Artificial chaperones based on mixed shell polymeric micelles: insight into the mechanism of the interaction of the chaperone with substrate proteins using Förster resonance energy transfer

Controlled and reversible interactions between polymeric nanoparticles and proteins have gained more and more attention with the hope to address many biological issues such as prevention of protein denaturation, interference of the fibrillation of disease relative proteins, removing of toxic biomolecules as well as targeting delivery of proteins, etc. In such cases, proper analytic techniques are needed to reveal the underlying mechanism of the particle-protein interactions. In the current work, Förster Resonance Energy Transfer (FRET) was used to investigate the interaction of our tailor designed artificial chaperone based on mixed shell polymeric micelles (MSPMs) with their substrate proteins. We designed a new kind of MSPMs with fluorescent acceptors precisely placed at the desired locations as well as hydrophobic domains which can adsorb unfolded proteins with a propensity to aggregate. Interactions of such model micelles with a donor-labeled protein-FITC-lysozyme, was monitored by FRET. The fabrication strategy of MSPMs makes it possible to control the accurate location of the acceptor, which is critical to reveal some unexpected insights of the micelle-protein interactions upon heating and cooling. Preadsorption of native proteins onto the hydrophobic domains of the MSPMs is a key step to prevent thermo-denaturation by diminishing interprotein aggregations. Reversible protein adsorption during heating and releasing during cooling have been confirmed. Conclusions from the FRET effect are in line with the measurement of residual enzymatic activity.