CAJ | 학술논문

酪氨酸酶是一种能氧化酪氨酸残基为对苯醌的生物活性酶,其活性部位含有双铜核心并参与氧化还原反应.实验证明这两个铜核心易与氧气结合生成两种异构体μ-η2:η2-Cu2O2(Ⅱ)和bis(μ-oxo)-Cu2O2(Ⅲ), 且它们具有不同的电子结构和化学性质.用量子化学密度泛函理论对乙(撑)二胺和乙腈配合的μ-η2:η2-Cu2O2(Ⅱ)和bis(μ-oxo)-Cu2O2(Ⅲ)进行了理论研究,结果表明该两种异构体能量差别较小,相互转化的势垒较低.μ-η2:η2-Cu2O2(Ⅱ)中的Cu-O主要是离子键,Cu2O2呈"Z"构型,而bis(μ-oxo)-Cu2O2(Ⅲ)中的Cu-O主要是共价键,Cu2O2呈"V"构型,在氧化还原反应中具有更强的亲电子能力.
락안산매시일충능양화락안산잔기위대분곤적생물활성매,기활성부위함유쌍동핵심병삼여양화환원반응.실험증명저량개동핵심역여양기결합생성량충이구체μ-η2:η2-Cu2O2(Ⅱ)화bis(μ-oxo)-Cu2O2(Ⅲ), 차타문구유불동적전자결구화화학성질.용양자화학밀도범함이론대을(탱)이알화을정배합적μ-η2:η2-Cu2O2(Ⅱ)화bis(μ-oxo)-Cu2O2(Ⅲ)진행료이론연구,결과표명해량충이구체능량차별교소,상호전화적세루교저.μ-η2:η2-Cu2O2(Ⅱ)중적Cu-O주요시리자건,Cu2O2정"Z"구형,이bis(μ-oxo)-Cu2O2(Ⅲ)중적Cu-O주요시공개건,Cu2O2정"V"구형,재양화환원반응중구유경강적친전자능력.
Tyrosinase is an enzyme which oxidizes tyrosine residues to their corresponding o-quinones within an active site containing two copper atoms. Both of the two coppers are involved in the oxidation reaction. It is widely accepted that the two supported copper(I) atoms can bind O2 to yield μ-η2:η2-peroxodicopper(Ⅱ) and bis(μ-oxo)dicopper(Ⅲ) species. However, it is experimentally described that μ-η2:η2-peroxodicopper(Ⅱ) and bis(μ-oxo)dicopper(Ⅲ) species have different chemical properties including the electronic structure and reactivity. In this paper, by means of density functional theory, the electronic structures and relative energetics of the μ-η2:η2 and bis(μ-oxo) peroxo isomers of [Cu2O2]2+ cores supported by ethylenediamine and acetonitrile ligands are theoretically investigated. The quantum mechanical calculations show that bis(μ-oxo)dicopper(Ⅲ) species are sufficiently close to μ-η2:η2-peroxodicopper(Ⅱ) in the relative energies, and their reversible interconversion undergoes readily with very low reaction barriers, even though the bonding for these two systems shows significant differences. In the μ-η2:η2-peroxodicopper(Ⅱ) species, Cu-O bond mainly characterizes ionic contribution and the main resonance structure of [Cu2O2]2+ core is a Z fashion of Cu-O-Cu-O. Differently, in the bis(μ-oxo)dicopper(Ⅲ) species, Cu-O bond mainly characterizes covalent contribution and the main resonance structure of [Cu2O2]2+ core shows a V shape of Cu-O-Cu. The bis(μ-oxo)dicopper(Ⅲ) species behave more electrophilic in redox reactions.