title: The energy of naturally curved elastic rods with an application to the stretching and contraction of a free helical spring as a model for DNA.
abstract: We give a contemporary and direct derivation of a classical, but insufficiently familiar, result in the theory of linear elasticity-a representation for the energy of a stressed elastic rod with central axis that intrinsically takes the shape of a general space curve. We show that the geometric torsion of the space curve, while playing a crucial role in the bending energy, is physically unrelated to the elastic twist. We prove that the twist energy vanishes in the lowest-energy states of a rod subject to constraints that do not restrict the twist. The stretching and contraction energies of a free helical spring are computed. There are local high-energy minima. We show the possibility of using the spring to model the chirality of DNA. We then compare our results with an available atomic level energy simulation that was performed on DNA unconstrained in the same sense as the free spring. We find some possible reflections of springlike behavior in the mechanics of DNA, but, unsurprisingly, the base pairs lend a material substance to the core of DNA that a spring does not capture.
authors.affiliation: Department of Chemistry and Chemical Biology, Rutgers University, 610 Taylor Road, Piscataway, New Jersey 08854-8087, USA.
authors.forename: Gerald S
authors.initials: GS
authors.lastname: Manning
mesh_terms: D003198:Computer Simulation; D004247:DNA / Q000737:chemistry; D004548:Elasticity; D008957:Models, Genetic; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D012399:Rotation
chemical_list: D004247:DNA