title: Synthesis of quadruplex-forming tetra-end-linked oligonucleotides: effects of the linker size on quadruplex topology and stability.
abstract: G-quadruplexes are characteristic structural arrangements of guanine-rich DNA sequences that abound in regions with relevant biological significance. These structures are highly polymorphic differing in the number and polarity of the strands, loop composition, and conformation. Furthermore, the cation species present in solution strongly influence the topology of the G-quadruplexes. Recently, we reported the synthesis and structural studies of new G-quadruplex forming oligodeoxynucleotides (ODNs) in which the 3'- and/or the 5'-ends of four ODN strands are linked together by a non-nucleotidic tetra-end-linker (TEL). These TEL-ODN analogs having the sequence TGGGGT are able to form parallel G-quadruplexes characterized by a remarkable high thermal stability. We report here an investigation about the influence of the reduction of the TEL size on the molecularity, topology, and stability of the resulting TEL-G-quadruplexes using a combination of circular dichroism (CD), CD melting, (1)H NMR spectroscopy, gel electrophoresis, and molecular modeling data. We found that all TEL-(TGGGGT)(4) analogs, regardless the TEL size and the structural orientation of the ODN branches, formed parallel TEL-G-quadruplexes. The molecular modeling studies appear to be consistent with the experimental CD and NMR data revealing that the G-quadruplexes formed by TEL-ODNs having the longer TEL (L1-4) are more stable than the corresponding G-quadruplexes having the shorter TEL (S1-4). The relative stability of S1-4 was also reported. (c) 2009 Wiley Periodicals, Inc. Biopolymers 91: 466-477, 2009.
authors.affiliation: Dipartimento di Chimica delle Sostanze Naturali, Università degli Studi di Napoli Federico II, Via D. Montesano 49, I-80131 Napoli, Italy.
authors.forename: Giorgia
authors.initials: G
authors.lastname: Oliviero
authors.forename: Nicola
authors.initials: N
authors.lastname: Borbone
authors.forename: Jussara
authors.initials: J
authors.lastname: Amato
authors.forename: Stefano
authors.initials: S
authors.lastname: D'Errico
authors.forename: Aldo
authors.initials: A
authors.lastname: Galeone
authors.forename: Gennaro
authors.initials: G
authors.lastname: Piccialli
authors.forename: Michela
authors.initials: M
authors.lastname: Varra
authors.forename: Luciano
authors.initials: L
authors.lastname: Mayol
mesh_terms: D001483:Base Sequence; D054856:G-Quadruplexes; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009841:Oligonucleotides / Q000138:chemical synthesis* / Q000737:chemistry* / Q000235:genetics
chemical_list: D009841:Oligonucleotides