Circular dichroism

Circular dichroism (CD) is dichroism involving circularly polarized light, i.e., the differential absorption of left- and right-handed light.^[1]^[2] Left-hand circular (LHC) and right-hand circular (RHC) polarized light represent two possible spin angular momentum states for a photon, and so circular dichroism is also referred to as dichroism for spin angular momentum.^[3] This phenomenon was discovered by Jean-Baptiste Biot, Augustin Fresnel, and Aimé Cotton in the first half of the 19th century.^[4] Circular dichroism and circular birefringence are manifestations of optical activity. It is exhibited in the absorption bands of optically active chiral molecules. CD spectroscopy has a wide range of applications in many different fields. Most notably, UV CD is used to investigate the secondary structure of proteins.^[5] UV/Vis CD is used to investigate charge-transfer transitions.^[6] Near-infrared CD is used to investigate geometric and electronic structure by probing metal d→d transitions.^[2] Vibrational circular dichroism, which uses light from the infrared energy region, is used for structural studies of small organic molecules, and most recently proteins and DNA.^[5]

^ P. Atkins; J. de Paula (2005). Elements of Physical Chemistry (4th ed.). Oxford University Press. ISBN 978-0-7167-7329-0.
^ ^a ^b Edward I. Solomon; A. B. P. Lever (3 February 2006). Inorganic electronic structure and spectroscopy. Wiley-Interscience. p. 78. ISBN 978-0-471-97124-5. Retrieved 29 April 2011.
^ Introduction to Quantum Theory 2ED David Park Sec 2.2 Pg32 "...the polarization of a beam of light is exactly the same kind of thing as the spin of a beam of electrons, the differences of terminology reflecting only the accidents of the historical order of discovery."
^ Gerald D. Fasman (1996). Circular dichroism and the conformational analysis of biomolecules. Springer. pp. 3–. ISBN 978-0-306-45142-3. Retrieved 29 April 2011.
^ ^a ^b Kōji Nakanishi; Nina Berova; Robert Woody (1994). Circular dichroism: principles and applications. VCH. p. 473. ISBN 978-1-56081-618-8. Retrieved 29 April 2011.
^ Solomon, Neidig; A. T. Wecksler; G. Schenk; T. R. Holman (2007). "Kinetic and Spectroscopic Studies of N694C Lipoxygenase: A Probe of the Substrate Activation Mechanism of a Non-Heme Ferric Enzyme". J. Am. Chem. Soc. 129 (24): 7531–7537. doi:10.1021/ja068503d. PMC 2896304. PMID 17523638.