Study of the ion channel behavior of didodecyldimethylammonium bromide formed bilayer lipid membrane stimulated by PF6-

Bilayer lipid membranes ( BLM) formed from didode-cyldimethylammonium bromide were made on the freshly exposed surface of a glassy carbon (GC) and were demonstrated by the ac impedance spectroscopy. The ion channels of membrane properties induced by PF6- were studied by the cyclic voltammetric methods. Experimental results indicated that the ion channel of BLM was open in the presence of the PF6- due to the interaction of PF6- with the BLM, while it was switched off in the absence of PF6-. Because the ion channel behavior was affected by the concentration of PF6-, a sensor for PF6- can be developed.

Ion channel behavior of amphotericin B in sterol-free and cholesterol- or ergosterol-containing supported phosphatidylcholine bilayer model membranes investigated by electrochemistry and spectroscopy

Amphotericin B (AmB) is a popular drug frequently applied in the treatment of systemic fungal infections. In the presence of ruthenium (II) as the maker ion, the behavior of AmB to form ion channels in sterol-free and cholesterol- or ergosterol-containing supported phosphatidylcholine bilayer model membranes were studied by cyclic votammetry, AC impedance spectroscopy, and UV/visible absorbance spectroscopy. Different concentrations of AmB ranging from a molecularly dispersed to a highly aggregated state of the drug were investigated. In a fixed cholesterol or ergosterol content (5 mol %) in glassy carbon electrode-supported model membranes, our results showed that no matter what form of AmB, monomeric or aggregated, AmB could form ion channels in supported ergosterol-containing phosphatidylcholine bilayer model membranes. However, AmB could not form ion channels in its monomeric form in sterol-free and cholesterol-containing supported model membranes. On the one hand, when AmB is present as an aggregated state, it can form ion channels in cholesterol-containing supported model membranes; on the other hand, only when AmB is present as a relatively highly aggregated state can it form ion channels in sterol-free supported phosphatidylcholine bilayer model membranes. The results showed that the state of AmB played an important role in forming ion channels in sterol-free and cholesterol-containing supported phosphatidylcholine bilayer model membranes.

Electrochemical study of ion channel behavior in incorporated poly L-glutamate bilayer lipid membranes

The lipid layer membranes were fabricated on the glassy carbon electrode (GC) and demonstrated to be bilayer lipid membranes by impedance spectroscopy. The formation of incorporated poly L-glutamate bilayer lipid membrane was achieved. The ion channel behavior of the incorporated poly L-glutamate membrane was determined. When the stimulus calcium cations were added into the electrolyte, the ion channel was opened immediately and exhibited distinct channel current. Otherwise, the ion channel was closed. The cyclic voltammogram at the GC electrode coated with incorporated poly L-glutamate DMPC film response to calcium ion is very fast compared with that at the GC electrode coated only with DMPC film. Ion channel current is not dependent on the time but on the concentration of calcium. The mechanism of the ion channel formation was investigated.

The channel behavior of gramicidin in mercaptan self-assembled monolayer membrane

The present paper reports the channel behavior of gramicidin in mercaptan self-assembled monolayer on the surface of the gold electrode by using the electrochemical method. The current responses to K+ ions and the electrode potential for the gold electrodes modified with self-assembled mercaptan monolayer incorporating and not incorporating gramicidin D were compared. The results firstly indicated that gramicidin D molecules can be incorporated into the mercaptan monolayer assembled on the surface of the gold electrode and form monovalent ion channel. A mechanism of the phenomenon was proposed.

Ion channel behavior of supported bilayer lipid membranes on a glassy carbon electrode

A new kind of solid substrate, a glassy carbon (GC) electrode, was selected to support lipid layer membranes. On the surface of the GC electrode, we made layers of didodecyldimethylammonium bromide (a synthetic lipid). From electrochemical impedance experiments, we demonstrated that the lipid layers on the GC electrode were bilayer lipid membranes. We studied the ion channel behavior of the supported bilayer lipid membrane. In the presence of perchlorate anions as the stimulus and ruthenium(II) complex cations as the marker ions, the lipid membrane channel was open and exhibited distinct channel current. The channel was in a closed state in the absence of perchlorate anions.

