Amide exchange

Figure 5. Schematic representation of four-stranded )9-sheet in RpII. Observed NOEs which were used to identify this secondary structure are shown by dashed lines. Dots indicate slowly exchanging amide hydrogens.

An additional useful parameter is the exchange rate of amide protons after dissolution of the sample in DgO. Slowly exchanging amide protons indicate protection from solvent and possible involvement in intramolecular hydrogen bonds associated with elements of secondary structure. All of the NMR and slow exchange data can be consolidated to give... 

The parallel decrease in the percentage of remaining AZI292 (Ad at 292 nm) between 30 and 50 C and the percentage of remaining hard-to-exchange amide... 

Stevens et al. (1964) have studied the effect of radiation on the enzymatic activity and hydrogen-exchange characteristics of lysozyme. Upon irradiation lysozyme lost its enzymatic activity at half the rate of loss of hard-to-exchange amide hydrogens, indicating that only half the native conformation of lysozyme is essential for activity. 

Carbonic Anhydrase. Rickli et al. (1964) have made some observations of infrared absorption of carbonic anhydrase B in D2O solution in the region 1800-1300 cm in order to determine the hard-to-exchange amide hydrogens. Analysis of their data led to the estimate that 20% of the peptide hydrogens in native carbonic anhydrase B, and 30% in the add-denatured enzyme, were difficult to exchange. 

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