| Summary: | 碩士 === 國立中央大學 === 光電科學研究所 === 95 === The conformation of DNA in the presence of condensing agent, spermidine is studied. The non-condensed, condensed, and reentrant states of DNA in different concentrations of spermidine are determined by the gel electrophoresis. The goal of this study is to compare the conformations of DNA in these three states. The atomic force microscope (AFM) is used to probe the DNA directly. The flower-shaped and the branch-like structures of DNA are observed in the non-condensed and the reentrant state, respectively.
We also estimate the structure of DNA from the distributions of the DNA fragments.The light induced fragmentation of DNA in the presence of fluorescent dye, YOYO-1 and spermidine is analyzed by the gel electrophoresis. By the comparison of the distributions in
the presence and absence of spermidine, it is found that a) spermidine enhances the fragmentation process, and b) in the presence of spermidine, the existence of the longer DNA fragments is observed during the early fragmentation process, and c) the form of the distribution of DNA fragments in the reentrant state is similar to the Lognormal distribution. These findings suggest that the higher order structures of DNA molecules are involved in the fragmentation process.
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