Circular Dichroism

Circular Dichroism (CD) spectroscopy measures the differential absorption of left- and right-circularly polarized light by optically active molecules, particularly proteins and nucleic acids. Introduced by Greenfield and Fasman in 1969, CD is a rapid, non-destructive technique for characterizing secondary structure (alpha-helix, beta-sheet), monitoring protein folding transitions, and assessing conformational changes in response to pH, temperature, or ligand binding.