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
History of Raman optical activity
The field began with the doctoral work of Laurence D. Barron
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.
Theory of Raman optical activity
The basic principle of Raman optical activity is that there is interference between light waves scattered by the polarisability
and optical activity tensors
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 wavenumbers
reveals information about chiral centres in the sample molecule.
Biological Raman optical activity spectroscopy
Due to its sensitivity to chirality, Raman optical activity is a useful probe of biomolecular
structure and behaviour in aqueous solution. It has been used to study protein
, nucleic acid
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).
Related spectroscopic methods
Raman optical activity spectroscopy is related to Raman spectroscopy
and circular dichroism
Raman optical activity instruments
A simple introduction to Raman optical activity instruments can be found on Laurence Barron's site
Much of the existing work in the field has utilised custom-made instruments, though commercial instruments are now available.