MALDI-TOF
Matrix Assisted Laser Desorption /Ionization- Time Of Flight (MALDI-TOF) mass spectrometry has become a popular tool for large molecule analyses. Published applications include nucleic acid and protein sequence, post-translational modification, cleavage, purity, structure and heterogeneity of samples among other uses. MALDI-TOF has become an important QC tool due to its high throughput capabilities and ease of automation. Some machines are claiming to analyze megadalton molecules in the femtomole sensitivity range.
As it turns out, MALDI-TOF is not just useful on high molecular weight molecules, but has found its stride in the elucidation of small molecules. By utilizing a matrix, the MALDI-TOF is able to clearly see small molecules without the complicated spectra often associated with electrospray mass spectrometry. Coupled with the software supplied with the MALDI-TOF, the spectra can be analyzed against the protein data bank and often the protein identified. There is an obvious draw back to this, as only proteins that have been previously elucidated and submitted will be in the data bank. Thus, if you have a complete unknown you will not receive useful information from the data base, but will receive valuable mass data from the spectra.
The MALDI-TOF in the Macromolecular Core Equipment Facility is a Voyager DE-PRO. This particular MALDI-TOF is designed to be at the forefront of biomolecule analysis. The Voyager DE-PRO is equipped with a reflector to get added resolution and is capable of performing Post Source Decay (PSD) for limited sequencing of peptides and proteins. MALDI-TOF is going to play a major role in protein and proteome analysis as more machines become available to researchers.
1 Accurate mass measurement of molecules.
o Theoretically the mass range is infinite, in practice it is not. Molecules less than 10 kDa can be done routinely, molecules of 10-30 kDa can be done accurately with greater effort. Molecules greater than 30 kDa will take considerable more effort and time to elucidate.
2 Protein/peptide identification.
o By getting well calibrated and clear spectra we can then determine if the protein or peptide of interest is contained within the protein data bank. The unfortunate aspect of this is if you have a complete unknown, then only mass measurements will be obtained.
3 Protein/peptide sequencing.
o Sequencing is not a very viable notion on the MALDI-TOF machine. There is currently no software to help the operator sequence proteins. However, if an operator or PI wishes we can attempt this with our machine. The time involved will most likely be extensive and the results will be unpredictable. As our experience with this methodology grows so should our ability to provide this service. Please contact Justin if you have any interest in sequencing with the MALDI-TOF.
4 Oligonucleotide sequencing.
The MALDI-TOF has the capability to sequence short Oligo’s. This is not a function that is routinely done and may pose some difficulty. Please contact Justin to determine if this application will work for your project.
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