Screening and Fundamental Length Scales in Semidilute Na-DNA Aqueous Solutions

Abstract

The fundamental length scales in semidilute Na-DNA aqueous solutions have been investigated by dielectric spectroscopy. The low- and the high-frequency relaxation modes are studied in detail. The length scale of the high-frequency relaxation mode at high DNA concentrations can be identified with the de Gennes-Pfeuty-Dobrynin correlation length of polyelectrolytes in semidilute solution, whereas at low DNA concentrations and in the low added salt limit the length scale shows an unusual exponent reminiscent of semidilute polyelectrolyte chains with hydrophobic backbone. The length scale of the low-frequency relaxation mode corresponds to a Gaussian chain composed of correlation blobs in the low added salt limit, and to the Odijk-Skolnick-Fixman value of the single chain persistence length in the high added salt limit.

Ionic state and chain conformation for aqueous solutions of supergiant cyanobacterial polysaccharide

“…Thus, the counterion condensation for both counterions is independent of the sacran concentration. This result roughly coincides with the data for DNA solutions [21,22] that the fraction of both counterions is independent of the DNA concentrations. To summarize the electrical and rheological properties of aqueous sacran solutions, a schematic illustration representing the chain conformation of sacran in pure water is given in Fig.…”

“…The diffusion constant for strongly bound counterions may be much lower than that for loosely bound counterions. In this paper, the diffusion constants of strongly bound counterions and loosely bound counterions were not distinguished, similar to the analysis by Tomic et al [21][22][23].…”

“…The observed long relaxation time is one evidence that the sacran chain is extremely long. Such long relaxation time has been reported for a cross-linked polyelectrolyte gel (0.7-2.1 ms) [28] or Na-DNA (τ = 0.68 ms: degree of polymerization 12 000) [21][22][23][24]. At 0.007 < c < 0.2 wt%, the relaxation time decreased with concentration showing a power dependency as τ 1 ∼ c −0.9 and subsequently was constant to be 40 μs at c 0.2 wt%.…”

“…This subtraction method has limitations in the sense that the effects are not necessarily the same for the sample and reference solutions [19,20]. On the other hand, there are some papers describing the dielectric relaxation of DNA [21][22][23] and hyaluronic acid solutions [24] using this method. It cannot be denied that their dielectric data gave us important knowledge to understand the function of biopolymers.…”

Continuity of states between the cholesteric → line hexatic transition and the condensation transition in DNA solutions

“…B b is the bare bulk compressibility modulus of the DNA cholesteric phase (relative change in the bare interaction pressure with changing cell area), i.e., K is the bending elastic constant defined as K = ρK c , where ρ is the 2D number density of DNA chains perpendicular to their helical axes and K c = (k B T) L p is the bending rigidity of a single DNA chain. We can ignore the effect of [NaCl] on the persistence length, L p (≈500Å for B-DNA), as it is less than 5% for 0.1 M ≤ [NaCl] ≤ 0.4 M4950. V DNA is the volume per DNA chain in the cylindrical cell model, i.e., V DNA = L ( πR 2 ), where L is the length of DNA chains.…”