Electrostatic Interactions Influence Protein Adsorption (but Not Desorption) at the Silica-Aqueous Interface.
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.
Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, Colorado 80309, United States.
Aaron C
AC
McUmber
Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, Colorado 80309, United States.
Theodore W
TW
Randolph
Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, Colorado 80309, United States.
Daniel K
DK
Schwartz
D000327:Adsorption; D004058:Diffusion; D011506:Proteins / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D012996:Solutions; D055672:Static Electricity; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
D011506:Proteins; D012996:Solutions; D014867:Water; D012822:Silicon Dioxide
DLVO; TIRF; electrostatic; hydrophobic; single molecule; van der Waals interactions