= Solution
<Chromatin> is a composite of charged <DNA>, folded <histone> cores, flexible <histone> tails and associated <proteins>. These parts differ in charge, hydrophobicity, flexibility, interaction partners and chemical modifications. It is therefore not a chemically uniform chain with one identical contact energy at every position.
Diversity also occurs along a <chromosome>: <nucleosome> occupancy, <linker DNA> length, <histone variants>, <histone acetylation> and other <histone modifications> change the local interaction pattern. Positively charged tails can contact <DNA> or neighbouring <nucleosome> surfaces; an acetylated lysine has different electrostatic properties and can recruit a modification-reading <protein>. The number, arrangement and lifetime of contacts matter as well as their average strength. A coarse-grained interaction parameter can summarize one preparation but should not be mistaken for a universal chemical constant of all <chromatin>.
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