Ion-channel sensing of ferricyanide anion based on a supported bilayer lipid membrane

Ferricyanide anion has usually been used as a marker of ion-channel sensors. In this work we first found that ferricyanide, itself, can act as a stimulus to regulate the permeability of sBLM prepared from didodecyldimethylammonium bromide (a kind of synthetic lipid) on a GC electrode. We used cyclic voltammetry and a.c. impedance to investigate this phenomenon. The interaction between sBLM and ferricyanide concerns time. Furthermore, we developed a sensor for ferricyanide anion. The ion-channel sensor is highly sensitive. It can detect ferricyanide concentration as low as 5 muM.

Induction effect of Ca2+ on ion-channel behavior of supported phospholipid membranes

As a kind of supported bilayer lipid membranes, hybrid bilayer membrane (HBM) was applied to the interaction between Ca2+ and lipid for the first time. By using Fe(CN)(6)(3-) as a probe, we found that Ca2+ could induce the ion channel of HBM to be in open state. STM images study proved this phenomenon.

The channel behavior of gramicidin D in the self-assembled monolayer

It was found for the first time that gramicidin D (GD) molecules can be incorporated into the ODM monolayer which is self-assembled on the surface of the gold electrode and form monovalent cation channels.

Phase identification in a series of liquid crystalline TPP polyethers and copolyethers having highly ordered mesophase structures. 6. Structure changes from smectic to columnar phases in a series of copolyethers containing odd and even numbers of methylene units in equal molar composition

A series of liquid crystalline copolyethers has been synthesized from 1-(4-hydroxy-4'-biphenyl)-2-(4-hydroxyphenyl)propane and different alpha,omega-dibromoalkanes [coTPP(n/m)]. In this report, coTPPs having n = 5, 7, 9, 11 and m = 12 are studied, which represent copolyethers having both varying odd number and a fixed even number of methylene units. The compositions were fixed at an equal molar ratio (50/50). These coTPPs(nlm) show multiple phase transitions during cooling and heating in differential scanning calorimetry experiments. The undercooling dependence of these transitions is found to be small, indicating that these transitions are close to equilibrium, Although the coTPPs possess a high-temperature nematic (N) phase, the periodicity order along the chain direction is increasingly disturbed when the length of the odd-numbered methylene units decreases from n 11 to 5. in the coTPPs(5/12, 7/12, and 9/12), wide-angle X-ray diffraction experiments at different temperatures show that, shortly after the N phase formation during cooling, the lateral molecular packing improves toward a hexagonal lattice, as evidenced by a gradual narrowing of the scattering halo. This process represents the possible existence of an exotic N phase, which serves as a precursor to the columnar (Phi(H)) phase. A further decrease in temperature leads to a (PH phase having a long-range ordered, two-dimensional hexagonal lattice. In coTPP(11/12), the phase structures are categorized as highly ordered and tilted, smectic and smectic crystal phases, similar to homoTPPs, such as the smectic F (S-F) and smectic crystal G (SCG) phases. An interesting observation is found for coTPP(9/12), wherein a structural change from the high-temperature Phi(H) phase to the low-temperature S-F phase occurs. It can be proven that, upon heating, the well-defined layer structure disappears and the lateral packing remains hexagonal. The overall structural differences in this series of coTPPs between those of the columnar and highly ordered smectic phases are related to the disorders introduced into the layer structure by the dissimilarity of the methylene unit lengths in the comonomers.

Ion channel sensor

The ion channel sensor is reviewed. The concept and sensing principle of this kind of sensor are briefly discussed. The fabrication of the sensing membrane and the application of the ion channel sensor in electroanalytical chemistry are evaluated. The future developing direction is also anticipated.

ANALYSIS OF ANGULAR OVERLAP PARAMETERS FOR THE LAOXEU3+ (X = CL, BR, I) SERIES

The Angular Overlap Model (AOM) is applied to the LaOX:Eu3+(X = Cl, Br, I) series involving sigma, pi, delta and phi effects based on the experimental energy levels. The calculations are made in two cases. (1) Consider oxygen and halogen having the same bond-length. (2) Consider the real structure. In both cases, the results show that for sigma-bonding parameters, the values of e(sigma) decrease with increasing charge number of halogen, i.e. Cl- > Br- > I-, this indicates that the bonding ability also decreases with this order. The absolute values of each parameter are much larger than zero-therefore they all must be included in a practical analysis. In the second case, the values of the e(pi) parameter are negative, which means a ''back-bonding'' is formed, and this is profitable for the formation of sigma-bonding, usually referred to as ''synergic effect''.

