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lishuaiguang

新虫 (初入文坛)

[求助] 蛋白质不稳定指数是什么?

我在一篇文章上看到利用ExPASy在线蛋白质分析软件ProtParam分析HMGR基因编码氨基酸的基本性质,其氨基酸组成见表1。该蛋白亚基分子量约为60.5 kD,等电点pI=7.55。蛋白质不稳定指数(Instability Index)为44.31,属于不稳定蛋白质 。
请问蛋白质不稳定指数究竟是怎么定义的?
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大王的拖拉机

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【答案】应助回帖

Instability index (II)
The instability index provides an estimate of the stability of your protein in a test tube. Statistical analysis of 12 unstable and 32 stable proteins has revealed [7] that there are certain dipeptides, the occurence of which is significantly different in the unstable proteins compared with those in the stable ones. The authors of this method have assigned a weight value of instability to each of the 400 different dipeptides (DIWV). Using these weight values it is possible to compute an instability index (II) which is defined as:

i=L-1

II = (10/L) * Sum     DIWV(xx[i+1])

                   i=1

where: L is the length of sequence

            DIWV(xx[i+1]) is the instability weight value for the dipeptide starting in position i.

A protein whose instability index is smaller than 40 is predicted as stable, a value above 40 predicts that the protein may be unstable.
2楼2017-04-15 14:25:17
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