A Simple Nondestructive, Cost-Effective Method for Differentiation of Protein Crystals from Salt Crystals by Using a Natural Dye

The identification of biomolecules including protein and peptides is a crucial step for moving toward data collection and structure determination. The previous identification methods include analyzing crystal through X-ray diffraction, or using sophisticated instrument having a UV-radiation source and camera. However, not all laboratories are able to afford these costly techniques. Recently, some dyes are also available in the market for the identification of protein crystals. However, they are costly, and they might have a destructive effect on protein crystals. Keeping in mind the aforementioned points, we have identified a new dye which can be used for the identification of protein crystal. Lawsone (2-hydroxy-1,4-naphthoquinone) is a natural dye isolated from Eichhornia crassipe. The dye was tested on lysozyme, proteinase K, and thaumatin. The data of only lysozyme crystals was collected and processed. The result shows that there is no binding interaction of lawsone with lysozyme.