Giardia telomeric sequence d[(TAGGG).sub.4] forms two intramolecular G-quadruplexes in [K.sup.+] solution: effect of loop length and sequence on the folding topology

The effect of loop length and sequence on the folding topology of G-quadruplexes is explored by examining the structure of the four-repeat Giardia telomeric sequence d[TAGGG[(TAGGG).sub.4]]. The recurrence of many structural elements in the structures have shown a ecut and pasteE principle for designing and predicting G-quadruplex topologies, for which different elements are extracted from one G-quadruplex and inserted into another.