Ion Channel Behavior of a Supported Bilayer Lipid Membrane Composed of 5,5－Ditetradecyl－2－ （2－trimethyl－ammonioethyl）－l, 3－dioxane Bromide Modified Glassy Carbon Electrode

A synthetic cationic surfactant, 5,5-ditetradecyl-2-(2-trimethyl-ammonioethyl)-l,3-dioxane bromide (DTDB), was used to construct a supported bilayer lipid membrane (s-BLM) coatedon an underlying glassy carbon electrode (GCE). Electrochemical impedance spectroscopy (EIS), small-angle X-ray diffraction (SAXD) and cyclic voltammetry were used to characterize the s-BLM. Both EIS and SAXD data indicated that the synthetic lipid exists as a well-oriented bilayer in the membrane.The voltammetric study showed that the lipid membrane can open ion channels in the presence of ClO4^- stimulant with Ru(bpy)3^2 as marker ions and give distinct channel currents.The channels can be dosed and open up again many times by removing or introducing ClO4^- anions.     

十二烷基磺基甜菜碱与铂电极支撑的磷脂双层膜作用的电化学研究

以铂电极支撑的磷脂双层膜(Supported Bilayer Lipid Membrane,s-BLM)作为生物膜的模型,以Fe(CN)36-和Fe(CN)64-为探针分子,利用循环伏安法(CV)和交流阻抗谱(EIS)研究两性表面活性剂十二烷基磺基甜菜碱(Dodecyl Sulfobetaine,DSB)对s-BLM相互作用。结果显示,DSB可以嵌入到s-BLM的疏水区,容易使其表面分子的排列发生变化,产生缺陷或孔洞,探针分子Fe(CN)63-和Fe(CN)64-可以通过这些微孔接近电极,产生氧化还原响应。并且作用时间、DSB的浓度以及胆固醇的存在与否对二者的相互作用有直接影响。此外作用后的双层膜在0.1mol/LKCl溶液中能够自我修复,这表明DSB与s-BLM的相互作用是可逆的。     

Nanostructured platinum-lipid bilayer composite as biosensor

The present work describes the preparation of supported bilayer lipid membrane (s-BLM) doped with metal nanoparticles for the design of biosensors. Platinum (Pt) nanoparticles were deposited through s-BLM to build a hybrid device of nanoscale electrode array by potential cycling in 1 mM K(2)PtCl(6) solution containing 0.1 M KCl. The properties of Pt nanoparticle-doped s-BLM composite were then characterized by cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM). Our results showed that Pt nanoparticles grew in voids of the s-BLMs, through which the underlying glassy carbon (GC) electrode was connected, with maximum length extended out of the lipid membrane around 40 nm. Doping of Pt nanoparticles through s-BLM increased the membrane capacitance and decreased the membrane resistance of s-BLM. Pt nanoparticles array in s-BLM electrocatalyzed the reduction of oxygen (O(2)) in phosphate buffer solution (PBS). Practical application of Pt nanoparticle-doped s-BLM for the construction of glucose biosensor was also demonstrated in terms of its dose-response curve, stability and reproducibility. Thus, lipid membrane doped with Pt nanoparticles is a novel electrode system at nanoscale that can penetrate through the insulating membrane to probe molecular recognition and catalytic events at the lipid membrane-solution interface.     

联萘酚与固体支撑双层类脂膜相互作用

采用循环伏安法、交流阻抗法研究了联萘酚(BINOL)与固体支撑双层类脂膜(s-BLM)之间的相互作用.结果表明,联萘酚通过氢键、疏水作用与s-BLM发生相互作用.随着相互作用时间的延长,联萘酚/s-BLM体系中的氧化峰电流先增大后减小,表明联萘酚逐渐破坏s-BLM的整体性,诱导膜内部形成微孔通道.联萘酚的浓度越大,联萘酚分子通过s-BLM的渗透时间越短.此外,随着卵磷脂浓度和胆固醇含量的增加,s-BLM的膜电阻变大,联萘酚渗透通过s-BLM速率减小,导致其对s-BLM的渗透性能减弱.     

