Protein crystallization imaging

The unambiguous and reliable identification of biological crystals remains a major obstacle in crystallography, particularly in the critical stage of initial screening experiments. Automated imaging at high-resolution in the visible range is often insufficient to identify all conditions that have or may result in crystals.

Crystallographers have often relied on the intrinsic fluorescence of aromatic amino acids, such as tryptophan, to differentiate between salt and protein crystals. UV fluorescence imaging detects the fluorescence from the tryptophan and in many cases yields high contrast images that aid in the characterization of crystallization drops. In some cases, proteins have very few tryptophan amino acids, or none at all, making it impossible to use UV fluorescence for imaging. The addition of a fluorescent molecule to one’s protein enables the ability to do visible fluorescence imaging and acquire high contrast images in very short imaging times with no sample damage.