The Ramachandran Plot was described on 1963 by Ramachandran, G.N.; Ramakrishnan, C.; Sasisekharan, V. [1]
Ramachandran outlier are those aminoacids with non favorable dihedral angles, and Ramachandran plot is a powerful tool for making those evident. Most of the times, Ramachandran outliers are a consequence of mistakes during the data processing.
However, sometimes, Ramachandran outliers might play a special role in the structure function. See for example the case of Ser-200 in the structure . Let's draw the .
Notice that the residues in are colored in yellow, the residues in colored in magenta, in blue and in white. At any time you may residues
