How to study proteins by circular dichroism

Circular dichroism (CD) is being increasingly recognised as a valuable technique for examining the structure of proteins in solution. However, the value of many studies using CD is compromised either by inappropriate experimental design or by lack of attention to key aspects of instrument calibration or sample characterisation. In this article, we summarise the basis of the CD approach and its application to the study of proteins, and then present clear guidelines on how reliable data can be obtained and analysed.