Peptides

The 20 amino acids specified by the genetic code are linked into proteins by the peptide bond, as illustrated here by the dipeptide, alanylserine.

  The partial double bond character of the peptide bond prevents free rotation around the bond. Six atoms that make up the peptide plane group lie in the same plane.
  Ball-and-stick model of Ala-Ser. Can you identify the six atoms in the peptide plane?
  Here the atoms of the peptide plane are shown in green. Take a moment to convince yourself that the peptide plane in Ala-Ser is planar by looking at the molecule from different directions.

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