STABILIZATION OF THE MEMBRANE-PROTEIN BACTERIORHODOPSIN TO 140-DEGREES-C IN 2-DIMENSIONAL FILMS

TWO-DIMENSIONAL assemblies of membrane proteins (see ref. 1, for examp le) such as bacteriorhodopsin are of current interest because of their potential application in technological areas as diverse as molecular electronics and optical switching2, molecular sieves3,4 and the lithog raphic fabrication of nanometre-scale patterns5,6. Here we report that bacteriorhodopsin7-9 can retain its folded native structure to temper atures as high as 140-degrees-C when incorporated in multilayer struct ures of self-assembled, ordered films. Synchrotron X-ray scattering re veals that, under hydrated conditions, the two-dimensional lattice in multilayer films exhibits a reversible solid-liquid transition at abou t 69-degrees-C, followed by irreversible denaturing of the bacteriorho dopsin at about 90-degrees-C. But in dry films the melting transition and denaturation are suppressed up to 140-degrees-C. These results sug gest that it may be feasible to use multilayer assemblies of functiona l proteins and enzymes10,11 in high-temperature applications.