found to increase with toxin concentration until a plateau was reached at 40 HU/mL. The method is highly sensitive such that 0.1 HU/mL of SLO (1.25 pM) can yield a well-defined response. In addition, it eliminates the need for a highly insulating layer in membrane sensing, which opens up new avenues in developing novel sensing interfaces for membrane-targeting proteins and peptides.     

Imaging Local Proton Fluxes through a Polycarbonate Membrane by Using Scanning Electrochemical Microscopy and Functionalized Alkanethiols

A new application of scanning electrochemical microscopy (SECM) to probe the transport of protons through membranes is described. Herein, a probe ultramicroelectrode (UME) is modified with a self‐assembled monolayer (SAM) of 11‐mercaptoundecanoic acid to qualitatively image areas within different pH regions above a track‐etched membrane. The current response of the modified electrode in the presence of potassium hexacyanoferrate as electroactive component is different in acidic and alkaline solutions. Depending on the pH value of the solution, the SAM‐covered electrode exposes either a neutral or a negatively charged insulating monolayer at pH 3 or 7, respectively, which leads to an increase/decrease in the faradaic current due to electrostatic interactions between the neutral/charged surface and the charged redox mediator. Therefore, local pH changes in the close vicinity of a membrane‐like substrate lead to different current responses recorded at the tip electrode when scanning above the surface.     

Incorporation of alpha-hemolysin in different tethered bilayer lipid membrane architectures

Tethered bilayer lipid membranes are stable solid supported model membrane systems. They can be used to investigate the incorporation and function of membrane proteins. In order to study ion translocation mediated via incorporated proteins, insulating membranes are necessary. The architecture of the membrane can have an important effect on both the electrical properties of the lipid bilayer as well as on the possibility to functionally host proteins. Alpha-hemolysin pores have been functionally incorporated into a tethered bilayer lipid membrane coupled to a gold electrode. The protein incorporation has been monitored optically and electrically and the influence of the molecular structure of the anchor lipids on the insertion properties has been investigated.     

Steady-state oxidation of cholesterol catalyzed by cholesterol oxidase in lipid bilayer membranes on platinum electrodes

Cholesterol oxidase is immobilized in electrode-supported lipid bilayer membranes. Platinum electrodes are initially modified with a self-assembled monolayer of thiolipid. A vesicle fusion method is used to deposit an outer leaflet of phospholipids onto the thiolipid monolayer forming a thiolipid/lipid bilayer membrane on the electrode surface. Cholesterol oxidase spontaneously inserts into the electrode-supported lipid bilayer membrane from solution and is consequently immobilized to the electrode surface. Cholesterol partitions into the membrane from buffer solutions containing cyclodextrin. Cholesterol oxidase catalyzes the oxidation of cholesterol by molecular oxygen, forming hydrogen peroxide as a product. Amperometric detection of hydrogen peroxide for continuous solution flow experiments are presented, where flow was alternated between cholesterol solution and buffer containing no cholesterol. Steady-state anodic currents were observed during exposures of cholesterol solutions ranging in concentration from 10 to 1000 μM. These data are consistent with the Michaelis-Menten kinetic model for oxidation of cholesterol as catalyzed by cholesterol oxidase immobilized in the lipid bilayer membrane. The cholesterol detection limit is below 1 μM for cholesterol solution prepared in buffered cyclodextrin. The response of the electrodes to low density lipoprotein solutions is increased upon addition of cyclodextrin. Evidence for adsorption of low density lipoprotein to the electrode surface is presented.     

Redox mediation enabled by immobilised centres in the pores of a metal-organic framework grown by liquid phase epitaxy

A layer of a metal-organic framework (SURMOF) was prepared on a thiol monolayer on Au. Charge transport across the insulating membrane could be established by using ferrocene as an immobilised redox mediator. Reversibility of the immobilisation and its role in the electrode kinetics are discussed.     