Distribution of uranium isotopes in the main channel of Yellow river (Huanghe), China

Uranium isotopes were measured in waters and suspended particulate matters (SPM) of the main channel of Yellow River, China that were sampled during four field trips between August 2005 and July 2006. The results show that the concentration of dissolved U (2.04-7.83 mu g/l) and the activity ratio of U-234/U-238 (1.36-1.67) are much higher than the average U concentrations and activity ratios of global major rivers. Mass balance calculations using the results of simulated experiments and measurement data show that the section of the Yellow River between Lanzhou and Sanmenxia has its dissolved U derived from two sources: suspended sediments (68%) and groundwater/runoff from loess deposits (32%). Both sources are related to the heavy erosion of the Chinese Loess Plateau. (C) 2008 Elsevier Ltd. All rights reserved.

Fine-grained Pleistocene deepwater turbidite channel system on the slope of Qiongdongnan Basin, northern South China Sea

Recently, as oil exploitation has become focused on deepwater slope areas. more multi-channel high resolution 2D and 3D seismic data were acquired in the deepwater part of the Qiongdongnan Basin, northern South China Sea. Based on 3D seismic data and coherence time slice, RMS and 3D visualization, a series of deepwater channels were recognized on the slope that probably developed in the late Quaternary period. These channels trend SW-NE to W-E and show bifurcations, levees, meander loops and avulsions. High Amplitude Reflections (HARs), typical for channel-levee complexes, are of only minor importance and were observed in one of the channel systems. Most of the detected channels are characterized by low-amplitude reflections, and so are different from the typical coarse-grained turbidite channels that had been discovered worldwide. The absence of well data in the study area made it difficult to determine the age and lithology of these channels. Using a neighboring drill hole and published data about such depositional systems worldwide, the lithology of these channels is likely to be dominated by mudstones with interbedded thin sandstones. These channels are formed by turbidity currents originated from the little scale mountain river of mid-Vietnam in SW direction and were probably accompanied by a relative sea level drop in the last glacial age. These channels discovered on the northern South China Sea slope are likely to be fine-grained, mud-dominant and low N:G deposits in a deepwater paleogeographic setting. (C) 2009 Elsevier Ltd. All rights reserved.

Seismic stratigraphy of the Qiongdongnan deep sea channel system, northwest South China Sea

Based on more than 4000 km 2D seismic data and seismic stratigraphic analysis, we discussed the extent and formation mechanism of the Qiongdongnan deep sea channel. The Qiongdongnan deep sea channel is a large incised channel which extends from the east boundary of the Yinggehai Basin, through the whole Qiongdongnan and the Xisha trough, and terminates in the western part of the northwest subbasin of South China Sea. It is more than 570 km long and 4-8 km wide. The chaotic (or continuous) middle (or high) amplitude, middle (or high) continuity seismic facies of the channel reflect the different lithological distribution of the channel. The channel formed as a complex result of global sea level drop during early Pliocene, large scale of sediment supply to the Yinggehai Basin, inversion event of the Red River strike-slip fault, and tilted direction of the Qiongdongnan Basin. The large scale of sediment supply from Red River caused the shelf break of the Yinggehai Basin to move torwards the S and SE direction and developed large scale of prograding wedge from the Miocene, and the inversion of the Red River strike-slip fault induced the sediment slump which formed the Qiongdongnan deep sea channel.

Geomorphology, sedimentary processes and development of the Zenisu deep-sea channel, northern Philippine Sea

The Zenisu deep-sea channel originates on the Izu-Ogasawara island arc, and disappears in the Shikoku Basin of the Philippine Sea. The geomorphology, sedimentary processes, and the development of the Zenisu deep-sea channel were investigated on the basis of swath bathymetry, side-scan sonar imagery, submersible observations, and seismic data. The deep-sea channel can be divided into three segments according to the downslope gradient and channel orientation. They are the Zenisu Canyon, the E-W fan channel, and the trough-axis channel. The sediment fill is characterized by turbidite and debrite deposition and blocky-hummocky avalanche deposits on the flanks of the Zenisu Ridge. In the Zenisu Canyon and the Zenisu deep-sea channel, sediment transport by turbidity currents generates sediment waves (dunes) observed during the Shinkai 6500 dive 371. The development of the Zenisu Canyon is controlled by a N-S shear fault, whereas the trough-axis channel is controlled by basin subsidence associated with the Zenisu Ridge. The E-W fan channel was probably affected by the E-W fault and the basement morphology.