Isoelectric membrane simulator: A computational approach for isoelectric Immobiline membranes

Abstract
Isoelectric membrane simulator (IMS) is a computer program meant for computation of pH, buffering power (β), ionic strength (I) and dissociation degree (α) of a mixture of up to 3 buffering and 1 titrant Immobilines, for generating in a reproducible manner isoelectric membranes. Such membranes, of precise isoelectric point, are then used for large‐scale protein purification by isoelectric focusing in multicompartment electrolyzers. IMS can be used, in a more general application, for titrating mixtures of buffers to a desired pH value. This versatile program is written in M. Q. BASIC rel.2.5 and it runs on any IBM hardware or compatible machine supported by MS‐DOS. An example of purification of superoxide dismutase in a multicompartment electrolyzer with a set of fixed pI membranes of widely differing composition is shown.