Bradykinin is a nonapeptide that is responsible for the severe pain most people feel after being stung by a wasp. Amino acid analysis of bradykinin gave the following composition of amino acids:

Pro3, Phe2, Arg2, Gly, Ser

Edman degradation indicated that the N-terminal amino acid was Arg. Carboxypeptidase treatment gave Arg as the first-appearing amino acid followed closely by Phe. Partial hydrolysis of bradykinin gave five fragments:

l. Pro2, Arg; N-terminal AA: Arg

2. Arg, Pro, Phe; N-terminal AA: Pro

3. Gly, Pro; N-terminal AA: Pro

4. Ser, Phe, Gly; N-terminal AA: Gly

5. Ser, Phe; N-terminal AA: Phe

Note: Commas separating amino acids in a list do not imply an order or specifÏc sequence of amino acids in the list.

1. Propose a primary structure for bradykinin.

2. Why is an alpha-helix not likely to be at least part of the secondary structure of bradykinin?