Which of the following statements about α-helices is false?

• A. Myoglobin & hemoglobin α-helices are right-handed α-helices.
• B. Each residue of an α-helix creates a 100˚ turn of the α-helix backbone.
• C. The core of an α-helix is tightly packed with backbone atoms.
• D. α-helices have an overall macrodipole with a partially positive C-terminus & partially negative N-terminus.
• E. Hydrogen bonds that hold the α-helix together are about parallel to the axis of the helix.

Answer: (D)

Verified step by step guidance

1. Understand the structure of α-helices: α-helices are a common secondary structure in proteins, characterized by a right-handed coil where the backbone atoms are tightly packed.
2. Examine the handedness of α-helices: Myoglobin and hemoglobin α-helices are indeed right-handed, which is typical for α-helices in proteins.
3. Consider the turn angle per residue: Each residue in an α-helix contributes to a 100˚ turn, which is consistent with the structural geometry of α-helices.
4. Analyze the macrodipole concept: α-helices have an overall macrodipole due to the orientation of the peptide bonds, typically with a partially positive N-terminus and partially negative C-terminus, not the reverse.
5. Evaluate hydrogen bonding: Hydrogen bonds in α-helices are parallel to the axis of the helix, stabilizing the structure, which is a true statement about α-helices.