Ligand-to-metal charge-transfer dynamics in a blue copper protein plastocyanin: A molecular dynamics study
Ligand-to-metal charge-transfer dynamics in a blue copper protein plastocyanin: A molecular dynamics study
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DOI：
10.1021/jp074822v
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发表时间：
2008-01-17
影响因子：
3.3
通讯作者：
Ando, Koji
中科院分区：
文献类型：
--
作者：
Ando, Koji
用分子动力学方法研究了蓝铜蛋白质质体蓝素氧化态的平衡和非平衡动力学。最低的七个电子态的势能函数，包括配体-金属电荷转移（LMCT）和铜d -> d激发态，取自我们以前的工作（Ando，K. J. Phys. Chem. B 2004，108，3940），其在活性位点模型上采用从头计算分子轨道和密度泛函计算。基态平衡态的分子动力学模拟表明，从基态到LMCT态跃迁的配体运动主要表现为Cu-S（Cys）距离、N-delta（His）-Cu-N-delta（His）角和S（Cys）-Cu-[N-delta（HiS）]（2）三角锥结构的伸缩和弯曲振动。LMCT势的非平衡动力学表现出快速的衰减，其中在70-80 fs内发生到d -> d和第一激发态的表面交叉。交叉动力学主要与Cu-S（Cys）键的断裂和N-δ（His）-Cu-N-δ（His）部分中的相关响应相关。垂直能隙坐标的平均动力学表现出过阻尼衰减，在500 fs的复发振荡，这表明明显的相干性后，系综平均生存。这种振荡主要源于N-δ（His）-Cu-N-δ（His）部分的反冲运动。在这种相干振荡之后的能隙的动态被随机化，使得系综平均产生沿沿着时间的平坦轮廓，尽管每个单个轨迹表现出具有足够大的振幅以到达表面交叉的波动。这些表明，从LMCT状态的松弛首先发生在70-80和500 fs的弹道和相干势交叉，其次是热激活的随机跃迁。
Equilibrium and nonequilibrium dynamics of a blue copper protein plastocyanin in an oxidized state are studied by molecular dynamics (MD) simulation. Potential energy functions of the lowest seven electronic states, including ligand-to-metal charge-transfer (LMCT) and copper d -> d excited states, were taken from our previous work (Ando, K. J. Phys. Chem. B 2004, 108, 3940), which employed ab initio molecular orbital and density functional calculations on the active-site model. The equilibrium MD simulations in the ground state indicate that ligand motions coupled to transition from the ground state to the LMCT state are mostly represented by stretching and bending vibrations of the Cu-S(Cys) distance, N-delta(His)-Cu-N-delta(His) angle, and S(Cys)-Cu-[N-delta(HiS)](2) trigonal pyramid structure. The nonequilibrium dynamics on the LMCT potential exhibit rapid decays in which surface crossings to the d -> d and the first excited states occur in 70-80 fs. The crossing dynamics mostly correlate with cleavage of the Cu-S(Cys) bond and the associated response in the N-delta(His)-Cu-N-delta(His) moiety. The average dynamics of the vertical energy gap coordinates exhibit an overdamped decay with a recurrence oscillation in 500 fs, which shows clear coherence surviving after the ensemble averaging. This oscillation stems mostly from the recoiling motion of the N-delta(His)-Cu-N-delta(His) part. The dynamics of the energy gaps after this coherent oscillation are randomized such that the ensemble average yields flat profiles along time, although each single trajectory exhibits fluctuations with amplitudes large enough to reach surface crossings. These indicate that the relaxation from the LMCT state first occurs via ballistic and coherent potential crossings in 70-80 and 500 fs, followed by thermally activated random transitions.