Photoinduced changes in structure and function of hexadecyl merocyanine dyes incorporated into lipid membranes

Abstract

In the purple membrane of Halobacterium halobium, bacteriorhodopsin (BR) acts as a proton pump leading to a transmembrane potential difference. A biomimetic system can be formed using merocyanine derivative dye which, when incorporated into a bilayer lipid membrane, creates a potential difference across the membrane. In this system, the dye molecules in combination with the lipid molecules act as a proton transport pump due to a light-induced conformational change of the dye. In this paper, we report the photovoltaic properties and crystal structure of hexadecyl merocyanine dye, together with the change in peak intensity in the X-ray diffraction pattern of the dye and dye-lipid system after illumination. We show that, at room temperature ( σ300 K), merocyanine dyes exhibit a crystalline form with a long-chain, fibre-like structure (diameter, 2.89 nm). However, on interaction with light, the crystalline form of the dye changes but the diameter remains the same.