Study of DNA Structure Transition by Atomic Force Microscope

• Main Authors: Chung-YuHsieh, 謝忠佑
• Other Authors: Yi-Chun Chen
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/53174069037431627553

碩士 === 國立成功大學 === 物理學系碩博士班 === 100 === Deoxyribonucleic acid (DNA) is the most important element for storing genetic information in biology. Until so far, there are still a lot of unknown properties which need to be investigated. In this study, we used mica and gold substrate for binding DNA and observed DNA structures by using atomic force microscopy (AFM). Both mica and DNA have negative charges, so multivalent cations can be the bridge to link DNA and mica substrate. In our experiments, cation concentration is changed as the parameter to improve the DNA binding efficiency. We also observed the transition of DNA conformation when the liquor of deionized water was replaced by ethanol. Both Gold and the base on DNA backbone are hydrophobic, so DNA can be bound to gold substrate strongly. As the result, we used the tip to stretch DNA that is both bound to the gold substrate and the tip, and then we can measure the force curve of DNA during structure transformation. The efficiency of DNA bound on mica is not really proportional to cation concentration. There are the best efficiency when the cation concentration is between 0.5 mM ~ 10mM. The conformation of DNA will change from B-form to A-form . During the stretching of DNA, The velocity of tip will affect the experiment data of force curve. The helical conformation of DNA will be unwinding under stretching with 27 pN.