Kidoaki S, Yoshikawa K
Department of Bioengineering, National Cardiovascular Center Research Institute, 5-7-1 Suita, Osaka, 565-8565, Japan.
Biophys Chem. 1999 Feb 1;76(2):133-43. doi: 10.1016/s0301-4622(98)00231-2.
To understand the conformational behavior of a giant duplex-DNA chain in a mixed solution with various biopolymers with different state of ionization, the higher-order structure of the DNA chain was analyzed with a fluorescence microscope in the presence of polycations (poly-arginine), polyanions (poly-glutamic acid), and neutral polymers (poly-ethylene glycol) as a model for cellular environment. Concentrated medium with neutral polymer induced the discrete folding transition of the DNA. At the threshold condition for the transition, addition of small amounts of either the polycation or the polyanion caused marked structural changes in the folded DNAs. Based on thermodynamic considerations on the experimental results, profile of free energy of a single giant DNA chain was depicted with respect to the size, or the expansion factor alpha, in the three-dimensional structure of the DNA. The effect of the neural crowding polymer on the degree of folding of a single giant DNA chain is discussed in a semi-quantitative manner.
为了理解巨型双链DNA链在含有不同电离状态生物聚合物的混合溶液中的构象行为，以聚阳离子（聚精氨酸）、聚阴离子（聚谷氨酸）和中性聚合物（聚乙二醇）作为细胞环境模型，用荧光显微镜分析了DNA链的高阶结构。含有中性聚合物的浓缩介质诱导了DNA的离散折叠转变。在转变的阈值条件下，添加少量聚阳离子或聚阴离子会导致折叠DNA发生显著的结构变化。基于对实验结果的热力学考虑，描绘了单个巨型DNA链的自由能随DNA三维结构大小或膨胀因子α的变化情况。以半定量方式讨论了中性拥挤聚合物对单个巨型DNA链折叠程度的影响。
