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Plot of the number of Na+ ions (solid circles) and protonated amine nitrogens (open circles) for system I (PEI(20)) within 10 Å of any C1′ DNA atom as a function of time for system I (PEI(20)). The dashed line shows the number of Na+ ions for system VI as a reference. The number of Na+ ion around DNA helix is reduced as PEI chain approaches the DNA helix.
