L3-5 - 1 1 Biochemistry Sixth Edition Chapter 2 Protein...

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Unformatted text preview: 1 1 Biochemistry Sixth Edition Chapter 2 Protein Composition and Structure Copyright 2007 by W. H. Freeman and Company Berg Tymoczko Stryer 2 Insulin-A protein crucial for blood sugar Folding is hierarchical Crystallizes (allows structure to be determined) 3 Proteins have many functions: 1.) They can interact with DNA This protein (a homodimer) is a DNA clamp. Try Living Figure (Fig 2.1) 2 4 2.) Proteins can interact with one another ( i.e. stiff) Insect tissue with 2 types of proteins interacting Form a hexagonal array 5 3.) Proteins can be exible Protein engulfs the iron Signals its iron-bound state to other biomolecules The iron atom Conformation: Open Closed 6 The amino acids mirror plane Chiral center The -carbon Proteins are exclusively made of L The side chain (20 of them) 3 7 The L isomer has S confguration 8 pKa 2 pKa 9 At neutrality, zwitterionic Form dominates 9 The 20 amino acids--A synthetic organic chemists dream toolbox Memorize all 20 structures and abbreviations For next quiz/all exams. Glycine is uniquely achiral 4 10 The aliphatic amino acids isomers * Follow hydrophobic effect 11 Proline--The cyclic amino acid Special shape=special function Terminates -helices 12 The aromatic amino acids Hydrophobic effect H-bond Fluorescent (Trp) aromatic (stable) phenyl phenol indole 5 13 The aliphatic alcohol amino acids * Hydrophobic effect H-bond 14 The carboxamide amino acids Hydrophobic effect H-bond 15 A primary thiol amino acid Cysteine (Cys, C) Thiol is a great nucleophile. Under oxidizing conditions, forms disulFde crosslinks--next slide 6 16 Example of Cys-Cys crosslinks Cytosol=reducing (due to glutathione) Mitochondria=oxidizing no e 17 Intra- and interstrand crosslinks in insulin 18 Guanido group Imidazole group The basic (cationic) amino acids pKas: 10.8 12.5 6 Often bind DNA and RNA....
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L3-5 - 1 1 Biochemistry Sixth Edition Chapter 2 Protein...

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