jz5b00933_si_001.pdf (349.52 kB)
Electrostatic Interactions Influence Protein Adsorption (but Not Desorption) at the Silica–Aqueous Interface
journal contribution
posted on 2015-12-17, 08:34 authored by Aaron
C. McUmber, Theodore W. Randolph, Daniel K. SchwartzHigh-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.