Synthesis and characterization of DNA quadruplexes containing T‐tetrads formed by bunch‐oligonucleotides

The solid phase syntheses of the bunch oligonucleotides 1 and 2 based on the sequences of the natural oligodeoxynucleotides (ODNs) d(TG 2 TG 2 C) ( 3 ) and d(CG 2 TG 2 T) ( 4 ), respectively, attached to a non‐nucleotidic tetrabranched linker, are reported. Bunch‐ODNs 1 and 2 were shown to form more stable monomolecular parallel G‐quadruplexes I and II when compared with their tetramolecular counterparts [d(TG 2 TG 2 C)] 4 ( III ) and [d(CG 2 TG 2 T)] 4 ( IV ), respectively. The structure and stability of all the synthesized complexes have been investigated by circular dichroism (CD), CD thermal denaturation experiments, and 1 H‐NMR (nuclear magnetic resonance) experiments at variable temperatures. Particularly, the spectroscopic data confirmed that 1 adopts a T‐tetrad containing parallel‐stranded quadruplex structure I as in the tetramolecular complex III . © 2005 Wiley Periodicals, Inc. Biopolymers 81: 194–201, 2006 This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com