The effect of phenyltin chlorides on the phase polymorphism of dipalmitoylphosphatidylcholine

The effects of diphenyltin dichloride (DPhT) and triphenyltin chloride (TPhT) on polymorphic phase behaviour of aqueous dispersions of a dipalmitoylphosphatidylcholine (DPPC) bilayer were investigated by means of ³¹P NMR. It is suggested that DPhT induces interdigitated gel phase formation and TPhT induces hexagonal phase formation. The toxic activities of DPhT and TPhT seem to be connected with their ability to induce changes in the membrane structure. Copyright © 2001 John Wiley & Sons, Ltd.     

The transformation of phenyltin species during sample preparation of biological tissues using multi-isotope spike SSID-GC-ICPMS

A multi-isotope spike species-specific isotope dilution (MI-SSID) calibration strategy in connection with gas chromatography-inductively coupled plasma mass spectrometry was applied to evaluate different extraction procedures for the speciation analysis of phenyltin (PhT) compounds in biological materials: mussel tissue BCR CRM-477 and fish tissue NIES-11. Three different isotope-enriched PhT compounds, ¹¹⁸Sn-enriched monophenyltin (MPhT), ¹²²Sn-enriched diphenyltin (DPhT), and ¹²⁴Sn-enriched triphenyltin (TPhT), were used for the preparation of spikes to follow and correct for six possible interconversion reactions between PhT species that can take place in a sample. The acidity of the extractant, the presence of complexing reagents, and the use of ultrasonic or microwave agitation were found to affect the degradation of PhT compounds. No formation of PhTs through phenylation and negligible degradation of MPhT to inorganic tin were observed under the conditions investigated. The degree of degradation increased with increased acidity of extractant and when ultrasonication or microwave agitation was used. Under relatively mild extraction conditions, the degradation factors for DPhT and TPhT in the two reference materials studied were found, using MI-SSID, to be between 10 and 55% and 2 and 10%, respectively. Using the degradation factors, we calculated corrected concentration values for the organotin species. When microwave extraction at high power output was used, hydrogen radicals were formed that can enhance the degradation of DPhT and TPhT. The hydrogen radicals were trapped using N-tert-butyl-α-phenylnitrone and detected by electron spin resonance spectrometry. The effect of different extraction parameters on the degradation of PhT compounds in biological samples is discussed.     

The effect of some phenyltin compounds on the thermotropic phase behaviour and the structure of model membranes

The effects of diphenyltin dichloride (DPhT), triphenyltin chloride (TPhT) and tetraphenyltin (TTPhT) on the thermotropic phase behaviour of phosphatidylcholine bilayers were studied. All the phenyltin compounds investigated affected phase transitions differently. TTPhT broadened the main phase transition but it left the transition temperatures and enthalpy unchanged. TPhT reduced the transition temperatures and the enthalpies while DPhT showed a dual effect on the pretransition and the main transition. At low concentrations DPhT reduced the temperatures of the transitions slightly and at higher concentrations it increased them. Based on differential scanning calorimetry (DSC) and also ¹H NMR and ³¹P NMR measurements, it is suggested that DPhT induces interdigitated gel phase formation and TPhT induces hexagonal phase formation. TTPhT seems to affect the structure only a little. The toxic activity of DPhT and TPhT seems to be connected with their ability to induce changes in the membrane structure. Copyright © 2000 John Wiley & Sons, Ltd.     

Toxicity of butyltin,phenyltin and inorganic tin compounds to sulfate‐reducing bacteria isolated from anoxic marine sediments

The toxicity of butyltin, phenyltin and inorganic tin compounds to three pure strains of sulfate‐reducing bacteria (SRB), isolated from a tributyltin (TBT)‐polluted sediment, was determined. The isolated strains were identified as belonging to the genus Desulfovibrio. A new toxicological index (GR₂₅) was developed to assay the toxicity of organotin compounds. Deleterious effects on suspended anaerobic cell cultures were observed for concentrations ranging between 500 and 600 µM for tin tetrachloride, 55 and 260 µM for triorganotins, 30 and 90 µM for diorganotins, and 1 and 6 µM for mono‐organotins. Whereas the number of substituents influenced the toxicity of organotins, the type of substituent (butyl or phenyl) proved to have little or no impact. Trisubstituted compounds (tributyl‐ and triphenyl‐tin) were less toxic to these strains of SRB than the monosubstituted forms (monobutyl‐ and monophenyl‐tin). This is the opposite trend to that currently reported for aerobic organisms. Under the given anoxic conditions, the toxicity of organotin compounds obtained yielded a significant negative correlation with the total surface area (TSA) of the tested molecules. Comparison of the TBT toxicity data observed for different microbial groups suggests that the tolerance of bacteria to organotin compounds might be related to organotin–cell wall interactions as well as to aerobic or anaerobic metabolise pathways. Copyright © 2000 John Wiley & Sons, Ltd.     

