Fluorescence-detected circular dichroism (FDCD) is used to measure the difference in fluorescence intensities when an optically active sample has been excited with circularly polarized light. This method takes advantage of the chiral specificities and the structural sensitivities of CD and fluorescence and is more specific than standard CD measurements.

Since FDCD selectivity measures the circular dichroism of a specific fluorescent chromophore in a group of non-fluorescent, chiral molecules, it is particularly useful for the study of proteins, which have multiple chromophores. FDCD can be measured with the standard CD detector when paired with the PTC-510, PTC-517 or MPTC-513 cell holder. When samples have no fluorescence anisotropy, this method is effective because the photoselection artifacts are small. However, when the sample has a larger fluorescence anisotropy, the photoselection artifact will distort the FDCD spectrum. The FDCD-551 attachment is specifically designed to reduce or eliminate these artifacts while greatly enhancing sensitivity due to much more efficient light collection.