Abstract
Caged-Ca 2+ compounds such as nitrophenyl-EGTA (NP-EGTA) and DM-nitrophen (DMn) are extremely useful in biological research, but their use in live cells is hampered by cytoplasmic [Mg 2+]. We determined the properties of Ca 2+ release from NP-EGTA and DMn by using Oregon green BAPTA-5N to measure changes in [Ca 2+] after ultraviolet flash photolysis in vitro, with or without Mg 2+ present. A large fraction (65%) of NP-EGTA, which has a negligible Mg 2+ affinity, uncages with a time constant of 10.3 ms, resulting in relatively slow increases in [Ca 2+]. Uncaging of DMn is considerably faster, but DMn has a significant affinity for Mg 2+ to complicate the uncaging process. With experimentally determined values for the Ca 2+ and Mg 2+ binding/unbinding rates of DMn and NP-EGTA, we built a mathematical model to assess the utility of NP-EGTA and DMn in rapid Ca 2+-uncaging experiments in the presence of Mg 2+. We discuss the advantages and disadvantages of using each compound under different conditions. To determine the kinetics of Ca 2+ binding to biologically relevant Ca 2+ buffers, such as Ca 2+-binding proteins, the use of DMn is preferable even in the presence of Mg 2+.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
