UV microscopy at 280 nm is effective in screening for the growth of protein microcrystals

This paper describes the relatively simple modification of a light microscope to operate with ultraviolet-based optics. Using a 280 nm UV illumination source, protein microcrystals are readily visualized in gels made from hydrated bilayers of phospholipids. Non-colored proteins stand out as clearly as colored proteins in this system, the imaging of which is based on UV absorption by tryptophan residues. In addition, protein crystals are easily distinguished from salt crystals. Artifacts from the lipid-based crystallization medium, which are frequently seen in brightfield microscopy, are greatly reduced when viewed in this UV-based microscope.