Circular dichroism (CD) is the difference in the absorption of left-handed circularly polarised light (L-CPL) and right-handed circularly polarised light (R-CPL) and occurs when a molecule contains one or more chiral chromophores (light absorbing groups).
Circular Dichroism = ΔA(λ) = A(λ)L-CPL ‐ A(λ)R-CPL, where λ is the wavelength
Circular Dichroism Spectroscopy is a spectroscopic technique by which the CD generated by specific molecules would be measured over a range of wavelengths. CD spectroscopy is used extensively to study chiral molecules of various types and sizes, especially biological macromolecules where it finds its most important applications.
This phenomenon was discovered by Jean-Baptiste Biot, Augustin Fresnel, and Aimé Cotton in the first half of the 19th century. It is exhibited in the absorption bands of optically active chiral molecules. CD spectroscopy has a wide range of applications in many different fields.
UV Circular Dichroism
investigate the secondary structure of proteins.
UV/Vis Circular Dichroism
investigate charge-transfer transitions.
Near-infrared Circular Dichroism
investigate geometric and electronic structure by probing metal d→d transitions.
Vibrational Circular Dichroism
With the light from the infrared energy region for structural studies of small organic molecules, and most recently proteins and DNA.
In Creative Proteomics, this technique primarily is utilized to explore the secondary structure/conformation of macromolecules, particularly since secondary structures of these macromolecules are sensitive to its environment, temperature or pH, Circular Dichroism can be utilized to observe how secondary structure changes with environmental conditions or on interaction with other molecules. Structural, kinetic and thermodynamic information about macromolecules can be obtained from Circular Dichroism Spectroscopy.