Matrix-assisted laser desorption/ionization (MALDI) is a soft ionization processes due to its capacity to transfer a moderate excess of energy to the analyte, which is crucial for fragile and non-volatile compounds such as proteins. MALDI is an ionization process from a solid phase: the protein of interest is dispersed in a saturated solution of a small aromatic molecule called matrix and the whole is co-crystallized by evaporation of the solvent. The solid phase obtained is irradiated, resulting in desorption of the ions. In MALDI, proteins mainly result in singly-charged or doubly-charged ion species. One of the main advantages is that the sample droplets can be prepared rapidly on the metal target, allowing the analysis of a large number of soluble or membrane proteins in a very short time.
For protein QC, an intact mass analysis is highly recommended to check both integrity and identity of the protein of interest. Top down-sequencing is a crucial QC parameter to ensure that the target protein is highly pure without any degradation at the N- or C-terminus.
This instrument is available in the QC service in complement to other technologies or after a training session for Institut Pasteur autonomous users.