2019 Volume 2019, p1-8
We examined the interactions of initial single-stranded DNA (ssDNA) and secondary ssDNA molecules on single-walled carbon nanotubes (SWNTs). Thymine 30-mers (T30) and 30-mers from a partial sequence of <jats:italic>φ</jats:italic>x174 DNA (<jats:italic>φ</jats:italic>30) were used to prepare the DNA-SWNT hybrids. First, the hybrids were annealed at various temperatures without secondary DNA to evaluate the stability of the hybrids. As a result, aggregates of SWNTs were formed in the T30-SWNT hybrids, even at 54°C, although the <jats:italic>φ</jats:italic>30-SWNT hybrids were stable up to 84°C. Second, we added secondary DNA molecules during the annealing procedure. We reacted adenine 30-mers (A30) with the T30-SWNT hybrids and characterized the samples by combining agarose gel electrophoresis with/without ethidium bromide and atomic force microscopy (AFM) as well as near-infrared photoluminescence (PL) spectroscopy. Cross-links appeared to form among the SWNTs because of nonspecific hybridization of T30 and A30. PL measurements revealed clear shifts in the PL emission wavelength of SWNTs. However, when complementary <jats:italic>φ</jats:italic>30 DNA (c<jats:italic>φ</jats:italic>30) was reacted with <jats:italic>φ</jats:italic>30-SWNT hybrids, there was no significant difference in the PL spectra after the reaction, although electrophoresis suggested the hybridization of the c<jats:italic>φ</jats:italic>30 and <jats:italic>φ</jats:italic>30 DNA molecules. Our results suggest that the hybridization manner of DNA molecules with unnatural sequences greatly differs from that of natural DNA molecules.
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