The technique where mass spectrometry is applied to study proteins is known as Protein mass spectrometry. There are two steps used for characterizing proteins: In the first step, proteins are ionized by electrospray ionization (ESI) or matrix-assisted laser desorption/ionization (MALDI). In the second, proteins are introduced to a mass analyzer and enzymatically digested into smaller peptides using a protease. At the end peptides are introduced into the mass spectrometer and identified by peptide mass fingerprinting or tandem mass spectrometry. Journal Article is sometimes called a Scientific Article, a Peer-Reviewed Article, or a Scholarly Research Article. Together, journal articles in a particular field are often referred to as The Literature.