IONIC MOBILITY TABLES

Some additional comments added in August 2005

LISTING OF SUPPLIED IONIC MOBILITIES WITH FULL ION NAMES FOR THE PROGRAM JPCalc/JPCalcW

 The following table of relative (generalised) mobility values (relative to K⁺; see Appendix below for more information and relationship to limiting equivalent conductivities) was extracted from Table 1 of Barry & Lynch¹, with a slightly amended value for choline following later direct measurements (Ng & Barry⁴).  A supplementary list of other ionic mobilities is given in Table 2.

For information about what ion concentrations or activities to use in calculations click on Ion Concentrations etc.

Note that a number of values in the tables of Lange (2) and CRC (7) have been updated in their most recent editions,  currently listed in the references.  Where these differ from the values previously listed and incorporated in JPCalc, the new updated values are now listed below in blue. These differences are invariably small.

TABLE 1.  These ions are currently included in the JPCalc/JPCalcW and Junction Potential Calculator (in Axon's pClamp) programs

For values of some other ions, see Table 1 of Barry & Lynch¹ and Table 2 following and Refs. 2, 6 and 7.

 TABLE 2:

SUPPLEMENTARY LISTING OF MOBILITIES WITH FULL ION NAMES FOR THE PROGRAM JPCalc/JPCalcW

 The following table of relative mobility values was extracted from Ng and Barry⁴ and Keramidas et al.³. 

where the following standard abbreviations apply: NMDG, N-methyl-D-glucamine; Tris, tris[hydroxymethyl]aminomethane; HEPES, N-[2-hydroxyethyl]piperazine-N’-[2-ethanesulfonic acid]; MOPS, 3-[N-morpholino]propanesulfonic acid; MES, 2-[N-morpholino]ethanesulfonic acid.  The estimated error in the measurements from Ng and Barry⁴ was considered to be less than about 0.005.  EGTA(2-) and EGTA(3-) are from Keramidas et al.³

TABLE 3.  ADDITIONAL LISTING OF MOBILITIES WITH FULL ION NAMES FOR THE PROGRAM JPCalc/JPCalcW

 The following table of relative mobility values was calculated from limiting equivalent conductivities in the references below. 

TABLE 4.  FURTHER LISTING OF ION MOBILITIES  ADDED IN OCTOBER 2003

*Note that both  methylsulfate ( Ref. 7) and methylsulfonate (Ref. 2) had identical limiting equivalent conductances. 

 The same was also true of ethylsulfate ( Ref. 7) and ethylsulfonate (Ref. 2).  This may mean that, in each case, one of

 the values was incorrectly copied from the other and is wrong.

**The relative proportions of each valency species depends on pH and the ionic composition of the solution.

***u_ATP/u_K was calculated from the value of 3.0x10^-6 cm².s^-1 for the diffusion coefficient of ATP in free solution (Ref. 9). 

REFERENCES FOR MOBILITY AND LIMITING EQUIVALENT CONDUCTIVITY DATA

1. Barry, P.H. and Lynch, J.W. (1991).  Topical Review.  Liquid junction potentials and small cell effects in patch clamp analysis.  J. Membrane Biol.  121: 101-117.

2.  Dean, J.A.. (1999). Lange’s Handbook of Chemistry, 15^th Edition, McGraw-Hill, New York.

3.  Keramidas, A., Kuhlmann, L., Moorhouse, A.J. and Barry, P.H. (1999). Measurement of the limiting equivalent conductivities and mobilities of the most prevalent ionic species of EGTA (EGTA^2- and EGTA^3-) for use in electrophysiological experiments.  J. Neurosci. Method., 89: 41-47.

4. Ng, B. and Barry, P.H. (1995).  The measurement of ionic conductivities and mobilities of certain less common organic anions needed for junction potential corrections in electrophysiology. J. Neurosci. Method., 56: 37-41.

5. Robinson, R.A. and Stokes, R.H. (1965).  Electrolyte Solutions. (2nd ed.revised), Butterworth's, London.

6. Zuidema, T., Dekker, K. and Siegenbeek van Heukelom, J. (1985).  The influence of organic counterions on junction potentials and measured membrane potentials. Bioelectrochem. Bioenerget., 14: 479-494.

7. Vanysek, P. (2002).  Ionic conductivity and diffusion at infinite dilution.  In: CRC Handbook of Chemistry and Physics (83rd  Edn; ed. D.R. Lide), CRC Press, Boca Raton.

8. Shapovalov, G. and Lester, H. (Division of Biology, Caltech, Pasadena, CA, USA). Personal communication (2001). Average of 4 measurements at pH 7.0.  Ion information: MW 75.11, Molecular Formula: C3H9NO, Structural Formula:  HOCH2CH2NHCH3, CAS: 109-83-1, MDL Number: MFCD00002839, pKa = 9.40.

9. Diehl, H., Ihlefeld, H., and Schwegler, H. (1991).  Physik fur Biologen.  Springer-Verlag, Berlin, p. 391 (also available at WWW site: http://ishtar.df.unibo.it/cgi-def/Ever?tabelle), quoted by Rostovtseva, T.K. and Bezrukov, S.M. (1998), Biophys. J., 74: 2365-2373.

Acknowledgement

The assistance of Jennifer Anderson in sourcing the new reference editions and in compiling the new mobility data for the 2003 update has been greatly appreciated.

Application of Junction Potential Corrections before an experiment.  

Although we prefer to recommend applying liquid junction potential corrections after an experiment, another option that some people prefer is to do it at the beginning of the experiment.  This is OK provided there are no solution changes during the experiment and the correction is applied correctly.  The way this is done can be a bit confusing. Click on the above link (Application .....) to see how these corrections should be applied.  Please also note link to updated (corrected) version of the junction potential calculations article in AxoBits 39 ( http://www.axon.com/axobits/AxoBits39.pdf or click  AxoBits39New.pdf.).

To return to Liquid Junction Potential Calculator and LJP Calculations, or for other information about such calculations and mobility values, click here. 

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P. H. Barry, July, 2009