PREPARATIVE AND ANALYTICAL CAPILLARY ZONE ELECTROPHORESIS ANALYSIS OFNATIVE ENDORPHINS AND ENKEPHALINS EXTRACTED FROM THE BOVINE PITUITARY- MASS-SPECTROMETRIC CONFIRMATION OF THE MOLECULAR-MASS OF LEUCINE-ENKEPHALIN

One proopiomelanocortin peptide [beta-endorphin (BE)] and two proenkep halin A peptides [methionine enkephalin (ME) and leucine enkephalin (L E); LE derives also from proenkephalin B] were searched for in a bovin e pituitary extract by capillary zone electrophoresis (CZE) and liquid secondary-ion mass spectrometry (LSIMS). A bovine pituitary homogenat e was subjected to acid precipitation/centrifugation and solid-phase e xtraction of peptides using an octadecylsilyl disposable cartridge. Th e peptide enriched fraction was subjected to CZE at pH 2.5 and at pH 5 .5, and fractions were collected under preparative CZE conditions with in defined time windows where synthetic BE, ME, and LE migrate. The re solving power of CZE was demonstrated by collecting biological fractio ns at pH 5.5 under preparative conditions and by subsequently analyzin g these fractions at pH 2.5 under analytical conditions. Preparative C ZE was further performed at pH 2.5 for fractions collected at pH 5.5. LSIMS analysis of this second-dimensional CZE fraction revealed the ap propriate protonated molecule ion[(M + H)(+), m/z 556.4] of LE. (C) 19 95 Academic Press, Inc.