双层脂和膜生物能量学中的826-氧化还原反应

本文对超薄人造双分子层膜(BLM)和叶绿体及线粒体生物膜中的电子过程进行了研究,总结了由伏安技术所得的近期实验。还讨论了基础电化学在膜研究中的应用,尤其对Eyring方程、Butler-Volmer方程和Tafel方程,以及按照膜孔电积作用在膜中的电子过程的起源进行了论述。讨论了在缺少双层脂的情况下确定氧化还原蛋白组分的标准电位(U′_0,对双层脂膜中有关的电子转移和生物氧化还原提出了设想。     

Agar-supported lipid bilayers — basic structures for biosensor design. Electrical and mechanical properties

The lipid bilayer is widely accepted as the basic structure of all biological membranes. Known as BLM (bilayer lipid membrane), it can be prepared artificially. Suitably modified, the BLM serves as a very appropriate model for biological membranes. Recent investigations have verified the high analytical potential of artificial lipid membranes. With a structure and composition almost identical to the lipid moiety of biomembranes, the BLM may serve as an ideal host for receptor molecules of biological origin, thus becoming a transducer which could “see” the environment the way the living cell does. For the construction of lipid bilayer based biosensors; however, stable, easy to prepare and long-lasting lipid membranes are required. With this aim in mind, we have prepared lipid bilayer membranes which use an agar gel as support. This as-BLM (agar-supported BLM) has been shown to possess the same electrical, mechanical and dynamic properties the conventional BLM is famous for, along with the benefits of long-term stability and considerably elevated breakdown voltages. Its preparation on the tip of an agar-filled Teflon tube of 0.5 mm diameter is easy and can be performed even by less-skilled personnel.

In an attempt of further miniaturization the concept of the as-BLM was applied to thin-film micro-systems manufactured by standard micro-electronic techniques. The result is a lipid bilayer system, which, while preserving all the essential properties of the bilayer lipid membrane, can serve as a basic building block for cheap, disposable biosensoric systems.     

Imaging of voltage-gated alamethicin pores in a reconstituted bilayer lipid membrane via scanning electrochemical microscopy

Voltage-gated biological ion channels were simulated by insertion of the peptaibol antibiotic alamethicin into reconstituted phosphatidylcholine bilayer lipid membranes (BLMs). Scanning electrochemical microscopy (SECM) was utilized to probe initial BLM resistivity, the insertion of alamethicin pores, and mass transport across the membrane. Acquired SECM images show the spatial location of inserted pore bundles, the verification of voltage control over the pore conformational state (open/closed), and variations in passive mass transport corresponding to different topographical areas of the BLM. SECM images were also used to evaluate overall BLM integrity prior to insertion as well as transport (flux in open state) and leakage (flux in closed state) currents following insertion.     

自组装ITO/双层磷脂膜的制备及其光电行为研究

在ITO(Indium-tin-oxide)导电玻璃电极上制备上自组装双层磷脂膜和经C60修饰的双层磷脂膜,研究了这种自组装双层磷脂膜的光电行为,考察了偏压、溶液中的给体和受体的浓度对自组装膜光电流强度的影响,讨论了C60分子对光电子跨膜传递过程的促进作用。     

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.     

Bilayer lipid membranes: An experimental system for biomolecular electronic devices development

The lipid bilayer postulated as the basic structural matrix of biological membranes is widely accepted. At present, the planar bilayer lipid membrane (BLM) together with spherical lipid bilayers (liposomes), upon suitable modification, serves as a most appropriate model for biological membranes. In recent years, advances in microelectronics and interest in ultrathin organic films, including BLMs and Langmuir-Blodgett (L-B) films, have resulted in a unique fusion of ideas toward the development of biosensors and transducers. Furthermore, recent trends in interdisciplinary studies in chemistry, electronics, and biology have led to a new field of research: biomolecular electronics. This exciting new field of scientific-technological endeavor is part of a more general approach toward the development of a new, post-semiconductor electronic technology, namely, molecular electronics with a long-term goal of molecular computers.

Recently, it has been demonstrated that BLMs, after suitable modification, can function as electrodes and exhibit nonlinear electronic properties. These and other experimental findings relevant to sensor development and to “biomolecular electronic devices” (BED) will be described in more details in the present review article. Also the potential use of the BLM system together with its modifications in the development of a new class of organic diodes, switches, biosensors, electrochemical photocells, and biofuel cells will be discussed. Additionally, this paper reports also a novel technique for obtaining BLMs (or lipid bilayers) on solid supports. The presence of solid support on one side of the BLM greatly enhances its mechanical stability, while retaining the dynamic properties of the lipid bilayer. Advantages of the new techniques for self-assembling amphiphilic molecules on rigid substrates are discussed in terms of their possible uses. It is evident that the new BLM system (s-BLMs) is potentially useful for technological applications in the area of biosensors and enzyme electrodes as well as molecular electronics.     

