BME 20100 Chapter Notes - Chapter 4: Alpha Helix, Alpha And Beta Carbon, Beta Sheet
27 Nov 2017
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Document Summary
Peptide is rigid and planar secondary structure. Organization around peptide bond, paired with identity of r groups, determines. Rotation around peptide bond is not permitted due to resonance structure. Rotation around bonds connected to the alpha carbon is permitted. In a fully extended polypeptide, both phi and psi are 180. Protein"s conformation comes from weak interactions between r groups. Interaction of n-h and c=o of peptide bonds lead to local regular structures such as alpha helices and beta sheets. Long range strong interaction between permanently charged groups. Medium-range weak interaction between all atoms contributes significantly to stability in interior of protein. Hydrogen bonds and ionic interactions within a protein are maximized. Peptide bond is a resonance hybrid of 2 canonical structures. To exhibit a large dipole moment in favored trans configuration. To be less reactive compared with esters. A-helix: stabilized by h-bonds between nearby residues. Held together by hydrogen bonds between n(c=o) and n+4(n-h)
