Effects of alternating electric field on the imaging of DNA double-helix structure by atomic force microscope
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ORIGINAL ARTICLE
Effects of alternating electric field on the imaging of DNA double‑helix structure by atomic force microscope Ying Wang1,2 · Ke Ma1,2 · Jiajia Wang1,2 · Yihui Wang4 · Li Li1,2 · Ziyu Liu1,2 · Jing Hu1,2 · Mingyan Gao1,2 · Zuobin Wang1,2,3 Received: 14 March 2020 / Accepted: 8 July 2020 © King Abdulaziz City for Science and Technology 2020
Abstract The effects of alternating electric field on the imaging of DNA double-helix structure were explored by atomic force microscope (AFM). First, the DNA sample was located under an alternating electric field in a fixed direction and dried. Then, AFM was used to obtain the DNA images under different alternating electric fields with the voltage range from 0.5 to 6.0 V and the frequency of 50 kHz. Thus, the DNA double-helix structures with different extensions were observed when the DNA molecules were gradually stretched under different field intensities. The distributions of DNA molecules in solution were random if there were no external forces, and the curved DNA molecules were observed in the AFM image. With the increase in alternating electric voltage (0.5–4.0 V), the DNA structure was shifted from random to oriented conformation and the DNA grooves were further unfolded. While the higher voltage (5.0–6.0 V) resulted in the rupture of DNA chains due to the excessive stretching force. It showed that the optimal voltage was 1.0 V, and the double-helix structure was observed. This method provides an efficient way for monitoring and measuring bio-macromolecules. It may also enable the exploration of the DNA–protein binding and DNA molecular self-assembly processes. Keywords Manipulating DNA · AC electric field · DNA stretching · DNA double-helix structures · Atomic force microscope · Single molecule imaging
Introduction As one of the most important biomolecules, the DNA molecules have contained nearly all the hereditary information of all known life forms. The biological function of DNA has been widely explored since the double-helix structure was discovered by Crick and Watson (1953), and various tools have been used to explore the DNA molecule structure. The scanning tunnelling microscope (STM) was first used to * Zuobin Wang [email protected] 1
Ministry of Education Key Laboratory for Cross‑Scale Micro and Nano Manufacturing, Changchun University of Science and Technology, Changchun 130022, China
2
CNM & JR3CN, Changchun University of Science and Technology, Changchun 130022, China
3
JR3CN & IRAC, University of Bedfordshire, Luton LU1 3JU, UK
4
Changchun Vocational Institute of Technology, Changchun 130033, China
exploit the DNA molecules and obtained the plasmid DNA images on mica by Guckenberger et al (1994). Wilton et al (2008) used nuclear magnetic resonance (NMR) to study the change of B-DNA structure under significant pressure and found that the minor grooves of DNA were widened as the structure was distorted. An atomic force microscope (AFM) (Snow and Campbell 1995; Cadena et al. 2017; Bose and Phan 2017) is a useful tool for rea
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