CD: Circular Dichroism

Circular dichroism (CD) is the differential absorption of left- and right-handed circularly polarised light. It is a form of spectroscopy used to determine the optical isomerism and secondary structure of molecules, and to study a wide variety of chiral materials in solution, particularly biologically important molecules such as proteins, nucleic acids, carbohydrates, lipids and drugs. It is an ideal technique to investigate protein/ligand binding interactions, such as those involved in signal transduction of normal and tumour cells, without the need for labelling or immobilising any of the components.

Synchrotron radiation is orders of magnitude brighter than that produced by conventional CD instruments, providing a much higher signal to noise ratio over a wide wavelength range (140-700nm). The combination of high photon flux and small spot size at Diamond will substantially reduce i) the measurement time for CD time resolved experiments and ii) the amount of chiral material required.

Circular dichroism is commonly used for investigating and observing structural, functional and dynamic interactions in elements such as proteins, nucleic acids and chiral molecules. Synchrotron radiation circular dichroism spectroscopy is a valuable technique for studies of protein folding, examination of macromolecular interactions, conformational changes and enzyme mechanisms, and secondary structure determination. Its particular strengths lie in the fact that it is a solution phase technique that is equally applicable to large or small biomolecules. Exciting new potential applications exist in fold recognition for Structural Genomics, protein folding and complex formation for Proteomics, and ligand and drug screening for Functional Genomics.