Linear rheological behavior and Microrheology measurements of sodium salt calf-thymus DNA aqueous solutions as a function of concentration are reported here. The microrheological behavior was obtained by a combination of experimental techniques: mechanical Rheometry and Dynamic light scattering (DLS). The viscoelastic properties of DNA in water as a function of concentration were performed at 20 °C and rheological and microrhelogical curves were performed. The result indicated that for concentrations lower than the entanglement concentration (Ce) the system exhibits a predominantly viscous behavior, whereas for higher concentrations exhibits a predominantly elastic behavior. The plateau modulus (G0) and the zero complex viscosity () follow a power law concentration dependence of the form: and , respectively The microrheology results overlap perfectly in a single line with the mechanical rheology results, extending the time resolution to faster breathing modes
In this work we present a study of transitional behavior of calfthymusDNA molecules in solution in a concentration range from0.01 to 2.5 mg mL-1 at different temperatures (10, 20, 30 and 40ºC) and a pH of 7.3 using Electrochemical ImpedanceSpectroscopy (EIS). The results are interpreted with amethodology similar to the one used in studies of linear-rheology.The Zo modulus and the characteristic time constant of the process(τc) were obtained through a variation of Bode graphics. From theanalysis of these parameters as a function of DNA concentration itis possible to determine the overlap (C*) and entanglement (Ce)concentrations of the system. These concentrations allowidentifying conditions where interactions and entanglementsbetween DNA molecules are present. An interpretation of thecharacteristic time constant values is proposed according to thestructural rearrangement of the electrochemical double-layer.
In this work, it is reported viscosity, density, sound velocity and electrochemical impedance spectroscopy (EIS) measurements of calf thymus DNA in aqueous solutions, in order to investigate the overlapping C* and entanglement concentrations C e . These critical concentrations demark the conditions at which start appearing interactions and entanglements between DNA molecules in solution. EIS has been proposed as new alternative analytical techniques to obtain C* and C e in polyelectrolyte solutions. A new parameter the characteristic time (τ c ) was defined, and it is obtained from a new type of log-log Bode plot using the crossover frequency (τ c =1/ω c ) of the real (Z') and imaginary (Z") components when they are plotted as a function of the frequency. Preliminary results show similar values C* and C e by EIS to those obtained from rheological, densimetry and sound velocity measurements.
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