The resolution to this issue is implied by our notation, and leads to the transfer matrix formation. If we step along a chain, we could come across a monomer that is paired to a monomer on the oppositely-charged chain. At this moment, it could be a run characterized by a single set of paired monomers, and we start by assuming that option (B 0± φ P ± ). This does not require any special considerations for N P + , since it is at this stage only a single binding site. However, if the next monomer along the chain is similarly paired, then now this is at least a doubly-paired state. This requires the ratio F ± to essentially 'replace' the integral by the one associated with B