Raman optical activity
Encyclopedia
Raman optical activity (ROA) is a vibrational spectroscopic
technique that is reliant on the difference in intensity of Raman scattered
right and left circularly polarised light due to molecular chirality
.
with Peter Atkins
at the University of Oxford
and was later further developed by Barron with David Buckingham at the University of Cambridge
.
More developments, including important contributions to the development of practical Raman optical activity instruments, were made by Werner Hug of the University of Friburg
, and Lutz Hecht with Laurence Barron at the University of Glasgow.
s of a chiral molecule, which leads to a difference between the intensities of the right- and left-handed circularly polarised scattered beams. The spectrum of intensity differences recorded over a range of wavenumber
s reveals information about chiral centres in the sample molecule.
Raman optical activity can be observed in a number of forms, depending on the polarization of the incident and the scattered
light. For instance, in the scattered circular polarization (SCP) experiment, the incident light
is linearly polarized and differences in circular polarization of the scattered light are measured.
In the dual circular polarization (DCP), both the incident and the scattered light are circularly
polarized, either in phase (DCPI ) or out of phase (DCPII ).
structure and behaviour in aqueous solution. It has been used to study protein
, nucleic acid
, carbohydrate
and virus
structures. Though the method does not reveal information to the atomic resolution of crystallographic
approaches, it is able to examine structure and behaviour in biologically more realistic conditions (compare the dynamic solution structure examined by Raman optical activity to the static crystal structure).the structures are very important
and circular dichroism
.
Spectroscopy
Spectroscopy is the study of the interaction between matter and radiated energy. Historically, spectroscopy originated through the study of visible light dispersed according to its wavelength, e.g., by a prism. Later the concept was expanded greatly to comprise any interaction with radiative...
technique that is reliant on the difference in intensity of Raman scattered
Raman scattering
Raman scattering or the Raman effect is the inelastic scattering of a photon. It was discovered by Sir Chandrasekhara Venkata Raman and Kariamanickam Srinivasa Krishnan in liquids, and by Grigory Landsberg and Leonid Mandelstam in crystals....
right and left circularly polarised light due to molecular chirality
Chirality (chemistry)
A chiral molecule is a type of molecule that lacks an internal plane of symmetry and thus has a non-superimposable mirror image. The feature that is most often the cause of chirality in molecules is the presence of an asymmetric carbon atom....
.
History of Raman optical activity
The field began with the doctoral work of Laurence D. BarronLaurence D Barron
Laurence David Barron FRS, FRSE is Gardiner Professor of Chemistry, at the University of Glasgow, Glasgow, since 1975. -Life:...
with Peter Atkins
Peter Atkins
Peter William Atkins is a British chemist and former Professor of Chemistry at the University of Oxford and a Fellow of Lincoln College. He is a prolific writer of popular chemistry textbooks, including Physical Chemistry, Inorganic Chemistry, and Molecular Quantum Mechanics...
at the University of Oxford
University of Oxford
The University of Oxford is a university located in Oxford, United Kingdom. It is the second-oldest surviving university in the world and the oldest in the English-speaking world. Although its exact date of foundation is unclear, there is evidence of teaching as far back as 1096...
and was later further developed by Barron with David Buckingham at the University of Cambridge
University of Cambridge
The University of Cambridge is a public research university located in Cambridge, United Kingdom. It is the second-oldest university in both the United Kingdom and the English-speaking world , and the seventh-oldest globally...
.
More developments, including important contributions to the development of practical Raman optical activity instruments, were made by Werner Hug of the University of Friburg
University of Fribourg
The University of Fribourg is a university in the city of Fribourg, Switzerland.The roots of the University can be traced back to 1582, when the notable Jesuit Peter Canisius founded the Collège Saint-Michel in the City of Fribourg. In 1763, an Academy of law was founded by the state of Frobourg...
, and Lutz Hecht with Laurence Barron at the University of Glasgow.
Theory of Raman optical activity
The basic principle of Raman optical activity is that there is interference between light waves scattered by the polarizability and optical activity tensorTensor
Tensors are geometric objects that describe linear relations between vectors, scalars, and other tensors. Elementary examples include the dot product, the cross product, and linear maps. Vectors and scalars themselves are also tensors. A tensor can be represented as a multi-dimensional array of...
s of a chiral molecule, which leads to a difference between the intensities of the right- and left-handed circularly polarised scattered beams. The spectrum of intensity differences recorded over a range of wavenumber
Wavenumber
In the physical sciences, the wavenumber is a property of a wave, its spatial frequency, that is proportional to the reciprocal of the wavelength. It is also the magnitude of the wave vector...
s reveals information about chiral centres in the sample molecule.
Raman optical activity can be observed in a number of forms, depending on the polarization of the incident and the scattered
light. For instance, in the scattered circular polarization (SCP) experiment, the incident light
is linearly polarized and differences in circular polarization of the scattered light are measured.
In the dual circular polarization (DCP), both the incident and the scattered light are circularly
polarized, either in phase (DCPI ) or out of phase (DCPII ).
Biological Raman optical activity spectroscopy
Due to its sensitivity to chirality, Raman optical activity is a useful probe of biomolecularBiomolecule
A biomolecule is any molecule that is produced by a living organism, including large polymeric molecules such as proteins, polysaccharides, lipids, and nucleic acids as well as small molecules such as primary metabolites, secondary metabolites, and natural products...
structure and behaviour in aqueous solution. It has been used to study protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
, nucleic acid
Nucleic acid
Nucleic acids are biological molecules essential for life, and include DNA and RNA . Together with proteins, nucleic acids make up the most important macromolecules; each is found in abundance in all living things, where they function in encoding, transmitting and expressing genetic information...
, carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
and virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
structures. Though the method does not reveal information to the atomic resolution of crystallographic
Crystallography
Crystallography is the experimental science of the arrangement of atoms in solids. The word "crystallography" derives from the Greek words crystallon = cold drop / frozen drop, with its meaning extending to all solids with some degree of transparency, and grapho = write.Before the development of...
approaches, it is able to examine structure and behaviour in biologically more realistic conditions (compare the dynamic solution structure examined by Raman optical activity to the static crystal structure).the structures are very important
Related spectroscopic methods
Raman optical activity spectroscopy is related to Raman spectroscopyRaman spectroscopy
Raman spectroscopy is a spectroscopic technique used to study vibrational, rotational, and other low-frequency modes in a system.It relies on inelastic scattering, or Raman scattering, of monochromatic light, usually from a laser in the visible, near infrared, or near ultraviolet range...
and circular dichroism
Circular dichroism
Circular dichroism refers to the differential absorption of left and right circularly polarized light. 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...
.