MODIFICATION OF CAPILLARY ELECTROPHORESIS SELECTIVITY IN HYDROORGANICSOLUTIONS - DISSOCIATION-CONSTANTS AND STOKES RADIUS MEASUREMENTS OF PEPTIDES IN WATER-2,2,2-TRIFLUOROETHANOL MIXTURES

Peptide electrophoretic mobilities were measured at different acidic p H in water-2,2,2-trifluoroethanol mixtures. Fit of experimental mobili ties according to binding equations allowed the calculation of peptide C-terminus dissociation constants and the Stokes radius of the differ ently protonated forms. Analysis of the data showed that the use of hy dro-organic solvents in capillary electrophoresis offers the following principal advantages: (a) a modification of dissociation constants an d Stokes radii that are strongly dependent upon peptide sequence and t hat can be conveniently utilised for selectivity manipulation; (b) an increase of separation performance arising from the stabilisation of p articular peptide conformations; (c) a solubility of large apolar pept ides with respect to aqueous solutions. (C) 1997 Published by Elsevier Science B.V.