Basic Concepts in Mass Spectrometry

This chapter introduces the basic principles and concepts of mass spectrometry (MS), based on the fact that if a molecule can be converted into a gas phase ion, then it can be interrogated by this technique. Indeed, amino acids, peptides, and proteins have several unique characteristics that make them particularly suitable for MS analysis. Naturally, the transition of these molecules into the gaseous phase, their ionization, and detection constitute a challenge that requires the introduction and development of specific MS techniques. The operating principles, advantages, and drawbacks of these processes are discussed in the chapter. In addition, the quantitation and the two main approaches to identifying and characterizing proteins using MS: the “bottom-up” method, which analyzes peptides by proteolytic digestion, and the “top-down” method, which analyzes intact proteins, will be described.