We demonstrate a simple method of stretching DNA to its full length, suitable for optical imaging and atomic force microscopy (AFM). Two competing forces on the DNA molecules, which are the electrostatic attraction between positively charged dye molecules (YOYO-1) intercalated into DNA and the negatively charged surface of glass substrate, and the centrifugal force of the rotating substrate, are mainly responsible for the effective stretching and the dispersion of single strands of DNA. The density of stretched DNA molecules could be controlled by the concentration of the dye-stained DNA solution. Stretching of single DNA molecules was confirmed by AFM imaging and the photoluminescence spectra of single DNA molecule stained with YOYO-1 were obtained, suggesting that our method is useful for spectroscopic analysis of DNA at the single molecule level.
Study of biological molecule DNA has contributed to developing many breaking thoughts and wide applications in
multidisciplinary fields, such as genomic, medical, sensing and forensic fields. Stretching of DNA molecules is an
important supportive tool for AFM or spectroscopic studies of DNA in a single molecular level. In this article, we
established a simple method of DNA stretching (to its full length) that occurred on a rotating negatively-charged surface
of glass substrate. The isolation of a single DNA molecule was attained by the two competitive forces on DNA
molecules, that is, the electrostatic attraction developed between the positively charged YOYO-1 stained DNA and the
negatively charged substrate, and the centrifugal force of the rotating substrate, which separates the DNA aggregates into
the single molecule. Density of stretched DNA molecules was controlled by selecting the specific parameters such as
spinning time and rates, loading volume of DNA-dye complex solution etc. The atomic force microscopy image
exhibited a single DNA molecule on the negatively-charged substrate in an isolated state. Further, the
photoluminescence spectra of a single DNA molecule stained with YOYO-1 were achieved using the method developed
in the present study, which is strongly believed to effectively support the spectroscopic analysis of DNA in a single
molecular level.
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