DM-nitrophen AM is caged magnesium

DM-nitrophen is a photolabile derivative of EDTA and therefore functions as either caged Ca(2+) or caged Mg(2+). Several papers have been published recently which use the AM ester to load intact cells with DM-nitrophen; under these conditions it is caged Mg(2+). In this commentary, I give a short history of the development and application of caged Ca(2+) probes, explaining why EGTA and BAPTA-based Ca(2+) cages are to be preferred for the photorelease of Ca(2+) under normal intracellular conditions.