# Kinetics of double stranded DNA overstretching revealed by 0.5-2 pN force steps

Source: [Kinetics of double stranded DNA overstretching revealed by 0.5-2 pN force steps](<https://www.sota2.com/research/paper/68fa2a141e209131ce83a335>)

Collection index: [llms.txt](<https://www.sota2.com/research/llms.txt>)

Data updated: 2025-10-28T13:53:08.343Z

Authors: Pasquale Bianco, Lorenzo Bongini, Luca Melli, Mario Dolfi, Vincenzo Lombardi

Published: 2011-03-03T17:32:37.000Z

## Abstract

A detailed description of the conformational plasticity of double stranded DNA (ds) is a necessary framework for understanding protein-DNA interactions. Until now, however structure and kinetics of the transition from the basic conformation of ds-DNA (B state) to the 1.7 times longer and partially unwound conformation (S state) have not been defined. The force-extension relation of the ds-DNA of lambda-phage is measured here with unprecedented resolution using a dual laser optical tweezers that can impose millisecond force steps of 0.5-2 pN (25 C). This approach reveals the kinetics of the transition between intermediate states of ds-DNA and uncovers the load-dependence of the rate constant of the unitary reaction step. DNA overstretching transition results essentially a two-state reaction composed of 5.85 nm steps, indicating cooperativity of ~25 base pairs. This mechanism increases the free energy for the unitary reaction to ~94 kBT, accounting for the stability of the basic conformation of DNA, and explains the absence of hysteresis in the force-extension relation at equilibrium. The novel description of the kinetics and energetics of the B-S transition of ds-DNA improves our understanding the biological role of the S state in the interplay between mechanics and enzymology of the DNA-protein machinery.

## Recorded benchmark results

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## Original sources and implementation

[Original paper](<https://arxiv.org/abs/1103.0740>)

[PDF](<https://arxiv.org/pdf/1103.0740.pdf>)