New horizons of adenosinetriphosphate energetics arising from interaction with magnesium cofactor |
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Authors: | Alexander A Tulub V E Stefanov |
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Institution: | (1) Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, USA;(2) Department of Biophysics and Biochemistry, Computational Modeling Group, Saint-Petersburg State University, Universitetskaya Embankment 7/9, Saint-Petersburg, 199034, Russian Federation |
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Abstract: | MD DFT:B3LYP (6-31G** basis set, T = 310 K) method is used to study interactions singlet (S) and triplet (T) reaction paths] between adenosinetriphosphate,
ATP4−, and Mg(H2O)6]2+ in water environment, modeled with 78 water molecules. Computations reveal the appearance of low and high-energy states (stable,
quasi-stable, and unstable), assigned to different spin symmetries. At the initial stage of interaction, ATP donates a part
of its negative charge to the Mg complex making the Mg slightly charged. As a result, the original octahedral Mg complex loses
two (S state) or four (T state) water molecules. Moving along S or T potential energy surfaces (PESs), Mg(H2O)4 or Mg(H2O)2 display different ways of complexation with ATP. S path favors the formation of a stable chelate with the O1–O2 fragment
of ATP triphosphate tail, whereas T path favors producing a single-bonded complex with the O2. The latter, being unstable,
undergoes a further conversion into a spin-separated complex, also unstable, and two metastable S complexes, which finally
arise in two stable, low-energy and high-energy, chelates. The spin-separated complex experiences rapid decomposition resulting
in the production of a highly reactive adenosinemonophosphate ion-radical •AMP, early observed in the CIDNP experiment (Tulub
2006). Biological consequences of the findings are discussed. |
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Keywords: | MD DFT ATP Mg complexes |
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