Figure Number: 23-00CO Title: Oxidized Glutathione Caption: Ball-and-stick model of oxidized glutathione. Notes: Oxidized glutathione is a tripeptide with a disulfide linkage connecting two molecules. The reduced form is used to keep sulfhydryl groups in proteins from forming disulfide links.

Figure Number: 23-00-22UN Title: Glycine, Leucine, Aspartate, and Lysine Caption: Potential maps of glycine, leucine, aspartate, and lysine. Notes: Glycine is hydrophilic, leucine is hydrophobic, aspartate is acidic, and lysine is a basic amino acid.

Figure Number: 23-00-29UN Title: Alanine Caption: Ball-and-stick model of l-alanine. Notes: l-Alanine is one of the 20 natural amino acids used by nature to build proteins.

Figure Number: 23-01 Title: Figure 23.1 Caption: Arginine, alanine, and aspartic acid separated by electrophoresis at pH = 5. Notes: Amino acids can be separated according to their pI values using electrophoresis. Amino acids having pI values greater than the pH of the electrophoresis buffer migrate toward the negative electrode, and amino acids having pI values lower than the pH value of the electrophoresis buffer migrate toward the positive electrode.

Figure Number: 23-02 Title: Figure 23.2 Caption: Separation of glutamate, alanine, and leucine by paper chromatography. Notes: Since paper is a carbohydrate polymer (very hydrogen-bonding) the most polar amino acids migrate the slowest.

Figure Number: 23-03 Title: Figure 23.3 Caption: Structure of a section of a cation-exchange resin called Dowex 50. Notes: Cation-exchange resins will release cations and impede cationic amino acids by replacing the released cations with the cationic amino acids. Anion-exchange resins will do the reverse.

Figure Number: 23-04 Title: Figure 23.4 Caption: Separtaion of amino acids by ion-exchange chromatography. Notes: A mixture of amino acids is run through an ion-exchange resin and fractions are collected in separate sample tubes. The concentration of amino acid in each tube is measured with ninhydrin and plotted vs. sample number. Enough fractions are collected so that each amino acid is collected in several tubes and separated from all other amino acids.

Figure Number: 23-05 Title: Figure 23.5 Caption: Chromatogram obtained from an automated amino-acid analyzer. Notes: Buffers of increasingly higher pH are used to elute amino acids having sidechains with increasingly higher pKa values. Shown in the figure is a chromatogram using a cation-exhange resin. Acidic (anionic) amino acids elute before hydrophobic amino acids, which elute before basic (cationic) amino acids.

Figure Number: 23-07-01UN Title: Intrachain and Interchain Disulfide Bridges Caption: Schematic of polypeptide chains showing interchain and intrachain disulfide bridges. Notes: Intrachain disulfide bridges bond together different parts of the same polypeptide molecule. Interchain disulfide bridges bond together different polypeptide molecules.

Figure Number: 23-08a Title: Figure 23.8 Caption: a. Side view of a protein segment with an a-helix structure. b. Longitudinal view of a protein segment with an a-helix structure. Notes: The a-helix structure is a secondary structure held together by amide N–H to amide carbonyl hydrogen bonding in the backbone of the protein molecule.

Figure Number: 23-10 Title: Figure 23.10 Caption: Backbone secondary structure of carboxypeptidase A. Notes: a-Helical sections are purple. b-Sheet sections are flat green arrows pointing toward the carboxy terminus of the protein.

Figure Number: 23-11 Title: Figure 23.11 Caption: Stabilizing interactions involved in maintaining the tertiary structure of a protein. Notes: Tertiary structure is maintained by interactions between sidechains of different amino acids within the same protein molecule.

Figure Number: 23-12 Title: Figure 23.12 Caption: Three-dimensional structure of carboxypeptidase A. Notes: Carboxypeptidase A, an elliptically shaped protein made from 307 amino acids, is used by the body to digest protein in the upper GI tract.

Figure Number: 23-13-02P42 Title: End-of-Chapter Problem 42 Caption: Two-dimensional chromatogram associated with end-of-chapter Problem 42. Notes: Identify the six amino acid spots in the two-dimensional chromatogram by calculating pI values for the six amino acids listed in the problem and arranging the amino acids with pI values near 5 in order of relative polarity.

Figure Number: 23-13-03P51 Title: End-of-Chapter Problem 51 Caption: Two-dimensional chromatogram associated with end-of-chapter Problem 51. Notes: Identify the amino-acid spots on the two-dimensional chromatogram by calculating pI values for the 15 amino acids listed in the problem, and by comparing polarities. Two of the amino acids do not separate. They form a single spot.

Figure Number: 23-13-05P54 Title: End-of-Chapter Problem 54 Caption: UV spectra associated with end-of-chapter Problem 54. Notes: Use the UV spectra of tryptophan, tyrosine, and phenylalanine shown in the figure to calculate the molar absorptivity of each of these amino acids at 280 nm.

Figure Number: 23-13-06P55 Title: End-of-Chapter Problem 55 Caption: Two-dimensional chromatograms associated with end-of-chapter Problem 55. Notes: Look at the two-dimensional chromatogram of the amino acids composing a mutant polypeptide on the right side of the figure. Find the amino-acid spot which is missing from the normal polypeptide two-dimensional chromatogram on the left, and find the amino-acid spot which is only found in the mutant polypeptide chromatogram on the right. These differences are due to the presence of a replacement amino acid found in the mutant polypeptide in place of the amino acid missing in the normal polypeptide. Determine whether the replacement amino acid is more or less polar than the normal amino acid, and determine whether the replacement amino acid has a higher or lower pI value than the normal amino acid.

Figure Number: Title: Table 23.1 The most Common Naturally Occuring Amin Acids pt1 Caption: Notes:

Figure Number: 23-TB01pt2 Title: Table 23.1 The most Common Naturally Occuring Amin Acids pt2 Caption: Notes:

Figure Number: Title: Table 23.1 The most Common Naturally Occuring Amin Acids pt3 Caption: Notes:

Figure Number: Title: Table 23.2 The pK2 Values of Amino Acids Caption: Notes:

Figure Number: Title: Table 23.3 Specificity of Peptides of Protein Cleavage Caption: Notes: