title: Conformational analysis of a ribopentanucleoside tetraphosphate in aqueous solution. A two-dimensional NMR study at 500 MHz.
abstract: The 30 ribose proton resonances of the pentaribonucleoside tetraphosphate m6(2)AUm6(2)AUm6(2)A have been assigned unequivocally by means of spin-echo-correlated spectroscopy, 2D J-resolved spectroscopy and Nuclear Overhauser difference spectroscopy, carried out at 500 MHz. A detailed comparison of the conformational properties of the title compound with its constituent fragments m6(2)AUm6(2)AU, m6(2)AUm6(2)A, m6(2)AU and the relevant monomers is given. Chemical shift data indicate the existence of a doubly "bulged out" conformer, in which the two interior U-fragments are not involved in regular nearest neighbour stacking interactions. The coupling constants of the ribose-ring are interpreted in terms of the N/S equilibrium, and population distributions along the backbone angles beta and gamma are presented. The combined data suggest a strong similarity between the 5'-terminal triplets in m6(2)AUm6(2)AUm6(2)A, m6(2)AUm6(2)AU and m6(2)AUm6(2)A2.
mesh_terms: D000225:Adenine; D009682:Magnetic Resonance Spectroscopy; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides; D009843:Oligoribonucleotides; D014498:Uracil
chemical_list: D009841:Oligonucleotides; D009843:Oligoribonucleotides; D014498:Uracil; D000225:Adenine