Nguyen, Thi-Huong Lee, Sang-Myung Na, Kyounghwan Yang, Sungwook Kim, Jinseok Yoon, Eui-Sung 2024-01-20T20:00:36Z 2024-01-20T20:00:36Z 2021-09-02 2010-02-19 0957-4484 https://pubs.kist.re.kr/handle/201004/131710 The mechanical properties of a small fragment (30 bp) of an individual double-stranded deoxyribonucleic acid (dsDNA) in water have been investigated by atomic force microscopy (AFM). We have stretched three systems including ssDNA, double-fixed dsDNA (one strand of the dsDNA molecules was biotinylated at the 3'-end and thiolated at the 5'-end, this was reversed for the other complementary strand) and single-fixed dsDNA (one strand of the dsDNA molecules was biotinylated at the 3'-end and thiolated at the 5'-end, whereas the other complementary strand was biotinylated at only the 5'-end). The achieved thiolation and biotinylation were to bind ds- or ssDNA to the gold surface and streptavidin-coated AFM tip, respectively. Analysis of the force versus displacement (F-D) curves from tip-DNA-substrate systems shows that the pull-off length (L-o) and stretch length (delta) from the double-fixed system were shorter than those observed in the ssDNA and the single-fixed system. The obtained stretch force (F-st) from the single-fixed dsDNA was much greater than that from the ssDNA even though it was about 10 pN greater than the one obtained in the double-fixed system. As a result, the Young's modulus of the double-fixed dsDNA was greater than that of the single-fixed dsDNA and the ssDNA. A more reliable stiffness of the dsDNA was observed via the double-fixed system, since there is no effect of the unpaired molecules during stretching, which always occurred in the single-fixed system. The unpaired molecules were also observed by comparing the stiffness of ssDNA and single-fixed dsDNA in which the end of one strand was left free. English IOP PUBLISHING LTD FORCE SPECTROSCOPY SINGLE-MOLECULE DNA TRANSITION An improved measurement of dsDNA elasticity using AFM Article 10.1088/0957-4484/21/7/075101 1 NANOTECHNOLOGY, v.21, no.7 NANOTECHNOLOGY 21 7 scie scopus 000273824500002 2-s2.0-77950465753 Nanoscience & Nanotechnology Materials Science, Multidisciplinary Physics, Applied Science & Technology - Other Topics Materials Science Physics Article FORCE SPECTROSCOPY SINGLE-MOLECULE DNA TRANSITION DNA elasticity AFM Youngs modulus stretching