Green Michael T
Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA.
J Am Chem Soc. 2006 Feb 15;128(6):1902-6. doi: 10.1021/ja054074s.
To gain insight into the protonation state of enzymatic ferryl species we have examined the applicability of Badger's rule to heme and non-heme iron-oxygen bonds. Using density functional theory we have calculated r(e) and nu(e) for the Fe-O bonds of complexes with different axial ligands, iron-oxidation, oxygen-protonation, and spin states. Our results indicate that Badger's rule holds for heme and non-heme oxo and hydroxo complexes. We find that the long Fe-O bonds that have been reported in the crystal structures of the ferryl forms of myoglobin, horseradish peroxidase, cytochrome c peroxidase, and catalase deviate substantially from the values predicted by Badger's rule, while the short Fe-O bonds obtained from X-ray absorption measurements are in good agreement with Badger's rule. In light of our analysis we conclude that the ferryl forms of myoglobin, horseradish peroxidase, and cytochrome c peroxidase are authentic iron(IV)oxos with Fe-O bonds on the order of 1.66 A and pKa's < 4.
为深入了解酶促铁（IV）氧物种的质子化状态，我们研究了巴杰规则对血红素和非血红素铁 - 氧键的适用性。利用密度泛函理论，我们计算了具有不同轴向配体、铁氧化态、氧质子化状态和自旋态的配合物中Fe - O键的r(e)和ν(e)。我们的结果表明，巴杰规则适用于血红素和非血红素的氧代和羟基配合物。我们发现，在肌红蛋白、辣根过氧化物酶、细胞色素c过氧化物酶和过氧化氢酶的铁（IV）氧形式的晶体结构中报道的长Fe - O键与巴杰规则预测的值有很大偏差，而从X射线吸收测量获得的短Fe - O键与巴杰规则吻合良好。根据我们的分析，我们得出结论，肌红蛋白、辣根过氧化物酶和细胞色素c过氧化物酶的铁（IV）氧形式是真实的铁（IV）氧代物，其Fe - O键约为1.66 Å，pKa < 4。
