Rational Design of an Optical Sensing System for Multivalent Proteins

A generic design principle for detection of multivalent interactions is described. A phospholipid bilayer consisting of natural and pyrene-derivatized phosphatidylcholines is used as both a supporting biomimetic surface and part of a signal transduction element. The pyrene excimer formed in the surface can act as fluorescence donor, and DABCY/BODIPY-FL covalently attached to receptor (GM1) can act as acceptors. Aggregation of the acceptor-tagged receptors resulting from multivalent binding of CT induces a decrease in efficiency of fluorescence quenching of the pyrene excimer by DABCY or energy transfer from pyrene excimer to BODIPY-FL. In the case using fluorescent acceptors that can undergo distance-dependent fluorescence self-quenching, combination of the lower energy transfer efficiency from the excimer and the acceptor's self-quenching capabililty make acceptor fluorescence go down even further by the binding. This scheme can achieve signal amplification and high surface density of the optical transduction elements, which, in return, require relatively small surface area.