A Ramachandran plot shows: A) the amino acid residues which have the greatest degree of rotational freedom. B) the sterically allowed rotational angles between R groups and α-carbons in a peptide. C) the sterically allowed rotational angles between Cα and the amide nitrogen (C_α−N) as well as between Cα and the amide carbonyl carbon (C_α−CO). D) the sterically allowed rotational angles about the amide nitrogen (NH) and CO. E) the amino acid residues that form α-helix, β-sheet, etc.

Question

Quizplus · Accepted Answer

A Ramachandran plot shows the sterically allowed rotational angles between Cα and the amide nitrogen (C_α−N) as well as between Cα and the amide carbonyl carbon (C_α−CO). It is used to determine the possible conformations of a polypeptide chain, and thus provides insights into protein folding and stability. The other choices are incorrect: A is too specific and does not accurately describe the purpose of a Ramachandran plot, B is partially correct but only considers the R groups and not the backbone angles, D is incorrect because it only considers the amide nitrogen and carbonyl carbon angles and not the entire backbone, and E is too broad and does not accurately describe the information provided by a Ramachandran plot.

A Ramachandran Plot Shows