engleski

Electrochemical impedance spectroscopy to understand interactions in phospholipid layers

A general mathematical model has been developed for the analysis of supported layers on conducting surfaces using electrochemi-cal impedance spectroscopy. The present paper describes the application of this model to two distinct systems: (i) Phospholipid monolayer of dioleoyl phosphatidylcholine (DOPC) on mercury which is undergoing a phase transition. It is shown that during the phase transition, the surface roughness increases, the zero frequency capacitance increases and the time constant of the extra capacitative element decreases. This is consistent with the co-existence of two phases on the electrode over a 0.02 V potential domain which is also commensurate with the layer on the electrode consisting of two components, phospholipid and water respectively. (ii)The second system is extracted ex situ sea surface microlayer material (ssm) deposited on mercury and also incorporated as a mixed monolayer with DOPC. The monolayers of hexane extracted ssm show less surface roughness than monolayers of dichloromethane extracted ssm. This is confirmed by BAM imaging of the layers at he air-water interface. Hexane extracted ssm shows less compatibility with DOPC than dichloromethane extracted ssm due to the formation of defects in mixed layers.

Impedance spectroscopy; sea-surface microlayer; phospholipids

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