Atomic Force Microscopy analysis is employed to study the geometrical and topological properties of 3000kbp DNA molecules fixed in mica substrates with MgCl2. We found that the aggregates on the substrate surface for certain salt concentrations form a honeycomb stable structure with the addition of salt. The honeycomb, and the transition to other structures, were characterized by the \emph{Betti numbers}, which is a topological invariant property and by \emph{Hausdorff-Besicovitch fractal dimension}.
@article{arxiv.1706.02685,
title = {Topology of DNA: a honeycomb stable structure under salt effect},
author = {Elsa de la Calleja and R. F Bazoni and M. S. Rocha and Marcia Barbosa},
journal= {arXiv preprint arXiv:1706.02685},
year = {2017}
}