Discontinuities at the DNA supercoiling transition
نویسندگان
چکیده
منابع مشابه
Discontinuities at the DNA supercoiling transition.
While slowly turning the ends of a single molecule of DNA at constant applied force, a discontinuity was recently observed at the supercoiling transition when a small plectoneme is suddenly formed. This can be understood as an abrupt transition into a state in which stretched and plectonemic DNA coexist. We argue that there should be discontinuities in both the extension and the torque at the t...
متن کاملSupplemental material for Discontinuities at the DNA supercoiling transition
Note that Ceff is a function of force: there is less “softening” at higher forces. In the experiments of Forth et al., the renormalized Ceff was measured directly via the torque. However, the range of applied forces was small enough that Ceff did not change appreciably, and a single value of C = (89 nm)kT was quoted. Here, we also use the same renormalized but force-independent value for C. Cha...
متن کاملNucleation at the DNA supercoiling transition.
Twisting DNA under a constant applied force reveals a thermally activated transition into a state with a supercoiled structure known as a plectoneme. Using transition-state theory, we predict the rate of this plectoneme nucleation to be of order 10(4) Hz. We reconcile this with experiments that have measured hopping rates of order 10 Hz by noting that the viscous drag on the bead used to manipu...
متن کاملTwist-stretch coupling and phase transition during DNA supercoiling.
As a single DNA molecule is positively supercoiled under constant tension, its extension initially increases due to a negative twist-stretch coupling. The subsequent attainment of an extension maximum has previously been assumed to be indicative of the onset of a phase transition from B- to scP-DNA. Here we show that an extension maximum in fact does not coincide with the onset of a phase trans...
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Despite the fact that in living cells DNA molecules are long and highly crowded, they are rarely knotted. DNA knotting interferes with the normal functioning of the DNA and, therefore, molecular mechanisms evolved that maintain the knotting and catenation level below that which would be achieved if the DNA segments could pass randomly through each other. Biochemical experiments with torsionally...
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ژورنال
عنوان ژورنال: Physical Review E
سال: 2009
ISSN: 1539-3755,1550-2376
DOI: 10.1103/physreve.80.040901