Secondary Conformation in the Same Quadrant of the Ramachandran Plot

The Ramachandran plot is a graphical representation that shows the allowed regions of phi (ϕ) and psi (ψ) angles for amino acid residues in proteins. It helps in understanding the secondary structure of proteins by providing information about the conformational preferences of amino acids.

In the Ramachandran plot, the phi (ϕ) angle is plotted on the x-axis, and the psi (ψ) angle is plotted on the y-axis. Each amino acid residue in a protein can adopt different combinations of phi and psi angles, and these combinations determine the secondary structure elements present in the protein.

Among the given options, the right-handed alpha helix and the 310 helix are in the same quadrant of the Ramachandran plot.

Right-Handed Alpha Helix
- Alpha helix is a common secondary structure element in proteins.
- The right-handed alpha helix is characterized by the phi (ϕ) angle of approximately -60 degrees and the psi (ψ) angle of approximately -45 degrees.
- In the Ramachandran plot, this combination of angles falls in the region of the plot where both phi and psi angles are negative.
- This conformation allows for the formation of a stable helical structure held together by hydrogen bonds between the carbonyl oxygen of one residue and the amide proton of another residue, four residues away in the sequence.

310 Helix
- The 310 helix is a less common secondary structure element compared to the alpha helix.
- It is characterized by the phi (ϕ) angle of approximately -49 degrees and the psi (ψ) angle of approximately -26 degrees.
- In the Ramachandran plot, this combination of angles falls in the region of the plot where the phi angle is negative and the psi angle is positive.
- The 310 helix is named after the 3 amino acid residues per turn and 10 atoms involved in the hydrogen bonding pattern.
- It is less stable than the alpha helix and is usually found in specific protein structures or regions with specific sequence patterns.

Therefore, both the right-handed alpha helix and the 310 helix are in the same quadrant of the Ramachandran plot, where the phi angle is negative. They represent different types of secondary structure elements commonly found in proteins.