Question

The helical content of a protein can be directly determined using

• A. infrared spectrometer
• B. fluorescence
• C. circular dichroism
• D. UV-visible spectrophotometer

Hint:

Circular Dichroism is a powerful tool to study the secondary structure of proteins and is widely used to determine alpha-helical and beta-sheet content.

Answer 1

The Correct Option is C

Step 1: Understand what is meant by 'helical content'.
Helical content refers to the proportion of alpha-helices in the secondary structure of a protein.

Step 2: Identify the most accurate technique for measuring secondary structure.
Circular Dichroism (CD) spectroscopy is the most reliable technique for analyzing protein secondary structures, including alpha-helices, beta-sheets, and random coils. It measures the differential absorption of left and right circularly polarized light, which is sensitive to the secondary structure.

Step 3: Evaluate other options.
Infrared spectrometer: Useful for functional group identification but not specific or quantitative for helical content.
Fluorescence: Mainly used for tertiary structure and the environment of aromatic residues, not secondary structure.
UV-visible spectrophotometer: Measures general absorbance, not suitable for assessing helicity.