Dolbier HW Solutions 675

Dolbier HW Solutions 675 - 769 AMINO ACIDS, PEPTIDES, AND...

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27.33 Somatostatin is a tetradecapeptide and so is composed of 14 amino acids. The fact that Edman degradation gave the PTH derivative of alanine identi f es this as the N-terminal amino acid. A major piece of information is the amino acid sequence of a hexapeptide obtained by partial hydrolysis: Ala-Gly-Cys-Lys-Asn-Phe Using this as a starting point and searching for overlaps with the other hydrolysis products gives the entire sequence. Ala-Gly-Cys-Lys-Asn-Phe Asn-Phe-Phe-Trp-Lys Phe-Trp Lys-Thr-Phe Thr-Phe-Thr-Ser-Cys Thr-Ser-Cys Ala-Gly-Cys-Lys-Asn-Phe-Phe-Trp-Lys-Thr-Phe-Thr-Ser-Cys 1234567891 01 11 2 1 3 1 4 The disul f de bridge in somatostatin is between cysteine 3 and cysteine 14. Thus, the primary struc- ture is 27.34 It is the C-terminal amino acid that is anchored to the solid support in the preparation of peptides by the Merri f eld method. Refer to the structure of oxytocin in Figure 27.8 of the text and note that oxytocin, in fact, has no free carboxyl groups; all the acyl groups of oxytocin appear as amide
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