Spin-orbit coupling and zero-field splitting of the high-spin ferric enzyme-substrate complex:Protocatechuate 3,4-dioxygenase complexed with 3,4-dihydroxyphenylacetate  

作　　者：Lü LingLing ZHU YuanCheng WANG XiaoFang ZUO GuoFang GUO Feng ZHAO SuRui WANG YongCheng 

机构地区：[1]College of Life Science and Chemistry,Tianshui Normal University [2]College of Chemistry and Chemical Engineering,Northwest Normal University

出　　处：《Chinese Science Bulletin》2013年第6期627-633,共7页

基　　金：supported by the "QingLan" Talent Engineering Fundsthrough Tian Shui Normal University;the Key Project of the Chinese Ministry of Education (211189)

摘　　要：We used density functional calculations to investigate the electronic origins of the magnetic properties of the high-spin ferric enzyme-substrate complex protocatechuate 3,4-dioxygenase(3,4-PCD).The calculated g-tensors show that ligand-to-metal charge transfer transitions are from the protocatechuate(PCA) and Tyr408 orbitals to the Fe d orbitals,which lead to x-and y-polarized transitions.These polarized transitions require a spin-orbit coupling(SOC) matrix element in the z-direction,Lz(z=z'),resulting in a g z value of 2.0158,significantly deviating from 2.0023.A large zero-field splitting parameter value of+1.147cm-1 is due to △S =-1 spin-orbit mixing with the quartet states for the sextet ground state,accounting for around 73% of the SOC contribution.The SOC matrix elements indicate that the high-spin d 5 system Fe(Ⅲ),3,4-PCD-PCA is a weak spin-crossover compound with an SOC of 31.56 cm-1.We used density functional calculations to investigate the electronic origins of the magnetic properties of the high-spin ferric en- zyme-substrate complex protocatechuate 3,4-dioxygenase （3,4-PCD）. The calculated g-tensors show that ligand-to-metal charge transfer transitions are from the protocatechuate （PCA） and Tyr408 orbitals to the Fe dπ orbitals, which lead to x- and y-polarized transitions. These polarized transitions require a spin-orbit coupling （SOC） matrix element in the z-direction, Lz （z = z＇）, resulting in a gz＇ value of 2.0158, significantly deviating from 2.0023. A large zero-field splitting parameter value of ＋1.147 cm-1 is due to AS = -1 spin-orbit mixing with the quartet states for the sextet ground state, accounting for around 73% of the SOC contribution. The SOC matrix elements indicate that the high-spin d5 system Fe（III）, 3,4-PCD-PCA is a weak spin-crossover compound with an SOC of 31.56 cm-1.

关 键 词：自旋轨道耦合 双加氧酶 原儿茶酸 零场分裂 高自旋 复合物 底物 密度泛函计算 

分 类 号：Q55[生物学—生物化学]