title: Telomere structure and stability: covalency in hydrogen bonds, not resonance assistance, causes cooperativity in guanine quartets.
abstract: We show that the cooperative reinforcement between hydrogen bonds in guanine quartets is not caused by resonance-assisted hydrogen bonding (RAHB). This follows from extensive computational analyses of guanine quartets (G(4)) and xanthine quartets (X(4)) based on dispersion-corrected density functional theory (DFT-D). Our investigations cover the situation of quartets in the gas phase, in aqueous solution as well as in telomere-like stacks. A new mechanism for cooperativity between hydrogen bonds in guanine quartets emerges from our quantitative Kohn-Sham molecular orbital (MO) and corresponding energy decomposition analyses (EDA). Our analyses reveal that the intriguing cooperativity originates from the charge separation that goes with donor-acceptor orbital interactions in the σ-electron system, and not from the strengthening caused by resonance in the π-electron system. The cooperativity mechanism proposed here is argued to apply, beyond the present model systems, also to other hydrogen bonds that show cooperativity effects.
authors: Department of Theoretical Chemistry and Amsterdam Center for Multiscale Modeling, VU University Amsterdam, Amsterdam, The Netherlands. C.FonsecaGuerra@vu.nl
authors: Célia
authors: C
authors: Fonseca Guerra
authors: Hester
authors: H
authors: Zijlstra
authors: Gábor
authors: G
authors: Paragi
authors: F Matthias
authors: FM
authors: Bickelhaupt
mesh_terms: D000465:Algorithms; D054856:G-Quadruplexes; D006860:Hydrogen Bonding; D008958:Models, Molecular; D015394:Molecular Structure; D016615:Telomere / Q000737:chemistry*