Subtopic: Fundamentals of Biomolecules, enzyme kinetics
Question Statement:
Tertiary structure of a protein consisting of a-helices and B-strands can be
determined by
Options:
(A) circular dichroism spectroscopy
(B) mass spectrometry
(C) nuclear magnetic resonance spectroscopy
(D) UV spectroscopy
Official Answer Key:
C
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2021 Q.44)**
**1. Governing Concept**:
- **Topic**: Biophysical Techniques & High-Resolution Protein Structure
- Methods for solving high-resolution 3D tertiary structures consisting of individual $\alpha$-helices and $\beta$-strands:
- **Nuclear Magnetic Resonance (NMR) spectroscopy** (along with X-ray crystallography and Cryo-EM) is an atomic-resolution structural biology technique that solves the complete three-dimensional coordinates and tertiary fold of proteins in solution.
- Circular Dichroism (CD) and UV spectroscopy provide secondary structure percentages or chromophore environments, but cannot determine tertiary atomic 3D coordinates.
- Mass spectrometry provides molecular mass and sequence, not 3D structure.
**2. Option Analysis**:
- **Option (A) is INCORRECT**: CD spectroscopy only provides global secondary structure percentages.
- **Option (B) is INCORRECT**: Mass spectrometry does not yield atomic 3D coordinates.
- **Option (C) [NMR spectroscopy] is CORRECT**: High-resolution technique determining complete tertiary structures of proteins in solution.
- **Option (D) is INCORRECT**: UV spectroscopy only reports electronic aromatic absorption.
**3. Final Answer**:
- **Correct Choice**: **C**
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