Intramolecular Hydrogen Bonding Propensities NMR chemical shift data obtained for phosphorylated serine and threonine dipeptides at varying pH levels suggest that the oxygen atoms of the phosphate group are able to form hydrogen bonds with the two backbone amide protons of the capped dipeptides. In the analysis that follows, we will refer to the amide nitrogen immediately N-terminal to the side chain as N self and the amide nitrogen that belongs to the C-terminal capping group as N cap .