Electron transfer between ferrocene-modified Au/octadecanethiol/lipid BLM electrode and redox couples in solution

Bilayers incorporated with ferrocene consisting of self-assembled octadecanethiol and lipid monolayer on gold substrates were fabricated. Its electrochemical behaviors in solutions containing different redox couples were investigated by cyclic voltammetry and ac impedance. The transmembrane electron transfer reaction across octadecanethiol self-assembled film and an adsorbed phospholipid layer mediated by ferrocene have been observed in the solution of Fe(CN)6(3-/4-). The formal potential difference between mediator in bilayer lipid membrane (BLM) and redox couple in solution has a great impact on the transmembrane electron transfer behavior. The ferrocene-modified BLM electrodes might be useful for constructing a bilayer-based electrochemical current rectifying device.     

荧光性自组装双层膜的制备及其性能研究

借助Au-S化学键的作用,在金基底上组装DL-半胱氨酸,利用DL-半胱氨酸与1-萘胺乙酸(NAA)的静电吸引作用在金表面间接组装荧光试剂NAA,从而构建了双层自组装膜NAA/Cys/Au.该自组装膜有较强的荧光信号,能被Cu²⁺猝灭,并具有较好的可逆再生性能,可用于超痕量铜离子的界面荧光测定,对Cu²⁺的检出下限为7.87×10^-11mol/L.同时采用电化学、荧光光谱及电子能谱等方法表征自组装膜的结构,并采用电化学阻抗谱技术和循环伏安法研究自组装膜在K₃[Fe(CN)₆]/K₄[Fe(CN)₆]溶液中的电化学行为研究.结果表明,金表面组装的单层膜具有良好的“针孔”效应,组装上荧光试剂之后形成的无“针孔”缺陷的自组装双层膜对溶液与基底间的界面电子转移有强烈的阻碍作用.     

钙离子对支撑磷脂膜离子通道行为的诱导作用

将一种支撑磷脂膜--杂化双层膜(Hybridbilayermembrane,HBM)用于钙离子与磷脂作用的研究,以Fe(CN)₆^3-为探针,发现钙离子可诱导HBM产生离子通道,且通道的打开与关闭可反复运转,并用STM观察了这一现象.     

Preparation and characterization of asymmetric planar supported bilayers composed of poly(bis-sorbylphosphatidylcholine) on n-octadecyltrichlorosilane SAMs

Planar supported lipid bilayers (PSLBs) have been widely studied as biomembrane models and biosensor scaffolds. For technological applications, a major limitation of PSLBs composed of fluid lipids is that the bilayer structure is readily disrupted when exposed to chemical, mechanical, and thermal stresses. A number of asymmetric supported bilayer structures, such as the hybrid bilayer membrane (HBM) and the tethered bilayer lipid membrane (tBLM), have been created as an alternative to symmetric PSLBs. In both HBMs and tBLMs, the inner monolayer is covalently attached to the substrate while the outer monolayer is typically composed of a fluid lipid. Here we address if cross-linking polymerization of the lipids in the outer monolayer of an asymmetric supported bilayer can achieve the high degree of stability observed previously for symmetric PSLBs in which both monolayers are cross-linked [E.E. Ross, L.J. Rozanski, T. Spratt, S.C. Liu, D.F. O'Brien, S.S. Saavedra, Langmuir 19 (2003) 1752]. To explore this issue, HBMs composed of an outer monolayer of a cross-linkable lipid, bis-sorbylphosphatidylcholine (bis-SorbPC), and an inner SAM were prepared and characterized. Several experimental conditions were varied: vesicle fusion time, polymerization method, and polymerization time and temperature. Under most conditions, bis-SorbPC cross-linking stabilized the HBM such that its bilayer structure was largely preserved after drying; however these films invariably contained sub-micron scale defects that exposed the hydrophobic core of the HBM. The defects appear to be caused by desorption of low molecular weight oligomers when the film is removed from water, rinsed, and dried. In contrast, poly(bis-SorbPC) PSLBs prepared under similar conditions by Ross et al. were nearly defect free. This comparison shows that formation of a cross-linked network in the outer leaflet of an asymmetric supported bilayer is insufficient to prevent lipid desorption; inter-leaflet covalent linking appears to be necessary to create supported poly(lipid) assemblies that are impervious to repeated drying and rehydration. The difference in stability is attributed to inter-leaflet cross-linking between monolayers which can form in symmetric bis-SorbPC PSLBs.