As an alternative method, photocatalytic conversion of arylazide to aniline has been utilized in photo-uncaging techniques. This approach also produces o-thioquinone methide, an electrophilic species used for protein modification and subcellular proteomic mapping. 101 Scheme 6. Protein modification utilizing energy transfer from a photocatalyst. (A) Activation of modifiers through energy transfer from an excited photocatalyst. (B) Reactive species that can be generated by this method, capable of labeling various amino acid residues. (C) The structure of the photocatalysts used in this method.