二硫键是什么 他和变性有甚么关系?
二硫键是什么 他和变性有甚么关系?
推荐回答（4个）
二硫键
disulfide bond
又称S－S键。是2个SH基被氧化而形成的—S—S—形式的硫原子间的键。在生物化学的领域中，通常系指在肽和蛋白质分子中的半胱氨酸残基中的键。此键在蛋白质分子的立体结构形成上起着一定的重要作用。为了确定蛋白质的一级结构，首先必须将二硫键打开，使成为线状多肽链。为此，需要在2-巯-乙醇、二硫苏糖类、巯基乙酸等的硫化合物与尿素那样的变性剂同时存在下使之发生作用，使还原成SH基（为了防止再氧化通常用适当的SH试剂将该基团烷基化）或是在过甲酸的氧化作用下衍生成-SO3H基或是采用在氧化剂共存下用亚硫酸的作用诱导成-S-SO3H基的方法。变性作用是蛋白质受物理或化学因素的影响，改变其分子内部结构和性质的作用。一般认为蛋白质的二级结构和三级结构有了改变或遭到破坏，都是变性的结果蛋白质的变性作用主要是由于蛋白质分子内部的结构被破坏。天然蛋白质的空间结构是通过氢键等次级键维持的，而变性后次级键被破坏，蛋白质分子就从原来有序的卷曲的紧密结构变为无序的松散的伸展状结构（但一级结构并未改变）。 在蛋白质分子中各氨基酸通过肽键及二硫键结合成具有一定顺序的肽链称为一级结构.
所以蛋白质变性时，二硫键未被破坏
二硫键多肽中一种很常见的化学键，它增加了多肽的稳定性。变性一般只改变蛋白质的空间结构，不会破坏蛋白质的一级结构。
又称S－S键。是2个SH基被氧化而形成的—S—S—形式的硫原子间的键。在生物化学的领域中，通常系指在肽和蛋白质分子中的半胱氨酸残基中的键。此键在蛋白质分子的立体结构形成上起着一定的重要作用。为了确定蛋白质的一级结构，首先必须将二硫键打开，使成为线状多肽链。
蛋白质变性时，二硫键被破坏打开，使成为线状多肽链。
蛋白质有20个常规氨基酸，二硫键是由其中一种氨基酸半胱氨酸(Cys)的R基末端的-SH和另一个半胱氨酸的-SH缩合而成 -S-S-,是氨基酸链之间的一种重要的连接。由于蛋白质需要经过完美的折叠形成精细的三维结构才能具备正常的功能，如果正常情况下对应的半胱氨酸之间的连接Cys-S-S-Cys,被断开，或者分别与另外的半胱氨酸连接，那么蛋白质就无法正确地折叠成有功能的三维结构，也就是所谓的蛋白质变性了。
当然-S-S-的改变，仅仅是蛋白质变性的多种原因中的一种。
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