JPCALC, A SOFTWARE PACKAGE FOR CALCULATING LIQUID-JUNCTION POTENTIAL CORRECTIONS IN PATCH-CLAMP, INTRACELLULAR, EPITHELIAL AND BILAYER MEASUREMENTS AND FOR CORRECTING JUNCTION POTENTIAL MEASUREMENTS

The JPCalc program has been designed to graphically illustrate how junction potential contributions arise in various electrophysiological situations, to enable the magnitude and direction of those values to be readily calculated and to show clearly how the resultant appropriate corrections need to be applied to experimental measurements. In particular, the program covers the analysis of junction potential contributions and corrections in all the various different patch-clamp configurations (intact patches, inside-out patches, outside-out patches, whole-cell recording and perforated patches), intracellular recording, epithelial and bilayer measurements. It can also be used to correct experimental measurements designed to try to directly measure junction potentials and to compare both the magnitude and direction of such corrected measurements with their theoretical values. Although it is recommended that all of the above measurements be done with salt-filled electrodes or salt bridges, the program will allow the use of Ag/AgCl reference electrodes in direct contact with bathing solution in most situations. JPCalc also makes use of a library file of mobility and valency data for about 30 ions which can be extended by the user. In addition to its value in correcting electrical measurements, the program with its graphical displays may also be of value in focusing discussion about the contribution of junction potentials to such measurements and in helping to design experiments to either minimize their contribution or to measure their values. The JPCalc program, designed for IBM-compatible computers with color or monochrome monitors, can also be run on Macintosh computers with SoftPC emulation software.1