Question

Which of the following techniques is/are used for determining the three-dimensional structure of proteins?

• A. Cryo-electron Microscopy
• B. Circular Dichroism
• C. Nuclear Magnetic Resonance (NMR) Spectroscopy
• D. X-ray Diffraction

Hint:

Cryo-EM, X-ray crystallography, and NMR spectroscopy are the three major techniques for protein 3D structure determination. Circular dichroism is useful for secondary structure, not full 3D.

Answer 1

The Correct Option is A, C, D

- Cryo-EM (A): Provides near-atomic resolution 3D structures of large protein complexes without crystallization.
- Circular Dichroism (B): Gives information on secondary structure content (e.g., alpha-helix, beta-sheet), but cannot resolve complete 3D structures.
- NMR spectroscopy (C): Determines 3D structures of proteins (especially small/medium-sized proteins) in solution.
- X-ray diffraction (D): Classical and widely used method for atomic-level 3D protein structures.
\fbox{Therefore, the correct answer is (A), (C), and (D).}