V. I. Salyanov

Invite Article: The Liquid-Crystalline Phases of Double-Stranded Nucleic Acids in Vitro and in Vivo

Abstract This article describes the state of and progress in experimental studies of liquid crystals of naturally occurring nucleic acids and synthetic polynucleotides. The areas considered in this review include: (i) the liquid-crystalline phase of nucleic acids in aqueous salt solutions, (ii) the liquid-crystalline phase of nucleic acids in aqueous polymer solutions, (iii) the liquid-crystalline phase of nucleic acids in living systems. Some unsolved problems which are of interest from both a physicochemical and a biological point of view are discussed.

Liquid Crystalline State of DNA Molecules Complexed with Biologically Active Compounds

Abstract Liquid crystalline microphases (LCMs) formed as a result of condensation of rigid double-stranded right-handed DNA molecules complexed with different antibiotics and dyes (external chromophores) are shown to be characterized by two bands in circular dichroism (CD) spectra; one of them is located in the region of absorption of DNA chromophores (nitrogen bases) at λ ∼ 270 nm, the other—in the region of absorption of external chromophores at λ ∼ 500 nm. The appearance of these two bands in the CD spectrum demonstrates that LCMs formed from DNA molecules of low-molecular-weight are helically twisted. Correlation between signs of bands in the CD spectrum of LCMs and orientation of molecules of external chromophores about the helical axis of DNA molecules has been established. The data obtained allow to draw a conclusion that the selective reflection band connected with the pitch (P) of the twisted structure formed from adjacent DNA molecules is located at λ > 600 nm.

Formation of polymeric chelate bridges between double-stranded DNA molecules fixed in spatial structure of liquid-crystalline dispersions

The formation of cholesteric liquid‐crystalline dispersions from DNA‐daunomycin complexes in water‐salt polyethyleneglycol‐containing solutions was investigated. In the case of nonclassical complex formation between DNA and daunomycin (DAU), reactive groups of DAU were used for the formation of polymeric chelate complex with divalent copper ions (‐DAU‐Cu‐…‐Cu‐DAU‐), located between neighboring double‐stranded DNA molecules, fixed in spatial structure of liquid‐crystalline dispersions. The formation of polymeric chelate complex does not depend upon the sense of helicoidal twist of DNA cholesterics. A many‐fold increase in the CD band in the DAU absorption region is specific to this process. A reduction of the divalent copper ions as a result of a redox‐process is accompanied by destroying of structure of polymeric chelate complex between DNA molecules and by disappearance of the abnormal CD band in daunomycin absorption region.

Analytical capacity of the DNA liquid-crystalline dispersions as biosensing units

Abstract The main theoretical principles used for creating biosensing units based on the liquid-crystalline dispersions formed from the linear double-stranded DNA molecules are considered in this paper. A broad range of analytical abilities of these units is illustrated. These units are capable of detecting various biologically active compounds influencing the DNA secondary structure. A new ‘sandwich-type’ of biosensing unit based on the liquid-crystalline (DNA-daunomycin) complexes is also proposed. Some unsolved problems are outlined.

Magnetic Properties of Copper as a Constituent of Nanobridges Formed between Spatially Fixed Deoxyribonucleic Acid Molecules

The number of copper ions as constituents of a nanobridge that links two deoxyribonucleic acid (DNA) molecules that are fixed in a particle of a liquid-crystalline dispersion has been evaluated from the measurements of the magnetic susceptibility of particles in the liquid-crystalline dispersion of DNA. It has been shown that the experimental data are consistent with both theoretical assumptions on the possible structure of a nanobridge and a thermodynamic model that describes the formation of these bridges.

Liquid-crystalline phases of circular superhelical plasmid DNA and their modification by the action of nuclease enzymes

Abstract CD spectra of liquid-crystalline dispersions, X-ray diffraction patterns and optical textures of liquid crystals prepared from native superhelical DNA in poly(ethyleneglycol)-containing water–salt solutions before and after treatment of DNA with micrococcal nuclease have been obtained. It was found that condensation of native superhelical DNA is accompanied by the formation of liquid crystals with a non-specific optical texture. After treatment of the DNA, liquid-crystalline dispersions, with Micrococcal nuclease the DNA is able to form two similar types of liquid crystals with abnormal optical activity which differ in the peculiarities of their textures. The data obtained demonstrate the formation of multiple types of liquid crystals from high molar mass double-stranded optically active DNA molecules.

DNA specific fluorescent symmetric dimeric bisbenzimidazoles DBP(n): The synthesis, spectral properties, and biological activity

A series of new fluorescent symmetric dimeric bisbenzimidazoles DBP(n) bearing bisbenzimidazole fragments joined by oligomethylene linkers with a central 1,4-piperazine residue were synthesized. The complex formation of DBP(n) in the DNA minor groove was demonstrated. The DBP(n) at micromolar concentrations inhibit in vitro eukaryotic DNA topoisomerase I and prokaryotic DNA methyltransferase (MTase) M.SssI. The DBP(n) were soluble well in aqueous solutions and could penetrate cell and nuclear membranes and stain DNA in live cells. The DBP(n) displayed a moderate effect on the reactivation of gene expression.

Sensing bioligical effectors through the response of bridged nucleic acids and polynucleotides fixed in liquid-crystalline dispersions

The formation of three-dimensional structures of double-stranded nucleic acid and polynucleotide molecules, fixed in the structure of liquid-crystalline dispersions and bridged by polymeric chelate complexes is described. The bridging elements consist of alternating daunomycin molecules and copper ions. It is shown that these bridges between nucleic acid molecules stabilize cholesteric structures of the DNA liquid-crystalline dispersion. The formation of polymeric chelate bridges is accompanied by a remarkable increase of the intense circular dichroism (CD) band characteristic of the DNA-daunomycin cholesterics. These bridges are destabilized by a number of biologically relevant compounds and macromolecules, such as ascorbic acid, homocarnosine, bovine serum albumin and lysozyme. The dramatic change in the optical activity of the liquid-crystalline dispersions upon addition of these compounds makes them easily detectable. The sensitivity of the method, in the range of analytic concentration 10(-4)-10(-8) M, depends on the nature of the compound being tested. The response of bridged DNA structures to biological effectors observed here foresees their further development as biosensor devices for detecting the presence of biologically and pharmacologically relevant compounds.

Liquid crystalline dispersions of double-stranded nucleic acids and their complexes as a background for nanodesign: Review

Different strategies in design of nanoconstructions whose building blocks are both linear molecules of double-stranded nucleic acids and nucleic acid molecules fixed in the spatial structure of particles of liquid crystalline dispersions have been considered.

Rare-Earth-Cation-Induced Change in the Cholesteric Twisting of Neighboring Nucleic Acid Molecules

Certain physicochemical characteristics of particles of the cholesteric liquid-crystal dispersions of complexes of double-stranded nucleic acids with rare earth elements have been determined. It is shown for the first time that the binding of the rare earth cations to linear nucleic acid molecules ordered in the structure of particles of the cholesteric liquid crystal dispersions is accompanied not only by amplification of the abnormal band in the circular dichroism spectrum, but also by the disappearance of the characteristic maximum on the X-ray scattering curves for small angles. The (cholesteric 1-cholesteric 2) transition induced by rare earth cations is an example of the operation of a microscopic machine consisting of spatially ordered nucleic acid molecules. Particles of the cholesteric liquid crystal dispersions of nucleic acid complexes with rare earth elements hold the abnormal optical properties for a long time.