peptide sequencing by mass spectrometry

Currently, the most commonly used technique for protein sequence analysis is mass spectrometry. Mass spectrometry is a highly efficient method for the accurate mass determination and characterization of proteins. Two mainly used mass spectrometers are electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI), respectively. Basically, proteins are pretreated with digestive enzymes to be digested into small fragments, which are analyzed by mass spectrometers. Depends on the projects need, MALDI and ESI are two used as ionization source for ionizing peptide fragments. Usually, MALDI is more frequently used when dealing with large amount of samples. Peptide sequences are then obtained by analyzing the mass spectrum of each of the fragments, which together consist of the full-length protein sequence.