ON LINE DUAL MICRODIALYSIS WITH ESI-MS FOR DIRECT ANALYSIS OF COMPLEXBIOLOGICAL SAMPLES AND MICROORGANISM LYSATES

A novel dual-microdialysis approach has been developed for fast and ef ficient fractionation and cleanup for ESI-MS and ESI MS/MS analyses of biological samples. A modified dynamic microdialyzer utilizing two mi rror-image serpentine channels, which sandwich a regenerated cellulose membrane of selected molecular weight cutoff, serves as the first sta ge for the removal of high-molecular-weight components and cellular re sidue. The second stage employs a hollow microdialysis capillary to re move low-molecular-weight species (e.g., salts) which can degrade or p reclude analysis ESI-MS, A protein mixture consisting of 30 mu M bovin e serum albumin (BSA), 4.0 mu M cytochrome c, 2.3 mu M ubiquitin, and 9.4 mu M bradykinin in 0.5 M NaCl was used to evaluate the performance of this system. Essentially complete removal of both BSA and NaCl was achieved, resulting in high-quality mass spectra containing only the lower molecular weight proteins. After passing through the on-line dua l-microdialysis system, a crude bacteria cell lysate yielded clean ESI -mass spectra in similar to 20 min. MS/MS of selected ions demonstrate d abundant fragment ions and provided a second-dimension ''fingerprint '' of the complex cellular fraction. Preliminary application of this t echnique for direct characterization of microorganism lysates is prese nted.