Nucleosome-like Structure from Dendrimer-Induced DNA Compaction

Genomic DNA in eukaryotes wraps around histone proteins to package into the limited space of cell nucleus. Since the precise structure of chromatin is not known in detail, attempts have been made to understand DNA–histone interaction and the associated self-organization behavior using synthetic model systems. Using small-angle X-ray and neutron scattering, here we show that the electrostatic attraction between DNA and polyamidoamine (PAMAM) dendrimer of generation nine (G9) led to the formation of beads-on-string structure, where DNA wrapped around the dendrimer tightly to yield the “chromatin-like fiber” composing of the interconnected “nucleosome-like particles”. A “stiff chromatin-like fiber model” and a “wormlike chromatin-like fiber model” were introduced to obtain the theoretical scattering patterns closely resembling the experimentally observed ones, from which the pitch length (P) of the DNA superhelix wrapping around the dendrimer and the interparticle distance (d) of the nucleosome-like particle...