Lead-poisoned zinc fingers: Quantum mechanical exploration of structure, coordination, and electronic excitations
Lead-poisoned zinc fingers: Quantum mechanical exploration of structure, coordination, and electronic excitations
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DOI：
10.1021/ic700731d
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发表时间：
2007-09-03
影响因子：
4.6
通讯作者：
Jarzecki, Andrzej A.
中科院分区：
文献类型：
--
作者：
Jarzecki, Andrzej A.
密度泛函理论（DFT）的结构计算和时间依赖性的DFT电子激发计算简单的单核铅结构证实了最近的报告在中毒蛋白质的三配位结构域的稳定。然而，在铅毒性机制的研究中，不应忽视形成四配位铅络合物的可能性，因为具有两种配位模式的结构是合理的，可能有助于观察到的紫外光谱。报告的计算沿着详细的分子轨道分析证实，在260 nm附近的强UV信号是配体-金属电荷转移（LMCT）带的指示剂，其中电子从硫3 p轨道转移到铅6p轨道。LMCT带的组成不仅揭示了从Pb-S成键轨道，而且还揭示了从硫孤对轨道到Pb-S反键轨道的显著激发，其中电子密度主要集中在Pb“6p-类”分子轨道上。有一个坚实的迹象表明，立体化学活性对轨道的铅是不强烈的杂化，并保持在很大程度上的6s字符在三配位的铅结构和最低限度的杂化在四配位的铅结构。计算的铅模型复合物的紫外光谱进行比较，实验的模型铅肽的紫外光谱。比较显示出与这些实验中观察到的主要光谱趋势和变化的良好一致性。
Density functional theory (DFT) structure calculations and time-dependent DFT electronic excitation calculations on simple mononuclear lead structures confirm recent reports on the stabilization of tricoordinated structural domains in poisoned proteins. However, the possibility of the formation of tetracoordinated lead complexes should not be disregarded in studies on mechanisms of lead toxicity because structures with both coordination modes are plausible and might contribute to observed UV spectra. Reported calculations along with detailed molecular orbital analysis confirm that the intense UV signal at around 260 nm is an indicator of the ligand-to-metal charge transfer (LMCT) band where the electrons are transferred from the sulfur 3p orbital to the lead 6p orbital. The composition of the LMCT band reveals significant excitations not only from the Pb-S bonding orbitals but also from sulfur lone-pair orbitals to the Pb-S antibonding orbitals for which the electron density is largely localized on the Pb "6p-like" molecular orbitals. There is a solid indication that the stereochemically active pair orbital of lead is not strongly hybridized and remains largely of the 6s character in tricoordinated lead structures and is minimally hybridized in tetracoordinated lead structures. Computed UV spectra of lead model complexes are compared to experimental UV spectra of model lead peptides. The comparison shows a good agreement with the major spectral trends and changes observed in these experiments.