A CE−MALDI Interface Based on the Use of Prestructured Sample Supports

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Abstract
We have developed an off-line coupling of capillary electrophoresis (CE) to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) based on CE fraction collection onto prestructured MALDI sample supports. Analyte carryover and detection sensitivity were investigated using a standard peptide mixture. Low femtomole amounts were detected, and no noticeable carryover was discovered. The performance of the method was evaluated with a mixture of tryptic digests of proteins from a human fetal brain cDNA expression library. The total number of identified peptides was increased from 47 to 211 when the CE−MALDI interface was used compared to direct MALDI-MS analysis. Sequence coverage with CE−MALDI was in the 25−60% range for the different proteins, corresponding to an increase of 1.3−4.9 times relative to that obtained with MALDI-MS of the crude mixture. Fractionation of sample components also facilitated protein identification by MALDI postsource decay analysis. Our initial results suggest this CE−MALDI interface can be used for the analysis of complex peptide mixtures isolated from biological tissues.