Correlated matrix-assisted laser desorption/ionization mass spectrometry and fluorescent imaging of photocleavable peptide-coded random bead-arrays

RATIONALERapidly performing global proteomic screens is an important goal in the post-genomic era. Correlated matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) and fluorescent imaging of photocleavable peptide-coded random bead-arrays was evaluated as a critical step in a new method for proteomic screening that combines many of the advantages of MS with fluorescence-based microarrays. METHODSSmall peptide-coded model bead libraries containing up to 20 different bead species were constructed by attaching peptides to 30-34 mu m diameter glass, agarose or TentaGel (R) beads using photocleavable biotin or a custom-designed photocleavable linker. The peptide-coded bead libraries were randomly arrayed into custom gold-coated micro-well plates with 45 mu m diameter wells and subjected to fluorescence and MALDI mass spectrometric imaging (MALDI-MSI). RESULTSPhotocleavable mass-tags from individual beads in these libraries were spatially localized as similar to 65 mu m spots using MALDI-MSI with high sensitivity and mass resolution. Fluorescently tagged beads were identified and correlated with their matching photocleavable mass-tags by comparing the fluorescence and MALDI-MS images of the same bead-array. Post-translational modification of the peptide Kemptide was also detected on individual beads in a photocleavable peptide-coded bead-array by MALDI-MSI alone, after exposure of the beads to protein kinase A (PKA). CONCLUSIONSCorrelated MALDI-MS and fluorescent imaging of photocleavable peptide-coded random bead-arrays can provide a basis for performing global proteomic screening. (c) 2013 The Authors. Rapid Communications in Mass Spectrometry published by John Wiley & Sons, Ltd.