Insertion of gramicidin A channel in an artificial DMPC membrane supported on polyaniline derivatized with 1-octadecanethiol.

摘要

Ion channels are nanosized proteins with highly selective pores that enable the transport of inorganic ions (K+, Cs +, Ca++, Li+ Na+) and charged molecules through biological membranes. During their transport, these ions or charged molecules create and electrochemical gradient. Due to their biological importance, engineered ion-channels incorporated in lipid bilayers become the focus of many research groups in the medical and biological fields. Currently, their investigations primarily focus on their interface architecture with the proper materials that can enhance the specific biological event of the ion channel. In this regard, a variety of polymeric materials have been investigated by the instrumentality of surface functionalization.;The aim of this thesis was to incorporate gramicidin A (a pentadecapeptide antibiotic isolated from Bacillus brevis) as a channel, embedded within a dymiristoyl-sn-glycero-phosphatidylcholine (DMPC) bilayer membrane. Gramicidin A has the property to bind certain ions such as K+, Cs+, Rb+, Li+ Na+, or transport them across the membrane through its pore. The objective is to evaluate the system for ionic response to potassium cation (K+), and an electrically conducting polymer such as polyaniline (PANI) was chosen as the material to support the lipid bilayers.;Conducting Polymers (CP) are known to be excellent materials and are widely used in several research areas. Their pi-conjugation system makes them prone to be oxidized or reduced, which can be used as a means to modify them with various functional groups. For instance, CP can be modified to bind biomolecules and provide mechanical strength to membranes. Owing to their electrical conductivity or charge transport properties, CP are good electrons promoters. Their modification only alters their surface properties without changing their bulk properties.;In this research, PANI film was covalently derivatized with 1-octadecanethiol to enhance its properties as a solid support of a lipid membrane. The film was characterized by cyclic voltammetry (CV) and potentiometric methods before and after derivatization. The membrane deposition and the incorporation of gramicidin A were carried out by the Langmuir-Blodgett technique (LB). Appyling this technique, layers of an amphiphile can be built on a surface by sequential immersion and/or retraction of the substrate at the air-water interface.;The customized system was tested potentiometrically for potassium ion binding. Data supporting the Gramicidin A channel formation in the same matrix used for Langmuir Blodgett deposition technique was also generated by circular dichroism.