The calcium concentration clamp: spikes and reversible pulses using the photolabile chelator DM-nitrophen

Cell Calcium. 1993 Feb;14(2):87-100. doi: 10.1016/0143-4160(93)90079-l.


New procedures are described for producing brief transients and reversible elevations in [Ca] that can be used to quantitatively control the concentration of cytoplasmic calcium. If the photolabile calcium chelator DM-nitrophen, partially bound to calcium, is exposed to steady illumination, [Ca] can be raised from a few nM to up to 10 microM for durations of 100 ms or longer, depending on light intensity and duration. An association rate of calcium with nitrophen of 1.5 x 10(6) M-1s-1 was estimated from measurements of [Ca] using the fluorescent indicator Fluo-3, and calcium was found to speed the photolysis of nitrophen 2.5-times. Partial photolysis of DM-nitrophen partly loaded with calcium elicits a [Ca] spike of over 100 microM lasting about 1 ms, depending on intensity and duration of the light flash. Simulations of the reactions involved predict changes in Fluo-3 fluorescence measured at high time resolution with a laser scanning confocal microscope. These procedures have been applied in physiological experiments to generate cytoplasmic [Ca] spikes and pulses and study the cellular responses to them.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acetates* / radiation effects
  • Aniline Compounds / metabolism
  • Binding, Competitive
  • Calcium / administration & dosage
  • Calcium / pharmacology*
  • Calibration
  • Chelating Agents* / radiation effects
  • Egtazic Acid / analogs & derivatives*
  • Egtazic Acid / radiation effects
  • Ethylenediamines* / radiation effects
  • Hydrogen / metabolism
  • Hydrogen / pharmacology
  • Magnesium / metabolism
  • Magnesium / pharmacology
  • Neurons / drug effects
  • Neurons / physiology
  • Photolysis
  • Xanthenes / metabolism


  • Acetates
  • Aniline Compounds
  • Chelating Agents
  • Ethylenediamines
  • Xanthenes
  • nitr 5
  • DM-nitrophen
  • Fluo-3
  • Egtazic Acid
  • Hydrogen
  • Magnesium
  • Calcium