Hydrogen exchange folded polypeptides

As noted in the timeline, hydrogen exchange in folded polypeptides had been recorded by MS before the work of Zhang and Smith.)... 

Amide hydrogen atoms of a polypeptide chain in a random conformation do not exchange at the same rate, but 10 -fold variations of rates have been observed (Molday et a/., 1972). For exchange of hydrogen atoms in native proteins, simple biphasic curves were obtained for several proteins (Nakanishi et al, 1972,1973 Takesada et a/., 1973). The fast and slow exchanging atoms corresponded to the fraction of exposed and shielded groups (Nakanishi and Tsuboi, 1974). 

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