A macro-ion of a
polyampholyte (in particular a protein) is said to be isoionic if besides the
polyampholyte and
H+
or
OH−
ions (in general ions of the solvent) no other ions are present in the system.
Source:
PAC, 1972, 31, 577
(Manual of Symbols and Terminology for Physicochemical Quantities and Units, Appendix
II: Definitions, Terminology and Symbols in Colloid and Surface Chemistry)
on page 618