Laser photolysis of caged calcium: rates of calcium release by nitrophenyl-EGTA and DM-nitrophen

Nitrophenyl-EGTA and DM-nitrophen are Ca2+ cages that release Ca2+ when cleaved upon illumination with near-ultraviolet light. Laser photolysis of nitrophenyl-EGTA produced transient intermediates that decayed biexponentially with rates of 500,000 s-1 and 100,000 s-1 in the presence of saturating Ca...

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Bibliographic Details
Published in:Biophysical journal 1996-02, Vol.70 (2), p.1006-1016
Main Authors: Ellis-Davies, G.C., Kaplan, J.H., Barsotti, R.J.
Format: Article
Language:English
Subjects:
Acetates - chemistry
Acetates - radiation effects
Biophysical Phenomena
Biophysics
Calcium - administration & dosage
Chelating Agents - chemistry
Chelating Agents - radiation effects
Egtazic Acid - analogs & derivatives
Egtazic Acid - chemistry
Egtazic Acid - radiation effects
Ethylenediamines - chemistry
Ethylenediamines - radiation effects
Fluorescent Dyes
Hydrogen-Ion Concentration
In Vitro Techniques
Indicators and Reagents
Kinetics
Lasers
Models, Chemical
Organic Chemicals
Photolysis
Temperature
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Summary:Nitrophenyl-EGTA and DM-nitrophen are Ca2+ cages that release Ca2+ when cleaved upon illumination with near-ultraviolet light. Laser photolysis of nitrophenyl-EGTA produced transient intermediates that decayed biexponentially with rates of 500,000 s-1 and 100,000 s-1 in the presence of saturating Ca2+ and 290,000 s-1 and 68,000 s-1 in the absence of Ca2+ at pH 7.2 and 25 degrees C. Laser photolysis of nitrophenyl-EGTA in the presence of Ca2+ and the Ca2+ indicator Ca-orange-5N produced a monotonic increase in the indicator fluorescence, which had a rate of 68,000 s-1 at pH 7.2 and 25 degrees C. Irradiation of DM-nitrophen produced similar results with somewhat slower kinetics. The transient intermediates decayed with rates of 80,000 s-1 and 11,000 s-1 in the presence of Ca2+ and 59,000 s-1 and 3,600 s-1 in the absence of Ca2+ at pH 7.2 and 25 degrees C. The rate of increase in Ca(2+)-indicator fluorescence produced upon photolysis of the DM-nitrophen: Ca2+ complex was 38,000 s-1 at pH 7.2 and 25 degrees C. In contrast, pulses in Ca2+ concentration were generated when the chelator concentrations were more than the total Ca2+ concentration. Photoreleased Ca2+ concentration stabilized under these circumstances to a steady state within 1–2 ms.
ISSN:0006-3495
1542-0086
DOI:10.1016/S0006-3495(96)79644-3