Abstract

In this study we investigate the behavior of protein clusters on solid surfaces. It is shown that clusters
consisting of up to several hundreds of protein monomers can form in solution even at low monomer
concentrations and subsequently adsorb to the surface. Using FRET imaging, a significant increase in
the inter-protein distance of cluster proteins in time (e.g. a 46% increase after 7 hours on a hydrophobic
surface) was revealed indicating that protein clusters spread upon contact with the surface. The
spreading rate was strongly dependent on the surface chemistry: fast spreading on hydrophobic, slow
spreading on hydrophilic surfaces. Moreover, we found that protein clusters could be deposited on
a hydrophobic, OTS-coated surface even though it was already covered with a layer of pre-adsorbed
protein monomers. As a result of their high surface mobility these monomers receded from that area to
which the protein clusters spread. The molecular rearrangements taking place when a protein cluster
deposits onto a surface are discussed in the context of the experimental results.