title: Lithium ion induced stabilization of the liquid crystalline DNA.
abstract: A comparative study of the effects of alkali metal ions Li(+), Na(+), K(+), Rb(+), and Cs(+) on the liquid crystalline organization of high-molecular-weight calf thymus DNA using polarized light microscopy was performed. Major differences in the behavior of Li(+) as compared to the other ions were found. Critical DNA concentration expected to exhibit anisotropic behavior was found to be the same for all the monovalent ions, except for Li(+). DNA initially showed cholesteric textures, which later changed to higher ordered columnar phase for all ions, with the cholesteric-columnar transition facilitated upon increasing the size of the counterion. For Li(+) ion, a nematic schlieren-like texture was formed initially, which after a few days changed to a highly stable (for more than 2 months) biphasic cholesteric-columnar arrangement. The observed differences between Li(+) and other alkali metal ions could be rationalized on the basis of the higher number of hydration water molecules of Li(+) and its complexation behavior. Highly stable DNA mesophases may find applications in the field of nanoelectronics, in designing biosensing units, and in DNA chips.
authors.affiliation: Chemical Sciences & Technology Division, Regional Research Laboratory, Council of Scientific and Industrial Research, Thiruvananthapuram 695019, India.
authors.forename: Neethu
authors.initials: N
authors.lastname: Sundaresan
authors.forename: Thresia
authors.initials: T
authors.lastname: Thomas
authors.forename: Thekkumkat John
authors.initials: TJ
authors.lastname: Thomas
authors.forename: Chennakkattu Krishna Sadasivan
authors.initials: CK
authors.lastname: Pillai
authors.forename: Chennakkatu Krishna Saolashiuan
authors.initials: CK
authors.lastname: Pillai
mesh_terms: D000818:Animals; D016880:Anisotropy; D002412:Cations; D002417:Cattle; D004247:DNA / Q000737:chemistry*; D050866:Liquid Crystals / Q000737:chemistry*; D008094:Lithium / Q000737:chemistry*; D008859:Microscopy, Polarization
chemical_list: D002412:Cations; D004247:DNA; D008094:Lithium