Description:
<jats:p>Classical fluctuation and scattering theory has enabled the study of equilibrium properties such as molecular mass, size and intermolecular interactions of synthetic and biological macromolecules. Photon correlation and light beating spectroscopy, using laser radiation, allows the measurement of dynamic properties such as diffusion coefficients and, perhaps, the characterization of internal motion. The recently discovered plasmid DNA molecules are excellent objects of study, being monodisperse, in a convenient molecular mass range, and obtainable in supercoiled, relaxed circular and open linear conformations. Structural transitions can be studied in a variety of solvents and folding properties of DNA investigated. Chromatin can be reconstituted by interaction of DNA under well chosen experimental conditions with a selected group of histones, basic proteins of the nucleoprotein complex in the chromosome. The plasmid DNA-histone interaction leads to well-defined monodisperse chromatin-like complexes; their formation, composition and solution properties have been studied by laser light scattering and related physico-chemical methods.</jats:p>