1. Amino Acids and the Primary Structures of Proteins

2. Firefly Luciferase and Luciferin

3. Hemoglobin in erythrocytes

4. Keratin

5. Chemical structure of an amino acid R = side chain C = alpha carbon Amino terminus Carboxyl terminus

6. The alpha  carbon of amino acids is chiral (except glycine). There are two stereoisomers of amino acids (L and D). Proteins contain L-amino acids

7. L-amino acid at neutral pH Figure 3.1

8. Amino acids with aliphatic R groups

10. The amino acid proline is a cyclic molecule

11. Amino acids with aromatic R groups

12. Amino acids with sulfur-containing R groups

13. Oxidation can form cystine from two cysteines Figure 3.4

14. Side chains with alcohol groups

15. Amino acids with basic R groups

16. Amino acids with acidic R groups

17. Amide derivatives of acidic R groups

18. Other amino acids and amino acid derivatives Figure 3.5

19. Selenocysteine is the 21 st amino acid

20. Ionization of amino acids Pages 60 – 64 pH ?

21. Ionization of amino acids Pages 60 – 64 pH 1pH 7

22. pH ? pH 7 Ionization of amino acids Pages 60 – 64

23. pH 12 pH 7 Ionization of amino acids Pages 60 – 64

25. Ionization of histidine Figure 3.7

26. Ionization of histidine Figure 3.7

28. Ionization of glutamate Figure 3.8

29. Ionization of arginine Figure 3.8

30. Peptide bonds link amino acids in proteins Figure 3.9

31. Peptide bonds link amino acids in proteins Figure 3.9 Alanine Ala (A)Serine Ser (S) Dipeptide Ala – Ser or AS

32. Practice Problem Draw the chemical structure of the tripeptide Ala – Thr– Cys at pH 7. Answer the following with regard to this tripeptide: 1. Indicate the charge present on any ionizable group(s). 2. Indicate, using an arrow, which covalent bond is the peptide bond. 3. What is the net, overall charge of this tripeptide at pH 7? __________ 4. What is this peptide called using the one-letter code system for amino acids? ______

33. Proteins can be very large, hundreds of amino acids long The enzyme HMG-CoA reductase MLSRLFRMHGLFVASHPWEVIVGTVTLTICMMSMNMFTGNNKICGWNYECPK FEEDVLSSDIIILTITRCIAILYIYFQFQNLRQLGSKYILGIAGLFTIFSSFVFSTVVIH FLDKELTGLNEALPFFLLLIDLSRASTLAKFALSSNSQDEVRENIARGMAILGPTF TLDALVECLVIGVGTMSGVRQLEIMCCFGCMSVLANYFVFMTFFPACVSLVLEL SRESREGRPIWQLSHFARVLEEEENKPNPVTQRVKMIMSLGLVLVHAHSRWIAD PSPQNSTADTSKVSLGLDENVSKRIEPSVSLWQFYLSKMISMDIEQVITLSLALL LAVKYIFFEQTETESTLSLKNPITSPVVTQKKVPDNCCRREPMLVRNNQKCDSV EEETGINRERKVEVIKPLVAETDTPNRATFVVGNSSLLDTSSVLVTQEPEIELPRE PRPNEECLQILGNAEKGAKFLSDAEIIQLVNAKHIPAYKLETLMETHERGVSIRR QLLSKKLSEPSSLQYLPYRDYNYSLVMGACCENVIGYMPIPVGVAGPLCLDEKE FQVPMATTEGCLVASTNRGCRAIGLGGGASSRVLADGMTRGPVVRLPRACDSA EVKAWLETSEGFAVIKEAFDSTSRFARLQKLHTSIAGRNLYIRFQSRSGDAMGM NMISKGTEKALSKLHEYFPEMQILAVSGNYCTDKKPAAINWIEGRGKSVVCEA VIPAKVVREVLKTTTEAMIEVNINKNLVGSAMAGSIGGYNAHAANIVTAIYIAC GQDAAQNVGSSNCITLMEASGPTNEDLYISCTMPSIEIGTVGGGTNLLPQQACL QMLGVQGACKDNPGENARQLARIVCGTVMAGELSLMAALAAGHLVKSHMIH NRSKINLQDLQGACTKKTA

34. Next: Chapter 4 Proteins: Three-Dimensional Structure and Function