The role of water and K+ ion in the charge transfer between groups of DNA and the lysine+ and arginine+ side chains of histone proteins

We have calculated the charge transfer (CT) between the PO 4 - group of DNA and the lysine (Lys) and arginine (Arg) positive side chains of histones in presence of water and K+ ions. The calculations were performed at the HF + MP2 level, using the TZVP basis set. The calculations were corrected for basis set superposition error and besides Mulliken’s population analysis we have introduced the – for charged systems more reliable – natural population analysis. The results show that the bare PO 4 - -Lys and the PO 4 - -Arg interactions become weaker, mainly, due to the presence of the K+ ion. We have found 0.067e CT for Lys and 0.050e for Arg.