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Some Features of Surfactant Organization in DNA Solutions at Various NaCl Concentrations.

ABSTRACT: The photosensitive azobenzene-containing surfactant C₄-Azo-OC₆TMAB is a promising agent for reversible DNA packaging in a solution. The simulation of the trans-isomer surfactant organization into associates in a solution with and without salt as well as its binding to DNA at different NaCl concentrations was carried out by molecular dynamics. Experimental data obtained by spectral and hydrodynamic methods were used to verify the results of simulation. It was shown that head-to-tail aggregates with close to antiparallel orientation of surfactant molecules were formed at certain NaCl and surfactant concentrations (below critical micelle concentration). Such aggregates have two positively charged ends, and therefore, they can be attracted to negatively charged DNA phosphates far located along the chain, as well as those that belong to different molecules. This contributes to the formation of intermolecular DNA-DNA contacts, and this way, the experimentally observed precipitation of DNA can be explained.

SUBMITTER: Silanteva IA

PROVIDER: S-EPMC7391854 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

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Some Features of Surfactant Organization in DNA Solutions at Various NaCl Concentrations.

Silanteva Irina A IA Komolkin Andrei V AV Mamontova Veronika V VV Vorontsov-Velyaminov Pavel N PN Santer Svetlana S Kasyanenko Nina A NA

ACS omega 20200713 29

The photosensitive azobenzene-containing surfactant C<sub>4</sub>-Azo-OC<sub>6</sub>TMAB is a promising agent for reversible DNA packaging in a solution. The simulation of the trans-isomer surfactant organization into associates in a solution with and without salt as well as its binding to DNA at different NaCl concentrations was carried out by molecular dynamics. Experimental data obtained by spectral and hydrodynamic methods were used to verify the results of simulation. It was shown that head ...[more]

PMID: 32743199

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Project description:Previous investigations were conducted on two concentrations of DNA solution: 4 mg/mL, for which it has been shown that no supramolecular organization is induced under flow at low shear rates; and 10 mg/mL, in which a liquid crystalline-type texture is formed under flow at low shear rates, attesting to an orientation of pre-organized chains. Rheological experiments are discussed and their results supported by small-angle X-ray scattering (SAXS) and flow birefringence visualization experiments. Scattering from polyelectrolytes has a characteristic signal, which is here observed in SAXS, showing a strong correlation peak between charged chains in water, for both concentrations. This peak is weaker in the presence of 0.01 M NaCl and suppressed in salt excess at 0.1 M NaCl. No plateau in the σ( γ ˙ ) plot was observed in analysis of rheological experiments on low DNA concentration (4 mg/mL). As typically observed in polyelectrolyte systems both the dynamic moduli and shear viscosity were higher in water as electrostatic forces dominate, than in the presence of salt, especially at low shear rates. The rheological results for concentrations of 0.01 M NaCl are lower than in water as expected due to partial screening of electrostatic repulsions. Rheological data for concentrations of 0.1 M NaCl are unexpected. Electrostatic forces are partially screened in the low salt concentration, leading to a drop in the rheological values. For high salt concentration there are no longer interchain repulsions and so steric interactions dominate within the entangled network leading to the subsequent increase in rheological parameters. Regardless of the solvent, at high shear rates the solutions are birefringent. In the 10 mg/mL case, under flow, textures are formed at relatively low shear rate before all the chains align going to a pseudonematic liquid crystalline phase at high shear rate. The electrostatic repulsion between semi-rigid chains induces a correlation between the chains leading to an electrostatic pseudo-gel in water and loosely in 0.01 M NaCl at low stress applied. To the best of our knowledge, this is the first time that such behavior is observed. In 0.1 M NaCl, DNA behavior resembles the corresponding neutral polymer as expected for polyelectrolyte in salt excess, exhibiting a yield stress. When texture appears in water and in 0.01 M NaCl, a critical transition is observed in rheological curves, where the viscosity decreases sharply at a given critical shear stress corresponding to a plateau in the σ( γ ˙ ) plot also observed in creep transient experiment.

Dataset Information

Some Features of Surfactant Organization in DNA Solutions at Various NaCl Concentrations.

Publications

Some Features of Surfactant Organization in DNA Solutions at Various NaCl Concentrations.

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