these data include ( 1 ) the conformation of the two disulfide bridges , ( 2 ) the flexibility of the three methionyl side chains , ( 3 ) the extent of exposure of the indole ring of a tryptophan , ( 4 ) the environment of the two histidines , ( 5 ) the environment of the tyrosines , and ( 6 ) the hydrogen-deuterium exchangeability of peptide nh 's .
C0020275
hydrogen
C0011744
deuterium