Ordered phases in concentrated DNA solutions
摘要：
Aqueous solutions of concentrated DNA, a strong polyelectrolyte, in 1:1 electrolyte form liquid-crystalline phases analogous to those observed for other semi-rigid neutral polymers and weak polyelectrolytes. Phase transitions were examined in detail for DNA fragments with a contour length (500 ) approximating the persistence length. These fragments form at least three lyotropic phases. The lowest density or "precholesteric" phase appears to be a nematic with a slight and easily variable twist. The intermediate density phase is a true cholesteric with a pitch of ≈2.1 μ m. With increasing concentration the cholesteric phase unwinds prior to formation of the third, high density, columnar phase. Phase transition boundaries were determined as functions of DNA concentration from 10 to 300 mg/ml solvent, supporting electrolyte concentration from 0.01 to 1.0 M, and temperature from 20°C to 60°C. Critical concentrations for formation of anisotropic phase ( C i ) and disappearance of isotropic phase ( C a ) were only moderately dependent on temperature. C i , C a , and the pitch of the cholesteric phase were surprisingly insensitive to the supporting electrolyte concentration. The insensitivity can be most simply related to the high concentrations required for anisotropic phase formation by these rather short, highly charged rod-like DNA fragments. At high concentrations the DNA counterions contribute significantly to the effective ionic strength, hence overall charge screening, and the counterion atmosphere as monitored by 23 Na NMR, appears to be perturbed by inter-rod interactions.
展开
关键词：
Bibliography, Experimental/ cholesteric liquid crystals DNA electrolytes liquid crystal phase transformations nematic liquid crystals nuclear magnetic resonance/ ordered phases aqueous solutions phase transitions precholesteric phase concentrated DNA solutions polyelectrolyte 1:1 electrolyte liquid-crystalline phases lyotropic phases nematic twist intermediate density phase cholesteric pitch columnar phase anisotropic phase counterions effective ionic strength charge screening 23Na NMR inter-rod interactions 20 to 60 degC/ A8715B Biomolecular structure, configuration, conformation, and active sites A8715M Interactions with radiations at the biomolecular level/ temperature 2.93E+02 to 3.33E+02 K
DOI：
10.1016/0378-4371(91)90435-F
被引量：
年份：
1991
相似文献
参考文献
引证文献
引用走势
站内活动
辅助模式
引用
文献可以批量引用啦~
欢迎点我试用！
