Investigations on the use of graphite electrodes using a Hull-type growth cell for the electrochemically-assisted protein crystallization

This paper describes the use of an electrochemical Hull type cell adapted for protein crystallization evaluating three inclination angles (45°, 60° and 90°). For optimization experiments, classical platinum wire electrodes were used and once the best geometry was known, they were replaced with 0.5 mm diameter low-cost graphite automatic pencil leads. Using Pt and graphite, the cell with electrodes fitted at 90° showed the most favorable geometry for promoting the growth of lysozyme crystals with enough size for protein crystallography (between 200-250 μm in solution, and between 500-650 μm in gel). The crystalline quality (mosaicity and I/σ(I) ratio) of crystals obtained at different current values, was studied using these graphite electrodes and was compared with those protein crystals grown using platinum wire electrodes in solution as well as in gel experiments. These studies showed that it is possible to efficiently substitute the platinum electrodes by the low-cost graphite electrodes. This cell could be a first approach to a disposable cell for a large-scale use of electrochemically-assisted crystal growth method.