GATE BT 2023 • Q28
MCQ • 1 Mark
Section 4: Bioprocess Engineering and Process Biotechnology
Mass transfer in bioprocesses (kLa)
Subtopic: Fundamentals of Mass transfer in bioprocesses (kLa)
Question Statement:
Which one of the following methods CANNOT be used to determine the
secondary structure content of a protein?
Options:
-
(A) Circular dichroism spectroscopy
-
(B) Fourier transform infrared spectroscopy
-
(C) Mass spectrometry
-
(D) X-ray crystallography
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2023 Q.28)**
**1. Governing Concept**:
- **Topic**: Biophysical Techniques & Protein Structure Determination
- Secondary structure content of proteins ($\alpha$-helix, $\beta$-sheet, random coil) can be quantitatively estimated by:
- **Circular Dichroism (CD) spectroscopy**: Far-UV spectra ($190-250\text{ nm}$) show distinct signatures for $\alpha$-helices (minima at 208 and 222 nm) and $\beta$-sheets (minimum at 218 nm).
- **FTIR spectroscopy**: Amide I vibrational band ($1600-1700\text{ cm}^{-1}$) deconvolutes into secondary structure components.
- **X-ray crystallography**: Atomic coordinates directly define secondary structure hydrogen bonding networks.
- **Mass spectrometry** measures mass-to-charge ratios ($m/z$) to determine molecular weight, primary sequence, and post-translational modifications; native MS or HDX can report conformational dynamics, but standard MS **cannot directly quantify secondary structure content**.
**2. Option Analysis**:
- **Option (A) is INCORRECT**: CD spectroscopy is the standard laboratory method for secondary structure quantification.
- **Option (B) is INCORRECT**: FTIR Amide I band readily quantifies secondary structure.
- **Option (C) [Mass spectrometry] is CORRECT**: Cannot directly determine secondary structure content.
- **Option (D) is INCORRECT**: X-ray diffraction yields atomic secondary structural assignments.
**3. Final Answer**:
- **Correct Choice**: **C**
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