Synthetic ion channels in bilayer membranes

Natural ion channels are large protein complexes that regulate key functions of cells. Supramolecular chemists have been able to take hints from Nature to design and prepare completely synthetic ion channel systems that reproduce many of the fundamental functions of natural channels. This tutorial review introduces the field to non-specialists. It examines the design, synthesis, incorporation, and characterization of synthetic ion channels in bilayer membranes, and points to potential applications of synthetic ion channels.     

Palladium(II)-gated ion channels

A simple ion channel has been developed that can be created or disassembled through the addition or removal of palladium(ii).     

Palladium(II)-mediated assembly of biotinylated ion channels

Simple synthetic methodology has been used to create biotinylated pyridyl cholate lipids that can undergo multiple self-assembly events when inserted into phospholipid vesicles; Pd(II) links cholates into transmembrane lipids, while avidin laterally clusters these complexes together and concomitantly assembles the vesicles into aggregates. The transmembrane assembly of cholates by Pd(II) "opened" the ion channels, whereas avidin addition produced vesicle aggregates, giving a system that mimicked both transmembrane transport and cellular adhesion. Complexation of these Pd(II)-linked cholates by avidin gave a measurable decrease in ion flow, suggesting some channels became blocked or were prevented from adopting the optimum geometry for ion conduction. This reflects the importance of spatially appropriate preorganisation when generating active supramolecular assemblies.     

Fluids near surfaces and in pores and membrane channels

The theory of fluids near surfaces and in pores is reviewed and some simulations of electrolytes with a continuum solvent near an electrode that agree qualitatively with experiment but that are inexplicable by current theories are outlined. Recent work with more realistic solvents and membranes is discussed.     

Synthetic membranes (vesicles) in inorganic ion analysis: a review

Vesicles are structures of amphiphile molecules occurring through a self-aggregation process at the molecular or nano scale level with a large structural variety and diverse properties providing a reaction environment for chemical reactions that resembles that of natural systems. Their high versatility and recognized utility in various applications have triggered a interdisciplinary scientific endeavor over their formation, characterization and potential applications with impressive results. However, in the vastness of applications surrounding vesicular structures, their utility in analytical chemistry has only received minor attention. Notwithstanding, studies demonstrating their potential as colorimetric or fluorescence sensors, extraction solvents of inorganic ions or their chelates and stationary phase modifiers in liquid chromatography have appeared. To this end, this article aims to present for the first time the analytical chemistry aspects behind the use of vesicle media with special emphasis on the detection and determination of inorganic ions and encourage further research on this promising field of analytical science.     

Spirodialkylation of 3-(Phenylthio)-3-Sulfolene and Subsequent Synthetic Transformations

3-(Phenylthio)-3-sulfolene (1) underwent spirodialkylation to give products 2 which were desulfonylated to afford the dienes 3. The Diels-Alder reaction of 3 was achieved for some reactive dienophiles to yield spiro compounds. Compounds 2 were also converted to sulfonyldienes 9 which reacted as Michael acceptors.     

Control of helix formation in vinylogous gamma-peptides by (E)- and (Z)-double bonds: a way to ion channels and monomolecular nanotubes

[structure: see text] A complete overview on the alternative and competitive helices in vinylogous gamma-peptides is given, which was obtained on the basis of a systematic conformational analysis at various levels of ab initio MO theory (HF/6-31G*, DFT/B3LYP/6-31G*, PCM/HF/6-31G*). Contrary to the parent gamma-peptides, there is a strict control of helix formation by the configuration of the double bond between the C(alpha) and C(beta) atoms of the monomer constituents. (E)-Double bonds favor helices with larger pseudocycles beginning with 14- up to 27-membered hydrogen-bonded rings, whereas the (Z)-configuration of the double bonds supports a distinct preference of helices with smaller seven- and nine-membered pseudocycles showing interactions between nearest-neighbor peptide bonds. The rather stable helices of the (E)-vinylogous peptides with 22-, 24-, and 27-membered hydrogen-bonded pseudocycles have inner diameters large enough to let molecules or ions pass. Thus, they could be interesting model compounds for the design of membrane channels and monomolecular nanotubes. Since (E)- and (Z)-vinylogous gamma-amino acids and their oligomers are synthetically accessible, our study may stimulate structure research in this novel field of foldamers.     

Synthetic ion channels with rigid-rod pi-stack architecture that open in response to charge-transfer complex formation

We describe the design, synthesis, and evaluation of synthetic ion channels with a new rigid-rod pi-stack architecture that open in response to guest binding by aromatic electron donor-acceptor interactions. Highly cooperative and highly selective ligand gating is shown to yield anion selective, small ion channels that have the characteristic plum color of the charge-transfer complexes formed between the dialkoxynaphthalene ligands and the stacked naphthalenediimide acceptors of the channel.     

Transport of redox probes through single pores measured by scanning electrochemical-scanning ion conductance microscopy (SECM-SICM)

We report scanning electrochemical microscopy-scanning ion conductance microscopy (SECM-SICM) experiments that describe transport of redox active molecules which emanate from single pores of a track-etch membrane. Experiments are performed with electrodes which consist of a thin gold layer deposited on one side of a nanopipet. Subsequent insulation of the electrode with parylene results in a hybrid electrode for SECM-SICM measurements. Electrode fabrication is straightforward and highly parallel. For image collection, ionic current measured at the nanopipet both controls the position of the electrode with respect to the membrane surface and reports the local conductance in the vicinity of the nanopipet, while faradaic current measured at the Au electrode reports the presence of redox-active molecules. Application of a transmembrane potential difference affords additional control over migration of charged species across the membrane.     

Synthetic route to 4-(2-aminoethyl)-5-hydroxyindole derivatives

In synthetic studies leading to the title compounds, application of the Claisen rearrangement of 5-allyloxyindole was investigated. Almost quantitative yields of Claisen rearrangement product were realized, and a strategy for oxidative cleavage of the allyl double bond to an indole-4-acetaldehyde derivative was developed. A new method for conversion of 2,3-dihydroindoles into indoles was utilized: air oxidation in a strongly basic environment. The Claisen rearrangement of allyloxyindoles is presented as a method having considerable potential utility in synthesis of a variety of polysubstituted indoles.     

N-二茂铁甲酰基-N′-芳(烷)基硫脲的合成及光谱性质研究

合成了二茂铁甲耽墓异硫氛酸始，并可与各种胺类(取代苯胺类，a-茶胺，低分于1的脂肪按，六红毗咬)反应，合成了未见报道的21种含二茂铁甲耽基的硫膝衍生物.本法简便，产物易分离提纯，产率高.二茂铁甲耽基异硫氛酸脂也可在低温(一5一0℃)下与强城性的脂肪胺在水溶液中石应.产物为经牙资夺娇_红夕卜产.讲_牙定磁共版讲确宁了里去构.     

1-［反式-4-（反式-4-正戊基环己基）环己基］乙炔制备的新方法

环己基乙炔;连二烯;液晶中间体;合成;消除反应     

Photochemical effect driven fluid behavior control in microscale pores and channels

Manipulating the fluid transport in the microscale pores and channels is playing a paramount role in the realization of the versatile functions of microfluidics. In recent years, using light to control the fluid behavior in the microchannels/pores has attracted many researchers’ attention due to the advantages of light such as non-contact stimulation, tunable excitation, high spatial and temporal resolution. With efforts, great achievements and progresses have been achieved for photochemical eff...