PH-DEPENDENT ISOFORM TRANSITIONS OF A MONOCLONAL-ANTIBODY MONITORED BY MICELLAR ELECTROKINETIC CAPILLARY CHROMATOGRAPHY

Within the pH range 2-12, the monoclonal chimeric antibody BR96 can be separated into one to five isoforms by micellar electrokinetic capill ary chromatography (MECC). The distribution of the immunoglobulin betw een these isoforms is pH dependent and apparently reversible, Some of the changes in the electrophoretic profile are represented by alterati ons in the immunoglobulin secondary structure, MECC and CD data demons trate that, in other cases, differences in electrophoretic mobilities of the intact and acid-stressed antibody molecules were not due to dif ferences in the ionization of the protein functional Groups or changes ire secondary structure, but rather resulted from differences in the exposure of the molecule's structural elements to the solvent The resu lts indicate that the interaction of the isoforms with sodium dodecyl sulfate micelles plays a crucial role in MECC isoform separations, The formation of analyte-micelle complexes was postulated to make electro phoretic mobilities, especially of large protein molecules, susceptibl e to subtle conformational changes that are not detectable by other me thods.