Chemistry of Synthetic Bilayer Membranes

The preparation of bilayer membranes from synthetic dialkyl amphiphiles is described. According to the electron microscopic observation, the bilayer structure similar to that of biomembranes is formed spontaneously when dialkyldimethyl-ammonium bromides with C₁₀-C₂₀ alkyl groups are dispersed in water by sonication. The line broadening in the NMR spectrum strongly suggests that these synthetic bilayers constitute liquid crystalline or solid phases. The hydrophilic head group may be sulfonium and modified ammonium moieties. The bilayer assembly is also formed from dialkyl amphiphiles with anionic head groups: (phosphate, sulfonate, and carboxylate), from nonionic dialkyl amphiphiles (oligomeric ethylene oxide) moiety) and from zwitterionic dialkyl amphiphiles. These bilayers incorporate equimolar cholesterol fairly readily. The redistribution of catalyst (a cholesterol derivative) and substrate (p-nitrophenyl palmitate) molecules is very slow when they are tightly bound to the aggregate. The intravesicle reaction is much faster than the intervesicle counterpart in the case of the di-dodecyldimethylammonium bromide vesicle.     

Ion‐Channel Gating in Transmembrane Receptor Proteins: Functional Activity in Tethered Lipid Membranes

Through thiolipids a planar lipid bilayer (1) was immobilized on a gold support (2) for use as an electrode. This allows the detection of the ligand‐gating function of the natural transmembrane channel protein OmpF (3) reconstituted in the artificial membrane: the binding of a domain (4) of the toxin colicin N, observed by surface plasmon resonance, induces the blocking of the OmpF channel protein, as shown by impedance spectroscopy.     

含萘（2,6）生色基的合成双分子膜研究

本文首次了报道系列单链、2,6-取代萘刚性生色基的双亲化合物C_nNaph(2,6)C_4N~+(CH_3)_3(n=16,12,7,4),C_(12)Naph(2,6)PO_4~-和C_(12)Naph(2,6)C_4N~+(CH_3)_2CH_2CH_2OH的合成。分别用AEM、~1HNMR和DSC考察了该系列化合物在稀水溶液中的自组织行为、聚集体内分子运动和物相变化。当n≥7时,该系列双亲化合物在稀水溶液中可自组织形成双分子层结构,亲水基团的种类直接影响双亲分子的自组织形态。     

Synthetic Membranes—Preparation,Structure, and Application

After a long period of dormancy, membrane separation processes have begun to emerge as technically significant and commercially relevant unit operations. Prior to the mid-sixties, synthetic membranes were employed for those few specialized laboratory applications which could tolerate low permeability and poor selectivity or in electrochemical applications excluding, e. g., batteries, fuel cells, chloride-alkali electrolysis, where marginal chemical stability remained a severe limitation. Within the framework of a broad R & D program started in the US in the mid-fifties and devoted to the production of fresh water from brackish and seawater, developments of more suitable membranes arose out of the application of the principles of physical chemistry, modern polymer chemistry (especially surface or interfacial polymerization and polycondensation technology), and electron microscopy. In particular, it was learned that asymmetric membrane structures comprise a very thin consolidated barrier layer (5000 Å or less for membranes with economically practical filtration rates) supported by an integral but less dense substrate which does not participate in the transport process. Later and after much effort, composite membranes were developed in which the salt-rejecting skin (still only 5000 Å thick) was placed atop a supporting matrix formed from a more chemically and mechanically stable polymer.—The main desalination research effort led to several spin-off developments in related membrane fields, e.g. the successful preparation and commercialization of ultrafiltration technology in the automobile, food, and chemical industries. Also, ion-exchange membranes prepared from perfluorinated polymers offered the electrochemical industry much better chemical stability than the earlier phenolic-resin-based ion-exchange membranes.—Current efforts are aimed at the improved selectivity and stability required for very specific separation processes (e.g. separation of heavy metal salts from waste water or selective enrichment of gases). In the future, the mechanisms of biological processes will have to be exploited for successful development of synthetic membranes suitable for more sophisticated separations.     

