Theory of packing of bihelical DNA: Globular state of uniform elastic macromolecule in a cavity of small volume

The globular state of a persistent chain modelling the double helix of DNA has been studied in a cavity with impermeable walls. The effect of the excluded volume is allowed for by the Onsager method. For the most interesting case when the size of the cavity is much smaller than the persistent length the globule is similar to a hoop wound inwards on the walls of the cavity. Depending on the thickness of the molecule, four limiting regions of parameters with qualitatively different properties of the globule are possible. The thicknesses of the "hoop" along the walls and across them have been found for all regions and also both characteristic widths of the orientation distribution of the chain elements.