Ramachandran plot

From Wikipedia, the free encyclopedia

A Ramachandran plot generated from the protein PCNA, a human DNA clamp protein that is composed of both beta sheets and alpha helices (PDB ID 1AXC). Points that lie on the axes indicate N- and C-terminal residues for each subunit.
A Ramachandran plot generated from the protein PCNA, a human DNA clamp protein that is composed of both beta sheets and alpha helices (PDB ID 1AXC). Points that lie on the axes indicate N- and C-terminal residues for each subunit.

A Ramachandran plot (also known as a Ramachandran map or a Ramachandran diagram), developed by Gopalasamudram Narayana Ramachandran, is a way to visualize dihedral angles φ against ψ of amino acid residues in protein structure. It shows the possible conformations of φ and ψ angles for a polypeptide.

One would expect that larger side chains would result in more restrictions and consequently a smaller allowable region in the Ramachandran plot. In practice this does not appear the case; only the methylene group at the β position has an influence.

Glycine has a hydrogen atom, with a smaller van der Waals radius, instead of a methyl group at the β position. Hence it is least restricted and this is apparent in the Ramachandran plot for Glycine for which the allowable area is considerably larger.

In contrast, the Ramachandran plot for proline shows only a very limited number of possible combinations of ψ and φ.

One can also plot the dihedral angles in polysaccharides in this fashion.

[edit] Software

  • STING
  • Pymol with the DynoPlot extension
  • VMD, distributed with dynamic Ramachandran plot plugin

[edit] External links

In other languages