4-Azido-L-phenylalanine hydrochloride is an unnatural amino acid. It is used as an effective vibrational reporter of local protein environments.

H-Ala-Ala-OH (L-Alanyl-L-alanine; Ala-Ala) is a nonpolar dipeptide that is absorbed by human intestinal Caco-2 cells. The transport of alanine (Ala), like proton/amino acid symport, can lead to cytoplasmic acidification.

[Pro18, Asp21] β - Amyloid (17 - 21), iAb5