Gas chromatography-high-resolution mass spectrometry based method for the simultaneous determination of nine organotin compounds in water,sediment and tissue

A GC-HRMS based method for the accurate and sensitive determination of nine organotin compounds, tetrabutyltin (TeBT), tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT), triphenyltin (TPhT), diphenyltin (DPhT), monophenyltin (MPhT), tricyclohexyltin (TCyT), and dicyclohexyltin (DCyT) in sediment, tissue and water samples is presented and discussed. Mass spectral features of these analytes via both low resolution quadrupole and high resolution magnetic sector, GC-HRMS conditions under selective ion monitoring mode and QA/QC criteria for the positive identification of analyte are all provided. Linearity of response and minimal detectable limits are illustrated for each of the nine compounds monitored and the estimates of method limits-of-detection were 7-29 ppt for water and 0.35-1.45 ppb for tissue or sediments. Sample preparation considerations and precision are discussed for spiked water and sediment samples, whereas method accuracy was established by analysing a certified reference material (CRM) mussel sample and comparing our results to the assigned values. Good agreement was found between our results and assigned or indicative values for MBT, DBT, TBT, DPhT and TPhT (cyclohexyl-tins were not present in the CRM).     

Stability of model membranes in the presence of organotin compounds

The influence of tri‐ and di‐alkyltins (TATs and DATs) as well as di‐ and triphenyltin compounds (DPhTs and TPhTs) on haemolysis of red blood cells (RBCs) and stability of planar lipid membranes (PLMs) has been studied. The results obtained show that the efficiency of TATs (trimethyl‐, triethyl‐, tri‐n‐propyl‐ and tributyl‐tin chlorides) in destroying PLMs did not differ greatly when the compounds were studied in solutions of physiological pH (phosphate buffer, pH 7.4). A decrease in pH to 5.0 caused small changes in the efficiency of the three largest TAT molecules and a significant decrease in the efficiency of trimethyltin chloride. Both haemolytic and PLM experiments showed that the most active TAT was tri‐n‐propyltin chloride. The destructive action of DAT (dimethyl‐ and dibutyltin) and DPhT dichlorides was somewhat more differentiated. Dimethyltin dichloride (DMT) interaction with model membranes was a little weaker than that of DPhT and dibutyltin dichlorides and all these compounds influenced the model membranes to a lesser extent than TATs or TPhT. To bring about comparable haemolysis effects the dichlorides had to be used at much greater concentrations than the chlorides. The haemolytic properties of the dichlorides, especially of that of DMT, significantly increased in solution at pH 5.0. TPhT chloride interacted with model membranes similarly to TAT chlorides. Also, no great difference in efficiency of this compound was found for the two buffer solutions used. Copyright © 2000 John Wiley & Sons, Ltd.     

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.     

Effect of phenyltin compounds on lipid bilayer organization

Phenyltin compounds are known to be biologically active. Their chemical structure suggests that they are likely to interact with the lipid fraction of cell membranes. Using fluorescence and NMR techniques, the effect of phenyltin compounds on selected regions of model lipid bilayers formed from phosphatidylcholine was studied. The polarization of N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) dipalmitoyl-L -phosphatidylethanolamine and desorption of praseodymium ions was used to probe the polar region, whereas the polarization of 1 - (4 - trimethylammoniumphenyl) - 6 - phenyl - 1,3,5-hexatriene p-toluenesulfonate measured the hydrophobic core of the membrane. In addition, changes in the N-(5-fluoresceinthiocarbanoly)dipalmitoyl - L - α - phosphatidyl - ethanolamine fluorescence intensity indicated the amount of charge introduced by organotin compounds to the membrane surface. There were no relevant changes of measured parameters when tetraphenyltin was introduced to the vesicle suspension. Diphenyltin chloride causes changes of the hydrophobic region, whereas the triphenyltin chloride seems to adsorb in the headgroup region of the lipid bilayer. When the hemolytic activity of phenyltin compounds was measured, triphenyltin chloride was the most effective whereas diphenyltin chloride was much less effective. Tetraphenyltin causes little damage. Based on the presented data, a correlation between activity of those compounds to hemolysis (and toxicity) and the location of the compound within the lipid bilayer could be proposed. In order to inflict damage on the plasma membrane, the compound has to penetrate the lipid bilayer. Tetraphenyltin does not partition into the lipid fraction; therefore its destructive effect is negligible. The partition of the compound into the lipid phase is not sufficient enough, by itself, to change the structure of the lipid bilayer to a biologically relevant degree. The hemolytic potency seems to be dependent on the location of the compound within the lipid bilayer. Triphenyltin chloride which adsorbs on the surface of the membrane, causes a high level of hemolysis, whereas diphenyltin chloride, which penetrates much deeper, seems to have only limited potency. © 1998 John Wiley & Sons, Ltd.     

Preparation, preservation and application of pure isotope-enriched phenyltin species

A method combining liquid/liquid extraction and chromatographic fractionation has been developed for the preparation of pure monophenyltin (MPhT), diphenyltin (DPhT), and triphenyltin (TPhT), synthesized from isotope-enriched Sn metal using phenylation of SnI₄ in diethylether (DEE) followed by quenching with HBr and water. After two successive extractions of the aqueous HBr phase with DEE, >99% of both DPhT and TPhT was recovered in the combined DEE phase and 94% of the MPhT remained in the aqueous phase. The MPhT in the aqueous phase was extracted into dichloromethane. The organic phases were vaporized and the PhTs were redissolved in MeOH/water/acetic acid/sodium acetate (59/30/6/8, v/v/v/w), which was also used as storing solution. Aliquots of the two solutions containing either DPhT and TPhT or MPhT were injected into a silica-based C₁₈ column for isolating and purifying single species. The yields of pure MPhT, DPhT, and TPhT, each synthesized from isotope-enriched ¹¹⁸Sn metal, ¹²²Sn metal, and ¹²⁴Sn metal, were better than 99%. After chromatographic separation, the single phenyltin compounds were mixed to prepare a spike for multiple-isotope species-specific isotope dilution (MI-SSID). MI-SSID was successfully used to determine phenyltin compounds in the certified reference material, mussel tissue BCR CRM-477. At −20 °C, all of the fractionated phenyltin species were stable in the storage solution for at least 197 days. When these standards were stored at 4 °C or 22 °C, 4–6% of the DPhT and TPhT degraded within 27 days. The degradation of DPhT and TPhT increased with the ionic strength and acidity of the storage solution.      

A Micromechanical Cantilever‐Based Liposome Biosensor for Characterization of Protein‐Membrane Interaction

We have newly evaluated the interaction of lipid membrane with two different proteins of lysozyme and carbonic anhydrase from bovine (CAB) using a micro cantilever‐based liposome biosensor with a new droplet‐sealing structure. Herein 1,2‐dipalmitoyl‐sn‐glycero‐3‐phosphocholine (DPPC) liposomes are used as model lipid membrane and are immobilized on the surface of cantilever. The interaction of DPPC liposome with the target protein causes deflection of the micro‐cantilever, which can stably be detected by measuring the resistance change of the strain gauge. The resistance change dependent on time is used to evaluate the characteristic of liposome‐protein interaction. The resistance of the cantilever‐based biosensor increases monotonously with time in both of the two protein solutions. Especially, chronological resistance change depends markedly on both the concentration and species of target proteins. Finally, these results lead us to conclude that the cantilever‐based liposome biosensor with the droplet‐sealing structure facilitates the characterization of protein‐membrane interaction. It also means that this biosensor is a promising candidate device for label‐free detection of concentration and species of different target proteins.     

