Calibrating the SIET humming bird logo

Calibration of the SIET


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Model of a Diffusional Point Source and the Non-invasive Scanning Ion-selective Electrode Technique, SIET

Ion probe Model

Predicted and observed ÁVolt difference curves for diffusion of protons (left) and potassium (right) from a point source:

Proton uvolt Potassium uvolt

Predictive equation for dV, the ÁV difference at a point in space, r Á from a point source:

                                            eff = efficiency of the measure
           S K dr                             r = distance to point source
  dV = eff ------- / (Cb + K/r) ,   where:   dr = oscillation distance
            z r2                              K = slope of [ion] curve
                                             Cb = background [ion]
                                              S = Nernst coeficient
                                              z = unit charge on the ion

This calibration curve allows one to estimate the efficiency, eff, of the electrode which can be used to turn any ÁV difference measured with a similar electrode into an observed flux of that ion in the space arround a cell or tissue.


Ion flux, J, emanating from a distant (Ám) point source:
Observed and predicted values for 2 LIXs
proton (left) and potassium (right).

Proton Flux Potassium Flux

Predictive equation for ionic flux, Jo:

                              D = diffusion coeficient for the ion (cm-2 sec-1)
  Jo  =  - D dC/dr ,  where  dC = concentration differential
                             dr = oscillation differential
Ion Do i Nernst
slope
LIX t90 Hz eff%
K+ 19.6 +1 58 K IB <1s. 0.3 70%
H+ 93.7 +1 58 H IIA ~0.6s 0.3 80%
Ca++ 7.9 +2 29 Ca IIA <5s 0.3 50%
Mg++ 7.1 +2 29 Mg IV <30s 0.25 30%
Cl- -20.3 -1 -58

D is expressed as 106D/cm2 sec-1.
Nernst Slope, S, is expressed in mV.


If you have questions about calibrating the various vibrating probes or the University of Massachusetts Vibrating Probe Facility, email its PI, Joe Kunkel


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Page maintained by Joe Kunkel, joe@bio.umass.edu. Copyright(c) 1995, 1996, 1997.
Created: 95/10/28 Updated: 97/06/22