The Jasco J-815 circular dichroism (CD) spectroscopy measures differences in the absorption of left-handed polarized light versus right-handed polarized light that arise due to structural asymmetry. The absence of regular structure results in zero CD intensity, while an ordered structure results in a spectrum which can contain both positive and negative signals.
CD can be used for:
- Determination if a protein is folded
- Characterization of secondary structure (α-helix, β-sheet)
- Detection of changes in structure upon mutagenesis
- Studying conformational stability of proteins:
- pH stability
- denaturant stability (urea, guadinium hydrochloride)
- addition of stabilizers
- Detection of Changes in the conformation of a protein upon protein:protein interaction
Characterization of secondary structure is probably the most used CD spectroscopy application. Secondary structure can be identified in the "far-UV" spectral region (190-250 nm). The protein peptide bond is the chromophore, and it is possible to detect a signal if the protein is in a specific secondary structural conformation (α-helix, β-sheet).