TY  - CHAP
AU  - Paragi, Gábor
AU  - Szolomájer, János
AU  - Kupihár, Zoltán
AU  - Batta, Gyula
AU  - Kele, Zoltán
AU  - Pádár, Petra
AU  - Penke, Botond
AU  - Zijlstra, Hester
AU  - Fonseca Guerra, Célia
AU  - Bickelhaupt, F.M
AU  - Kovács, Lajos
ED  - Wolfgang, Fritzsche
ED  - Lea, Spindler
TI  - Guanine, xanthine and uric acid assemblies: comparative theoretical and experimental studies
T2  - Guanine quartets: structure and application
PB  - Royal Society of Chemistry (RSC)
CY  - Cambridge
SN  - 9781849734608
PY  - 2013
SP  - 179
EP  - 193
PG  - 15
DO  - 10.1039/9781849736954-00179
UR  - https://m2.mtmt.hu/api/publication/2016537
ID  - 2016537
AB  - Proceeding from promising dimer calculations, tetramer and quadruplex assemblies of 9-methylxanthine and 9-methyluric acid have been investigated by quantum-chemical calculations. In the gas phase, the new structures are less stable than the guanine tetrad as a consequence of the absence of a cooperative effect in the former and its presence in the latter. The lack of cooperativity in the new structures can be only partly compensated by strong low-barrier hydrogen bonds (LBHB). Moreover, the new tetramers are positively charged and probably can exist only in the presence of ions.
 Similar calculations suggest that 3-methylxanthine (3MX) is a good candidate for tetrad and quadruplex structures and the existence of (3MX)n  cat+ aggregates (n = 4, 8; cat+ = NH4+, Na+, K+) has been experimentally observed in the gas phase through mass spectrometry (MS) measurements. Detailed NMR studies in solution have also verified that the „internal” H-bonds (N1H...O6) in the (3MX)4 structures must be stronger than the „external” H-bonds (N7H...O2).
 In general, we found that guanine quartets (G4) are still more strongly bound than xanthine quartets (X4), despite the fact that they have the same number of hydrogen bonds. This is due to a cooperativity effect in the former case, as follows from our computational analyses. This is true not only in the gas phase but also in telomere-like structures where the quartet coordinates to two sodium ions and this complex is stacked in between two other quartets. In aqueous solution and in the absence of stacking quartet partners, however, the cooperativity is quenched and G4 and X4 are equally strongly bound.
LA  - English
DB  - MTMT
ER  -