Quiz Next Tuesday (09/18) Figure 4.18 Cation (a) and anion (b) exchange resins commonly used for biochemical separations. Figure 4.21 Chromatographic fractionation of a synthetic mixture of amino acids on ion exchange columns using Amberlite IR-120, a sulfonated polystyrene resin similar to Dowex-50. A second column with different buffer conditions is used to resolve the basic amino acids. (Adapted from Moore, S., Spackman, D., and Stein, W., Chromatography of amino acids on sulfonated polystyrene resins. Analytical Chemistry 30:11851190.) 5.1 - What Is the Fundamental Structural Pattern in Proteins? Figure 5.3 The -COOH and - NH 3 + groups of two amino acids can react with the resulting loss of a water molecule to form a covalent amide bond. Figure 5.4 Anatomy of an amino acid. Except for proline and its derivatives, all of the amino acids commonly found in proteins possess this type of structure. The Coplanar Nature of the Peptide Bond Six atoms of the peptide group lie in a plane! 5.2 What Architectural Arrangements Characterize Protein Structure? Proteins are classed according to shape and and solubility Shape - globular or fibrous The four levels of protein structure - Primary- - Secondary - - Tertiary - Quaternary - Proteomics: Studying Protein Structure and Function -Proteins tend to be least soluble at their isoelectric point -Increasing ionic strength at first increases the solubility of proteins (salting-in), then decreases it (salting-out) Gel Filtration Chromatography Affinity Chromatography SDS-PAGE Electrophoresis