Influence of organotin compounds on phosphatidylserine membranes

Organotin compounds are widely distributed toxicants. They are membrane‐active molecules with broad biological toxicity. We have studied the interaction of tributyltin and triphenyltin with phosphatidylserine model membranes using differential scanning calorimetry, infrared spectroscopy and X‐ray diffraction techniques. Organotin compounds produced a broadening of the gel to the liquid‐crystalline phase transition of the phospholipid and a shifting of the phase transition temperature to lower values. Infrared spectroscopy experiments showed that tributyltin exerted a fluidizing effect on the apolar part of the bilayer, and that both tributyl‐ and triphenyltin interact with the interfacial region of the bilayer, making the carbonyl groups less accessible to water. As seen by X‐ray diffraction experiments, organotin compounds were unable to change the bilayer macroscopic organization of the phospholipid, but they were able to reduce the long‐range order of the multibilayer system and to disorder the packing of the phospholipid molecules. The observed interaction between organotin compounds and phosphatidylserine membranes promotes physical perturbations that could affect membrane function and may mediate some of their toxic effects. Copyright © 2004 John Wiley & Sons, Ltd.     

气相色谱-质谱法同时测定聚氯乙烯塑料制品中的10种有机锡化合物

采用气相色谱-质谱法(GC-MS)同时快速有效地测定了聚氯乙烯（PVC）塑料制品中的二丁基氯化锡、单丁基氯化锡、三乙基氯化锡、三苯基氯化锡、三丁基氯化锡、三丙基氯化锡、二苯基氯化锡、四丁基锡、二辛基氯化锡和单苯基氯化锡等10种有机锡化合物。使用四氢呋喃溶解PVC样品,甲醇沉淀样品中的聚合物,超声萃取其中的有机锡化合物,将提取液衍生化后用正己烷萃取,采用GC-MS总离子流和选择离子进行定性定量测定。对衍生化时间、衍生化pH值、衍生化试剂用量、沉淀试剂用量等样品前处理条件进行了优化,并进行了线性关系、回收率、精密度等考察。结果表明,方法的线性范围为0.5～50 mg/L,线性相关系数为0.9978～0.9997。10种有机锡化合物的回收率及相对标准偏差(n=9)分别为84.23%～109.1%和4.24%～10.75%。所建立的方法能很好地应用于PVC塑料制品中有机锡化合物的检测。     

Determination of organotin compounds by headspace solid-phase microextraction–gas chromatography–pulsed flame-photometric detection (HS-SPME–GC–PFPD)

A method based on Headspace solid-phase microextraction (HS-SPME, with a 100 μm PDMS-fiber) in combination with gas-chromatography and pulsed flame-photometric detection (GC-PFPD) has been investigated for simultaneous determination of eight organotin compounds. Monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), monophenyltin (MPhT), and the semi-volatile diphenyltin (DPhT), triphenyltin (TPhT), monooctyltin (MOcT), and dioctyltin (DOcT) were determined after derivatization with sodium tetraethylborate. The conditions used for the extraction and preconcentration step were optimised by experimental design methodology. Tripropyltin (TPrT) and diheptyltin (DHepT) were used as internal standards for quantification of volatile and semi-volatile organotin compounds, respectively. The analytical precision (RSD) for ten successive injections of a standard mixture containing all the organic tin compounds ranged between 2 and 11%. The limits of detection for all the organotin compounds were sub ng (Sn) L⁻¹ in water and close to ng (Sn) kg⁻¹ in sediments. The accuracy of the method was evaluated by analysis of two certified reference material (CRM) sediment samples. The HS-SPME–GC–PFPD was then applied to the analysis of three harbour sediment samples. The results showed that headspace SPME is an attractive tool for analysis of organotin compounds in solid environmental matrices.     

