title: Effect of a modified thymine on the structure and stability of [d(TGGGT)]4 quadruplex.
abstract: Telomeric guanine-rich sequence can adopt quadruplex structures that are important for their biological role in chromosomal stabilisation. G quartets are characterised by the cyclic hydrogen bonding of four guanine bases in a coplanar arrangement and their stability is ion-dependent. In this work we compare the stability of [d(TGGGT)](4) and [d(T*GGGT)](4) quadruplexes. The last one contains a modified thymine, where the hydroxyl group substitutes one hydrogen atom of the methyl group of the thymine in the [d(TGGGT)](4) sequence. We used a combination of spectroscopic, calorimetric and computational techniques to characterise the G-quadruplex formation. NMR and CD spectra of [d(T*GGGT)](4) were characteristic of parallel-stranded, tetramolecular quadruplex. CD and DSC melting experiments reveal that [d(T*GGGT)](4) is less stable that unmodified quadruplex. Molecular models suggest possible explanation for the observed behaviour.
authors.affiliation: Dipartimento di Chimica, Via Cintia, Università Federico II di Napoli, Monte Sant' Angelo, 80126 Naples, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Petraccone
authors.forename: Eva
authors.initials: E
authors.lastname: Erra
authors.forename: Lucia
authors.initials: L
authors.lastname: Nasti
authors.forename: Aldo
authors.initials: A
authors.lastname: Galeone
authors.forename: Antonio
authors.initials: A
authors.lastname: Randazzo
authors.forename: Luciano
authors.initials: L
authors.lastname: Mayol
authors.forename: Guido
authors.initials: G
authors.lastname: Barone
authors.forename: Concetta
authors.initials: C
authors.lastname: Giancola
mesh_terms: D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D006147:Guanine / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D013696:Temperature; D013941:Thymine / Q000737:chemistry*; D013997:Time Factors
chemical_list: D006147:Guanine; D004247:DNA; D013941:Thymine