Species-specific acid-base characterization of carnosine and homocarnosine using nuclear magnetic resonance

Carnosine and homocarnosine have long been known to be important constituents of the human metabolome, performing pH-and redox homeostasis-related roles. These are the most important imidazole-containing 'small' chemical entities in biological media. In this work these dipeptides were studied by 1H NMR-pH titration under near-physiological conditions. The resulting acid-base properties are quantified in terms of 6 macroscopic and 24 microscopic protonation constants, which show good agreement with previous results. A deeper knowledge in the physicochemical properties of the studied dipeptides may give further insight into the molecular level interpretation of their biosynthesis pathways, and biochemical reactions.