In biochemistry, a Janin plot is like a Ramachandran plot

Ramachandran plot

-Introduction and early history:A Ramachandran plot , originally developed in 1963 by G. N. Ramachandran C. Ramakrishnan and V...

 — a way to visualize dihedral angle

Dihedral angle

In geometry, a dihedral or torsion angle is the angle between two planes.The dihedral angle of two planes can be seen by looking at the planes "edge on", i.e., along their line of intersection...

distributions in protein structures. While a Ramachandran plot relates the two backbone dihedral angles, a Janin plot relates the first side chain dihedral angle χ-1 against χ-2. Because not all amino acids have these dihedral angles, a Janin plot is not applicable to all such acids.

This correlation is different for the various amino acids and can depend on the type of secondary structure (Helix, Sheet, etc.) local to that residue. The plot is named for J. Janin, who studied these correlations in 1978.