A study was made of the formation of cholesteric liquid-crystalline dispersions (ChLCDs) of double-stranded DNA molecules that were treated with positively charged superparamagnetic cobalt ferrite nanoparticles and the effect the particles exert on DNA liquid-crystalline dispersions (LCDs). When magnetic nanoparticles (MNPs) were bound to linear double-stranded DNA molecules at a high ionic strength (0.3 M NaCl), subsequent phase exclusion of the complexes from a polyethylene glycol (PEG)-containing solution failed to produce a dispersion wherein particles have a spatially twisted arrangement of neighbor double-stranded DNA molecules. When MNPs were added to a DNA ChCLD (1 MNP per 1 DNA molecule), the DNA structure was distorted at MNP binding sites so that the spatial ordering of DNA LCD particles was blown up, abolishing both abnormal optical activity and the characteristic Bragg maximum on a small-angle X-ray scattering (SAXS) curve. The effect may have important biological consequences, considering that physicochemical properties of double-stranded DNA LCD particles reflect features of the DNA spatial organization in chromosomes of primitive organisms.
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