Understanding the formation and adsorption of 2-dimensional and 3-dimensional protein aggregates on a solid surface
M. Rabe, D. Verdes, S. Seeger
University of Zurich, CH
Keywords: protein aggregation, FRET imaging, protein-surface interactions
Abstract:We have comprehensively investigated the structure of protein assemblies that form spontaneously upon protein adsorption on solid interfaces using a surface sensitive fluorescence imaging technique. It was found that proteins usually do not cover surfaces in a homogeneous monolayer but tend to group together into lose assemblies or even into tight aggregates. If several proteins are organized in a monolayer-like, flat assembly they are typically referred to as 2-dimensional surface crystal although they do not necessarily need to be tightly packed. In our work we show that the formation of such structures is the consequence of cooperative protein adsorption. Macroscopically these effects necessarily lead to an inhomogeneous surface distribution which can be imaged with our technique. However, also 3-dimensional protein aggregates are frequently observed on solid surfaces. In contrast to 2-dimensional surface aggregates they do not build up on the surface but are already formed in solution before they can adsorb on the surface. Once a protein cluster has settled onto the surface it immediately starts to spread and thereby occupies a steadily growing surface area. This process has been visualized using FRET imaging and was found to strongly depend on the surface chemistry.