Naslov
Polyelectrolyte Composite: Hyaluronic Acid Mixture with DNA

Autori
Marion, Ida Delač ; Grgičin, Danijel ; Salamon, Krešimir ; Bernstorff, Sigrid ; Vuletić, Tomislav

Izvornik
Macromolecules (0024-9297) 48 (2015), 8; 2686-2696

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
DNA; SAXS; osmotic pressure; Manning condensation; liquid crystal; composites

Sažetak
We studied salt-free, highly concentrated (5–200 g/L) mixtures of unfragmented (μm contour length) DNA and hyaluronic acid (HA) as a borderline example of rigid-rod/flexible-chain composite, across a broad range of concentration ratios cHA/cDNA = 0.05–50. By polarizing microscopy, we established that the DNA and HA form clearly separated thread-like domains defined and oriented by solution shear. Within its domains, DNA shows birefringent banded patterns, routinely observed for long chain mesogens. We applied small-angle X-ray scattering (SAXS) to the mixtures and observed a polyelectrolyte (PE) correlation peak at q★ wave vector. This peak was ascribed to DNA subphase and was used as a measure of the effective DNA concentration in the subphase cDNA★, according to deGennes scaling relationship between the DNA mesh size ξ = 2π/q★∝ c–1/2 and monomer concentration c. From cDNA★ (and initial cHA and cDNA), we inferred the effective cHA★ of HA subphase. We find a concentration-independent ratio Γ = cHA★/ cDNA★ ≈ 0.85 across a broad range of 0.02–0.4 M. As there is the osmotic pressure (Π) equilibrium between DNA and HA subphases, the constant Γ indicates that Π ∝ c9/8 scaling common for DNA and other highly charged PEs is valid also for HA (a weak PE—does not feature counterion condensation). Therefore, we propose that this deviation from the conventional osmotic pressure scaling Π ∝ c cannot originate from the concentration dependence of counterion condensation, which is an implicit but common interpretation in the literature. Further, as HA releases all its counterions into the solution, the HA osmotic coefficient ϕHA we took as a measure of the DNA osmotic coefficient which we found to be ϕDNA ≈ 0.28. This, double the Manning value, corroborates a result by Raspaud et al.1

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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