Linear Dichroism

Linear dichroism (LD) is the anisotropic absorption of plane or linearly polarized light. As most commonly implemented, LD spectroscopy probes electronic transitions using visible or ultraviolet light. The basic requirements for experimental implementation of LD spectroscopy are a plane polarized light source, a photon detection system, and a method for orienting the sample. To interpret the data fully, the degree and mechanism of orientation, the polarizations of transitions within the molecule, and the maximum possible LD signal must be known. The principles of the technique are discussed to design and implement an experimental setup that is most appropriate for their needs, to interpret results as fully as possible in terms of orientation and, where appropriate, binding constants, and to appreciate the range of applications of LD currently being exploited. Where possible, reference is made to LD studies of systems containing proteins or metal ions. However, currently available applications of LD to such systems are not extensive.