In situ PM-IRRAS Studies of a Floating Bilayer Lipid Membrane at Au(111) Electrode Surface

应用电化学原位偏振红外反射光谱法研究了构建于金（111）电极表面的浮动磷脂双层膜。金电极表面先自组装一层巯基葡萄糖单层来增加表面的亲水性，浮动磷脂双层膜通过LB-LS技术构建在巯基葡萄糖单层上.双层膜由双肉豆蔻磷脂酰胆碱（DMPC），胆固醇和神经节苷脂GM1构成.GM1分子中的糖链可以物理吸附在巯基葡萄糖表面，在双层膜和基底间形成一个富含水的隔层.红外光谱表明浮动双层膜中的DMPC分子比传统的支撑双层膜中的DMPC分子有更强的水合作用，证实了双层膜和基底间水层的存在.该浮动双层膜更接近于实际的生物膜体系，并且在金电极表面有宽的电位区间，非常适合于进一步的离子通道蛋白质研究.In situ Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) was used to study the structure of a DMPC + cholesterol + GM1 floating bilayer lipid membrane (fBLM) at a Au(111) surface. 1-thio-beta-D-glucose (beta-Tg) was self-assembled onto the Au electrode to increase the overall hydrophilicity of the surface. The fBLM was deposited on the beta-Tg self-assembled monolayer (SAM) using a combination of Langmuir-Blodgett/Langmuir-Schaefer (LB/LS) techniques. The carbohydrate headgroups of the GM1 molecules were physically adsorbed to the beta-Tg SAM forming a water rich cushion between the fBLM and the modified gold substrate. The PM-IRRAS spectra indicate that the DMPC molecules within the fBLM are more hydrated than previous studies involving supported bilayer lipid membranes (sBLM) where the membrane is directly adsorbed onto the surface. The tilt angle of the DMPC acyl chains in the fBLM is smaller than that of the sBLM composed of similar components. The results from this work confirmed that the fBLM is stable over a wide range of electrode potentials and that a water rich region is present between the bilayer and gold electrode surface. The addition of this water region more closely mimics the natural environment of a biological membrane making the fBLM a desirable candidate for future in situ studies involving transmembrane proteins.This work was supported by Discovery grant from the Natural Sciences and Engineering Research Council of Canada. J.L. acknowledges support from the Canada Research Chairs (CRC) program.This work was supported by Discovery grant from the Natural Sciences and Engineering Research Council of Canada. J.L. acknowledges support from the Canada Research Chairs (CRC) program.作者联系地址：圭尔夫大学化学系，加拿大 安大略省 N1G 2W1, 圭尔夫Author's Address: Department of Chemistry, University of Guelph, Guelph, Ontario N1G 2W1, Canada通讯作者E-mail：[email protected]

Direction of the polymorphic form of entacapone using an electrochemical tuneable surface template

The ability to direct the surface crystallisation of different polymorphs of entacapone by tuning the electrochemical potential of Au(100) templates is demonstrated. Under quiescent conditions, without polarization (at open circuit potential), entacapone crystallises in its stable form A on the template surface and concomitantly in its metastable form D in the bulk solution. When Au(100) is negatively polarized (-150 mV), form D is still formed in the bulk solution but the metastable form α is found to crystallise at the edges of the template. Both crystals of form A and α were observed to grow epitaxially over the Au template surface. The electrochemical templating effect is consistent with the polarisation changing the structure of the initially adsorbed layers of supersaturated solution at the template surface which directs the nuclei formation and the subsequent crystal growth processes. This study demonstrates, for the first time, the direction of polymorphic form using a low field polarized nucleation template

Electron-topological, energetic and π-electron delocalization analysis of ketoenamine-enolimine tautomeric equilibrium

The ketoenamine-enolimine tautometic equilibrium has been studied by the analysis of aromaticity and electron-topological parameters. The influence of substituents on the energy of the transition state and of the tautomeric forms has been investigated for different positions of chelate chain. The quantum theory of atoms in molecules method (QTAIM) has been applied to study changes in the electron-topological parameters of the molecule with respect to the tautomeric equilibrium in intramolecular hydrogen bond. Dependencies of the HOMA aromaticity index and electron density at the critical points defining aromaticity and electronic state of the chelate chain on the transition state (TS), OH and HN tautomeric forms have been obtained

Interference of H-bonding and substituent effects in nitro- and hydroxy-substituted salicylaldehydes

Two intramolecular interactions, i.e., (1) hydrogen bond and (2) substituent effect, were analyzed and compared. For this purpose, the geometry of 4- and 5-X-substituted salicylaldehyde derivatives (X = NO2, H or OH) was optimized by means of B3LYP/6-311 + G(d,p) and MP2/aug-cc-pVDZ methods. The results obtained allowed us to show that substituents (NO2 or OH) in the para or meta position with respect to either OH or CHO in H-bonded systems interact more strongly than in the case of di-substituted species: 4- and 3-nitrophenol or 4- and 3-hydroxybenzaldehyde by ∼31%. The substituent effect due to the intramolecular charge transfer from the para-counter substituent (NO2) to the proton-donating group (OH) is ∼35% greater than for the interaction of para-OH with the proton-accepting group (CHO). The total energy of H-bonding for salicylaldehyde, and its derivatives, is composed of two contributions: ∼80% from the energy of H-bond formation and ∼20% from the energy associated with reorganization of the electron structure of the systems in question