Study on physisorption between phycocyanin and gold nanoparticles.

Interactions between nanoparticles (NPs) and biomolecules, especially proteins, have attracted increasing attention. Photoresponsive proteins have shown high potential for optogenetic research. The combination between optogenetics and nanotechnology will bring a new biological era in which photoresponsive proteins will inevitably encounter NPs, therefore their interactions will be a key point to investigate. Here, we have systematically studied the interactions between a photoresponsive protein (called phycocyanin, PC) and a typical kind of amphiphilic polymer-coated gold NPs (AP-AuNPs) using fluorescence quenching methods. The results showed that the binding constant between PCs and AP-AuNPs is 4.427 × 106  M-1 with a positive cooperativity, and the robust affinity was hydrophobic interaction driven mortise-tenon conjugation, which could even resist gel electrophoresis. These results could also shed light on potential designs for building up artificial protein-NP light-harvesting systems.