Direct detection of native proteins in biological matrices using extractive electrospray ionization mass spectrometry

Abstract

The high-throughput and sensitive characterization of native proteins in biological samples is of increasing interest in multiple disciplines. Extractive electrospray ionization (EESI) forms ions of native proteins including lysozyme, α-chymotrypsin, myoglobin, human serum albumin, RNAse A and blood hemoglobin in extremely complex biosamples or PBS buffer solutions by softly depositing charges on the protein molecules. This method produces no significant conformational changes of the proteins in the ion formation process, and features direct detection of trace proteins present in biological matrices. The detection limit of low pmol L⁻¹ for lysozyme in untreated biological liquids such as human urine and tears was demonstrated using EESI mass spectrometry (MS), showing an attractive MS platform for the direct analysis of native proteins in actual biological samples.