  DNA oligomers with properly designed sequences self-assemble into well
defined constructs. Here, we exploit this methodology to produce bulk
quantities of tetravalent DNA nanostars (each one composed by 196 nucleotides)
and to explore the structural signatures of their aggregation process. We
report small-angle neutron scattering experiments focused on the evaluation of
both the form factor and the temperature evolution of the scattered intensity
at a nano star concentration where the system forms a tetravalent equilibrium
gel. We also perform molecular dynamics simulations of one isolated tetramer to
evaluate the form factor theoretically, without resorting to any approximate
shape. The numerical form factor is found to be in very good agreement with the
experimental one. Simulations predict an essentially temperature independent
form factor, offering the possibility to extract the effective structure factor
and its evolution during the equilibrium gelation.
