Bending and twisting elasticity: A revised Marko-Siggia model on DNA chirality

A revised Marko-Siggia elastic model for the DNA double helix [Macromolecules 27, 981 (1994)] is proposed, which includes the inextensible wormlike chain bending energy and a new chiral twisting energy term. It is predicted that the mean helical repeat length (HRL) for short DNA rings increases with decreasing chain length, while for very long chains in solution, their mean HRL has the same value longer than that for rectilinear DNAs, independent both of the chain length and of whether the ends are closed. These theoretical results are in good agreement with recent experimental investigations, and it might be possible that the chirality in twisting will account for the long-standing linking number deficit puzzle observed in organelle DNAs. [S1063-651X(98)06210-2].