P-31 and H-1 NMR studies of the effect of the counteracting osmolyte trimethylamine-N-oxide on interactions of urea with ribonuclease A

P-31 NMB spectroscopy has been used to show that the activity of RNase A, w hich is lowered in the presence of urea, can be recovered with trimethylami ne-N-oxide (TMAO). A 1:1 ratio of TMAO:urea was sufficient to recover the e nzyme activity. H-1 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 biomolec ule is apparent.