Which Technique is Able to Investigate Secondary Structural Features of Proteins

Question

Which technique is able to investigate secondary structural features of proteins?
A) Infrared spectroscopy
B) Ultraviolet spectroscopy
C) Fluorescence spectroscopy
D) Circular dichroism
E) All of the above

Accepted Answer

All the listed techniques can be used to investigate secondary structural features of proteins, but they do so in different ways. Infrared spectroscopy can detect the amide bonds characteristic of proteins, which are influenced by the protein's secondary structure. Ultraviolet spectroscopy can detect the absorbance of peptide bonds and aromatic amino acids, which can be influenced by the protein's conformation. Fluorescence spectroscopy can be used to study the environment of fluorescent amino acids like tryptophan, which changes with the protein's folding. Circular dichroism is directly used to analyze the secondary structure of proteins by measuring the differential absorption of left and right circularly polarized light, which is affected by the protein's geometry.