Hydrogen tunneling in enzymes and biomimetic models.
Hydrogen tunneling in enzymes and biomimetic models.
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DOI：
10.1021/cr400400p
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发表时间：
2014-04-09
期刊：
影响因子：
62.1
通讯作者：
Hammes-Schiffer, Sharon
中科院分区：
文献类型：
--
作者：
Layfield, Joshua P.;Hammes-Schiffer, Sharon
氢转移反应在化学和生物学中发挥着重要作用。一般来说，氢转移反应包括质子和氢化物转移，它们分别与带正电或带负电的物质的转移相关，以及质子耦合电子转移（PCET），其对应于最简单情况下一个电子和一个质子的净转移。这种PCET反应可以通过顺序机制（其中质子或电子首先转移）或协调机制（其中电子和质子在没有稳定中间体的单一动力学步骤中转移）发生。此外，协同PCET反应可以细分为氢原子转移（HAT），其对应于同一供体和受体之间电子和质子的转移（即主要中性物质的转移），以及电子-质子转移（EPT），其对应于不同供体和受体之间电子和质子的转移，甚至可能在不同方向。在所有这些类型的氢转移反应中，氢隧道效应可能会发挥重要作用。氢隧道效应的大多数实验证据都与动力学同位素效应 (KIE) 有关，KIE 分别由氢、氘和氚转移的速率常数 kH、kD 和 kT 的比率定义。特别是，大的氢/氘 KIE（即 kH/kD 大于~7）被认为涉及氢隧道效应。 1 隧道效应的另一个指标是 Swain− Schaad 指数，定义为 ln (kH/kT)/ln (kD/kT)。大于 3.3 的 Swain−Schaad 指数被认为是隧道效应的表现，因为它超过了在没有隧道效应的情况下半经典获得的上限。 2− 5 此外，KIE 的温度依赖性也在氢隧道效应的背景下得到了解释。具体来说，阿伦尼乌斯图中的曲率程度对于表现出氢隧道效应的系统来说是同位素相关的。因此，在实验可达到的温度范围内拟合氢、氘和氚转移的速率常数的温度依赖性通常会导致斜率偏离活化能的预期趋势，并且导致阿累尼乌斯前因子不收敛于单点。 1 次级 KIE 的这些类型的行为，其中同位素
Hydrogen transfer reactions play an important role throughout chemistry and biology. In general, hydrogen transfer reactions encompass proton and hydride transfer, which are associated with the transfer of a positively or negatively charged species, respectively, and proton-coupled electron transfer (PCET), which corresponds to the net transfer of one electron and one proton in the simplest case. Such PCET reactions can occur by either a sequential mechanism, in which the proton or electron transfers first, or a concerted mechanism, in which the electron and proton transfer in a single kinetic step with no stable intermediate. Furthermore, concerted PCET reactions can be subdivided into hydrogen atom transfer (HAT), which corresponds to the transfer of an electron and proton between the same donor and acceptor (ie, the transfer of a predominantly neutral species), and electron− proton transfer (EPT), which corresponds to the transfer of an electron and proton between different donors and acceptors, possibly even in different directions. In all of these types of hydrogen transfer reactions, hydrogen tunneling could potentially play a significant role.The majority of experimental evidence for hydrogen tunneling is related to the kinetic isotope effects (KIEs), as defined by ratios of the rate constants kH, kD, and kT for hydrogen, deuterium, and tritium transfer, respectively. In particular, a large hydrogen/deuterium KIE (ie, kH/kD greater than∼ 7) is considered to implicate hydrogen tunneling. 1 Another indicator of tunneling is the Swain− Schaad exponent, defined as ln (kH/kT)/ln (kD/kT). A Swain− Schaad exponent greater than 3.3 is considered to be a manifestation of tunneling because it exceeds the upper limit obtained semiclassically in the absence of tunneling. 2− 5 In addition, the temperature dependence of the KIEs has also been interpreted in the context of hydrogen tunneling. Specifically, the degree of curvature in the Arrhenius plots is isotope dependent for systems exhibiting hydrogen tunneling. Thus, fitting the temperature dependence of the rate constants for hydrogen, deuterium, and tritium transfer in the experimentally accessible temperature range often leads to slopes that deviate from the expected trend for the activation energies and to Arrhenius prefactors that do not converge toward a single point. 1 These types of behaviors for secondary KIEs, in which an isotopic
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影响因子：
15
作者：
Bandaria JN;Cheatum CM;Kohen A
通讯作者：
Kohen A
DOI：
10.1073/pnas.94.24.12797
发表时间：
1997-11-25
影响因子：
11.1
作者：
Bahnson, BJ;Colby, TD;Klinman, JP
通讯作者：
Klinman, JP
影响因子：
2.3
作者：
Basilevsky, MV;Rostov, IV;Newton, MD
通讯作者：
Newton, MD
影响因子：
--
作者：
Borgis, D;Hynes, JT
通讯作者：
Hynes, JT
影响因子：
15
作者：
Billeter, SR;Webb, SP;Hammes-Schiffer, S
通讯作者：
Hammes-Schiffer, S