Torus-globule transition

To predict the coil-torus and torus-globule transition lines we have to make an ansatz for the excess free energy of the collapsed states with respect to the coil state ... 

By substituting the equilibrium torus radii (5.41) to Eq. (5.40), we obtain the expression for the equilibrium value of the globular free energy, from which it can be seen that upon heating the toroidal globule transforms into the coil state, the corresponding phase transition being of the first order. For the temperature and the heat of the transition we obtain... 

Especially close to the transition lines the structures are easily interconvertible. At the transition line between torus and globule other intermediate structures like disks and rods are also found at a significant percentage. This agrees well with recent findings from atomic force microscopy studies of collapsed DNA and polysaccharide chains [33]. 

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See also in sourсe #XX -- [ ]

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