JBS Deep Purple

Crystallization screening with high concentrations of precipitant and salt may lead to the formation of salt crystals. It is quite difficult to make a distinction between these false positives and true protein crystals. Staining of crystals with appropriate dyes is a very straightfor-ward method to differentiate between macromolecular crystals and salt crystals. Protein and salt crystals differ substantially in their solvent content. Small crystal dyes, like Biorbyt Deep Purple, are able to permeate the solvent channels of a protein, thus coloring the protein purple. In contrast, salt crystals are tightly packed and do not possess large solvent channels. They will therefore remain colourless.