By Steve Knight BSc Hons, MA, Marketing Manager, Genevac Ltd
Matrix-assisted laser desorption/ionisation-time of flight mass spectrometry (MALDI-TOF MS) is a now an accepted and routine analysis for the elucidation and quantitation of biomolecules in life science research. In this technique a co-precipitate of a UV-light absorbing matrix and a biomolecule are irradiated by a nanosecond laser pulse. The technique involves spotting small concentrated aliquots of material on to a matrix-coated “target”. The target is then positioned inside the Mass Spectrometer and the biomolecule of interest is desorped from the matrix surface and ionised by the laser. Most of the laser energy is absorbed by the matrix, which prevents unwanted fragmentation of the biomolecule, whilst some of the energy causes ionisation of the biomolecule. These ionized biomolecules are accelerated in an electric field and enter the flight tube of a time- of-flight mass spectrometer. During the flight in this tube, different molecules are separated according to their mass-to-charge ratio and reach the detector at different times. In this way each molecule yields a distinct signal. The method is used for detection and characterization of biomolecules, such as proteins, peptides, oligosaccharides and oligonucleotides, with molecular masses between 400 and 350,000 Da. It is a very sensitive method, which allows the detection of low (10-15 to 10-18 mole) quantities of sample with an accuracy of 0.1 - 0.01 %. Although the technique can be very sensitive, concentrated samples achieve the best results.