Thermodynamic Analysis of Protein-Nanoparticle Interactions Links Binding Affinity and Structural Stability

When nanoparticles and nanoplastics enter biological fluids, their surfaces are rapidly coated with proteins, forming a corona that governs biological responses. However, understanding protein- surface interaction energetics remains a significant challenge. Here, we examine how protein charge distribution affects adsorption to polystyrene nanoparticles (PSNPs) by generating a series of lysine-to-alanine variants of the GB3 protein. Using isothermal titration calorimetry (ITC), we found that the K19A variant binds most strongly to both non-functionalized and carboxylate- functionalized PSNPs. ITC thermograms indicate that K19A forms a stable monolayer, while other variants exhibit multilayer adsorption. We hypothesize that removing lysine at position 19 creates a flatter, more neutral interaction surface that promotes efficient initial binding. Fluorescence denaturation experiments show that PSNPs destabilize GB3 protein variants, and binding correlates strongly with protein unfolding (r = 0.82, p View larger version (31K): org.highwire.dtl.DTLVardef@1741baforg.highwire.dtl.DTLVardef@1c5be81org.highwire.dtl.DTLVardef@15e3118org.highwire.dtl.DTLVardef@e92583_HPS_FORMAT_FIGEXP M_FIG C_FIG