Building up DNA (and other molecules), bit by bit

The properties of large aggregates of particles, be they colloidal clusters ormacromolecules, often depend crucially on the precise arrangement of their buildingblocks. Examples are the nature of the de-mixing in reacting polymer blends; theability of some elastomers to exhibit strain-induced periodic textures; or the selfhealing nature of some copolymers over a narrow range of compositions.

However, theactual sequence of building blocks is not usually experimentally accessible: knowing itwould allow, e.g., the reverse engineering of structures with desirable behaviours.

Wedevelop a simple theory that treats self-assembly as reversible chemical reactions. Wethen apply this to the assembly of DNA copolymers from two types of duplexes, asdescribed by the oxDNA model. We find that the theory reproduces well the statisticsof chain lengths from simulations.

Our results suggest that theories incorporating verylimited molecular detail may be useful for predicting the broad equilibrium features,and even some kinetic aspects, of copolymerisation.