  We introduce bonding grammars, a graph grammar formalism developed to model
DNA computation by means of graph transformations. It is a modification of
fusion grammars introduced by Kreowski, Kuske and Lye in 2017. Bonding is a
graph transformation that consists of merging two hyperedges into a single
larger one. We show why bonding models interaction between DNA molecules better
than fusion. Then, we investigate formal properties of this formalism. Firstly,
we study the relation between bonding grammars and hyperedge replacement
grammars proving that each of these kinds of grammars generates a language the
other one cannot generate. Secondly, we prove that bonding grammars naturally
generalise regular sticker systems. Finally, we prove that the membership
problem for bonding grammars is NP-complete and, moreover, that some bonding
grammar generates an NP-complete set.
