Supramolecularly Oriented Immobilization of Proteins Using Cucurbit[8]uril

A supramolecular strategy is used for oriented positioning of proteins on surfaces. A viologen-based guest molecule is attached to the surface, while a naphthol guest moiety is chemoselectively ligated to a yellow fluorescent protein. Cucurbit[8]uril (CB[8]) is used to link the proteins onto surfaces through specific charge-transfer interactions between naphthol and viologen inside the CB cavity. The assembly process is characterized using fluorescence and atomic force microscopy, surface plasmon resonance, IR-reflective absorption, and X-ray photoelectron spectroscopy measurements. Two different immobilization routes are followed to form patterns of the protein ternary complexes on the surfaces. Each immobilization route consists of three steps: (i) attaching the viologen to the glass using microcontact chemistry, (ii) blocking, and (iii) either incubation or microcontact printing of CB[8] and naphthol guests. In both cases uniform and stable fluorescent patterns are fabricated with a high signal-to-noise ratio. Control experiments confirm that CB[8] serves as a selective linking unit to form stable and homogeneous ternary surface-bound complexes as envisioned. The attachment of the yellow fluorescent protein complexes is shown to be reversible and reusable for assembly as studied using fluorescence microscopy.