Isocyanates are good electrophiles that have been used for protein modification. However, they have limited stability in water. As a result isothiocyanates have been developed at less hydrolytically sensitive variants. Molecules like fluorescein isothiocyanate (FITC) have been used extensively to fluorescently modify proteins. Draw the product of a lysine side chain with FITC. (for the sake of simplicity we are just using a model for lysine's side chain butyl amine)