脱氧胆酸钠与支撑磷脂双层膜作用的电化学研究

以支撑磷脂双层膜(supported bilayer lipid membrane, 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脱氧胆酸钠(sodium deoxycholate, NaDC)与s-BLM的相互作用. 结果表明, NaDC能降低磷脂分子的有序性, 诱发s-BLM上形成孔洞或缺陷, 并且它们之间的这种相互作用对作用时间、NaDC溶液的浓度和pH值以及胆固醇的存在与否具有依赖性, 并且作用后的s-BLM在0.1 mol/L的KCl溶液中能够自我修复, 这表明NaDC与s-BLM的相互作用是可逆的.     

胆酸钠与支撑磷脂双层膜作用的电化学研究

采用电化学方法研究胆酸钠(NaC)与s-BLM的相互作用, 并结合实验结果对NaC与s-BLM的作用机理进行了讨论.     

羟自由基对支撑磷脂双层膜的破坏及水溶性抗氧化剂保护作用的电化学研究

以支撑磷脂双层膜(supported bilayer lipid membrane, s-BLM)作为生物膜模型, 利用Fenton体系产生羟自由基(hydroxyl free radical, •OH), 采用循环伏安法研究了s-BLM与•OH之间的相互作用. 结果表明: •OH通过与磷脂发生化学反应, 诱发s-BLM上形成孔洞或缺陷, 这种作用对时间、FeSO₄和H₂O₂的浓度具有依赖性, 且不可恢复. 具有还原性基团的抗氧化剂维生素C, 还原型谷胱甘肽和L-半胱氨酸, 通过与•OH发生氧化还原反应, 可抑制•OH与s-BLM的相互作用, 降低•OH对s-BLM结构的破坏程度.     

Photoelectric measurements of s-BLM/nucleoli: a new technique for studying apoptosis

A new method based on photoelectric measurement for analyzing apoptosis of cell-free MCF-7 nucleoli is reported. Supported bilayer lipid membrane (s-BLM) was used to enclose nucleoli in biological environment. The s-BLM was self-assembled on the wall of a super-thin cell. During the apoptosis induced by Taxol, the photoelectric current of the self-assembled s-BLM/nucleoli was found decreasing with time, suggesting the degradation of nucleus DNA. Electron transfer along the DNA double helix and along nuclear skeleton is assumed in the interpretation. This novel photoelectric analytical method may provide a rapid and sensitive technique to evaluate apoptosis.     

Stabilization of bilayer lipid membranes on solid supports by trehalose

Using the electrostriction method the effect of the glucose and trehalose on the elasticity modulus perpendicular to the membrane plane, E_⊥, and the electrical capacitance, C, of supported bilayer lipid membranes (s-BLM) formed on the freshly cut tip of Teflon-coated Ag wire was studied. Addition of saccharides into the electrolyte resulted in a decrease in the elasticity modulus of the s-BLM formed from the soybean phosphatidylcholine in n-hexadecane, while the capacitance was increased. In addition, the trehalose has a considerable stabilizing effect on the above parameters of the s-BLM. Treatment of the s-BLM in an electrolyte containing 0.3 M of the trehalose allowed storage of the s-BLM under dry conditions and under refrigeration, with the subsequent recovery of membrane parameters after the wire had been dipped into the electrolyte.     

单烷基乙二胺稀水溶液头基相互作用自组装形成 双分子膜

提出普通表面活性剂(单链两亲分子)亲水头基相互作用诱导疏水尾链平行聚集形成双分子膜的新机制。设计和合成了系列单烷基取代乙二胺C~nH~2~n~+~1NHC~2H~4NH~2(n=8,12,14,16,18)。通过电镜形态,分散液凝胶/液晶相变和对应铸膜的二维双层结构,表明单链两亲分子头基相互作用和脂链引入刚性片断一样,两者形成的双分子膜具有类似的结构和性能;展示了各体系取代乙二胺双层结构和性能的密切联系。指出了广泛认同的单链两亲分子形成双分子膜必须引入刚性片断的单一成膜机制的片面性,为组装新一类功能头基表面活性剂双分子膜独辟蹊径。     

Electrostriction of biotin-streptavidin-modified bilayer lipid membranes on a metal support

