Photochemical DNAzyme inactivation using the caged DNA decoy DD4 (4 nM) complementary to the catalytic core of the DNAzyme (40 nM) in the presence of RNA substrate (4 nM; 10 mM MgCl2, pH 8.2, 15 mM Tris buffer). Prior to UV irradiation normal DNAzyme function is observed. However, upon decaging (1 min, 365 nm, 25 W), the DNA decoy is capable of hybridizing to the catalytic core, completely inhibiting DNAzyme catalyzed cleavage of RNA.