Burger Jessica, Yamamoto Hideki, Suzuki Takamasa, Laesecke Arno
Applied Chemicals and Materials Division, National Institute of Standards and Technology, Boulder, CO, USA.
Department of Chemical, Energy and Environment Engineering, Kansai University, Yamate, Suita, Osaka, Japan.
Biorheology. 2014;51(1):29-45. doi: 10.3233/BIR-140650.
High-concentration DNA solutions are common both in vitro and in vivo, and understanding the rheological properties is a critical area of bioscience. Our previous measurements on high-concentration DNA solutions (2-6 mg/ml) interestingly provided evidence for a viscosity maximum with temperature. Under the influence of temperature, the measured viscosities indicated distinct differences in the interactions of highly polymerized DNA in unbuffered and buffered aqueous solutions. Under the same conditions, the buffered solutions were always less viscous, and in addition the viscosity maximum was not observed. In this research we have utilized a falling-needle rheometer in order to gain more insight into the nature of the previously observed viscosity maxima. The shape of the flow curves for all the DNA solutions indicated that the solutions are shear-thinning and has allowed us to confirm the existence of the viscosity maximum in unbuffered DNA solutions. Also we have been able to measure flow curves at very low shear rates, <10 s⁻¹. These results showed that the flow curves intersect and that the lower the concentration of DNA in solution, the lower is the temperature where the flow curves will intersect. Thus, the viscosity-temperature dependence is also a function of the shear rates experienced by the solution. Finally, as expected, the flow behavior of the DNA solutions becomes more Newtonian with increasing temperature, and there appears to be a small yield stress that decreases with increasing temperature.
高浓度DNA溶液在体外和体内都很常见，了解其流变特性是生物科学的一个关键领域。我们之前对高浓度DNA溶液（2 - 6毫克/毫升）的测量有趣地提供了粘度随温度呈现最大值的证据。在温度的影响下，测量的粘度表明，在未缓冲和缓冲的水溶液中，高度聚合的DNA相互作用存在明显差异。在相同条件下，缓冲溶液的粘度总是较低，此外未观察到粘度最大值。在本研究中，我们使用了落针流变仪，以便更深入地了解先前观察到的粘度最大值的本质。所有DNA溶液的流动曲线形状表明这些溶液是剪切变稀的，这使我们能够确认未缓冲DNA溶液中存在粘度最大值。我们还能够在非常低的剪切速率（<10 s⁻¹）下测量流动曲线。这些结果表明流动曲线相交，并且溶液中DNA的浓度越低，流动曲线相交的温度越低。因此，粘度 - 温度依赖性也是溶液所经历的剪切速率的函数。最后，正如预期的那样，随着温度升高，DNA溶液的流动行为变得更接近牛顿流体，并且似乎存在一个随温度升高而降低的小屈服应力。
