Gangadhar Dhulipala, J. Miksovska
Feb 1, 2009
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Journal
Biophysical Journal
Abstract
DM-nitrophen is a popular caged calcium compound that allows for a rapid increase in calcium concentration from hundred nanomolar to tens to hundred micromolar level on the microsecond timescale. To fully understand the mechanism of calcium photo-release from DM-nitrophen, we have used photothermal beam deflection technique to investigate time-profiles of volume and enthalpy changes associated with DM-nitrophen photodissociation. Our data show that the photodissociation of calcium loaded DM-nitrophen occurs as a two-step process. The first step takes place within ∼ 10 μs upon photolysis and is associated with a volume decrease of -7 mL mol−1 and enthalpy change of 66 kcal mol−1. On the longer timescale (τ = 200 μs), the second event with a positive volume change of 7 mL mol−1 and enthalpy change of 8 kcal mol−1 was detected. These data are in agreement with the previous fluorescence studies showing that calcium release from DM-nitrophen occurs as a two step process.View Large Image | View Hi-Res Image | Download PowerPoint Slide