Linder Douglas P, Rodgers Kenton R
Department of Chemistry, Biochemistry, and Molecular Biology, North Dakota State University, Fargo, ND 58105-5516, USA.
J Biol Inorg Chem. 2007 Jun;12(5):721-31. doi: 10.1007/s00775-007-0223-0. Epub 2007 Mar 14.
A density functional theory account of the changes in FeNO bonding that occur in response to both bonded and nonbonded structural perturbations is reported for a series of {FeNO}(6) heme-thiolate model complexes. Using [Fe(porphine)(SCH(3))NO] as the reference complex, we constructed models to mimic equatorial (cis), distal, and proximal influences of protein environments. Overall, the results from these calculations reveal that the Fe-NO and N-O bond strengths change in the same direction upon variations in structure and environment. These bonding changes are manifested in unique direct correlations between the Fe-NO and N-O vibrational frequencies and bond lengths, as evidenced by their positive slopes (slopes of the familiar inverse or backbonding correlations are negative). The electronic origin of the direct correlations appears to derive from the electron density distribution in high-energy molecular orbitals. This variability modulates the FeNO antibonding character throughout the triatomic FeNO moiety. The results of this study suggest that the stabilities and reactivities of {FeNO}(6) centers in heme-thiolate enzymes can be modulated over a significant range through a variety of bonded and nonbonded means.
报道了一系列{FeNO}(6)血红素硫醇盐模型配合物中，由于键合和非键合结构扰动而发生的FeNO键变化的密度泛函理论解释。以[Fe(卟啉)(SCH(3))NO]作为参考配合物，我们构建了模型来模拟蛋白质环境的赤道（顺式）、远端和近端影响。总体而言，这些计算结果表明，在结构和环境变化时，Fe-NO和N-O键强度朝着相同方向变化。这些键合变化表现为Fe-NO和N-O振动频率与键长之间独特的直接相关性，其正斜率证明了这一点（常见的反键或反馈键相关性的斜率为负）。直接相关性的电子起源似乎来自高能分子轨道中的电子密度分布。这种变异性调节了整个三原子FeNO部分的FeNO反键特征。这项研究的结果表明，通过各种键合和非键合方式，可以在很大范围内调节血红素硫醇盐酶中{FeNO}(6)中心的稳定性和反应性。