单链2,7-取代萘刚性生色基双亲化合物的合成及其在稀溶液中的自组织

合成了系列单链含2,7-取代萘刚性生色基的双亲化合物C_nNaph(2,7)C₆N⁺(n=4,7,10,12,16),分别用透射电镜、¹HNMR和DSC观测了该系列双亲物在稀溶液中的聚集形态,研究了聚集体内的分子运动和凝胶态到液晶态的相变.结果表明,当尾链n≥7时,该系列化合物在稀溶液中自组织成双分子层排列的囊泡,当n=4时聚集体无确定形态.     

Potential of membrane-mimetic polymers in membrane technology

Development of new generations of membranes with high degrees of permeabilities and controllable mass transport properties requires a fundamental understanding of the relationship between molecular structures and permeabilities. Initiation of interdisciplinary research in biology, biophysics, polymer and colloid chemistry is proposed to provide the insight to membrane transport processes at the molecular level. Mother nature's most talented transporter — the biological membrane — should inspire this endeavor. Following a survey of the properties of, and recognized transport mechanisms in, biomembranes, membrane-mimetic chemistry is introduced to serve as a bridge between biological and polymeric membranes. Surfactant aggregates — micelles, monolayers, organized multilayers (Langmuir—Blodgett films), bilayer lipid membranes (BLMs), vesicles and polymerized vesicles — are shown to be the media in membrane-mimetic chemistry. Properties of these organized surfactant assemblies are summarized. Emphasis is placed on the control of molecular transport in membrane-mimetic systems. Perspectives and prospectives of biomimetic membranology are discussed.     

Planar bilayer lipid memebranes

The planar bilayer lipid membrane, also known as lipid bilayer membrane, black lipid membrane or simply BLM(s), for short, has been investigated since its inception in 1960, the details of which have been described in a monograph published in 1974. This review is a report on the advances in the BLM research since that time.After a brief introduction, the first five sections consider various aspects of experimental methods, optical properties, thermodynamics of lipid bilayers, permeability, and electrical properties of BLMs. Section 7 deals with the use of BLM as energy transducer, particularly the transduction of light into electrical energy. Section 8, the longest portion of the paper, is devoted to modelling of biomembranes, such as the plasma membrane of cells, the thylakoid membrane of chloroplasts, the cristae membrane of mitochondria, the visual receptor membrane of the eye, and the nerve membrane. The concluding section points out that studies of BLMs facilitate the initial testing of working hypothses and may lead to a better choice of appropriate $\text{in vivo}$ and reconstituted membrane experiments.     

The lipid bilayer concept and its experimental realization: from soap bubbles,kitchen sink,to bilayer lipid membranes

The inspiration for lipid bilayer research, without question, comes from the biological world. Although self-assembled bilayer lipid membranes (BLMs) in vitro, were first reported in 1961, experimental scientists have been dealing with BLM-type interfacial adsorption phenomena since Robert Hooke’s time (1672). BLMs (of planar lipid bilayers) have been used in a number of applications ranging from basic membrane biophysics including transport, practical AIDS research, and ‘microchips’ studies, to the conversion of solar energy via water photolysis, to biosensor development using supported bilayer lipid membranes (s-BLMs), and to photobiology comprising apoptosis and photodynamic therapy. This paper presents an overview of the origin of the lipid bilayer concept and its experimental realization, as well as the studies of our laboratory and recent research of others on the use of BLMs as models of certain biomembranes. In addition, we describe briefly our present work on supported BLMs as biosensors and molecular devices; the experiments carried out in close collaboration with colleagues on s-BLMs are delineated.     

PHOTOSENSITIVE BILAYER MEMBRANES AS MODEL SYSTEMS FOR PHOTOBIOLOGICAL PROCESSES

Abstract— Photobiological processes such as photosynthesis, photomorphogenesis, photomovement, and photoreception are all associated with the membranous portions of cells. The unique properties of membrane surfaces are apparently required to achieve biologically relevant energy transduction and photocontrol phenomena and consequently the use of model membrane systems is suggested as an advantageous approach to elucidation of the important physical and chemical processes involved. Black lipid membrane (BLM) and liposome techniques are critically reviewed as preferred techniques for constructing and manipulating lipid bilayers. The lipid bilayer is considered to be the basic foundation for biological membrane models, and specific physical phenomena observed with the bilayers and their biological ramifications are analyzed. Light-stimulated polarization of the membrane and electron transfer across the bilayer are viewed as appropriate analogs of vision and photosynthesis, respectively. Bilayer-adsorbed dye experiments are the simplest systems explored that exhibit polarization and charge transfer across the membrane. Chloroplast extract BLM experiments are cited as an example of the light-stimulated transfer of electrons across the membrane under the influence of a preexisting redox gradient. Biliprotein (phycocyanin or phycoerythrin) on one side of the chloroplast extract membrane permits the direction of electron flow across the membrane so that a redox gradient is created in a manner truly analogous to photosynthesis. The potential for solar energy conversion from such membranes is explicitly considered utilizing a schematic photoelectrochemical cell. Model membranes containing bacterial rhodopsin and phytochrome represent examples of ionic gradients that result in biological energy transduction. Studies of membranes that exhibit transient photoeffects are considered potentially relevant for the elucidation of phototaxis. The analysis of many properties of photosensitive membranes is greatly aided by the use of appropriate theoretical models. It is apparent that there is a great potential for the application of photosensitive model membranes in many research areas involving complex photobiological phenomena and novel methods for solar energy conversion.     

