The caged Ca2+ chelator, DMNP-EDTA (also known as DM-Nitrophen) upon photolysis, the Kd for Ca2+ increases from 5 nM to 3 mM. Thus, photolysis of DMNP-EDTA complexed with Ca2+ results in a pulse of free Ca2+.
MSDS (PDF): MSDS 50050