Asymmetric Membranes: Preparation and Applications

The separation of molecular mixtures by semipermeable membranes under the driving force of hydrostatic pressure has assumed major importance in recent years. Among other factors the development of membranes with asymmetric structure which, while having the same separating properties, afford a filtration output many times greater than that of the previously known symmetrical membranes, was decisive for this method. In the present progress report the structures of asymmetric membranes are discussed, as well as their preparation from various polymers and their application to the separation of molecular mixtures.     

On the preparation of asymmetric CaTi0.9Fe0.1O3−δ membranes by tape-casting and co-sintering process

Commercial deployment of membrane-based technology for high temperature gas separation requires the development of reliable processing of thin supported ceramic membranes. The asymmetric membranes should also demonstrate high oxygen flux in long term operation often encountered in stringent conditions. These requirements may be fulfilled by designing thin membrane films of chemically and mechanically strong CaTi_0.9Fe_0.1O_3−δ oxide material, as prepared in this work. The supported membranes were produced by means of a versatile manufacturing protocol with potential for mass production. It makes use of tape-casting, co-lamination and co-sintering of green laminates. The porosity of the mechanical supports was tailored through the addition of different pore formers, like corn starch and ammonium oxalate, in order to form a well-connected porous network. As-produced 30-μm thin supported CaTi_0.9Fe_0.1O_3−δ membranes were thoroughly characterized to establish relationships between manufacturing parameters and membrane microstructure. The oxygen permeation rates under air/argon gradient in the temperature range 800–1050 °C were investigated. It is concluded that pressure drop resistance in supports strongly contributed to reduce the oxygen flux. Appropriate selection of pore former type and content reduced this effect yielding increased oxygen flux, which became under control of bulk diffusion.     

双层类脂膜及其在电化学生物传感器中的应用

详细评述了各种双层类脂膜包括传统的双层类脂膜（ＢＬＭ）、固体载体支撑的自组双层类脂膜（ｓ－ＢＬＭ）、固体载体支撑的混合双层类脂膜（ｅ－ＢＬＭ）的制备方法和特性,比较了其优缺点。介绍了双层类脂膜在电化学生物传感器中的应用,并展望了发展前景。     

Domain Formation in Lipid Bilayer Membranes: Control of Membrane Nanostructure by Molecular Architecture

Summary. Lipid-polymer conjugates with differing hydrophobic to hydrophilic dimensions were prepared. The polymer part consisted of hydrophilic poly(2-methyl-1,3-oxazolines) (POZO), whose chain length can be controlled by living polymerization methods. The lipid-polymer conjugates were incorporated into vesicles composed of L--dimyristoylphosphatidylcholine (DMPC) or L--dipalmitoylphosphatidylcholine (DPPC) in amounts of up to 25mol%. The formation of domains within the lipid bilayer membrane is observed by atomic force microscopy (AFM), thermal analysis (DSC), and fluorescence spectroscopy. The synthetic design of the lipids allows control over the distribution of polymer chains on the vesicle surface.     

Domain Formation in Lipid Bilayer Membranes: Control of Membrane Nanostructure by Molecular Architecture

Lipid-polymer conjugates with differing hydrophobic to hydrophilic dimensions were prepared. The polymer part consisted of hydrophilic poly(2-methyl-1,3-oxazolines) (POZO), whose chain length can be controlled by living polymerization methods. The lipid-polymer conjugates were incorporated into vesicles composed of L--dimyristoylphosphatidylcholine (DMPC) or L--dipalmitoylphosphatidylcholine (DPPC) in amounts of up to 25mol%. The formation of domains within the lipid bilayer membrane is observed by atomic force microscopy (AFM), thermal analysis (DSC), and fluorescence spectroscopy. The synthetic design of the lipids allows control over the distribution of polymer chains on the vesicle surface.     

