Kinetics of DNA supercoiling studied by Brownian dynamics simulationстатья из журнала
Аннотация: Abstract We have developed a model for the simulation of the structure and dynamics of covalently closed circular DNA. It is based on the generalization of the original Brownian dynamics algorithm [D. L. Ermak & J. A. McCammon (1978) Journal of Chemical Physics , Vol. 69 , pp. 1352–1359; M. Fixman (1978) Journal of Chemical Physics , Vol. 69 , pp. 1527–1537] developed for bead‐chain models of linear DNA to a second order numerical integration [ A. Iniesta & J. Garcia de la Torre (1990) Journal of Chemical Physics. Vol. 92 , pp. 2015–2018], which we extended here to accommodate the torsional potential. The topological constraints and torsional‐bending coupling in superhelical DNA are explicitly taken into account in this work by adapting a model for torsional‐bending motion of linear DNA developed by Allison et al. [S. A. Allison, R. Austin, & M. Hogan (1989) Journal of Chemical Physics , Vol. 90, pp. 3843–3854]. The dynamics of closed DNAs of 1124 base pairs (380 nm in length) were simulated up to ≅ 40 μs for linking number differences Δ Lk between 0 and −6. Each bead in the model corresponded to 37 base pairs. For −2 ≅ Δ Lk −6, the writhing number appears to decay to a limiting negative value with a single exponential law, and the relaxation time of this decay, starting from a planar closed molecule, is 3–6 μs. For the trajectories studied here, the formation of the superhelix proceeds through an initial phase of 1–2 μs where a toroidal‐like structure is formed, which then converts into an interwound structure starting from a random nucleation site. For one simulation at Δ Lk = −6, a branched structure was observed that did not convert into the linear interwound form for the time course of the simulation (31 μs). A verification of the simulation was performed by computing the diffusion coefficient of the 1124 base pair circle through known hydrodynamic formulas or through the center of mass displacement, and comparing these theoretical values with diffusion coefficients previously measured by dynamic light scattering. © 1994 John Wiley & Sons, Inc.
Год издания: 1994
Авторы: Giuseppe Chirico, Jörg Langowski
Издательство: Wiley
Источник: Biopolymers
Ключевые слова: DNA and Nucleic Acid Chemistry, Electrostatics and Colloid Interactions, Bacteriophages and microbial interactions
Открытый доступ: closed
Том: 34
Выпуск: 3
Страницы: 415–433