1559r.ch26_454-46810/20/0515:39Pag0456 456.chapter 26 AMINO ACIDS,PEPTIDES,PROTEINS,AND NUCLEK ACIDS:NITROGEN-CONTAINING POLYMERS IN NATURE Solutions to Problems 26. COOH COOH HN- H.cH HN- CH2CHs CHs L-Isoleucine t-Threonine Systematic name for Lthreonine:()-2-amino-3-hydroxybutanoic acid. 27. COOH HN-H H-CHS Systematic name for allo-L-isoleucine:(2S.3R)-2-amino-3-methylpentanoic acid 28.Structures are presented in order of increasing pH(in parentheses). COOH C00- C00- aH衣H④HHm,N H(12) CH CH CH COOH C00 (b)HaN--H (1)HN-H (7) H2N--H (12) CH-OH CH2OH CH-OH COOH C00 C00 C00 (e)HN-H (1) HaN- H -H(9.5) N +H(12) (CH24-NH; (CH2)4-NHs (CH2)4-NH3 (CH2)4-NH2 COOH C00- C00 900 @HNH是a)HNH() HN十H() H.N- -H思(12 H COOH C00- C00- H (7)H-H (9)HN- H(12) CH-SH COOH C00- C00 C00 (f)HN-H (1)HN-H (3)HsN-H (7) HN-H(12) CH-COOH CH-COOH CH-COO CHCOOSolutions to Problems 26. Systematic name for L-threonine: (2S, 3R)-2-amino-3-hydroxybutanoic acid. 27. Systematic name for allo-L-isoleucine: (2S, 3R)-2-amino-3-methylpentanoic acid. 28. Structures are presented in order of increasing pH (in parentheses). (a) (b) (c) (d) (e) (f) H3N (1) H COOH CH2COOH CH2COOH CH2COO CH2COO H3N (3) H COO H3N (7) H COO H2N H (12) COO H3N (1) H COOH CH2SH H3N (7) H COO CH2SH H3N (9) H COO CH2S H2N H (12) COO CH2S H3N (1) (5) (7) H H N NH COO COO COO CH2 H3N H H N NH COOH CH2 H2N H H N N CH2 H3N H H N N CH2 (12) H3N (1) NH3 H COOH (CH2)4 COO H2N H (9.5) COO H3N (7) NH3 H (CH2)4 NH3 (CH2)4 H2N H (12) COO (CH2)4 NH2 H3N (1) H COOH CH2OH CH2OH CH2OH H3N (7) H COO H2N H (12) COO H3N (1) H COOH CH3 H3N (7) H COO CH3 H2N H (12) COO CH3 H H2N S H COOH CH2CH3 CH3 Allo-L-isoleucine R H3C H2N S H H COOH CH2CH3 L-Isoleucine S H H2N S OH H COOH CH3 L-Threonine R 456 • Chapter 26 AMINO ACIDS, PEPTIDES, PROTEINS, AND NUCLEIC ACIDS: NITROGEN-CONTAINING POLYMERS IN NATURE 1559T_ch26_454-468 10/20/05 15:39 Page 456