二维材料膜在气体分离领域的最新研究进展

Two-dimensional (2D) materials, led by graphene, have emerged as nano-building blocks to develop high-performance membranes. The atom-level thickness of nanosheets makes a membrane as thin as possible, thereby minimizing the transport resistance and maximizing the permeation flux. Meanwhile, the sieving channels can be precisely manipulated within sub-nanometer size for molecular separation, such as gas separation. For instance, graphene oxide (GO) channels with an interlayer height of about 0.4 nm assembled by external forces exhibited excellent H₂/CO₂ sieving performance compared to commercial membranes. Cross-linking was also employed to fabricate ultrathin (< 20 nm) GO-facilitated transport membranes for efficient CO₂ capture. A borate-crosslinked membrane exhibited a high CO₂ permeance of 650 GPU (gas permeation unit), and a CO₂/CH₄ selectivity of 75, which is currently the best performance reported for GO-based composite membranes. The CO₂-facilitated transport membrane with piperazine as the carrier also exhibited excellent separation performance under simulated flue gas conditions with CO₂ permeance of 1020 GPU and CO₂/N₂ selectivity as high as 680. In addition, metal-organic frameworks (MOFs) with layered structures, if successfully exfoliated, can serve as diverse sources for MOF nanosheets that can be fabricated into high-performance membranes. It is challenging to maintain the structural and morphological integrity of nanosheets. Poly[Zn₂(benzimidazole)₄] (Zn₂(bim)₄) was firstly exfoliated into 1-nm-thick nanosheets and assembled into ultrathin membranes possessing both high permeance and excellent molecular sieving properties for H₂/CO₂ separation. Interestingly, reversed thermo-switchable molecular sieving was also demonstrated in membranes composed of 2D MOF nanosheets. Besides, researchers employed layered double hydroxides (LDHs) to prepare molecular-sieving membranes via in situ growth, and the as-prepared membranes showed a remarkable selectivity of ~80 for H₂-CH₄ mixture. They concluded that the amount of CO₂ in the precursor solution contributed to LDH membranes with various preferred orientations and thicknesses. Apart from these 2D materials, MXenes also show great potential in selective gas permeation. Lamellar stacked MXene membranes with aligned and regular sub-nanometer channels exhibited excellent gas separation performance. Moreover, our ultrathin (20 nm) MXene nanofilms showed outstanding molecular sieving property for the preferential transport of H₂, with H₂ permeance as high as 1584 GPU and H₂/CO₂ selectivity of 27. The originally H₂-selective MXene membranes could be transformed into membranes selectively permeating CO₂ by chemical tuning of the MXene nanochannels. This paper briefly reviews the latest groundbreaking studies in 2D-material membranes for gas separation, with a focus on sub-nanometer 2D channels, exfoliation of 2D nanosheets with structural integrity, and tunable gas transport property. Challenges, in terms of the mass production of 2D nanosheets, scale-up of lab-level membranes and a thorough understanding of the transport mechanism, and the potential of 2D-material membranes for wide implementation are briefly discussed.     

521—Light-induced redox reactions in pigmented BLM

This paper is concerned with light-mediated phenomena in membranes of photosynthesis and vision and their in vitro model bilayer lipid membranes (BLM) of planar configuration containing appropriate photoactive compounds. Chloroplast extract BLM, bovine rhodopsin BLM and bacteriorhodopsin BLM are used as examples. Particular emphasis is placed on those molecular mechanisms of photoelectrochemical energy transduction in these pigmented lipid bilayers, which are relevant for the elucidation of photosynthetic and visual processes. Additionally, a pigmented BLM separating two aqueous solutions containing redox couples has been likened to that of a double Schottky barrier cell.     

