MALDI-ToF/ToF and LC/MS/MS Services
Mass spectrometry (MS) is an analytical technique for the determination of the elemental composition of a sample or molecule. The MS principle consists of ionizing peptides to generate charged molecules or molecule fragments and measurement of their mass-to-charge ratios. In a typical MS procedure:
- a sample is loaded onto the MS instrument, and undergoes vaporization.
- the components of the sample are ionized by one of a variety of methods (e.g., by impacting them with an electron beam), which results in the formation of charged particles (ions)
- the positive ions are then accelerated by an electric field
- computation of the mass-to-charge ratio (m/z) of the particles based on the details of motion of the ions as they transit through electromagnetic fields, and
- detection of the ions, which in step 4 were sorted according to m/z.
For protein sequencing by tandem MS (matrix-assisted laser desorption ionization time-of-flight - MALDI-TOF/TOF or electrospray ionization MS/MS), protein samples are enzymatically digested by trypsin to produce fragmented peptides. Spectra are obtained for the major peptide ions in MS mode; and sequence data will be obtained when the spectrometers automatically revert to MS/MS mode. These spectra are then compared to databases to provide hits that identify matching or similar sequences. The end result is positive verification of protein identity.
Of recent, peptide mass fingerprinting (PMF) for protein identification using mass spectrometry has been superseded by the mass spectrometry sequencing (our service SS001).
For pure protein sample from Coomassie stained gels and 2D gel spots, it is optimal to be analyzed by MALDI-TOF/TOF (PMF+MS/MS).
For low abundant samples or sample from a single gel band that containing two or more proteins, low abundant samples, it is optimal to be analyzed by electrospray (LC/MS/MS) mass spectrometry.
Samples should be submitted with our Service Order Form.