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Yu. M. Yevdokimov¹, S. G. Skuridin¹, V. I. Salyanov¹, E. R. Muzipov², S. V. Semenov³, E. I. Kats⁴

Author affiliations
¹Engelhardt Institute of Molecular Biology of the Russian Academy of Sciences,
32 Vavilova St., Moscow, 119991 Russia
E-mail: yevdokim@eimb.ru
²Limited Liability Company «D-Micro»,
74 Flotskaya St., Moscow, 125413, Russia
³National Research Centre «Kurchatov Institute»,
1 Kurchatov square, Moscow, 123182, Russia
⁴Landau Institute for Theoretical Physics of the Russian Academy of Sciences,
2 Kosygina St., Moscow, 119334, Russia

Abstract
n this research we compared the optical properties of liquid-crystalline DNA dispersion particles formed as a result of the phase exclusion of double-stranded (ds) DNA molecules from aqueous-salt of poly(ethylene glycol) solutions and the phases obtained from these dispersions. It is shown that the liquid-crystalline dispersions with cholesteric packing of double-stranded DNA molecules are characterized by an intense (abnormal) negative band in the circular dichroism (CD) spectrum. The phases obtained from these dispersions possess «fingerprint» texture at both room and elevated temperatures. The CD spectra without abnormal band are found for double-stranded DNA dispersions with an initial hexagonal packing of molecules, which are formed at room temperatures. However, the temperature increase results in the appearance of an abnormal band in the CD spectrum of the hexagonal double-stranded DNA dispersion particles. The observed optical effect corresponds to a new “hexagonal → re-entrant cholesteric” phase transition in the case of the particles formed by both the semi-rigid and flexible ds DNA molecules. Unlike the dispersion particles, the textures of phases obtained from these particles do not demonstrate any attributes typical of conventional cholesteriсs. These textures present anisotropic domains with beautiful colors at room and elevated temperatures. In the agreement with the measured magnitude of the abnormal CD band, the colors can reveal a very small helical pitch well below the values known for classical cholesterics.

Keywords: liquid-crystalline ds DNA dispersion particles, circular dichroism, abnormal optical activity, textures, hexagonal packing of ds DNA molecules in dispersion particles, cholesteric packing of ds DNA molecules in dispersion particles, hexagonal → cholesteric phase transition