Circular Dichroism Spectrum of Proteins

Circular Dichroism (CD) is a spectroscopic technique commonly used to study the secondary structure of biological macromolecules such as proteins and nucleic acids. This technique is based on the characteristic of chiral centers in molecules (such as α-helices and β-folds in proteins) absorbing left and right circularly polarized light differently.

 

In the CD spectrum of proteins, the following aspects are usually focused on:

 

Judgement of Secondary Structure

By analyzing the shape and intensity of the CD spectrum, the composition of the protein's secondary structure (α-helix, β-fold, random coil, etc.) can be inferred.

 

Observation of Conformational Changes

By measuring the protein's CD spectrum under different conditions (such as different pH, temperature, or in the presence of a ligand), the conformational changes of the protein can be studied.

 

Thermal Stability Studies

The CD spectrum of the protein is measured at a series of temperatures to evaluate its thermal stability and study the protein's thermal denaturation process.

 

Study of Protein Folding

CD can be used to track the protein folding process and observe the structural changes of the protein at different time points.

 

Monitoring of Ligand Binding

CD can also be used to monitor the binding process of the ligand and the protein.

 

Specific Characteristics of Typical Protein CD Spectra in the UV Region (Usually 190-250nm)

1. α-helix shows two negative peaks at about 222 and 208 nm.

2. β-fold manifests as a positive peak at about 217 nm

3. The random coil structure has a negative peak at around 200 nm.