DNA凝聚过程中离子浓度效应及温度效应研究

DNA凝聚一直以来都备受关注，原因之一在于平衡离子的复杂性，最近实验又指出，温度、高价平衡离子浓度对DNA分子驻留长度的影响要比以往理论和实验结果复杂；不同价态阴离子浓度的增加会影响DNA分子凝聚构象和过程；随着温度升高，DNA凝聚更加稳定。鉴于此，开展以下探索工作:(1)基于我们已建立的DNA凝聚的强关联模型，研究温度、高价平衡离子浓度对自由DNA分子凝聚的影响；(2) 在温度梯度变化的情况下，开展研究DNA凝聚的单分子实验，研究温度变化对DNA凝聚过程的影响，并在已建立的DNA凝聚强关联模型中引入恒力，研究温度、高价平衡离子浓度对DNA凝聚过程的影响，并与单分子实验结果对比；(3)考量DNA溶液中DNA分子的构象熵，溶液的混合熵、DNA分子与周围离子环境间的平移熵等，研究该体系的热力学，揭示温度、溶液中阴离子浓度增加对DNA分子凝聚构象和过程影响的机制

More and more attentions have been put on DNA condensation, one of the most important reasons is related to the complexity of counterions. Recent experiments have pointed out that effects of temerature and concentration of counterions on the persistence length of DNA are more complex than the theoritical and experimental results before, the anions with different valence also have effects on the conformation and process of DNA condensation.Surprisingly,the DNA condensates more stably with the temperature increasing from 5℃to 53℃. Considering these important experimental phenomena, the following works will be carried out. First，based on the strong correlation model on DNA condensation propoed by us before, effects of temperature and concentration of counterions on DNA condensation and effects of temperature on the topology of DNA minicircle will be detected;second,with temerature changing gradiently, a magnetic tweezers experiment on DNA condensation will be carried out to detect the effects of temeperature during the process of DNA condensation. At the same time, a simulation work is also implemented by appling a constant force to the DNA molecule in the strong correlation model propoed by us before to imitate the single molecule experiment.The comparision between the theoretical and experimental results should show some highlights on the mechanism of DNA condensation.Finally,the DNA solution will be taken as binary mixing solution, and its thermodynamics will be investigated by considering the conformation entropy of DNA ,mixing entropy of the solution、and the translational entrpy between the DNA and solution enviroment around it to desclose mechanism of the dependence of DNA condensation on temperature.