Thermal Diffusion of Dextran in Aqueous Solutions in the Absence and the Presence of Urea
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- 作者：Rei Sugaya ; Bernhard A. Wolf ; and Rio Kita
- 刊名：Biomacromolecules
- 出版年：2006
- 出版时间：February 2006
- 年：2006
- 卷：7
- 期：2
- 页码：435 - 440
- 全文大小：103K
- 年卷期：v.7,no.2(February 2006)
- ISSN：1526-4602
文摘
The Ludwig-Soret effect was studied for aqueous solutions of dextran in the temperature range 15 < T < 55 
Ctaking into account the effect of the addition of urea. In the absence of urea, the Soret coefficient ST changessign; it is positive for T > 45.0 C but negative for T < 45.0 C. The positive sign of ST means that the dextranmolecules migrate toward the cold side of the fluid; this behavior is typical for polymer solutions, whereas anegative sign indicates the macromolecules move toward the hot side. The addition of urea to the aqueous solutionof dextran rises ST and reduces the inversion temperature. For 2 M urea the change in the sign of ST is observedat T = 29.7 C and beyond that value ST is always positive in the studied temperature range. To rationalize theseobservations, it is assumed that the addition of urea leads to an opening of hydrogen bonds similar to that inducedby an increase in temperature.
Ctaking into account the effect of the addition of urea. In the absence of urea, the Soret coefficient ST changessign; it is positive for T > 45.0 C but negative for T < 45.0 C. The positive sign of ST means that the dextranmolecules migrate toward the cold side of the fluid; this behavior is typical for polymer solutions, whereas anegative sign indicates the macromolecules move toward the hot side. The addition of urea to the aqueous solutionof dextran rises ST and reduces the inversion temperature. For 2 M urea the change in the sign of ST is observedat T = 29.7 C and beyond that value ST is always positive in the studied temperature range. To rationalize theseobservations, it is assumed that the addition of urea leads to an opening of hydrogen bonds similar to that inducedby an increase in temperature.