Electrochemical and Photon Polarization Modulation Infrared Reflection Absorption Spectroscopy Study of the Electric Field Driven Transformations of a Phospholipid Bilayer Supported at a Gold Electrode Surface

Abstract

Electrochemistry and polarization modulation Fourier transform infrared reflection absorption spectroscopy (PM-FTIRRAS) was employed to investigate fusion of small unilamellar vesicles of 1,2dioyl- sn-glycero-3-phosphatidyl choline (DOPC) onto the Au(111) electrode. Electrochemical studies demonstrated that the DOPC vesicles fuse and spread onto the gold electrode surface at small charge densities −8 μC cm −2 < σ M < 0 μC cm −2(if the static electric field is <2 × 10 8 V/m) to form a bilayer. At σ M < −8 μC cm −2, the film is detached from the electrode surface; however, the film remains in close proximity to the surface. The PM-FTIRRAS experiments demonstrated that the field-driven transformation of the film involves changes in hydration, orientation, and conformation in the polar headgroup region and that changes in the packing and tilt of the acyl chains are consequences of the headgroup rearrangements.