Differential scatter of left and right circularly polarized light by optically active particulate systems.

Because of the many heterogeneous systems which are of interest to the chemist and biochemist, the problems of distortions in circular dichroism patterns have been investigated. Specifically in this communication it is shown with a relatively well-characterized particular system (a suspension of alpha-helical poly-L-glutamic acid) that there is a measurable differential scatter of left and right circularly polarized light by suspensions of the optically active particles. This is a specific example of Perrin's assertion in 1942 (Perrin, F., J. Chem. Phys., 10, 415 (1942)) that the polarization characteristics of scattered light would differ depending on whether or not the scattering particle was optically active. Differential scatter is included with the concentration obscuring effects to demonstrate that distorted circular dichroism spectra on poly-L-glutamic acid suspension can be calculated with satisfying accuracy. The approach should be applicable to correcting the circular dichroism spectra for the many particles of biological interest, e.g., membranes, viruses, mitochondria, and insoluble proteins and polypeptides, and for small crystals in an effort to answer the crystal solution problem.