7,546 research outputs found
Unzipping DNA by force: thermodynamics and finite size behaviour
We discuss the thermodynamic behaviour near the force induced unzipping
transition of a double stranded DNA in two different ensembles. The Y-fork is
identified as the coexisting phases in the fixed distance ensemble. From finite
size scaling of thermodynamic quantities like the extensibility, the length of
the unzipped segment of a Y-fork, the phase diagram can be recovered. We
suggest that such procedures could be used to obtain the thermodynamic phase
diagram from experiments on finite length DNA.Comment: 10 pages, accepted for publication in special issue of Journal of
Physics: Condensed Matte
Manipulating a single adsorbed DNA for a critical endpoint
We show the existence of a critical endpoint in the phase diagram of
unzipping of an adsorbed double-stranded (ds) polymer like DNA. The competition
of base pairing, adsorption and stretching by an external force leads to the
critical end point. From exact results, the location of the critical end point
is determined and its classical nature established.Comment: 6 pages, 5 figures, Published versio
DNA sequence from the unzipping force? : one mutation problem
The possibility of detecting mutations in a DNA from force measurements (as a
first step towards sequence analysis) is discussed theoretically based on exact
calculations. The force signal is associated with the domain wall separating
the zipped from the unzipped regions. We propose a comparison method
(``differential force microscope'') to detect mutations. Two lattice models are
treated as specific examples.Comment: 11 pages, 4 figures. Revised version with minor changes. Paragraph
with discussion on experiments added. Accepted for publication in J. Phys. A
as a Letter to the Edito
Frequency Dependent Viscosity Near the Critical Point: The Scale to Two Loop Order
The recent accurate measurements of Berg, Moldover and Zimmerli of the
viscoelastic effect near the critical point of xenon has shown that the scale
factor involved in the frequency scaling is about twice the scale factor
obtained theoretically. We show that this discrepancy is a consequence of using
first order perturbation theory. Including two loop contribution goes a long
way towards removing the discrepancy.Comment: No of pages:7,Submitted to PR-E(Rapid Communication),No of EPS
files:
Dynamic phase transition in the conversion of B-DNA to Z-DNA
The long time dynamics of the conformational transition from B-DNA to Z-DNA
is shown to undergo a dynamic phase transition. We obtained the dynamic phase
diagram for the stability of the front separating B and Z. The instability in
this front results in two split fronts moving with different velocities. Hence,
depending on the system parameters a denatured state may develop dynamically
eventhough it is thermodynamically forbidden. This resolves the current
controversies on the transition mechanism of the B-DNA to Z-DNA.Comment: 5 pages, 4 figures. New version with correction of typos, new
references, minor modifications in Fig 2, 3. To appear in EP
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