A ferrochelatase inhibitor and turn-on biosensor for DNA; inhibits ferrochelatase in mouse liver mitochondria in vitro; inhibits ferrochelatase in mice at 80 nmol, i.v. leading to porphyrin accumulation in isolated liver mitochondria; has been used as a turn-on biosensor for target DNA sequences when used in complex with a G-quadruplex-forming sequence fused to a DNA sequence complementary to the target sequence; ex/em = 399/610, respectively