title: Quadruplex and pentaplex self-assemblies of oligonucleotides containing short runs of 8-aza-7-deaza-2'-deoxyisoguanosine or 2'-deoxyisoguanosine.
abstract: Oligonucleotides containing 8-aza-7-deaza-2'-deoxyisoguanosine (4) were investigated regarding their self-assembly in aqueous solution. The aggregation of 4 was compared with that of oligonucleotides containing 2'-deoxyisoguanosine (2b) and 2'-deoxyguanosine (1b). For this purpose the phosphoramidite of 4 was synthesized which was protected by a dibutylaminomethylidene residue at the amino group and a diphenylcarbamoyl residue at the 2-oxo function. Solid-phase synthesis furnished oligonucleotide containing short runs of the nucleoside 4. The self-assembly of the oligonucleotide 5'-d(T(4)4(4)T2) was studied by ion-exchange chromatography. The formation of a pentaplex was observed in the presence of Cs+, while a tetraplex is formed when the counter ion is Na+ or Rb+. The cation selectivity of the oligonucleotide 5'-d(T(4)4(4)T2) was found to be different from the parent 5'-d(T(4)isoG(4)T2) which was forming the tetraplex as well as a pentaplex in aq RbCl solution.
authors.affiliation: Laboratorium für Organische und Bioorganische Chemie, Institut für Chemie, Universität Osnabrück, Barbarastrasse 7, D-49069 Osnabrück, Germany. frank.seela@uni-osnabrueck.de
authors.forename: F
authors.initials: F
authors.lastname: Seela
authors.forename: R
authors.initials: R
authors.lastname: Kröschel
mesh_terms: D000241:Adenosine; D000577:Amides / Q000737:chemistry; D001482:Base Composition; D002586:Cesium / Q000494:pharmacology; D002852:Chromatography, Ion Exchange; D004247:DNA; D019281:Dimerization; D054856:G-Quadruplexes; D006151:Guanosine / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D009690:Nucleic Acid Conformation / Q000187:drug effects; D009841:Oligonucleotides / Q000737:chemistry*; D010756:Phosphoric Acids / Q000737:chemistry; D012413:Rubidium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology
chemical_list: D000577:Amides; D009841:Oligonucleotides; D010756:Phosphoric Acids; D006151:Guanosine; C008184:isoguanosine; D002586:Cesium; D004247:DNA; D012964:Sodium; C011067:phosphoramidic acid; D000241:Adenosine; D012413:Rubidium