Characterization of proteins by ambient mass spectrometry

Proteins play important roles in living systems and are topics of many fundamental and applied research projects. With the introduction of electrospray ionization and matrix-assisted laser desorption/ionization for analysis of biomacromolecules in the late 1980s, mass spectrometry has become an important tool for characterization of proteins. Characterization of proteins in raw samples by these mass spectrometric techniques, however, usually requires extensive sample pretreatment. Ambient ionization techniques are new mass spectrometric techniques that allow direct analysis of samples with no or little sample preparation. Can these techniques facilitate or even eliminate sample preparation for mass spectrometric analysis of proteins? Apart from sample preparation, do these techniques offer any new features for characterization of proteins as compared with conventional ESI or MALDI? Recent advances in characterization of proteins by ambient mass spectrometry are summarized and commented in this article.