A heme (HEM) is a multi-atom, non-proteinaceous organic structure capable of positioning an iron (FE) ion in its center.

亚铁血红素 (HEM) 是一个多原子、非蛋白质的有机结构，能够将一个铁 (FE) 离子置于其中心。

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So, for example, if I have a sodium ion over here, and I have a chloride ion over here, where the distance from center to center r I'm denoting as r, this is nucleus to nucleus separation.

所以，比如这有一个钠离子，和一个氯离子，它们中心与中心间的距离,我把它设为，这是原子核和原子和的间距。

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The metal ion may be the catalytic center of the cofactor, or it may serve to bind the enzyme and substrate together to hold the enzyme in a catalytically active conformation.

金属离子可以是辅助因素的催化中心，也可以帮助形成酶活性所必须的构象。

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