ELECTRONIC PROCESSES AND PHOTOELECTRIC ASPECTS OF BILAYER LIPID MEMBRANES

Abstract— Owing to the complexity of biological membranes, many model systems have been studied in order to gain insight into the molecular mechanism of specific functions. One such model membrane extensively investigated in the past decade is the so-called bilayer lipid membrane (BLM). With suitable modifications, a BLM less than 100 A thick separating two aqueous solutions has been used as a model for a variety of biological membranes. This paper is devoted to a review of the properties and electronic processes of modified BLM.
Recent experiments using these membranes which contain photosynthetic pigments or dyes have demonstrated that, upon illumination, an EMF and a current can be generated. The connection between the photoelectric BLM and light-sensitive biological membranes and the rationale for this work are described.
Additionally, the effects of physical chemical parameters such as electric field, temperature, light intensity, duration of illumination and chemical agents (electron acceptors, donors, uncouplers, etc.) on the photoresponses of BLM are discussed. Other results indicate that BLM containing photoactive compounds behave similar to that of a silicon solar cell with one side of the membrane reducing and the other side oxidizing. The transverse pathway for the electron across the BLM could be provided by carotenoids such as β-carotene. Photoelectric BLM of this type represents a unique kind of energy transducing system and may well be useful in the conversion of solar energy into electricity and/or other forms of energy.     

Facilitated Transport of Ions and Glucose by Amphotericin B Across Lipid Bilayers in the Presence or Absence of Cholesterol

The transport of ions and glucose across bilayer lipid membranes (BLM) facilitated by amphotericin B (AmB) is studied by use of planar BLMs and liposomal membranes. The transport characteristics change with time in the presence of cholesterol, while it is independent of time in the absence of cholesterol. The carrier‐type transport is observed immediately after the addition of AmB. In the presence of cholesterol, AmB forms a 1 : 1 complex with cholesterol and the channel is formed by aggregation of AmB‐cholesterol complexes. It is concluded that the number of the channels increases with time and that the carrier‐type transport decreases instead.     

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.     

The Role of Amyloid β-Biomembrane Interactions in the Pathogenesis of Alzheimer's Disease: Insights from Liposomes as Membrane Models

The aggregation and deposition of amyloid β (Aβ) peptide onto neuronal cells, with consequent cellular membrane perturbation, are central to the pathogenesis of Alzheimer's disease (AD). Substantial evidence reveals that biological membranes play a key role in this process. Thus, elucidating the mechanisms by which Aβ interacts with biomembranes and becomes neurotoxic is fundamental to developing effective therapies for this devastating progressive disease. However, the structural basis behind such interactions is not fully understood, largely due to the complexity of natural membranes. In this context, lipid biomembrane models provide a simplified way to mimic the characteristics and composition of membranes. Aβ-biomembrane interactions have been extensively investigated applying artificial membrane models to elucidate the molecular mechanisms underlying the AD pathogenesis. This review summarizes the latest findings on this field using liposomes as biomembrane model, as they are considered the most promising 3D model. The current challenges and future directions are discussed.     

Electrochemical biosensor based on supported planar lipid bilayers for fast detection of pathogenic bacteria

This paper presents a new ion-channel biosensor based on supported bilayer lipid membrane for direct and fast detection of Campylobacter species. The sensing element of a biosensor is composed of a stainless-steel working electrode, which is covered by artificial bilayer lipid membrane (BLM). Antibodies to bacteria embedded into the BLM are used as channel forming proteins. The biosensor has a strong signal amplification effect, which is defined as the total number of ions transported across the BLM. The total number of (univalent) ions flowing through the channels is 10¹⁰ ions s⁻¹. The biosensor showed a very good sensitivity and selectivity to Campylobacter species.     

Glutamate receptor incorporated in a mixed hybrid bilayer lipid membrane array, as a sensing element of a biosensor working under flowing conditions

The realization of a reliable receptor biosensor requires stable, long-lasting, reconstituted biomembranes able to supply a suitable biomimetic environment where the receptor can properly work after incorporation. To this end, we developed a new method for preparing stable biological membranes that couple the biomimetic properties of BLMs (bilayer lipid membranes) with the high stability of HBMs (hybrid bilayer membranes); this gives rise to an innovative assembly, named MHBLM (mixed hybrid bilayer lipid membrane). The present work deals with the characterization of biosensors achieved by embedding an ionotropic glutamate receptor (GluR) on MHBLM. Thanks to signal (transmembrane current) amplification, which is typical of natural receptors, the biosensor here produced detects glutamate at a level of nmol L(-1). The transmembrane current changes linearly vs glutamate up to 100 nmol L(-1), while the limit of detection is 1 nmol L(-1). In addition, the biosensor response can be modulated both by receptor agonists (glycine) and antagonists (Mg(2+)) as well, and by exploiting the biosensor response, the distribution of different kinds of ionotropic GluR present in the purified sample, and embedded in MHBLM, was also evaluated. Finally, one of the most important aspects of this investigation is represented by the high stability of the biomimetic system, which allows the use of biosensor under flowing conditions, where the solutions flow on both biomembrane faces.