A fragment of polypeptide backbone is shown above without the actual side chains. (Choose "peptide_view2" for a second image of this model.) Note the following general features of peptide units: Label the atoms in residue 1. Highlight the four atoms in the first peptide unit as Ball & Stick. Color black, the peptide bond. Rotation, with preferred dihedral angles, occurs around these two backbone bonds: (Psi), rotation about the CA1-C1 single bond; and (Phi), rotation about the N1-CA1 single bond. Some facts on Peptide bonds. The atom-labelling used above are RasMol abbreviations: N, the amino nitrogen. CA, the a-carbon. R, the R-group (or side chain). C & O, the carbonyl group. The peptide bond (C1-N2, and colored black above) joins amino acids in the primary structure of polypeptides. The partial double bond character of the peptide bond keeps the peptide unit rigidly planar. The oxygen of each peptide unit is nearly always trans to the amide hydrogen. The peptide bond is sometimes designated as "omega". Return to image of peptide bonds.
Some facts on Peptide bonds. The atom-labelling used above are RasMol abbreviations:
Return to image of peptide bonds.
