CHM361H5 Chapter Notes - Chapter 6: Alpha Helix, Steric Effects, Beta Sheet
Document Summary
Chapter 6 - proteins: secondary, tertiary, and quaternary structure. Due to the double bond characteristic of peptide bonds, a planar structure around the bond is formed: the resonance stabilization energy of the structure is 88 kj/mol. Each turn has 3. 6 amino acid residues. Each amino acid residue extends 1. 5 a (0. 15 nm) The pitch of the helix for one turn is 5. 4 a. Each carbonyl group is hydrogen bonded to a nitrogen four residues away. Ignoring the side chains, the helix has a diameter of 6 a. It has an overall dipole moment, the n-terminus is slightly positively charged, while the c-terminus is slightly negatively charged. All the hydrogen bonds point in the same direction. There is helix capping, it provides h-bonds for the n-h and c=o groups and. If there are 12 residues then (n-4), there are 8 hydrogen bonds provides a hydrophobic cap for exposed nonpolar side chains.
