✍ Scribed by Neethu Sundaresan; Thresia Thomas; Thekkumkat John Thomas; Chennakkatu Krishna Saolashiuan Pillai
No coin nor oath required. For personal study only.
Summary: 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.
Nematic schlieren‐like texture obtained in presence of Li^+^ ion after 5 h of incubation at 37 °C. Magnification 10×.
magnified imageNematic schlieren‐like texture obtained in presence of Li^+^ ion after 5 h of incubation at 37 °C. Magnification 10×.
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