Aggregation
Kinetics of Hematite Particles in the
Presence of Outer Membrane Cytochrome OmcA of <i>Shewanella oneidenesis</i> MR‑1
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Abstract
The aggregation behavior
of 9, 36, and 112 nm hematite particles
was studied in the presence of OmcA, a bacterial extracellular protein,
in aqueous dispersions at pH 5.7 through time-resolved dynamic light
scattering, electrophoretic mobility, and circular dichroism spectra,
respectively. At low salt concentration, the attachment efficiencies
of hematite particles in all sizes first increased, then decreased,
and finally remained stable with the increase of OmcA concentration,
indicating the dominant interparticle interaction changed along with
the increase in the protein-to-particle ratio. Nevertheless, at high
salt concentration, the attachment efficiencies of all hematite samples
gradually decreased with increasing OmcA concentration, which can
be attributed to increasing steric force. Additionally, the aggregation
behavior of OmcA–hematite conjugates was more correlated to
total particle–surface area than primary particle size. It
was further established that OmcA could stabilize hematite nanoparticles
more efficiently than bovine serum albumin (BSA), a model plasma protein,
due to the higher affinity of OmcA to hematite surface. This study
highlighted the effects of particle properties, solution conditions,
and protein properties on the complicated aggregation behavior of
protein–nanoparticle conjugates in aqueous environments