Chapter 24: Q25P (page 1289)
Show how you would synthesize Leu-Gly-Ala-Val-Phe starting with Fmoc-Ala-Val-Phe— P
Short Answer
The synthesis of Leu-Gly-Ala-Val-Phe starting from Fmoc-Ala-Val-Phe-P is given as follows:
Chapter 24: Q25P (page 1289)
Show how you would synthesize Leu-Gly-Ala-Val-Phe starting with Fmoc-Ala-Val-Phe— P
The synthesis of Leu-Gly-Ala-Val-Phe starting from Fmoc-Ala-Val-Phe-P is given as follows:
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Get started for freeAfter treatment with peroxyformic acid, the peptide hormone vasopressin is partially hydrolyzed. The following fragments are recovered. Propose a structure for vasopressin.
Phe-Gln-Asn Pro-Arg-Gly.NH2 Cys-Tyr-Phe
Asn-Cys-Pro-Arg Tyr-Phe-Gln-Asn
Complete hydrolysis of an unknown basic decapeptide gives Gly, Ala, Leu, Ile, Phe, Tyr, Glu, Arg, Lys, and Ser. Terminal residue analysis shows that the N terminus is Ala, and the C terminus is Ile. Incubation of the decapeptide with chymotrypsin gives two tripeptides, A and B, and a tetrapeptide, C. Amino acid analysis shows that peptide A contains Gly, Glu, Tyr, and; peptide B contains Ala, Phe, and Lys; and peptide C contains Leu, Ile, Ser, and Arg.Terminal residue analysis gives the following results.
Incubation of the decapeptide with trypsin gives a dipeptide D, a pentapeptide E, and a tripeptide F. Terminal residue analysis of F shows that the N terminus is Ser and the C terminus is Ile. Propose a structure for the decapeptide and for fragments A through F.
A molecular weight determination has shown that an unknown peptide is a pentapeptide, and an amino acid analysis shows that it contains the following residues: one Gly, two Ala, one Met, one Phe. Treatment of the original pentapeptide with carboxypeptidase gives alanine as the first free amino acid released. Sequential treatment of the pentapeptide with phenyl isothiocyanate followed by mild hydrolysis gives the following derivatives:
Propose a structure for the unknown pentapeptide.
Show how solid-phase peptide synthesis would be used to make Ile-Gly-Asn.
Most naturally occurring amino acids have chiral centers (the asymmetric α carbon atoms) that are named (S) by the Cahn-Ingold-Prelog convention (Section 5-3). The common naturally occurring form of cysteine has a chiral center that is named (R), however.
(a) What is the relationship between (R)-Cysteine and (S)-alanine? Do they have the opposite three-dimensional configuration (as the names might suggest) or the same configuration?
(b) (S)-Alanine is an L-amino acid (Figure 24-2). Is (R)-cysteine a D-amino acid or an L-amino acid?
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