The melting of tetramolecular DNA or RNA quadruplexes is kinetically irreversible. However, rather than being a hindrance, this kinetic inertia allows us to study association and dissociation processes independently. General rules have been extended to longer DNA motifs or sequences containing modified bases such as 8-oxo or 7-deaza guanine. Results were compared with the canonical TG4T and TG5T tetramers: we demonstrate huge differences (up to 10(5)-fold) in the association constants of these quadruplexes depending on primary sequence.