Using the electrostriction method we have studied the elasticity modulus perpendicular to the membrane plane, E⊥, electrical capacitance, C, coefficient of dynamic viscosity, η, and membrane potential difference δф_m of supported bilayer lipid membranes (s-BLM) modified by biotin-streptavidin, as a function of d.c. voltage applied to the membrane. Binding of streptavidin to biotin-modified s-BLM resulted in a slight decrease of membrane capacitance, increase of E_⊥ and increase of η, while δф_m did not change. The val of E_⊥ of unmodified membranes was found to change considerably with increasing d.c. voltage and the rate of voltage change. Modification of s-BLM by streptavidin leads to reduced changes of E_⊥ with the rate of d.c. voltage change, and it made s-BLM extremely stable even at an external d.c. voltage of 2 V. Our results indicate that streptavidin considerably stabilized s-BLM by means of the formation of a complex with biotin-modified phospholipids.     

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.     

Unmodified supported thiol/lipid bilayers: studies of structural disorder and conducting mechanism by cyclic voltammetry and AC impedance.

Supported thiol/lipid bilayer assembly, one of the most spectacular bilayer systems in recent years, has provided a good model to study biomembranes because of its high mechanical stability. In this work, the structural and conducting property of unmodified Au supported octadecanethiol/phosphatidylcholine bilayers were investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The forming process of bilayer was monitored by capacitance plane plot. The normalized membrane capacitance of supported bilayer is 0.52 microF cm(-2). Kinetically controlled voltammograms determined by Butler-Volmer equation were obtained for both thiol monolayer and thiol/lipid bilayer in linear sweep voltammetry. Results of EIS experiment indicate that collapsed sites and pinhole defects exist in thiol monolayer and lipid monolayer, respectively. The difference between the values of experimental and theoretical standard electron transfer rate constant indicates that the conducting mechanism of Au supported thiol monolayer is electron tunneling at collapsed sites. The conducting mechanism of Au supported thiol/lipid bilayer is attributed as the following: the electroactive species could diffuse through pinholes in the lipid monolayer and reach collapsed sites in thiol monolayer, where electron transfer occurs via a tunneling process. The fractional coverage of the lipid monolayer measure by EIS experiments is about 0.98 or higher.     

Cyclic voltammetry study of glucose and insulin interactions with supported lipid membrane

The effect of D-glucose and insulin on conducting properties of supported bilayer lipid membranes (s-BLM) modified by anthraquinone-2-sulphonic acid (AQS) at the presence of potassium ferricyanide was studied by means of cyclic voltammetry (CV). Both the oxidation and the reduction current peaks were found to decrease at the presence of glucose in concentration range varying from 10 to 320 mM. The influence of insulin on membrane properties is ambiguous. While the pretreatment of membrane with 20 mU l(-1) of insulin evoked slight increase of the current with unchanged course of the dependence of peak current on glucose, the decrease of conductance was observed above 10(5) mU l(-1) of insulin.     

Transmembrane Signaling with Lipid‐Bilayer Assemblies as a Platform for Channel‐Based Biosensing

Artificial and natural lipid membranes that elicit transmembrane signaling is are useful as a platform for channel‐based biosensing. In this account we summarize our research on the design of transmembrane signaling associated with lipid bilayer membranes containing nanopore‐forming compounds. Channel‐forming compounds, such as receptor ion‐channels, channel‐forming peptides and synthetic channels, are embedded in planar and spherical bilayer lipid membranes to develop highly sensitive and selective biosensing methods for a variety of analytes. The membrane‐bound receptor approach is useful for introducing receptor sites on both planar and spherical bilayer lipid membranes. Natural receptors in biomembranes are also used for designing of biosensing methods.     

