Uncaging

Uncaging of Ca²⁺ from DM-Nitrophen

The UV-Flash was coupled via a 2-port epifluorescence condenser to a Zeiss Axiovert 100 microscope. The preparation was viewed through a Zeiss FLUAR 100x, 1.3, oil immersion objective. A cell was loaded via the patch pipette with a solution containing: 4 mM DM-Nitrophen, 2 mM CaCl₂ , 0.2 mM fura-2, 20 mM Na-Hepes,... A single full flash elevates intracellular free Ca²⁺ to a concentration that rapidly activates Ca²⁺-dependent K⁺ channels.

Figure 1: A single full flash elevates Ca²⁺ to several tenths of micromolar. The ratio changed from 1.29 to 12.8 (fura-2 is completely saturated), and BK-channels were rapidly activated.

Comment: The estimated free Ca²⁺ concentration was in the order of tenths of micromolars. Higher concentrations can easily be reached by increasing the Ca²⁺-loading of DM-Nitrophen and its concentration.