Lamellar nanocomposite films of purple membrane and poly(acrylate)

Thin films comprising ordered stacks of purple membrane (PM) sheets containing the light-driven proton pump bacteriorhodopsin, were infiltrated with methacrylic acid monomers to produce intercalated lamellar bionanocomposites with expanded interlayer spacing. Subsequent in situ polymerization and crosslinking of the guest methacrylic acid molecules resulted in intercalated poly(acrylate)/PM free-standing films, which showed increased stability in water, structural integrity and enhanced resistance to ethanol degradation compared with PM control films or non-polymerized methacrylic acid/purple membrane layered nanocomposites. Studies on photocycle kinetics confirmed that the polymerized purple membrane films were functionally active, and showed an increase in the lifetime for the M-state intermediate of the photocycle. The results indicate that nanometre-thin layers of crosslinked poly(acrylate) can be synthesized in situ between the PM sheets to produce novel functional bionanocomposites with proton transfer and photochromic properties.