Ramachandran plot

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Example of a ramachandranplot

A Ramachandran plot visualizes the torsion angles φ against ψ (phi-psi angle) of all amino acids in a protein.

Residues in α-helices can occupy other torsion angles than residues β-sheets, this can be seen in the figure. Glycine has a considerably larger allowable area because it has only a hydrogen as sidechain. In contrast, the Ramachandran plot for proline shows only a very limited number of possible combinations of ψ and φ.