Twist-stretch profiles of DNA chains

摘要: Helical molecules change their twist number under the effect of a mechanical load. We study twist-stretch relation for set short DNA modeled by mesoscopic Hamiltonian. Finite temperature path integral techniques are applied to generate large ensemble possible configurations base pairs sequence. The model also accounts bending and twisting fluctuations between adjacent along stack. Simulating broad range conformation, we compute helix structural parameters averaging over configurations. method selects, any force, average angle which minimizes molecule's free energy. It is found that chains generally over-twist an stretching over-twisting physically associated contraction diameter, i.e. damping pair fluctuations. Instead, assuming maximum amplitude may decrease against external load, molecule first over-twists weak forces then untwists above characteristic force value. Our results discussed in available experimental information albeit kilo-base long molecules.