Hydrogen bonding in proteins
From NMR Wiki
Baxter et al. [1] showed that temperature dependence of amide proton chemical shift is a good indicator of hydrogen bonding. A temperature coefficient above -4.5 ppb/K indicated presence of hydrogen bond in BPTI and egg hen lysozyme. This criterion had successfully delineated non-hydrogen bound protons that are in slow exchange with solvent due to being buried in the core of the protein.