Aviñó Andrés, AnnaMazzini, StefaniaFàbrega i Claveria, Ma. CarmePeñalver, PabloGargallo Gómez, RaimundoMorales, J.C.Eritja i Casadellà, Ramon2017-02-162017-10-022016-10-020304-4165https://hdl.handle.net/2445/107055Background Guanine-rich oligonucleotides are capable of forming tetrahelical structures known as G-quadruplexes with interesting biological properties. We have investigated the effects of site-specific substitution in the loops and in the tetrads model G-quadruplexes using thymine glycol nucleic acid (GNA) units, l-thymidine and 8-Br-2′-deoxyguanosine. Methods Modified oligonucleotides were chemically synthesized and spectroscopic techniques were used to determine the relative stability of the modified G-quadruplex. The double 8-BrdG-modified quadruplexes were further characterized by Nuclear Magnetic Resonance. Binding to thrombin of selected quadruplex was analyzed by gel electrophoresis retention assay. Results The most interesting results were found with a 8-bromoG substitution that had the larger stabilization of the quadruplex. NMR studies indicate a tight relationship between the loops and the tetrads to accommodate 8-bromoG modifications within the TBA. Conclusions The substitutions of loop positions with GNA T affect the TBA stability except for single modification in T7 position. Single l-thymidine substitutions produced destabilization of TBA. Larger changes on quadruplex stability are observed with the use of 8-bromoG finding a single substitution with the highest thermal stabilization found in thrombin binding aptamers modified at the guanine residues and having good affinity for thrombin. Double 8-BrdG modification in anti positions of different tetrads produce a conformational flip from syn to anti conformation of 8-Br-dG to favor loop-tetrad interaction and preserve the overall TBA stability.29 p.application/pdfengcc-by-nc-nd (c) Elsevier B.V., 2016http://creativecommons.org/licenses/by-nc-nd/3.0/esBiologia molecularBioquímicaOligonucleòtidsG-estructuresMolecular biologyBiochemistryOligonucleotidesG-structuresinfo:eu-repo/semantics/article6676362017-02-16info:eu-repo/semantics/openAccess27705754