How does mass spectrometry identify proteins?

In Mass Spectrometry, proteins are identified following an analysis of different factors and series of steps. First, the masses of different proteins and peptides are determined through measuring the m/z ratio of their gas-phase ions. Mass spectrometers convert protein molecules into gas-phase ions using an ion source. Ionization radiation such as electrospray ionization and electron ionization are commonly used to ionize proteins. Next, a mass analyzer separates ionized analytes based on their m/z ratio. A detector then measures the number of ions present at each m/z value.  The acquired mass spectra are then put into a database to identify the proteins present in the sample. Proteins are identified by the best match between the observed mass spectra and predicted spectra.