POLYETHYLENE MEMBRANE AS A SAMPLE SUPPORT FOR DIRECT MATRIX-ASSISTED LASER-DESORPTION IONIZATION MASS-SPECTROMETRIC ANALYSIS OF HIGH-MASS PROTEINS

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) of high mass proteins (> 100 000 Da), directly deposited on polyethylene membranes, is demonstrated. The spectral quality obtained, using standard sample preparation conditions, is equal or superior to that obtained with metal sample stages. Compared to the use of poly(vinylidene difluoride) transfer membranes, this material allows the acquisition of excellent quality MALDI mass spectra from high-mass proteins with a standard UV laser. This gain in capability is not at the expense of either mass accuracy or signal reproducibility; both approach that obtained with standard sample preparations on stainless steel. In addition, for the applications shown, the use of PE as a sample support reduces the severe ion suppression effects typically observed in the MALDI analysis of high-mass mixtures. This permits more precise mass measurements to be made via the use of internal calibration and is illustrated by the mass measurement of a chimeric mouse/human antibody (MW similar to 150 000 Da) by coaddition of bovine albumin dimer (MW similar to 130 000 Da).