5. RAMACHANDRAN PLOT
It was developed in 1963 by G.N. Ramachandran, C. Ramakrishnan and V. Sasisekharan. The degree of freedom in peptide bond of polypeptide chain is indicated by the dihedral angles named Phi () and Psai (). Ramchandran plots show the possible conformations of Phi () and Psai () angles for a polypeptide.
The value of f and y is 0 to ± 180° from left hand corner starts from – 180 degree and extends to + 180 for both axis. Highest density of dots on the plot indicates the allowed regions or energy regions. At this region torsion angle come close to each other results in steric hindrance.
In Ramachandran plot glycine provide high flexibility to the polypeptide chain i.e. it may adopt torsion angles, which are normally not allowed for other amino acids.
0 to ± 180 are the theoretical values to Phi () and Psai () that could be clustered around – 57, – 47 and – 80, + 150 respectively, all these are practical value given by Ramachandran.
Ramachandran plot provide valuable information on the quality of a protein. Structure and amino acid sequence and tertiary protein structure.