Effects Of Temperature On The Topological States Of Circular DNA And The Mechanism Of Condensation On Surface Of DNA

The topological structure of circular DNA has important effects on a series of molecule processes.The different states of circular DNA is determined by its own linking number.Gel electrophoresis was often used to study the difference of linking number of circular DNA.The experimental results show that the Gel electrophoresis fluorescence band of the circular DNA is gradually widened with increasing temperature,which indicates that the distribution of linking number and its variance become larger.In addition,DNA attachment on mica surface or bio-film has a significant application on single molecule level.Therefore,the study of the interaction between DNA and surface has important significance.By using Monte Carlo simulation,we have carried out the following works:Firstly,the persistence length and torsional rigidity of DNA strongly depend on temperature.Based on the temperature dependence of DNA persistence length and the relation of their topologies,effects of temperature on the topology of circular DNA is explored.The results show that the distribution of linking number and writhe number are gradually widened and the variance of linking number become larger with the increasing temperature;The contribution to the variance of writhe number and linking number per unit length is increasing as the length elongate,and become gently while the effect of temperature is becoming obvious in the longer length.The variance of linking number fit well with experimental results in 900 nm length.Secondly,based on the Worm-Like-Rod model,the writhe number distribution of circular DNA at different temperature is explored,and by comparison with previous results based on the Worm-Like-Chain model,the critical length at different length was obtained.The results indicate that the critical length decay gradually with the increasing temperature.At last,Based on the Worm-Like-Chain model of DNA,the Morse potential is introduced to describe the interaction between DNA and the surface.The relationship between the bending energy and the Morse potential and the curvature of the surface were identified in the process of DNA adsorption.The results show that DNA can be adsorbed on the spherical surface effectively when the Morse potential is relatively deep or the curvature is rather small,...