Polarized attenuated total reflection Fourier transform infrared spectra were recorded on multilayer stacks of native gastric tubulovesicle membranes. The spectral intensity and linear dichorism were measured for average thicknesses ranging between 0 and 100 bilayers. Atomic force microscopy was used to investigate the orientation of the membranes at the top of the stack. Height profiles were obtained along randomly drawn lines and slopes were computed over various distances. Orientation distribution functions were obtained from the slopes and decomposed into Legendre polynomials. It was found that the second Legendre polynomials coefficient characterizing the membrane orientation was always larger than 0.9. It could therefore be concluded that the membrane tilt does not significanatly contribute to teh infrared dichorism, even for the largest thicknesses tested.
Ivanov, Dimitri, Nicolas Dubreuil, Vincent Raussens, Jean-Marie Ruysschaert, Erik Goormaghtigh