All high-spin (S = 2) iron(ii) hemes are NOT alike.
All high-spin (S = 2) iron(ii) hemes are NOT alike.
复制标题
所有高自旋 (S = 2) 铁(ii) 血红素都不相同。
DOI：
10.1039/c5dt02795k
复制
发表时间：
2015
期刊：
影响因子：
--
通讯作者：
Scheidt,WRobert
中科院分区：
文献类型：
--
作者：
Hu,Chuanjiang;Schulz,CharlesE;Scheidt,WRobert
血红素蛋白中常见的结构基序是五配位种类，其中铁由组氨酰残基配位。具有该基序的广泛分布的血红素蛋白对于人类和其他生物体的健康是必需的。我们详细介绍了高自旋铁（II）卟啉衍生物的分子结构和物理性质的差异，中性咪唑，氢键咪唑，咪唑或其他阴离子配位。观察到两种不同的（高自旋）电子态，它们具有不同的d轨道占位性和明显不同的五配位四方锥配位基团。咪唑类中的双占据轨道是倾斜于血红素平面的低对称轨道，而咪唑酯类中的双占据轨道是血红素平面中的高对称轨道，即，主双占据d轨道是不同的。可用于将特定复合物分类为一种或另一种状态的方法包括X射线结构测定，高场穆斯堡尔光谱，振动光谱，磁性圆二色性和偶数自旋EPR光谱。血红素蛋白的基态差异可能的功能意义尚未确定，但可能在氧运输与氧利用的途径中发现。
A common structural motif in heme proteins is a five-coordinate species in which the iron is coordinated by a histidyl residue. The widely distributed heme proteins with this motif are essential for the well being of humans and other organisms. We detail the differences in molecular structures and physical properties of high-spin iron(II) porphyrin derivatives ligated by neutral imidazole, hydrogen bonded imidazole, and imidazolate or other anions. Two distinct (high spin) electronic states are observed that have differing d-orbital occupancies and discernibly different five-coordinate square-pyramidal coordination groups. The doubly occupied orbital in the imidazole species is a low symmetry orbital oblique to the heme plane whereas in the imidazolate species the doubly occupied orbital is a high symmetry orbital in the heme plane, i.e., the primary doubly-occupied d-orbital is different. Methods that can be used to classify a particular complex into one or the other state include X-ray structure determinations, high-field Mössbauer spectroscopy, vibrational spectroscopy, magnetic circular dichroism, and even-spin EPR spectroscopy. The possible functional significance of the ground state differences has not been established for heme proteins, but is likely found in the pathways for oxygen transport vs. oxygen utilization.