This slide shows a peptide bond between two amino acids in 3D with one R group coming towards you and one R group facing away from you. The peptide bonds linking amino acids are planar, meaning that both alpha carbons and the atoms of the peptide bond lie in the same plane. From this structure, we learn the concepts of resonance and the difference between cis and trans configurations.
Resonance
- Accounts for the double bond within the peptide bond shifting between carbon-oxygen to carbon-nitrogen.
- Constrains the peptide bond, so that it CANNOT rotate, which gives the polypeptide sequences a backbone with little room for conformational change.
Peptide Bond Configurations
- Trans – the oxygen and hydrogen atoms face two different directions,
- Cis – the oxygen and hydrogen atoms face the same directions.