Cell-Directed Localization and Orientation of a Functional Foreign Transmembrane Protein within a Silica Nanostructure

A simple procedure for introducing functional exogenous membrane-bound proteins to viable cells encapsulated within a lipid templated silica nanostructure is described. In one method, bacteriorhodopsin (bR) was added directly to a Saccharomyces cerevisiae solution along with short zwitterionic diacylphosphatidylcholines (diC6 PC) and mixed with equal volumes of a sol precursor solution. Alternatively, bR was first incorporated into liposomes (bR-proteoliposomes) and then added to an S. cerevisiae solution with diC6 PC, and this was followed by mixing with sol precursor solution. Films prepared from bR added directly to diC6 PC resulted in bR localization near S. cerevisiae cells in a disordered and diffuse fashion, while films prepared from bR-proteoliposomes added to the diC6 PC/yeast solution resulted in preferential localization of bR near yeast cell surfaces, forming bR-containing multilayer vesicles. Importantly, bR introduced via proteoliposomes was observed to modulate pH gradients developed at the...