Impact of Strong and Weak Lipid–Protein Interactions on the Structure of a Lipid Bilayer on a Gold Electrode Surface

A lipid bilayer deposited on an electrode surface can serve as a benchmark system to investigate lipid–protein interactions in the presence of physiological electric fields. Recoverin and myelin‐associated glycoprotein (MAG) are used to study the impact of strong and weak protein–lipid interactions on the structure of model lipid bilayers, respectively. The structural changes in lipid bilayers are followed using electrochemical polarization modulation infrared reflection–absorption spectroscopy (PM IRRAS). Recoverin contains a myristoyl group that anchors in the hydrophobic part of a cell membrane. Insertion of the protein into the 1,2‐dimyristoyl‐sn‐glycero‐3‐phosphatidylcholine (DMPC)–cholesterol lipid bilayer leads to an increase in the capacitance of the lipid film adsorbed on a gold electrode surface. The stability and kinetics of the electric‐field‐driven adsorption–desorption process are not affected by the interaction with protein. Upon interaction with recoverin, the hydrophobic hydrocarbon chains become less ordered. The polar head groups are separated from each other, which allows for recoverin association in the membrane. MAG is known to interact with glycolipids present on the surface of a cell membrane. Upon probing the interaction of the DMPC–cholesterol–glycolipid bilayer with MAG a slight decrease in the capacity of the adsorbed lipid film is observed. The stability of the lipid bilayer increases towards negative potentials. At the molecular scale this interaction results in minor changes in the structure of the lipid bilayer. MAG causes small ordering in the hydrocarbon chains region and an increase in the hydration of the polar head groups. Combining an electrochemical approach with a structure‐sensitive technique, such as PM IRRAS, is a powerful tool to follow small but significant changes in the structure of a supramolecular assembly.     

Trace determination of organotin compounds in water,sediment and mussel samples by low-pressure gas chromatography coupled to tandem mass spectrometry

A fast method for the determination of eight organotin compounds (OTs), monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), tetrabutyltin (TeBT), monophenyltin (MPhT), diphenyltin (DPhT), triphenyltin (TPhT) and tetraphenyltin (TePhT), in water, sediments and mussels, was developed using low-pressure gas chromatography/tandem mass spectrometry (LPGC/MS/MS). The method is based on sodium diethyldithiocarbamate (DDTC) complexation of the ionic organotins, followed by extraction of the target matrices and derivatization by a Grignard reagent, as described in a previously published method for water samples. Solid-phase extraction was selected as extraction method from water samples after comparison with liquid-liquid extraction, but extraction of the OTs from sediment and mussel samples was performed using toluene. Matrix-matched calibration standards were used to minimize matrix effects. The analytical process was validated by the analysis of spiked blank samples. Performance characteristics such as linearity, detection limit (LOD), quantitation limit (LOQ), precision, and recovery were determined. Recoveries of OTs in spiked matrices ranged from 86-108% in water and from 78-110% in sediments and mussels, with precision values lower than 18%. Detection limits ranged from 0.1-9.6 ng L(-1) in water, and 0.03-6.10 microg kg(-1) in the other matrices. The present implementation of LPGC rather than conventional capillary GC permitted use of large-volume injection and reduced analysis time by a factor of two. The proposed methodology was applied to the determination of OTs in real samples of water, marine sediments and mussels from the west coast of the Mediterranean Sea (Spain).     

Fast and effective low‐temperature freezing extraction technique to determine organotin compounds in edible vegetable oil

Most organotin compounds that have been widely used in food packaging materials and production process show serious toxicity effects to human health. In this study, a simple and low‐cost method based on high‐performance liquid chromatography with inductively coupled plasma mass spectrometry for the simultaneous determination of four organotins in edible vegetable oil samples was developed. Four organotins including dibutyltin dichloride, tributyltin chloride, diphenyltin dichloride, and triphenyltin chloride were simultaneously extracted with methanol using the low‐temperature precipitation process. After being concentrated, the extracts were purified by matrix solid‐phase dispersion using graphitized carbon black. The experimental parameters such as extraction solvent and clean‐up material were optimized. To evaluate the accuracy of the new method, the recoveries were investigated. In addition, a liquid chromatography with tandem mass spectrometry method was also proposed for comparison. The procedures of extracting and purifying samples for the analysis were simple and easy to perform batch operations, also showed good efficiency with lower relative standard deviation. The limits of detection of the four organotins were 0.28–0.59 μg/L, and the limits of quantification of the four organotins were 0.93–1.8 μg/L, respectively. The proposed method was successfully applied to the simultaneous analysis of the four organotins in edible vegetable oil. Some analytes were detected at the level of 2.5–28.8 μg/kg.     

