Telomere structure and stability: covalency in hydrogen bonds, not resonance assistance, causes cooperativity in guanine quartets |
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Authors: | Fonseca Guerra Célia Zijlstra Hester Paragi Gábor Bickelhaupt F Matthias |
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Affiliation: | Department of Theoretical Chemistry and Amsterdam Center for Multiscale Modeling, VU University Amsterdam, Amsterdam, The Netherlands. C.FonsecaGuerra@vu.nl |
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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. |
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Keywords: | cooperative effects covalency density functional calculations DNA hydrogen bonds resonance‐assisted hydrogen bonding |
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