Nanoparticles of negatively charged gold "Regulate" the Spatial Packing of Double-Stranded DNA Sequences

• Shtykova EV

  English

  Author

• Khlebtsov NG

  English

  Author

• Komarov PV

  English

  Author

In this paper, we detail recent visual and small-angle X-ray scattering (SAXS) observations of the dispersion development in ds DNA
molecules doped with nano-Au, which are negatively charged nanoparticles. The amplitude of the abnormal negative band in the circular
dichroism spectra of the formed cholesteric liquid-crystalline dispersions (CLCD) is reduced when nano-Au is fixed near the surfaces of
linear double-stranded DNA in a solution of high ionic strength (0.3 M NaCl) and then the (ds DNA-nano-Au) complexes are phase-extracted
from a solution containing poly(ethylene glycol). The standard structural parameters derived from SAXS data, which represent the local
ordering of ds DNA molecules, are unaffected by doping linear ds DNA with nano-Au and then phase excluding the resulting (ds DNA-nano-
Au) complexes; however, the amplitude of the characteristic Bragg maximum is reduced. Doping double-stranded DNA with negatively
charged nano-Au causes a population of "modified" double-stranded DNA molecules to emerge, according to our experimental data and a
basic model numerical calculation of screened electrostatic energies for ds DNA molecules and negatively charged but polarizable nano-Au
in a water-salt solution of high ionic strength. In contrast to free ds DNA molecules, these molecules are unable to form spatially twisted
structures during phase exclusion, leading to the formation of chaotic aggregates rather than the ordered spatial structure often seen in ds
DNA CLCD.

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