1. Organic Chemistry 4 th Edition Paula Yurkanis Bruice Chapter 23 Amino Acids, Peptides, and Proteins Irene Lee Case Western Reserve University Cleveland, OH ©2004, Prentice Hall

2. Peptides and proteins are polymers of amino acids linked together by amide bonds

3. Aliphatic Side-Chain Amino Acids glycinealanine valineleucine isoleucine

4. Hydroxy-Containing Amino Acids Sulfur-Containing Amino Acids serinethreonine cysteine methionine

5. Acidic Amino Acids Amides of Acidic Amino Acids aspartatic acid glutamic acid asparagineglutamine

6. Basic Amino Acids lysine arginine

7. Benzene-Containing Amino Acids phenylalaninetyrosine

8. Heterocyclic Amino Acids proline histidine tryptophan

9. Configuration of Amino Acids

10. Acid–Base Properties of Amino Acids An amino acid can never exist as an uncharged compound

12. Some amino acids have ionizable hydrogens on their side chains

13. The isoelectric point (pI) of an amino acid is the pH at which it has no net charge

14. The pI of an amino acid that has an ionizable side chain is the average of the pK a values of the similarly ionizing groups

15. A mixture of amino acids can be separated by electrophoresis on the basis of their pI values Ninhydrin is used to detect the individual amino acids

17. A mixture of amino acids can also be separated on the basis of polarity

18. Ion-exchange chromatography can be used to perform preparative separation of amino acids Negatively charged resin binds selectively to positively charged amino acids

19. Cations bind most strongly to cation-exchange resins Anions bind most strongly to anion-exchange resins An amino acid analyzer is an instrument that automates ion-exchange chromatography Ion-Exchange Chromatography

20. Resolution of Racemic Mixtures of Amino Acids

21. Formation of a Peptide

22. Peptide Bond

23. Formation of Disulfide Bonds Disulfides can be reduced to thiols

24. The disulfide bridge in proteins contributes to the overall shape of a protein

26. Because amino acids have two functional groups, a problem arises when one attempts to make a particular peptide

27. Strategy for Making a Specific Peptide Bond

31. Amino acids can be added to the growing C-terminal end by repeating these two steps

32. When the desired number of amino acids has been added to the chain, the protecting group can be removed

33. An Improved Peptide Synthesis Strategy

38. The first step in determining the sequence of amino acids in a peptide or protein is to cleave the disulfide bridges

39. The next step is to determine the number and kinds of amino acids in the peptide or protein proteinamino acids 6 N HCl 100 ° C 24 h

40. The N-terminal amino acid of a peptide or a protein can also be determined by Edman degradation

41. The particular PTH-amino acid can be identified by chromatography using known standards

42. The C-terminal amino acid can be identified by treating the protein with carboxypeptidase

44. Cyanogen bromide causes the hydrolysis of the amide bond on the C-side of a methionine residue

47. Secondary Structure of Proteins Describe the conformation of segments of the backbone chain of a peptide or protein Three factors determine the choice of secondary structure: the regional planarity about each peptide bond maximization of the number of peptide groups that engage in hydrogen bonding adequate separation between nearby R groups

48. The  -Helix Is Stabilized by Hydrogen Bonds Prolines are helix breakers

49. Two Types of  -Pleated Sheets

50. Most globular proteins have coil conformations

51. The tertiary structure is the three-dimensional arrangement of all the atoms in the protein

52. The stabilizing interactions include covalent bonds, hydrogen bonds, electrostatic attractions, and hydrophobic interactions The tertiary structure is defined by the primary structure Disulfide bonds are the only covalent bonds that can form when a protein folds Proteins that have more than one peptide chain are called oligomers