Even though they are present in nature, non-proteinogenic amino acids are usually defined as unnatural or non-natural. Beside their structural diversity, interest in these compounds is due to their occurrence in nature, their biological properties, the analytical aspects, their use as probes, and their incorporation into peptides and proteins, among other reasons. Divided into five convenient sections, "Unnatural Amino Acids: Methods and Protocols" deals with enzymatic methods used to produce non-natural amino acids, aspects concerning the presence of unnaturalamino acidsin peptides with...