MALDI TOF - Matrix-assisted laser desorption ionization time-of-flight spectrometry

MALDI is a soft ionization technique used in mass spectrometry, allowing the analysis of biomolecules such as proteins, peptides and sugars and large organic molecules, which tend to be fragile and fragment when ionized by alternative ionization methods. The ionization is triggered by a laser beam. The analyte is cocrystalised with a matrix, which is a special low molecular organic compound. The matrix facilitates the absorption of the laser energy as well as the ionisation of analyte molecules.  Inonised molecules are subsequently accelerated within an electric field and their velocity over a known distance measured giving Time Of Flight. With this time and the known experimental parameters, the mass-to-charge ratio of the ion can be found.

Brukers MALDI Biotyper enables the identification of bacteria by its own molecular composition. Proteins and peptides are arranged in a spectrum with increasing mass revealing a characteristic peak pattern. A pattern matching algorithm identifies the microorganisms by comparing the generated spectra with a reference library. Subsequently automatic expansion of reference spectra can be performed.