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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Ultrafast Relaxation Dynamics of Photoexcited Heme Model Compounds: Observation of Multiple Electronic Spin States and Vibrational Cooling
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Ultrafast Relaxation Dynamics of Photoexcited Heme Model Compounds: Observation of Multiple Electronic Spin States and Vibrational Cooling

机译：光孔血红素模型化合物的超快放松动态：多种电子旋转状态观察和振动冷却

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摘要

Hemin is a unique model compound of heme proteins carrying out variable biological functions. Here, the excited state relaxation dynamics of heme model compounds in the ferric form are systematically investigated by changing the axial ligand (Cl/Br), the peripheral substituent (vinyl/ethylmeso), and the solvent (methanol/DMSO) using femtosecond pump-probe spectroscopy upon excitation at 380 nm. The relaxation time constants of these model compounds are obtained by global analysis. Excited state deactivation pathway of the model compounds comprising the decay of the porphyrin excited state (S*) to ligand to metal charge transfer state (LMCT, tau(1) back electron transfer from metal to ligand (MLCT, tau(2)), and relaxation to the ground state through different electronic spin states of iron (tau(3) and tau(4))are proposed along with the vibrational cooling processes. This is based on the excited state absorption spectral evolution, similarities between the transient absorption spectra of the ferric form and steady state absorption spectra of the low-spin ferrous form, and the data analysis. The observation of an increase of all the relaxation time constants in DMSO compared to the methanol reflects the stabilization of intermediate states involved in the electronic relaxation. The transient absorption spectra of met-myoglobin are also measured for comparison. Thus, the transient absorption spectra of these model compounds reveal the involvement of multiple iron spin states in the electronic relaxation dynamics, which could be an alternative pathway to the ground state beside the vibrational cooling processes and associated with the inherent features of the heme b type.
机译：血红素是血红素蛋白的独特模型化合物，呈现可变生物功能。这里，通过使用飞秒泵改变轴向配体（Cl / Br），外周取代基（乙烯基/乙基/乙基甲基）和溶剂（甲醇/ DMSO）来系统地研究了血红素模型化合物的激发状态弛豫动态。使用Femtosecond泵 - 380nm激发探针光谱学。通过全局分析获得这些模型化合物的弛豫时间常数。包含卟啉激发态（S *）的模型化合物的激发状态去激活途径，以与金属电荷转移状态（LMCT，Tau，Tau（1）从金属转移到配体（MLCT，Tau（2）），通过不同的电子旋转的铁（Tau（3）和Tau（4））与振动冷却过程一起放松地面状态。这是基于激发的状态吸收光谱演化，瞬态吸收光谱之间的相似性在低旋转黑色形式的公铁形式和稳态吸收光谱和数据分析。与甲醇相比，DMSO中所有弛豫时间常数增加的观察反映了电子放松中涉及的中间状态的稳定。也测量了Met-yeglobin的瞬态吸收光谱以进行比较。因此，这些模型化合物的瞬态吸收光谱揭示了多铁SP的参与在电子弛豫动态中的状态，这可能是振动冷却过程旁边的接地状态的替代路径，并且与血红素B型的固有特征相关联。

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