Function and Physical Chemistry of a Novel Porphyrin Isomer, Corrphycene.

本研究的目的是对一种新的卟啉结构异构体--柯拉菲林进行功能和物理化学分析。与常规卟啉中的(1，1，1，1)排列形成鲜明对比。柯氏石中的金属空腔呈梯形。梯形核中铁原子的反应性与常规的血红素铁不同。考察了有机溶剂中铁(III)对1-甲基咪唑的反应性。光谱分析表明，在配基滴定过程中，1-甲基咪唑有明显的单加合物积累，而铁(III)卟啉不形成单加合物。在铁环中的观察表明，铁原子的平面外构型随着金属空穴的梯形变形而稳定。我们进一步分析了铁(II)环作为血红素蛋白的修复基团的生物学功能。肌红蛋白RECO…更多的被亚铁取代，被发现具有可逆结合氧和一氧化碳的功能活性。然而，定量分析揭示了功能异常：氧和一氧化碳的缔合常数极低。与天然肌红蛋白相比，环菲取代肌红蛋白对氧和一氧化碳的亲和力分别只有1/13和1/128。红外光谱分析表明，丙二烯肌红蛋白的铁-CO键减弱。功能和结构上的异常是由于铁(II)从卟啉平面上置换较大而导致铁-CO相互作用减弱所致。叠氮化铁(III)-冠茂铁络合物处于高自旋(S=5/2)和低自旋(S=1/2)之间的平衡状态，平衡位置受大环核心形变的影响较大。我们研究了考拉菲肌红蛋白叠氮化络合物中铁(III)的磁性，以支持考拉菲林中铁的较大位移。可见光吸收随温度的变化表明，Fe(III)为80%的高自旋。高自旋分数比报道的天然肌红蛋白的8%大一个数量级。伴随的红外观测一致地表明，高自旋带比低自旋峰大4倍。平衡的反常高自旋偏向与铁从新辉石平面的大位移完全一致。叠氮化合物的电子自旋共振谱表明，铁-组氨酸键在5K时发生断裂，铁-组氨酸键的异常断裂归因于丙二烯取代的肌红蛋白的弱轴向键。综上所述，我们揭示了该铁的独特性质。赤道配位核中的几何应变对新铁离子的能力有很大的影响。因此，考拉菲林是一种有希望的、潜在的血色素蛋白功能调节剂。较少

Purpose of the proposed research is the functional and physicochemical analysis of a novel structural isomer of porphyrin, corrphycene. The meso-carbon array in corrphycene is in (2, 1, 0, 1), in remarkable contrast with the (1, 1, 1, 1) array in regular porphyrin. The metal cavity in corrphycene is trapezoidal. The reactivity of the iron atom in trapezoidal core is expected to be distinct from that of regular heme iron.The reactivity of iron (III) corrphycene in organic solvent toward 1-methylimidazole was examined. Spectroscopic analysis revealed the appreciable accumulation mono-adduct of 1-methylimidazole during the ligand titration, contrary to iron (III) porphyrin that does not form the mono-adduct. The observation in corrphycene demonstrates that the out-of-plane configuration of iron atom is stabilized with the trapezoidal deformation of e metal cavity.We further analyzed the biological function of iron (II) corrphycene as the prosthetic group of hemoprotein. The myoglobin reco … More nstituted with ferrous corrphycene was fund to be functionally active to reversibly bind oxygen and carbon monoxide. Quantitative analysis, however, revealed that the functional anomalies : the association constants for oxygen and carbon monoxide are extremely low. The affinities of etiocorrphycene-substituted myoglobin for oxygen and carbon monoxide are only 1/13 and 1/128, respectively, as compared with those of native myoglobin. The infrared analysis of corrphycene myoglobin indicates that the iron-CO bond is weakened. The functional and structural anomalies are suggested to arise from decreased iron-CO interactions owing to the larger iron (II) displacement from the plane of corrphycene.The azide complex of iron (III) corrphycene is in an equilibrium between the high-(S=5/2) and low-spin (S=1/2) states, and the equilibrium position is much susceptible to the core deformation of the porphyrin macrocycle. We investigated the magnetic property of the iron (III) in the azide complex of corrphycene myoglobin to support the larger displacement of the iron in corrphycene. The temperature-dependent visible absorption changes revealed that the iron (III) is 80% high-spin. The high-spin fraction is one-order of magnitude larger than 8% reported for native myoglobin. The accompanied infrared observation consistently indicated that the high-spin band is 4-fold larger than the low-spin peak. The anomalous high-spin bias of the equilibrium is fully consistent with the large displacement of the iron from the corrphycene plane. The electron spin resonance spectrum of azide complex demonstrates that the iron-histidine bond is cleaved at 5 K.Anomalous break of the iron-histidine bond was ascribed to the weakened axial bond of the corrphycene-substituted myoglobin.In summary, we revealed unique properties of the iron corrphycene. The abilities of corrphycene iron are substantially modified by the geometric strain in the equatorial coordination core. Therefore, corrphycene is a promissing and potential modulator of the functions of hemoproteins. Less