含核酸碱基混合脂质体的制备与膜内分子识别

在生物体系DNA中,碱基对间互补形成的基于氢键的分子识别是生命体系的重要特征,近年来,一些含核酸碱基的化合物在非竞争性介质中,也能进行分子选择性识别,一般来说,单体核酸苷在水溶液中不能通过氢键彼此键合,这主要是因为环境水的竞争性使核酸的碱基对间几乎不可能形成氢键,     

Preparation and Properties of Nanoporous Triblock Copolymer Membranes

“ Unplug those pores!” could be a slogan common to cosmetologists and polymer chemists. Membranes with nanochannels can be obtained by first forming a film by casting a solution of a triblock and homopolymer mixture, then selectively cross-linking domains in the film by photolysis, and finally forming nanochannels through removal of the homopolymer by solvent extraction. Such membranes are not liquid permeable but have gas-permeability constants about six orders of magnitude higher than that of low-density polyethylene films.     

Growth and Chemical Thermodynamics Analysis of SiC Film on Si Substrate by Heating Polystyrene/Silica Bilayer Method

SiC films were prepared by modified heating polystyrene/silica bilayer method on Si (111) substrate in normal pressure flowing Ar ambient at 1300 o C. The films were investigated by Fourier transform infrared absorption, X-ray diffraction, and scanning electron microscopy measurements. The chemical thermodynamics process is discussed. The whole reaction can be separated into four steps. The carburizing of SiO is the key step of whole reaction. The main reaction-sequence is figured out based on Gibbs free energy and equilibrium constant. Flowing Ar is necessary to continue the progress of whole reaction by means of carrying out accumulating gaseous resultants. The film is very useful for application in a variety of MOS-based devices for its silica/SiC/Si(111) structure, in which the silica layer can be removed thoroughly by the standard RCA cleaning process.     

Design,Synthesis, and Properties of Molecule-Based Assemblies with Large Second-Order Optical Nonlinearities

The design, synthesis, characterization, and understanding of new molecular and macromolecular assemblies with large macroscopic optical nonlinearities represents an active field of research at the interface of modern chemistry, physics, and materials science. Challenges in this area of photonic materials typify an important theme in contemporary chemistry: to create new types of functional materials by the rational construction of supramolecular assemblies exhibiting preordained collective phenomena by virtue of “engineered” molecule–molecule interactions and spatial relationships. This review surveys several approaches to, and the microstructural and optical properties of, second-order nonlinear optical materials built from noncentrosymmetric assemblies of chromophores having large molecular hyperpolarizabilities. Such types of materials can efficiently double the frequency of incident light, exhibit other second-order nonlinear optical effects, and contribute to the knowledge base needed for new photonic device technologies. Systems described include chromophore macromolecule guesthost matrices, chromophore-functionalized glassy macromolecules, thermally crosslinked chromophore-macromolecule matrices, and intrinsically acentric self-assembled chromophoric superlattices.     

Polypyrrole Bilayers: Charge Trapping and Application for Amperometric Ions Sensing

Bilayers composed of polypyrrole: doped by perchlorate ions (PPy(ClO₄) – anion exchanging inner layer) and by dodecyl sulfate ions (PPy(DS) – cation exchanging outer layer) are very effective charge trapping systems that are usually not observed for other bilayers comprised of polypyrrole. Chronopotentiometric experiments carried out for oxidation and reduction showed that the trapping effect in the inner layer resulted from different ion exchange properties of the component polymers, leading to a low permeability of the reduced outer layer towards anions. Estimated diffusion coefficients of Cl^? anions in the oxidized and reduced PPy(DS) are in the range of 10^?9 and lower than 10^?10 cm² s^?1, respectively. The presence of the outer layer limiting the ion transfer was found to be beneficial to improve the signal resolution in amperometric mode of ion sensing within wide KCl concentration range, from 10^?5 M up to 3 M. The influence of experimental conditions (film thickness, response time) on optimization of this novel kind of polymeric bilayer ion sensors was studied.     

