Q. Why is proline an exception?
When proline is in a peptide bond, it does not have a hydrogen on the α amino group, so it cannot donate a hydrogen bond to stabilize an α helix or a β sheet. It is often said, inaccurately, that proline cannot exist in an α helix.
Q. Why are some regions disallowed in Ramachandran plot?
In computing a Ramachandran plot, atoms are treated as hard spheres whose dimensions correspond to their van der Waals radii. Any angle that results in the collision of the spheres is regarded as sterically unfavorable; hence, such conformations are also sterically not allowed.
Table of Contents
- Q. Why is proline an exception?
- Q. Why are some regions disallowed in Ramachandran plot?
- Q. Where is proline in Ramachandran plot?
- Q. Why is glycine Ramachandran plot symmetrical?
- Q. Why is proline Ramachandran plot different?
- Q. What does Ramachandran plot tell you?
- Q. What is the purpose of a Ramachandran plot?
- Q. What makes glycine a special amino acid when it comes to Ramachandran plots?
Q. Where is proline in Ramachandran plot?
Proline has restrictions in phi-psi space that arise from the 5-membered ring. Phi is restricted to approxamatly -60 by the ring and psi angles fall into two groupings near -45 and +135 in the helical and sheet regions of the Ramachandran plot.
Q. Why is glycine Ramachandran plot symmetrical?
The glycine plot is approximately symmetrical around the center, because glycine can adopt both right-handed and left-handed versions of any allowed conformation; however, there are some deviations from that symmetry, such as the different shapes and positions of the left- and right-handed α clusters.
Q. Why is proline Ramachandran plot different?
Its van der Waals radius is smaller and is thus less restricted. Proline, on the other hand has a 5-membered ring as a side chain. Therefore it is much more restricted than the other amino acids and allows for only a limited number of ψ and φ. Gly is the only amino acid that has no chiral center.
Q. What does Ramachandran plot tell you?
The Ramachandran plot is a plot of the torsional angles – phi (φ)and psi (ψ) – of the residues (amino acids) contained in a peptide. By making a Ramachandran plot, protein structural scientists can determine which torsional angles are permitted and can obtain insight into the structure of peptides.
Q. What is the purpose of a Ramachandran plot?
By making a Ramachandran plot, protein structural scientists can determine which torsional angles are permitted and can obtain insight into the structure of peptides.
Q. What makes glycine a special amino acid when it comes to Ramachandran plots?
Regions in the glycine Ramachandran plot. Glycine is fundamentally different to the other amino acids in that it lacks a sidechain. In particular, glycine does not have the Cβ atom, which induces many steric clashes in the generic Ramachandran plot.
