Experimental Thermodynamics of Biomolecular Hydrogen Bonds

To emphasize the variation in reported experimental quantification of hydrogen bonds, we list several studies of the energetics (enthalpy or free energy) of hydrogen bond formation in biological interactions and related model systems. Early 

Fersht et al., in a very well-known study of the binding of tyrosyl-tRNA synthetase to its substrate [39], found that deletion of a strong hydrogen bond donor or acceptor from the enzyme reduced the free energy of binding by only 2.1-6.3 kJ mol , whereas removal of the partner of a very strong donor or acceptor weakened binding by an additional 12 kJ mol . Data on mutants of ribonuclease Tl by Shirley et al. 

An important feature of all these observed energy changes resulting from rearrangement of hydrogen bonds is that they are of the same order of magnitude as 

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