The image is of an untwisted DNA helix and its ion atmosphere. As the movie progresses, the viewer moves down the helix.

The white balls represent RNA bases with little negative charge, and the red balls represent highly negatively charged phosphates. The other balls represent ions: blue for magnesium, yellow for sodium, and green for chloride. The ions are summed over 100 frames, to give an idea of the distribution of ions over time around this fixed DNA. (from a Grand Canonical Monte Carlo simulation)

Note:

  • the much denser ion cloud near the center of the helix, and
  • the much greater accumulation of magnesium than sodium around the helix