title: [Structural polymorphism of the liquid-crystalline dispersions formed from the double-stranded DNA molecules complexed with synthetic polycations].
abstract: The double-stranded, linear DNA molecules form the liquid-crystalline dispersions (LCD) in water-salt solutions containing positively charged polyconidin molecules. It was established from the analysis of the absorption spectra of the LCDs formed from (DNA-polyconidin) complexes, that the mean size of the particles of these dispersions is equal to -6000 angstroms. The small-angle X-ray data show, that in the LCD particles different density of packing of the (DNA-polycation) complexes is realized. The comparison of the X-ray data of the liquid-crystalline phases of (DNA-polyconidin) complexes formed under various conditions with the phase diagram, that reflects the polymorphism of the linear double-stranded DNA liquid crystals, demonstrates that the hexagonal mode of the LCD packing is existing in 0.15-0.4 M NaCl solutions, whereas in 0.4-0.55 M NaCl solutions-- the cholesteric one. As a result of specific spatial organization the cholesteric LCD possesses of an abnormal optical activity in the CD spectrum. The similar situation takes place in the case of another synthetic polycation--poly(2,5-ionen), whose chemical structure differs from that of polyconidin. Thus, the structural polymorphism of the (DNA-polyconidine) LCDs was evidenced. It means that change of NaCl concentration opens a gate to control the spatial packing of the molecules of (DNA-polycation) complexes in the particles of LCDs. The supposition about mechanism of formation of the DNA cholesteric liquid-crystalline state in the narrow interval of NaCl concentrations was suggested.
authors.forename: S G
authors.initials: SG
authors.lastname: Skuridin
authors.forename: Zh G
authors.initials: ZhG
authors.lastname: Guliaeva
authors.forename: Iu M
authors.initials: IuM
authors.lastname: Evdokimov
mesh_terms: D004247:DNA / Q000737:chemistry*; D050866:Liquid Crystals / Q000737:chemistry; D009690:Nucleic Acid Conformation; D011073:Polyamines / Q000138:chemical synthesis / Q000737:chemistry*; D000071228:Polyelectrolytes; D011108:Polymers / Q000737:chemistry; D053838:Scattering, Small Angle; D012965:Sodium Chloride / Q000737:chemistry; D012996:Solutions / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D004247:DNA; D011073:Polyamines; D000071228:Polyelectrolytes; D011108:Polymers; D012965:Sodium Chloride; D012996:Solutions; D014867:Water; C039164:conidine