硫醇/卵磷脂混合双层膜电化学行为研究

【作者】 左卫霞；

【导师】 童汝亭； 丁克强；

【作者基本信息】 河北师范大学 ， 物理化学， 2004， 硕士

【摘要】 生物膜是细胞表面的屏障，是细胞内外环境进行物质交换的通道，卵磷脂是构成生物膜的重要组成成分，参与生命的各种代谢。由于生物膜本身结构、组成、环境的复杂性，目前还不能在生物膜原位进行现场的观测与研究，HBM既具有SAMs的稳定性，在结构上又与生物膜相似，因此，普遍认为HBM是目前研究电子跨膜转移最理想的体系。Ca²⁺可以和某些生物膜相互作用，在生命活动中起重要作用。生物膜体系的制备是开展实验的前提与基础。本文应用HBM作为生物膜模拟体系，其基底是Au／十八硫醇SAMs，在此基底上组装上卵磷脂，采用电化学方法研究电极电位及Ca²⁺和HBM作用机理。主要内容如下： ◆ 综述了几种生物膜模拟体系的制备及特性、卵磷脂的生理功能及应用以及膜的表征技术等反面研究进展。 ◆ 交流阻抗法测试了极化电势对Au／硫醇／卵磷脂双层膜电化学行为的影响，其电容复数平面图和Nyquist图互相映证，说明了在一定的极化电势作用下，无论是给电极施加阳极极化电势还是阴极极化电势，双层膜的表观界面电容随极化电势的增大而增大，通过膜的异相电子传递表观反应电阻随极化电势的增大而减小，极化电势能提高电子隧穿的几率，加快电化学反应的进行。 ◆ 利用循环伏安测试技术，讨论了Au／硫醇／卵磷脂双层膜结合Ca²⁺的电化学行为。支持电解质溶液中，电极溶液界面电容随Ca²⁺浓度增大而增大，则膜厚减小。含Fe（CN）₆^3-/4-氧化还原对的支持电解质溶液，随Ca²⁺浓度增加及浸泡时间的延长，CV图倒“S”型曲线总体均有ΔI变宽趋势。表明Ca²⁺可能是和卵磷脂头基络合，削弱了卵磷脂头基和十八硫醇之间的作用，因此使双层膜变疏散。 ◆ 采用交流阻抗测试技术，从双层膜结合Ca²⁺后的电容图可得出，随Ca²⁺浓度增大，膜电容增大；从交流阻抗图谱得出，Ca²⁺浓度越大，浸泡时间越长，电化学反应电阻越小。进一步验证了前述结论，推断Ca²⁺诱导产生离子通道与HBM上有少量缺陷类似。首先，Ca²⁺能够束缚卵磷脂头基之后增加膜电容；其次，通过Ca²⁺诱导的微孔，离子和水分子渗透到HBM中，使相关电介质常数明显增加；最后，在HBM上的微孔扩大了HBM／电解质界面的面积。河北师范大学理学硕士学位论文 .以未组装良好存在针孔缺陷的金/十八硫醇成膜电极为电化学沉积模板，控制一定电位、采用计时电流法制备铜粒子。而有关利用自组装膜缺陷电沉积铜的研究，文献中少见报道，我们将自组装膜与纳米结合起来，力图为制备纳米颗粒提供一种新方法。更多还原

【Abstract】 Biomembrane is the barrier of cell surface and exchange channels of substance between inside and outside circumstance. Lecithin is the important ingredient of biomembrane and is connected with the metabolism of life. Due to the complexity of biomembrane, now it is impossible to observe and investigate the original biomembrane. People all along search one good model system of biomembrane to study the transmembrane electron transfer mechanism. HBM has both the stability of SAM and the resemblance of biomembrane. So it is generally considered that HBM is now the best system of transmembrane electron transfer. Ca2+ interaction with has long been reported. The base and premise of the experiments is to prepare the model system of biomembrane. HBM is chosen as the experiment model in this thesis. The substrate of HBM is SAMs of octadecanethiol. Then it is used to assemble the lecithin. The influence of Ca2+ ions on the electron transfer of Fe(CN)63-/4- couple on Au supported HBM is investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The main contents are as follows: Several models system of biomembrane has been summarized. Physiologicalfunction and application have been introduced briefly. Token technology of membrane has been reviewed. Effects of over potential to electrochemical behaviors of the octadecanethiol/lecithin HBM on gold has been measured by EIS. The complex plane capacitance plot and Nyquist plot reflect mutually. The results of EIS indicate that polar potential could augment apparent interface capacitance and decrease the electrochemical reaction resistance and accelerate the electron tunneling. The electrochemical behavior of HBM combined Ca2+ has been tested by CV. In the 0.2 M KC1 solution, interface capacitance becomes larger when increasing the concentration of Ca2+ ions. Then the membrane thickness becomes lower. In 0.2 M KC1 solution containing Fe(CN)63-/4- couple, the inverse sigmoid CV curves become broader. The interaction Ca2+ with the HBM may be a complexation of Ca2+ with lecithin head groups, which lowers the interactions between lecithin head group and octadecanethiol, making the HBM looselypacked. With the increase of Ca2+ concentration, the membrane capacitance is accelerated; With the increase of Ca2+ concentration and the immersed time of the electrode in the CaCl2, the electrochemical reaction is decreased. This is consistent with the conclusion drawn from CV experiments. It is concluded that ion-channels generated by Ca2+ ions play the role similar to micro defects. First, calcium ions can bind with lecithin head group and then increase the membrane capacitance. Second, the relative dielectric constant is greatly increased as the result of the permeation of ions and water molecules into HBM through Ca2+ induced micropores. Third, micropores in Au-HBM enlarge the area of the HBM/electrolyte interface. Cu particles have been prepared by chronoamperometry(C A) on not well-assembled thiol monolayers on gold for the first time, the study of electrodeposited Cu by SAM has been little reportded. The final aim is to provide a novel way to prepare nanoparticles.更多还原