Supporting Material for the manuscript “Computer Modelling Reveals That Modifications of the Histone Tail Charges Define Salt-Dependent Interaction of the Nucleosome

i) Supporting computational methods for the “Sphere ” model of the NCP ii) Supporting computational methods for the “Sphere-Bead ” model of the NCP iii) Selected data on NCP-NCP interaction determined for the systems with Sphere-Bead model of the NCP i) Supporting computational methods for the “Sphere ” model of NCP Description of the “Sphere ” model of the NCP (Figure 1S, Table 1S) The recombinant NCP was modelled as a spherical particle of effective radius 4.85 nm with net charge −236e combined with 8 strings of linearly-connected +1e charges of effective radius 0.25 nm and bond length 0.7 nm, which represent the histone tails (1). The charge of the central particle reflects the electrostatic balance between 147 base pairs of the double-stranded DNA (charge −294e) and the net positive charge +58e of the amino acids comprising the globular domains of the histones. The distance between charged groups of the histone tails (0.7 nm) was evaluated assuming extended conformation of the polypeptide chain and even distribution of the Lys+/Arg+ amino acids. The number of charged groups in each tail was set according to the charges of the real histone tails. The total charge of histone tails was +88e