Adsorption of Poly(rA) on the Carbon Nanotube Surface and its Hybridization with Poly(rU)

Abstract

Adsorption of poly(rA) on a single-walled carbon nanotube surface in aqueous suspension and the subsequent hybridization of this polymer with free poly(rU) is studied. A comparison of the temperature dependence of the absorbance of free poly(rA) and poly(rA) adsorbed on the nanotube surface [poly(rA)(NT)] at nu(max)= 38,500 cm(-1) shows that the thermostability of the adsorbed polymer is higher. Molecular dynamics simulations demonstrate that more than half of the adenines are not stacked on the tube surface and some of them undergo self-stacking. After addition of a complementary poly(rU) to the poly(rA)(NT) suspension, a double-stranded polymer is formed as confirmed by the characteristic S-like form of its melting curve. However, the melting temperature of this polymer is lower than that of the free poly(rA)poly(rU) duplex. This result indicates that poly(rU) hybridization with poly(rA)(NT) occurs with defects along the whole length of the polymer because of pi-pi stacking between nitrogen bases and the nanotube surface, which hinders the usual hybridization process. Computer modeling demonstrates different possible structures of hybridized polymers on the nanotube surface.

Label-free single-molecule detection of DNA-hybridization kinetics with a carbon nanotube field-effect transistor

“…The melting temperature of the DNA duplex (where α=0.5) as measured by the nanotube (T m = 27.7°C) is slightly lower and the transition is sharper compared to the free DNA (T m = 32.3°C). A similar observation has been made for DNA linked to gold nanoparticles 23 and RNA adsorbed to carbon nanotubes 24 due to interactions between the molecules and the surface 25 . This is considered further below in the context of analyzing the results of the kinetic studies.…”

Comparative study on protection properties of anionic surfactants (SDS, SDBS) and DNA covering of single‐walled carbon nanotubes against pH influence: luminescence and absorption spectroscopy study

“…In comparison with the peak position of SWNT:SDBS, the band shift of the electronic level to lower energy is observed, the value of which is reached 20-30 meV. The red shift of nanotube emission bands can be explained by the protonation effect [20] which exhibits due to the partial covering of the nanotube surface with the polymer at 1:1 nanotube: DNA weight ratio (please see AFM image in [21]) and, in a result, the polymer free nanotube surface contacts with water. Emission intensity transformation of SWNTs covered with ss-DNA at different pH is shown in Fig.…”

Raman spectroscopy of DNA-wrapped single-walled carbon nanotube films at 295 and 5K

“…This process takes place not only during ultrasonication but after this treatment too, due to self-ordering to find its optimal energetic position on the nanotube surface in water. As experiments revealed, the process can proceed for weeks and even months [5,6].…”