Under “physiological” conditions (a 0.1 molar solution of NaCl), a DNA molecule takes on the form of a disordered coil with a radius of gyration of several micrometers; if any lengths of the molecule come within 1 nm of one other, they strongly repel. But under different conditions—in a highly dilute aqueous solution that also contains a small concentration of polyvalent cations—the same DNA molecule condenses into a tightly packed, circumferentially wound torus. Figure 1a shows just such a DNA torus. Its average radius is about 50 nm, and the distance between the axes of neighboring, parallel portions of the molecule is only slightly larger than its diameter.
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September 01 2000
Not just the repository of our genetic information, DNA is also a fascinating, shape‐shifting molecule whose behavior in solution counters our intuition and challenges our physical understanding.
William M. Gelbart;
Robijn F. Bruinsma;
Philip A. Pincus;
Physics Today 53 (9), 38–44 (2000);
William M. Gelbart, Robijn F. Bruinsma, Philip A. Pincus, V. Adrian Parsegian; DNA‐Inspired Electrostatics. Physics Today 1 September 2000; 53 (9): 38–44. https://doi.org/10.1063/1.1325230
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