A Synergistic Effect of Select Organotin Compounds and Ionic Surfactants on Liposome Membranes

Organometallic compounds and surfactants constitute a potential threat to the environment. For that reason we have embarked on a study of their joint action on membranes. Model lecithin liposome membranes were modified with the cationic surfactant trimethyldodecylammonium bromide or the anionic surfactant sodium dodecylsulfonate, and the effect of tripropyltin chloride on the process of calcium (Ca²⁺) and praseodymium (Pr³⁺) desorption from the liposome membrane was studied. Kinetic constants for the process of Ca²⁺ ion desorption from lecithin liposome membranes were determined using the radiotracer method. The percentage of Pr³⁺ ion desorption from liposome membranes was measured by the ¹H NMR method. Trimethyltin, triethyltin and tripropyltin alone caused increased Ca²⁺ and Pr³⁺ desorption from liposome membranes with increasing concentration of the compounds and alkyl chain length. For both the processes studied, a cationic surfactant brought about a lower effectiveness of tripropyltin and an anionic surfactant resulted in a higher effectiveness. The effect observed can be explained by changes in the surface charge of the membrane, induced by the surfactant modifiers and by the concomitant change in the partition coefficient of the organotin. The results obtained indicate a protective or harmful joint action of the surfactants used with tripropyltin on membranes. © 1997 John Wiley & Sons, Ltd.     

Certification of butyltins and phenyltins in marine sediment certified reference material by species-specific isotope-dilution mass spectrometric analysis using synthesized <Superscript>118</Superscript>Sn-enriched organotin compounds

A new marine sediment certified reference material, NMIJ CRM 7306-a, for butyltin and phenyltin analysis has been prepared and certified by the National Metrological Institute of Japan at the National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). Candidate sediment material was collected at a bay near industrial activity in Japan. After air-drying, sieving, and mixing the material was sterilized with γ-ray irradiation. The material was re-mixed and packaged into 250 glass bottles (15 g each) and these were stored in a freezer at −30 °C. Certification was performed by use of three different types of species-specific isotope-dilution mass spectrometry (SSID–MS)—SSID–GC–ICP–MS, SSID–GC–MS, and SSID–LC–ICP–MS, with ¹¹⁸Sn-enriched organotin compounds synthesized from ¹¹⁸Sn-enriched metal used as a spike. The ¹¹⁸Sn-enriched mono-butyltin (MBT), dibutyltin (DBT), and tributyltin (TBT) were synthesized as a mixture whereas the ¹¹⁸Sn-enriched di-phenyltin (DPhT) and triphenyltin (TPhT) were synthesized individually. Four different extraction methods, mechanical shaking, ultrasonic, microwave-assisted, and pressurized liquid extraction, were adopted to avoid possible analytical bias caused by non-quantitative extraction and degradation or inter-conversion of analytes in sample preparations. Tropolone was used as chelating agent in all the extraction methods. Certified values are given for TBT 44±3 μg kg⁻¹ as Sn, DBT 51 ± 2 μg kg⁻¹ as Sn, MBT 67 ± 3 μg kg⁻¹ as Sn, TPhT 6.9 ± 1.2 μg kg⁻¹ as Sn, and DPhT 3.4 ± 1.2 μg kg⁻¹ as Sn. These levels are lower than in other sediment CRMs currently available for analysis of organotin compounds.     

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.     

Effect of organotin compounds on membrane lipids: Fluorescence spectroscopy studies

The temperature dependence of 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1-(4-trimethylaminophenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) fluorescence anisotropy has been studied to investigate the influence of mono-n-butyltin chloride (MBTC), di-n-butyltin chloride (DBTC) and tri-n-phenyl chloride (TPTC) on the physicochemical state of dipalmitoyl phosphatidylcholine. Below the lipid chain melting transition (T_m), fluorescence anisotropy values of DPH and TMA-DPH are increased by the presence of the organotins, without important modifications of the phase transition temperature. A possible difference in localization of the organotin compounds is suggested by the differential effect of the probes. It is suggested that there is localization in the hydrophobic core of the bilayer for TPTC, and at the head-group level for DBTC, and a homogeneous distribution in the bilayer for MBTC. Similar studies have been performed in liposomal suspensions of cardiolipin, phosphatidylserine and egg phosphatidylcholine.