A discontinuous Tris-Cl/acetate (OAc) buffer system, unprecedently containing OAc as the trailing constituent, and operative in polyacrylamide gel electrophoresis (PAGE) at low polyacrylamide concentration (T = 4.8%) is described in the paper. The characteristics of the electrophoretic system are illustrated by the resolution of fluorescent 8-aminonaphthalene-1,3,6-trisulfonic acid (ANTS)-labeled malto-oligosaccharides and dextran homopolymers. In this buffer system, the resolving phase is constituted by Tris-OAc behind a moving boundary formed between the leading chloride ion of Tris-HCl gel buffer and the trailing OAc ion provided by a catholyte of NH(4)OAc. In contrast with the results obtained with Tris-CI/glycinate buffer commonly used in electrophoresis, or with Tris-CI/borate, the best resolution of the glucose oligomers containing 1-4 glucose units in Tris-OAc, pH 8.8, ionic strength of 0.08, was obtained at 4.8% polyacrylamide concentration, using 0.5 M NH(4)OAc, pH 9.5 as the catholyte. Under those conditions, the ANTS-glucose oligomers were separated with mobilities decreasing from glucose to maltohexaose. The linear Ferguson plots (log relative mobility, R(f), vs.%T) of the glucose oligomers show that the surface net charge of those oligomers is inversely related to their sizes, given by the slopes, K(R), of the plots. The molecular weight of the oligomers is directly but nonlinearly related to K(R). The novel electrophoretic system illustrated here for separation of short ANTS-saccharides can be potentially applied to the resolution of other biomolecules such as rapidly migrating DNA, peptides or proteins.