Electrostatic Interactions Influence Protein Adsorption (but Not Desorption) at the Silica–Aqueous Interface Aaron C. McUmber Theodore W. Randolph Daniel K. Schwartz 10.1021/acs.jpclett.5b00933.s001 https://acs.figshare.com/articles/journal_contribution/Electrostatic_Interactions_Influence_Protein_Adsorption_but_Not_Desorption_at_the_Silica_Aqueous_Interface/2051610 High-throughput single-molecule total internal reflection fluorescence microscopy was used to investigate the effects of pH and ionic strength on bovine serum albumin (BSA) adsorption, desorption, and interfacial diffusion at the aqueous–fused silica interface. At high pH and low ionic strength, negatively charged BSA adsorbed slowly to the negatively charged fused silica surface. At low pH and low ionic strength, where BSA was positively charged, or in solutions at higher ionic strength, adsorption was approximately 1000 times faster. Interestingly, neither surface residence times nor the interfacial diffusion coefficients of BSA were influenced by pH or ionic strength. These findings suggested that adsorption kinetics were dominated by energy barriers associated with electrostatic interactions, but once adsorbed, protein–surface interactions were dominated by short-range nonelectrostatic interactions. These results highlight the ability of single-molecule techniques to isolate elementary processes (e.g., adsorption and desorption) under steady-state conditions, which would be impossible to measure using ensemble-averaging methods. 2015-12-17 08:34:55 nonelectrostatic interactions energy barriers pH diffusion coefficients adsorption kinetics reflection fluorescence microscopy strength 1000 times silica surface BSA desorption surface residence times Electrostatic Interactions Influence Protein Adsorption serum albumin