Double-Stranded DNA Packing in Particles of Liquid-Crystalline Dispersions and Liquid-Crystalline Phases Obtained from These Particles

Abstract

In 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.

Liquid-Crystalline Dispersions of Double-Stranded DNA

“…It depends, mainly, on the peculiarities of ds DNA molecules (secondary structure, molecular mass, etc.) [74] and it is quiteconsistent with the concept of the improvement of the cholesteric packing of dispersion particle structure as a result of the thermal "training" [75,76] of ds DNA CLCDs.…”