Abstract: Disclosed is a method for preparing a photosensitive peptide which is capable of being activated or deactivated in a biological system, including the steps of: (a) providing an amino acid including a photolabile molecule; and (b) incorporating the amino acid into a peptide during synthesis, wherein incorporation of the amino acid into the peptide produces a photosensitive peptide. Also disclosed is a method of introducing a photosensitive cleavage site into a synthetic peptide, including synthesizing a synthetic peptide having at least one photolabile amino acid, wherein the photolabile amino acid is positioned within the synthetic peptide so that upon irradiation the synthetic peptide is cleaved.