The size and shape of nucleosomes and the manner in which DNA is bent when it wraps around the nucleosomal protein core are problems of intense current interest. Electric dichroism is a technique of considerable potential utility for addressing such questions because it is highly sensitive not only to the size and shape of a macromolecular species, but also to the angular disposition of the nucleic acid bases relative to the macromolecular orientation axis in the electric field. We describe here electric dichroism measurements on DNA, on DNA distorted by a small ligand (a steroidal diamine), on nucleosomal core particles, and on an unusual dinucleosome which contains only 240 base pairs of DNA. In each case the time required for the particle to orient in the field gives us information about its size or shape (or both), and the magnitude of the dichroism, when extrapolated to perfect molecular orientation, indicates...
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Klevan et al. (1978) studied this question.