Syntheses,structures, and thermal properties of new Au(III) organometallic compounds with ancillary S-, O-, and/or N-donor ligands

((CH₃)₂Au)₂C₂O₄ (1), ((CH₃)₂AuSCN)₂ (2), (CH₃)₂AuSSP(OCH₃)₂ (3), and (CH₃)₂AuSSP(OC₂H₅)₂ (4) were prepared and recrystallized from hexane to determine their crystal structures and analyze them by thermal methods (TGA). The compounds have been investigated as new possible precursors for metal–organic chemical vapor deposition (MOCVD). Compounds 1 and 2 are solids, while 3 and 4 are liquids. Crystal structures of 1 and 2 have been studied by single-crystal X-ray diffraction (XRD): compounds are monoclinic, space group for 1 P2₁/c, for 2 P2₁/n. Compound 1 has crystal parameters a?=?7.6952(5)?Å, b?=?11.1814(8)?Å, c?=?12.2893(8)?Å, α?=?90°, β?=?104.922(4)°, γ?=?90°; 2 has crystal parameters a?=?5.6184(3)?Å, b?=?15.2744(6)?Å, c?=?6.9202(3)?Å, α?=?90°, β?=?102.864(2)°, γ?=?90°. These are neutral complexes, in which molecules are only connected by van der Waal's interactions. Thermal gravimetric analyses (TGA) have shown that 3 and 4 evaporate practically without decomposition. MOCVD experiments were carried out at lower pressure using 3 and 4 as precursors. The films were grown on Si substrate and investigated by XRD and SEM.     

The Impact of an Anchoring Layer on the Formation of Tethered Bilayer Lipid Membranes on Silver Substrates

Tethered bilayer lipid membranes (tBLMs) have been known as stable and versatile experimental platforms for protein–membrane interaction studies. In this work, the assembly of functional tBLMs on silver substrates and the effect of the molecular chain-length of backfiller molecules on their properties were investigated. The following backfillers 3-mercapto-1-propanol (3M1P), 4-mercapto-1-butanol (4M1B), 6-mercapto-1-hexanol (6M1H), and 9-mercapto-1-nonanol (9M1N) mixed with the molecular anchor WC14 (20-tetradecyloxy-3,6,9,12,15,18,22 heptaoxahexatricontane-1-thiol) were used to form self-assembled monolayers (SAMs) on silver, which influenced a fusion of multilamellar vesicles and the formation of tBLMs. Spectroscopic analysis by SERS and RAIRS has shown that by using different-length backfiller molecules, it is possible to control WC14 anchor molecules orientation on the surface. An introduction of increasingly longer surface backfillers in the mixed SAM may be related to the increasing SAMs molecular order and more vertical orientation of WC14 at both the hydrophilic ethylenoxide segment and the hydrophobic lipid bilayer anchoring alkane chains. Since no clustering of WC14 alkane chains, which is deleterious for tBLM integrity, was observed on dry samples, the suitability of mixed-component SAMs for subsequent tBLM formation was further interrogated by electrochemical impedance spectroscopy (EIS). EIS showed the arrangement of well-insulating tBLMs if 3M1P was used as a backfiller. An increase in the length of the backfiller led to increased defectiveness of tBLMs. Despite variable defectiveness, all tBLMs responded to the pore-forming cholesterol-dependent cytolysin, vaginolysin in a manner consistent with the functional reconstitution of the toxin into phospholipid bilayer. This experiment demonstrates the biological relevance of tBLMs assembled on silver surfaces and indicates their utility as biosensing elements for the detection of pore-forming toxins in liquid samples.     

Thin films of mesoporous silica: preparation and characterization

Preparation of mesoporous materials in a thin film geometry was first reported in 1996. Recently, improvement of the preparation methods yielded stable films with well-defined symmetries, controlled pore orientation, continuity and film thickness. The ability to tailor film properties is important for their utilization in applications ranging from catalysis to microelectronics, where morphological control in the meso-domain is vital.     

平板双分子层脂膜的制备及锌离子跨该膜的输运过程

制备了氧化胆固醇 卵磷脂(脑磷脂)平板双分子层脂膜,研究了膜配方对双分子层脂膜的稳定性和离子通透性的影响,得到了最佳制膜工艺,建立了锌离子跨卵 (脑 )磷脂膜的吸附 -扩散模型,其计算值与实验值基本吻合.     

The Guanidinium Group in Molecular Recognition: Design and Synthetic Approaches

The guanidinium group is found in many natural products and has been extensively incorporated into various drug designs as well as artificial receptor structures. In this paper we critically review the various synthetic routes to guanidiniums and describe a novel approach that allows the mild formation of multi-substituted derivatives.