Gramicidin A interaction at a dioleoyl phosphatidylcholine monolayer on a mercury drop electrode

A biosensor where the sensing surface is a fluid dioleyl phosphatidylcholine monolayer (DOPC) deposited on a mercury drop was used. The lipid monolayer was held in 0.1 M NaCl and a concentration of gramicidin A in the range 0-12 nM was used. Electrochemical impedance spectroscopy in the frequency range 0.1-65 kHz was employed to investigate how the defect-free monolayer responds to interactions of gramicidin A in solution. The data was analyzed both with multivariate data analysis and classical electrochemical methods. The principal component analysis of the resulting impedance spectra gave a linear dependence on the concentration of gramicidin A. An increasing permittivity was observed in the low-frequency regime with increasing concentration of gramicidin A in solution.