Counterion dependence of water of hydration in DNA gel
| Autor: | Yasunori Tominaga, Hisako Urabe, Kazuhito Kajiwara, Midori Kato |
|---|---|
| Rok vydání: | 1990 |
| Předmět: |
inorganic chemicals
chemistry.chemical_classification Chemistry Analytical chemistry General Physics and Astronomy Endothermic process law.invention symbols.namesake Differential scanning calorimetry law symbols Water of crystallization Relaxation (physics) Physical and Theoretical Chemistry Crystallization Counterion Raman spectroscopy Magnesium ion |
| Zdroj: | The Journal of Chemical Physics. 92:768-774 |
| ISSN: | 1089-7690 0021-9606 |
| DOI: | 10.1063/1.458430 |
| Popis: | The cooling process of DNA gel (20 wt./wt.%–40 wt./wt.%) with various counterions has been investigated by low frequency Raman spectroscopy and differential scanning calorimetry (DSC). We have found that the dynamics of water of hydration is different among counterion species below 0 °C. For K‐, Rb‐, Sr‐, and Ba‐DNA gels, a part of nonfreezing water slowly changes its dynamical structure, when the gel is kept at ∼−30 °C after cooling below −50 °C. This relaxation process can be monitored both by the frequency increment of the lowest Raman band from ∼17 to ∼20 cm−1 and by the intensity increment of an extra endothermic peak in DSC heating curves. We propose that this relaxation process corresponds to the crystallization of a part of nonfreezing water and is caused by the rearrangement of the secondary hydrated water including counterions when the temperature is held at ∼−30 °C. This relaxation process cannot be observed for NH4‐ and Li‐DNA gels. For Na‐, Mg‐, and Ca‐DNA gels, this phenomenon is more compli... |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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