Desorption Electrospray Ionization (DESI) Analysis of Intact Proteins/Oligopeptides.

INTRODUCTIONDesorption electrospray ionization (DESI) is amenable to the study of intact proteins in complex mixtures, including blood or other biological media. Intact proteins can be desorbed and ionized from the surface under gentle (soft) conditions to produce compact conformations of the protein. A procedure for DESI analysis of intact proteins and oligopeptides using mass spectrometry (MS) is described here. DESI-MS is an emerging technique with great promise, but its application range is still being investigated. Therefore, the protocol presented here provides general procedures used for the applications that have been investigated so far. Optimal ion source parameters and surface types may vary depending on the application.