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Yu. M. Yevdokimov¹, S. G. Skuridin¹, V. I. Salyanov¹, V. I. Popenko¹, E. V. Shtykova², N. G. Khlebtsov³, G. A. Shafeev⁴, E. I. Kats⁵

Author affiliations
¹Engelhardt Institute of Molecular Biology, Russian Academy of Sciences,
Vavilov str., 32, 119991 Moscow, Russia. 
E-mail: yevdokim@eimb.ru
²Shubnikov Institute of Crystallography, Russian Academy of Sciences,
Leninsky ave., 59, 119333 Moscow, Russia. 
E-mail: viwopisx@yachoo.co.uk
³Institute of Biochemistry and Physiology of Plants and Microorganisms, Russian Academy of Sciences,
Entuziastov ave., 13, 410049 Saratov, Russia. 
E-mail: nkhlebtsov@gmail.com
⁴Prokhorov General Physics Institute, Russian Academy of Sciences,
Vavilov str., 38, 119991 Moscow, Russia. 
E-mail: gashafeev@gmail.cov
⁵Landau Institute for Theoretical Physics, Russian Academy of Sciences,
Kosygin str., 2, 119334, Moscow, Russia. 
E-mail: kats@landau.ac.ru

Abstract
The negatively charged gold nanoparticles (nano-Au) in solutions of high ionic strength interact with free, linear double-stranded (ds) DNA or synthetic poly(ribonucleotide) (poly(I)×poly(C) or poly(A)×poly(U)) molecules or with these molecules ordered in the spatial structure of the cholesteric liquid-crystalline dispersion (CLCD) particles formed as a result of their phase exclusion from solutions containing poly(ethylene glycol). However, the consequences of these interactions differ noticeably. If we first pretreate free ds nucleic acid (NA) molecules with nano-Au and then create dispersion, the orientationally ordered structures do not form. This leads to disappearance of abnormal band in the circular dichroism spectra at a very low concentration of added nano-Au. If we treat condensed ds NA, i.e. ds NA in the content of CLCD particles, with nano-Au, the orientational order remains stable. This order evolves (from cholesteric to untwisted, nematic-like) upon increase in nano-Au concentration. The preliminary measurements and evaluations show that the analogous spectral changes are also typical for palladium nanoparticles. The differences in nano-Au action on free and condensed ds NA molecules can result in various damaging effects in living cells and be accompanied by various genetic consequences.

Keywords: nanoparticles of noble metals; free double-stranded nucleic acids; circular dichroism of nucleic acid molecules; cholesteric liquid-crystalline DNA dispersions; cholesteric → nematic transition; aggregated DNA molecules