Surface-induced spreading phenomenon of protein clusters

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.