| Autor: |
Kodikara SG; Department of Physics, Kent State University, Kent, Ohio 44242, United States., Gyawali P; Department of Physics, Kent State University, Kent, Ohio 44242, United States., Gleeson JT; Department of Physics, Kent State University, Kent, Ohio 44242, United States., Jákli A; Department of Physics, Kent State University, Kent, Ohio 44242, United States.; Advanced Materials and Liquid Crystal Institute, Kent State University, Kent, Ohio 44242, United States., Sprunt S; Department of Physics, Kent State University, Kent, Ohio 44242, United States.; Advanced Materials and Liquid Crystal Institute, Kent State University, Kent, Ohio 44242, United States., Balci H; Department of Physics, Kent State University, Kent, Ohio 44242, United States. |
| Abstrakt: |
The layered liquid crystalline phases formed by DNA molecules, which include rigid and flexible segments ("gapped DNA"), enable the study of both end-to-end stacking and side-to-side (helix-to-helix) lateral interactions, forming a model system to study such interactions at physiologically relevant DNA and ion concentrations. The observed layer structure exhibits long-range interlayer and in-layer positional correlations. In particular, the in-layer order has implications for DNA condensation, as it reflects whether these normally repulsive interactions become attractive under certain ionic conditions. Using synchrotron small-angle X-ray scattering measurements, we investigate the impact of divalent Mg 2+ cations (in addition to a constant 150 mM Na + ) on the stability of the inter- and in-layer DNA ordering as a function of temperature between 5 and 65 °C. DNA constructs with different terminal base pairings were created to mediate the strength of the attractive end-to-end stacking interactions between the blunt ends of the gapped DNA constructs. We demonstrate that the stabilities at a fixed DNA concentration of both interlayer and in-layer order are significantly enhanced even at a few mM Mg 2+ concentration. The stabilities are even higher at 30 mM Mg 2+ ; however, a marked decrease is observed at 100 mM Mg 2+ , suggesting a change in the nature of side-by-side interactions within this Mg 2+ concentration range. We discuss the implications of these results in terms of counterion-mediated DNA-DNA attraction and DNA condensation. |
