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732 Chapter 21
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80.
a.
Acid-catalyzed hydrolysis indicates the peptide contains 12 amino acids.
b.
Treatment with Edman’s reagent indicates that Val is the N-terminal amino acid.
Val
c.
Treatment with carboxypeptidase A indicates that Ala is the C-terminal amino acid.
Val Ala
d.
Treatment with cyanogen bromide indicates that Met is the fifth amino acid with Arg, Gly, Ser in an
unknown order in positions 2, 3, and 4.
Val Met Ala
Arg, Gly, Ser
e.
Treatment with trypsin indicates that Arg is the third amino acid, Ser is second, Gly is fourth, Tyr is
sixth, and Lys is seventh. Because Lys is in the terminal fragment, cleavage did not occur at Lys, so Pro
must be at lysine’s cleavage site, but we don’t know whether Lys-Pro comes before of after Phe and Ser.
Val Ser Arg Gly Met Tyr Lys Ala
Lys-Pro, Phe, Ser
f.
Treatment with chymotrypsin indicates that Phe is the tenth amino acid and Ser is the eleventh.
Val Ser Arg Gly Met Tyr Lys Lys Pro Phe Ser Ala