Characterization of Proton Transport across a Waveguide-Supported Lipid Bilayer

Abstract

Cellular energy transduction processes are often driven by transmembrane ion gradients, and numerous artificial biomembrane systems have been developed that allow for chemically or light-induced charge transport into/out of liposomes. Liposomal architectures, however, are not readily interfaced to a solid-state transducer. Formation of an ion gradient across a planar-supported membrane, "wired" to a substrate electrode, may ultimately allow utilization of the potential energy to drive other electrochemical processes. Described here is a novel conductive polymer/planar waveguide assembly that provides for highly sensitive transduction of proton transport across a planar-supported lipid bilayer (PSLB). A quinone proton shuttle is embedded in the PSLB, which is coupled to the planar optical waveguide electrode through a pH-sensitive, self-assembled conductive polymer film. Interfacial potential and absorbance changes in the conductive polymer film provide for sensitive characterization of transmembrane proton transport. The general and flexible nature of this architecture makes it adaptable to many different types of transmembrane transport chemistries, particularly light-activated systems.

Final Scientific/Technical Report - Biomimetic Energy Transduction: Artificial Photosynthesis in a Stabilized Lipid Membrane Coupled to a Semiconductor

“…From estimates of the pK a for ITO/(PANI/PAA) 2 and the number of proton acceptor sites in the ionic reservoir, a transmembrane proton flux of 74 pmol/minute is calculated. 1 This value equates to a transport rate of 0.07 s -1 per BQ, which agrees well with previous estimates of diffusion-limited, charge transport by benzoquinone and its structurally related analogs in lipid bilayers. 14,18,21,23 C. Light-driven, transmembrane proton pumping.…”

“…More detailed accounts of the research supported in whole or part by this grant have appeared or will appear in publications. [1][2][3][4][5][6][7][8][9][10][11][12][13] B. Transduction of an ion gradient across a PSLB coupled to an electroactive waveguide through a conductive polymer film. A number of liposome-based systems have been developed that allow for chemically-or light-induced transport of ions into or out of the vesicle interior.…”

Surface Coatings Based on Polysilsesquioxanes: Solution‐Processible Smooth Hole‐Injection Layers for Optoelectronic Applications

“…TCOs find increasing application in many optoelectronic devices, such as organic light-emitting diodes (OLED), [1,2] organic photovoltaics (OPV), [3][4][5] or electrochemical sensors. [6,7] Interfacial engineering of electrical devices between the anode surface and the overlying organic layer is an important method for tuning electronic properties. In particular, the need for precise control of the electrode/ organic semiconductor interface is apparent in the area of polymer light-emitting diodes (PLED).…”

ITO/Poly(Aniline)/Sol-Gel Glass: An Optically Transparent, pH-Responsive Substrate for Supported Lipid Bilayers

“…For example, doping/dedoping of poly(aniline) (PANI) can be accomplished by changing the pH of the surrounding medium, and this property makes PANI useful as a pH-sensing material [24]. Both electrochemical and optical pH sensors based on PANI have been reported [22, 23, 25–27], which suggests the possibility of using a PANI-coated electrode as a proton-selective substrate for a planar supported lipid bilayer (PSLB) [28, 29]. …”