Use of Protein Thin Film Organized by External Electric Field as a Template for Protein Crystallization

The well-known difficulty to obtain high-quality protein crystals has motivated researchers to come up with new methods or modifications of established crystallization methods to stimulate the growth of good diffracting crystals. In the present work, a new approach, using a protein thin film organized by external electric field (EEF) as a template for protein crystal growth, is introduced. This method increased nucleation of hen egg white lysozyme (HEWL) in comparison with the classical vapor diffusion method, besides improving crystal morphology and size. X-ray diffraction analyses indicated improvements in crystal quality. When HEWL was crystallized at pH 6.2, in which this protein presents biological activity, the control crystal presented a poorly ordered crystalline structure and a low resolution cutoff at 3.42 Å, whereas the crystal grown with the EEF protein film revealed a high-resolution limit at 1.67 Å. These results suggest that protein films organized by EEF may improve protein crystals and their data quality.