Instability of Protein Drops via Applied Electric Field: Mathematical and Experimental Aspects

Drops (5–15 μL) consisting of a protein solution readily crystallize and could provide an opportunity for a simultaneous examination of their thermodynamic and kinetic properties at various sizes. These drops experienced different pressures and therefore different surface tensions. Starting from the expression for the interface traction between protein fluid and silicon medium (with different dielectric constants), we have derived an equation accounting the influence of the electric field strength on the geometry of a protein drop. If the field strength increases, the lysozyme drop between two electrodes elongates and some crystals nucleate on the cathode side. In this situation numerous factors besides the intensity of the electric field—such as the solution composition, the charge and size of the protein molecule, the purity of the protein substance, and the consistency of bubbles of water—can have a significant effect on the crystallization rate and location.