Circular Dichroism
The world's leading synchrotron
circular dichroism (CD) system is based at Daresbury SIC and is
operated by dedicated, internationally competitive beamline
specialists, working on beamlines they have designed
in-house.
Although CD is a well established laboratory technique, the
limitations of laboratory light sources mean that a huge amount of
information about a given protein is not
available. Synchrotron UV circular dichroism on the other
hand, allows investigation deep into the UV spectrum giving much
more detail on protein structure, on very small quantities in
solution.
Definition of Circular Dichroism
Circular Dichroism (CD) is the difference in absorption between
left and right circularly polarised light by an asymmetric or
chiral sample. In the ultraviolet part of the spectrum, CD reports
on the secondary structure content of proteins and other
macromolecules. Synchrotron radiation provides orders of magnitude
more photon flux than conventional CD instruments. This provides
high signal-to-noise data over a wide wavelength range, allowing
the much more accurate quantification of secondary structure
content, such as alpha helix, beta strand, beta turns and other
structure types. Dynamic measurements can be made using
stopped-flow or temperature-jump methods. These measurements allow
the monitoring of secondary structure in the millisecond time
domain as proteins fold or interact with other molecules.