31P and 1H NMR Studies of the Effect of the Counteracting Osmolyte Trimethylamine-N-oxide on Interactions of Urea with Ribonuclease A

31P NMR spectroscopy has been used to show that the activity of RNase A, which is lowered in the presence of urea, can be recovered with trimethylamine-N-oxide (TMAO). A 1:1 ratio of TMAO:urea was sufficient to recover the enzyme activity. (1)H nuclear Overhauser effect spectroscopy NMR studies with RNase A have shown that even at relatively low effective concentrations of TMAO, some modification of the three-dimensional structure of the biomolecule is apparent.