Direct evidence for a hydrogen bond to bound dioxygen in a myoglobin/hemoglobin model system and in cobalt myoglobin by pulse-EPR spectroscopy
Direct evidence for a hydrogen bond to bound dioxygen in a myoglobin/hemoglobin model system and in cobalt myoglobin by pulse-EPR spectroscopy
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DOI：
10.1002/anie.200705180
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发表时间：
2008-01-01
影响因子：
16.6
通讯作者：
Diederich, Francois
中科院分区：
文献类型：
--
作者：
Dube, Henry;Kasumaj, Besnik;Diederich, Francois
区分与呼吸蛋白肌红蛋白(Mb)和血红蛋白(Hb)结合的氧气和一氧化碳对有氧生命至关重要。关于这种区别的性质和分子机制仍有一个持续不断的争论。[1]人们普遍认为，远端组氨酸通过氢键相互作用来稳定结合氧，尽管对这种提出的氢键的直接观察和表征一直是困难和模糊的。[1，2b]含有FeII的天然Mb和Hb的功能CoII类似物可以用EPR方法来研究结合氧与其周围环境的相互作用。[2]已经表明，Co-Mb和天然Mb的氧加成物采用非常相似的几何结构。我们提出了一个新的含有CoII的模型络合物1-Co，用于Mb和Hb的氧结合位置，并提供了相应的氧加合物1-Co-O2中远端氢键的直接脉冲EPR证据。此外，我们将我们的研究扩展到Co-Mb，并对Co-Mb-O2中的远端氢键进行了全面的脉冲EPR研究。化合物1-Co由一个带有烷基连接咪唑碱基的CoII卟啉核和一个模拟Mb和Hb近端组氨酸的苯并咪唑残基组成(方案1)。络合物1-Co中的D2O只能交换远端的氢键供体质子。
Discrimination between dioxygen and carbon monoxide binding to the respiratory proteins myoglobin (Mb) and hemoglobin (Hb) is vital for aerobic life. There is still an ongoing debate about the nature and molecular mechanism of this discrimination.[1] It is widely believed that the distal histidine stabilizes bound dioxygen by a hydrogen-bond interaction, although a direct observation and characterization of this proposed hydrogen bond has been difficult and ambiguous.[1, 2b] Functional CoII analogues of the natural, FeII-containing Mb and Hb can be used to study the interactions of bound dioxygen with its surroundings by EPR methods.[2] It has been shown that the dioxygen adducts of Co-Mb and natural Mb adopt very similar geometries.[3] Herein, we present a new CoII-containing model complex 1-Co for the dioxygen-binding site of Mb and Hb, together with a direct pulse-EPR evidence for a distal hydrogen bond in the corresponding dioxygen adduct 1-Co-O2. Furthermore, we extended our study to Co-Mb and provide a comprehensive pulse-EPR study of the distal hydrogen bonding in Co-Mb-O2 as well.Compound 1-Co consists of a CoII porphyrin core with an alkyl-tethered imidazole base to mimic the proximal histidine in Mb and Hb, and an alkyne-appended benzimidazole residue mimicking the distal histidine (Scheme 1). Only the distal hydrogen-bond-donating proton can be exchanged by D2O in complex 1-Co.