Non-specific clustering of histidine tagged green fluorescent protein mediated by surface interactions: the collective effect in the protein-adsorption behaviour

Abstract

The chemically programmed non-fouling surfaces were used to observe the surface assembly behaviour of hexahistidine tagged Green Fluorescent Protein (His-GFP) as a model protein. In this particular case, site-selective physisorption of His-GFP was achieved in the absence of metal ions. This preference does not arise from surface charge, wettability or topographic differences between regions. We found that His-GFP has a tendency to centre into an array of marked squares and acquires a template shape on the entire non-fouling surface when both the internal and surrounding areas present carboxylate groups. This surface-directed organization of protein in assemblies is an unusual example of non-specific molecular interactions transfer to a higher scale objects organization. Furthermore, we performed a proof-of-concept study for the autonomous formation of protein microarrays with uniform orientation of the tagged protein molecules on the surface. Periodic protein microarrays were formed spontaneously within about one minute after the deposition of a few drops of protein solutions on the substrate. We propose a simple, gentle and cost-effective approach to fabrication of protein microarrays, which can be done by the end-user. This phenomenon of collective protein clustering into large scale patterns may help to assess experimentally how the peripheral proteins arrange into separate domains of the cell membrane.