Single ion-channel recordings using glass nanopore membranes

Protein ion-channel recordings using a glass nanopore (GNP) membrane as the support structure for lipid bilayer membranes are presented. The GNP membrane is composed of a single conical-shaped nanopore embedded in a approximately 50 microm-thick glass membrane chemically modified with a 3-cyanopropyldimethylchlorosilane monolayer to produce a surface of intermediate hydrophobicity. This surface modification results in lipid monolayer formation on the glass surface and a lipid bilayer suspended across the small orifice (100-400 nm-radius) of the GNP membrane, while allowing aqueous solutions to fully wet the glass nanopore. The GNP membrane/bilayer structures, which exhibit ohmic seal resistances of approximately 70 GOmega and electrical breakdown voltages of approximately 0.8 V, are exceptionally stable to mechanical disturbances and have lifetimes of at least 2 weeks. These favorable characteristics result from the very small area of bilayer (10(-10)-10(-8) cm(2)) that is suspended across the GNP membrane orifice. Fluorescence microscopy and vibrational sum frequency spectroscopy demonstrate that a lipid monolayer forms on the 3-cyanopropyl-dimethylchlorosilane modified glass surface with the lipid tails oriented toward the glass. The GNP membrane/bilayer structure is well suited for single ion-channel recordings. Reproducible insertion of the protein ion channel, wild-type alpha-hemolysin (WTalphaHL), and stochastic detection of a small molecule, heptakis(6-O-sulfo)-beta-cyclodextrin, are demonstrated. In addition, the insertion and removal of WTalphaHL channels are reproducibly controlled by applying small pressures (-100 to 350 mmHg) across the lipid bilayer. The electrical and mechanical stability of the bilayer, the ease of which bilayer formation is achieved, and the ability to control ion-channel insertion, coupled with the small bilayer capacitance of the GNP membrane-based system, provide a new and nearly optimal system for single ion-channel recordings.     

2-(5-甲基-2-苯基-4-噁唑基)乙醇的合成工艺改进

以L-天门冬氨酸为原料,经过β-甲酯化,苯甲酰化,Dak in-W est反应,环合和氢化铝锂还原等反应步骤,以36.1%的总收率得到抗糖尿病药物的重要中间体2-(5-甲基-2-苯基-4-噁唑基)乙醇.用浓硫酸取代三氯氧磷作为关环剂,简化了环合工艺和后处理操作.     

(R)-2-羟基-4-苯基丁酸乙酯的合成

综述了血管紧张素转化酶抑制剂类治疗高血压和充血性心力衰竭药物的关键中间体（R）－2－羟基－4－苯基丁酸乙酯的合成方法。参考文献25篇。     

Interactions of membrane active peptides with planar supported bilayers: an impedance spectroscopy study

Membrane active peptides exert their biological effects by interacting directly with a cell's lipid bilayer membrane. These therapeutically promising peptides have demonstrated a variety of activities including antimicrobial, cytolytic, membrane translocating, and cell penetrating activities. Here, we use electrochemical impedance spectroscopy (EIS) on polymer-cushioned supported lipid bilayers constructed on single crystal silicon to study two pairs of closely related membrane active peptides selected from rationally designed, combinatorial libraries to have different activities in lipid bilayers: translocation, permeabilization, or no activity. Using EIS, we observed that binding of a membrane translocating peptide to the lipid bilayer resulted in a small decrease in membrane resistance followed by a recovery back to the original value. The recovery may be directly attributable to peptide translocation. A nontranslocating peptide did not decrease the resistance. The other pair, two membrane permeabilizing peptides, caused an exponential decrease of membrane resistance in a concentration-dependent manner. This permeabilization of the supported bilayer occurs at peptide to lipid ratios as much as 1000-fold lower than that needed to observe effects in vesicle leakage assays and gives new insights into the fundamental peptide-bilayer interactions involved in membrane permeabilization.     

Enzyme activity to augment the characterization of tethered bilayer membranes

The rate of Ca2+ -triggered phospholipase A2 (PLA2) degradation of tethered bilayer membranes (tBLMs), composed of a synthetic lipid, beta-mercaptoethanol, and palmitoyloleoylphosphatidylcholine (POPC), is approximately 80 times greater than for those prepared with diphytanoylphosphatidylcholine (DPhyPC). Electrochemical impedance spectroscopy (EIS) and neutron reflectivity (NR) data indicate complete, water-free tBLMs that exhibit near ideal capacitive behavior and the presence of a water reservoir in the bilayer subspace proximal to the substrate (Au) surface for both tBLMs. Together these data indicate that the POPC and the DPhyPC tBLMs are structurally similar along the surface normal but markedly different at the outer leaflet/solution interface and that PLA2 is a sensitive probe of short length scale structural differences not revealed by EIS and NR.