Design of a Liquid Cell for Structural Investigations of Supported Lipid Membrane by Synchrotron X-Rays Over a Wide Temperature Range, from Lower to Higher than Ambient

Abstract

An oxygen-free copper-based cell has been designed to perform X-ray scattering experiments from the solid-supported lipid membranes immersed in water. This cell can be used to investigate the structural changes in the membrane depending on the composition of the lipids, the effects of temperatures, and the changes in arrangements of the lipids in the membrane on the addition of the external molecules. The design of the cell has been optimized to get a good signal-to-noise ratio (SNR) for the measurements of  X-ray reflectivity and grazing incidence diffraction by controlling the X-ray path within the liquid in the cell and easy operation for variable liquid temperature. This very low-cost temperature-controlled setup, developed in our laboratory, can perform in situ X-ray measurements at various temperature ranges—starting from around 4°C up to 70°C which is very relevant to study the phase transition temperature of the lipids constituting the cell membranes. The detailed mechanical design of the cell and electrical control mechanism of the temperature of the liquid inside the cell has been discussed here. One such X-ray reflectivity measurement is shown here to express the capability of the cell for the study of the solid-supported bilayer sample composed of dipalmitoyl phosphocholine lipid at two different temperatures, below its phase transition temperature.