Selective Enrichment and Analysis of Acidic Peptides and Proteins Using Polymeric Reverse Micelles and MALDI-MS

摘要

The typical difficulties associated with the detection ofnacidic peptides (i.e., those with low isoelectric points (pI))nby matrix-assisted laser desorption/ionization-mass spectrometryn(MALDI-MS) represent a challenge in somenproteomic analyses. Here, reverse micelle-forming amphiphilicnhomopolymers with positively charged interiorsnare synthesized and used to selectively enrich low pInpeptides from complex mixtures for MALDI-MS detection.nWhen using these polymers, acidic proteolytic peptidesnthat are undetectable during normal MALDI-MS analysisnare selectively detected. We show that enrichment of thesenlow pI peptides allows acidic proteins to be selectivelyntargeted for detection in multiprotein digests. In addition,nthe presence of the positively charged polymers duringnMALDI-MS analyses enhances peptide ion signals bynalmost an order of magnitude, thereby achieving reproduciblenion signals for acidic peptides at concentrationsnas low as 100 fM. Concurrent detection of acidic and basicnpeptides was also facilitated by utilizing a sequentialnextraction process involving reverse micelle forming polymersnwith positively and negatively charged interiors.