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Ramachandran Plot definitions

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  • Ramachandran Plot
    Graphical representation showing permissible and non-permissible phi and psi angles in polypeptides, revealing protein secondary structure regions.
  • Phi Angle
    Rotation angle around the alpha carbon-nitrogen bond in the peptide backbone, ranging from -180 to +180 degrees.
  • Psi Angle
    Rotation angle around the alpha carbon-carbonyl carbon bond in the peptide backbone, ranging from -180 to +180 degrees.
  • Omega Angle
    Rotation angle of the peptide bond, restricted due to partial double bond character, and excluded from Ramachandran plots.
  • Alpha Carbon
    Central carbon atom in an amino acid, bonded to the R group, nitrogen, and carbonyl carbon, serving as the axis for phi and psi rotations.
  • Peptide Bond
    Chemical linkage between amino acids, exhibiting partial double bond character, resulting in limited rotational freedom.
  • Steric Hindrance
    Spatial restriction caused by R groups and backbone carbonyl oxygens, limiting permissible phi and psi angles.
  • Permissible Region
    Area on the Ramachandran plot, often colored blue, where phi and psi angles are allowed due to minimal steric clashes.
  • Non-Permissible Region
    Area on the Ramachandran plot, often colored white, where phi and psi angles are forbidden due to steric hindrance.
  • Alpha Helix
    Secondary protein structure, typically found in the bottom left quadrant of the Ramachandran plot.
  • Beta Sheet
    Secondary protein structure, typically found in the upper left quadrant of the Ramachandran plot.
  • Amino Acid Residue
    Individual unit within a polypeptide, each possessing unique phi and psi angles influencing protein structure.
  • Carbonyl Group
    Functional group consisting of a carbon double-bonded to oxygen, forming part of the peptide backbone.
  • Newman Projection
    Molecular depiction used to visualize bond angles by looking down the length of a bond, relevant for phi and psi measurements.
  • Quadrant
    Section of the Ramachandran plot used to localize secondary structure regions such as alpha helices and beta sheets.