A gold nanoparticle platform for protein-protein interactions and drug discovery.

Gold nanoparticles hold great promise for studying protein-protein interactions because of their intrinsic optical properties. Pink when in a homogeneous suspension, the solution turns blue-gray when particles are drawn close together, for example, when immobilized proteins specifically interact with each other. However, the nanoparticle stability, size, and method of protein attachment contribute to the unreliable outcome of current assays. To overcome these hurdles, we developed novel and reliable methods first to synthesize homogenous particles of optimal diameter and second to apply a heterologous NTA-Ni-SAM coating for controlled orientation and optimal presentation of histidine-tagged proteins. Both methods were proven to greatly enhance assay sensitivity and specificity by increasing the signal and minimizing the nonspecific binding. Our assay reproducibly detected known protein-protein interactions and unambiguously identified small molecules that inhibited them. We believe our gold nanoparticle bioassay is a versatile and trustworthy new platform for analyzing protein-protein interactions and high-throughput screening of small-molecule inhibitors.