TY - JOUR
T1 - Hydrogen bonding mediated by key orbital interactions determines hydration enthalpy differences of phosphate water clusters
AU - Ruben, Eliza A.
AU - Chapman, Michael S.
AU - Evanseck, Jeffrey D.
PY - 2007/10/25
Y1 - 2007/10/25
N2 - Electronic structure calculations have been carried out to provide a molecular interpretation for dihydrogen phosphate stability in water relative to that of metaphosphate. Specifically, hydration enthalpies of biologically important metaphosphate and dihydrogen phosphate with one to three waters have been computed with secondorder Møller-Plesset perturbation and density functional theory (B3LYP) with up to the aug-cc-pvtz basis set and compared to experiment. The inclusion of basis set superposition error corrections and supplemental diffuse functions are necessary to predict hydration enthalpies within experimental uncertainty. Natural bond orbital analysis is used to rationalize 0underlying hydrogen bond configurations and key orbital interactions responsible for the experimentally reported difference in hydration enthalpies between metaphosphate and dihydrogen phosphate. In general, dihydrogen phosphate forms stronger hydrogen bonds compared to metaphosphate due to a greater charge transfer or enhanced orbital overlap between the phosphoryl oxygen lone pairs, n(O), and the antibonding O-H bond of water. Intramolecular distal lone pair repulsion with the donor n(O) orbital of dihydrogen phosphate distorts symmetric conformations, which improves n(O) and σ*(O-H) overlap and ultimately the hydrogen bond strength. Unlike metaphosphate, water complexed to dihydrogen phosphate can serve as both a hydrogen bond donor and a hydrogen bond acceptor, which results in cooperative charge transfer and a reduction of the energy gap between n(O) and σ*(O-H), leading to stronger hydrogen bonds. This study offers insight into how orbital interactions mediate hydrogen bond strengths with potential implications on the understanding of the kinetics and mechanism in enzymatic phosphoryl transfer reactions.
AB - Electronic structure calculations have been carried out to provide a molecular interpretation for dihydrogen phosphate stability in water relative to that of metaphosphate. Specifically, hydration enthalpies of biologically important metaphosphate and dihydrogen phosphate with one to three waters have been computed with secondorder Møller-Plesset perturbation and density functional theory (B3LYP) with up to the aug-cc-pvtz basis set and compared to experiment. The inclusion of basis set superposition error corrections and supplemental diffuse functions are necessary to predict hydration enthalpies within experimental uncertainty. Natural bond orbital analysis is used to rationalize 0underlying hydrogen bond configurations and key orbital interactions responsible for the experimentally reported difference in hydration enthalpies between metaphosphate and dihydrogen phosphate. In general, dihydrogen phosphate forms stronger hydrogen bonds compared to metaphosphate due to a greater charge transfer or enhanced orbital overlap between the phosphoryl oxygen lone pairs, n(O), and the antibonding O-H bond of water. Intramolecular distal lone pair repulsion with the donor n(O) orbital of dihydrogen phosphate distorts symmetric conformations, which improves n(O) and σ*(O-H) overlap and ultimately the hydrogen bond strength. Unlike metaphosphate, water complexed to dihydrogen phosphate can serve as both a hydrogen bond donor and a hydrogen bond acceptor, which results in cooperative charge transfer and a reduction of the energy gap between n(O) and σ*(O-H), leading to stronger hydrogen bonds. This study offers insight into how orbital interactions mediate hydrogen bond strengths with potential implications on the understanding of the kinetics and mechanism in enzymatic phosphoryl transfer reactions.
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U2 - 10.1021/jp0748112
DO - 10.1021/jp0748112
M3 - Article
C2 - 17915844
AN - SCOPUS:35748970211
SN - 1089-5639
VL - 111
SP - 10804
EP - 10814
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 42
ER -