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Proteomics Facility Core Matrix Assisted Laser Desorption Ionization ToF-MS (MALDI) 1. Description: Matrix assisted laser desorption ionization time of flight mass spectrometry. Sample of relatively pure and desalted proteins are spotted on a MALDI target plate. A matrix is added to aid in ionization of the protein/ peptides of interest. Lasers hit the target and induce ionization of proteins/peptides and matrix and they are separated by the time it takes each to reach the detector. Time of Flight is proportional to the mass:charge ratio so mass is determined for singly and multiply charged species. 2. Application: Peptide mass fingerprinting for protein identification by database searching Peptide mass determination 3. Limitations: Post-translational modifications such as phosphorylation are labile and the laser desorption process usually causes them to be lost The sample has to be relatively pure and desalted. Gel slices or spots are typical types of sample that will be analyzed The sample has to be digested and then desalted in order to obtain a peptide mass fingerprint. There is some technical skill 4. Advantages: If a spot or band can be seen on a SDS-PAGE gel it usually will yield a preliminary identification Usually a robust platform that is amenable to users who are not mass-spec experts The entire sample is not usually used in analysis and the same spot can be queried again in a higher end MS/MS instrument so sequence data can be obtained 5. Equipment: Ciphergen Mass Spectrometer: Can be used in MALDI mode 6. Services: At this time we act as a conduit to the Michigan Proteome Consortium Laboratories. We are available for consultation and will provide protocols for how samples need to be prepared When the Bruker MALDI is operational in the Department of Chemistry, protein digestion and peptide mass fingerprinting analysis will be available as well as MALDI analysis for peptides |
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