Proline Uses
Proline and its derivatives are often used as asymmetric catalysts in organic reactions. The CBS reduction and proline catalysed aldol condensation are prominent examples.
L-Proline is an osmoprotectant and therefore is used in many pharmaceutical, biotechnological applications.
In brewing, proteins rich in proline combine with polyphenols to produce haze (turbidity).

Proline Specialities
Proline is one of the two amino acids that do not follow along with the typical Ramachandran plot, along with glycine. Due to the ring formation connected to the Beta-carbon, the ? and f angles about the peptide bond have less allowable degrees of rotation. As a result it is often found in "turns" of proteins as its free entropy (?S) is not as comparatively large to other amino acids and thus in a folded form vs. unfolded form, the change in entropy is less. Furthermore, proline is rarely found in a and ß structures as it would reduce the stability of such structures, due to the fact that its side chain a-N can only form one hydrogen bond.
Additionally, proline is the only amino acid that does not form a blue/purple colour when developed by spraying with ninhydrin for uses in chromatography. Proline, instead, produces an orange/yellow colour.

Proline (abbreviated as Pro or P) is an a-amino acid, one of the twenty DNA-encoded amino acids. Its codons are CCU, CCC, CCA, and CCG. It is not an essential amino acid, which means that the human body can synthesize it. It is unique among the 20 protein-forming amino acids in that the a-amino group is secondary. The more common L form has S stereochemistry.