lecture 5 outline

lecture 5 outline - Lecture #5: Proteins II:...

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Lecture #5: Proteins II: Structure/Function I. Overview A. General Principles Handout #14 B. Four main levels of protein structure (fig 3-16) II. Secondary Structure A. The peptide bond is rigid and planar (fig 4-2) 1. Resonance hybrid has partial double bond character 2. No rotation occurs about the peptide bond 3. All peptide bonds are in a trans configuration. Exceptions to this can occur when proline is involved 4. Rotation about the N-C α and C α -C bonds ( φ and ψ ) is limited by steric overlap between the carbonyl O and the α -amino H. Significance: These properties limit the number of conformations that a protein can assume.
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B. The alpha-helix ( α -helix) 1. Basis of the model Handout #15, (fig 4-4) 2. Amino acids rarely found in α -helices 3. Dipoles are connected, via H-bonds, within the helix to give an overall electric dipole that increases with helix length. (fig 4-6)
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C. The β -pleated sheet Handout #16, (fig 4-7) 40-60% of amino acids in a protein are in an α -helix or
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This note was uploaded on 04/07/2008 for the course BIO 100 taught by Professor Rothwell during the Summer '08 term at UCSC.

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lecture 5 outline - Lecture #5: Proteins II:...

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