High-resolution label-free studies of molecular distribution and orientation in ultrathin, multicomponent model membranes with infrared nano-spectroscopy AFM-IR.

Affiliation

Jagiellonian University, Faculty of Physics, Astronomy and Applied Computer Science, Łojasiewicza 11, 30-348 Kraków, Poland; The Henryk Niewodniczański Institute of Nuclear Physics, Polish Academy of Sciences, Radzikowskiego 152, 31-342 Kraków, Poland. Electronic address: [Email]

Abstract

Biological membranes are undoubtedly very interesting systems. Unfortunately, their analysis is very complicated and therefore simplified artificial models, like Langmuir monolayers, are frequently applied. In this work a novel method of label-free monomolecular films analysis based on infrared nano-spectroscopy (AFM-IR) is presented. In order to verify applicability of this approach well-defined referential system of sphingomyelin (SM), cholesterol (Chol) and cyclosporin A (CsA) is applied. AFM-IR method allows to directly and chemoselectively map the distribution of components in model lipid membranes. Additionally the orientation of Chol and SM molecules in the monolayer is determined by application of two perpendicular infrared laser polarizations. This paper is the first report of using AFM-IR to analyze LB films with extremely high sensitivity.

Keywords

AFM-IR,Cyclosporin A,Langmuir-Blodgett films,Lipid rafts,Phase separation,

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