Bio-Optical Composites for Rapid Analyte Detection

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DESCRIPTION: (Applicant's abstract) Using well established immunological and phage-display technologies proteins can be designed that bind almost any arbitrary analyte with great specificity and affinity. These features suggests that biomaterials would be ideally suited for use in sensor applications. Unfortunately, however, there are no convenient and general means of detecting protein-ligand binding in near real-time. A potentially generalizable solution to this difficulty stems from the observation that many proteins fold only upon binding their target ligands. This folding represents effectively the largest possible change in the physical properties (structure and dimensions) of the polypeptide chain. Here we propose to rationally introduce binding-induced folding into otherwise well folded proteins and to couple this large, binding-specific conformational change with an easily detectable change in the properties of covalently attached, optical reporter groups. In order to generate binding-specific optical signals we will use conjugated polymers and semiconductoi ianomaterials with optical properties far superior to those of naturally occurring chromaphores. These materials act as a "sensor ensemble" (SE) that has the capability to terminate the optical emission of multiple )ptical sites in the presence of a single specific quencher molecule. By building a quencher-protein-SE construct, we will generate large, binding-specific changes in sensor emissivity as folding removes the quencher from proximity to the SE. This provides the means for a biosensor-optical platform capable of extremely large optical amplification. The proposed research integrates the complimentary expertise researchers in the diverse fields of biochemistry, organic and inorganic materials science and optical spectroscopy. The proposal details an approach suitable for the rational production of binding-induced folding Lnd the synthesis of conjugated polymer-protein and inorganic nanomaterial-protein composites. Also included are simple diagnostic tests for determining the utility of these biocomposites for the detection of important substrates such as specific DNA sequences and retroviral products. Successful completion of the proposed research will prove the feasibility a novel biophotonic sensor technology suitable for the real-time detection array of compounds of significant clinical, industrial or defense interest.