Fabrication and Control of Two-Dimensional Crystalline Arrays of Protein Molecules

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Abstract
Fabrication methods to produce two-dimensional (2D) crystalline arrays of protein particles are reported. The key innovation in this fabrication is the spreading wetting process which uses the deformable substrate surface such as mercury surface (mercury method) or the air-water interface (subphase method), where protein solution spread to yield a thin liquid film. The thin film of protein solution leaves a monolayer state of protein molecules, for example 2D crystalline films, after the condensation of solute protein molecules by solvent removal by evaporation. The significance of the film fabrication lies in its active natures to harness the directional transport of particles driven by spreading or convective flow of the solution. Wild type and mutant ferritins were employed to spread their solution on substrates and align them to 2D arrays. The control of crystal forms, say hexagonal or tetragonal, has been pursued by changing the interprotein interaction through mutagenic replacements of amino acids at specific sites on the protein surface. With recombinant ferritins, conversion of crystal forms from hexagonal to oblique is observed by eliminating strong interaction of salt bridge kind between adjacent molecules in the crystal.