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.