生物化学:求小肽lys-ile-glu的等电点

生物化学:求小肽lys-ile-glu的等电点
2025-03-16 17:11:28
推荐回答(1个)
回答1:

首先辨别每个氨基酸的带电性质,特别侧链基团的带电量,获得每个氨基酸的等电点.
氨基酸是是两性电解质,在碱性溶液中表现出带负电荷,在酸性溶液中表现出带正电荷,在某一定PH溶液中,氨基酸所带的正电荷和负电荷相等时的PH,称为该氨基酸的等电点.
此题还应有附加条件,即溶液的PH,不然无法计算,在不同ph条件下,等电点会变化.
计算等电点的关键:找出兼性离子(静电荷为0)两侧的pK值,取二者的平均值即可。
该四肽在PH<2.4时,带2个单位正电荷;在2.4至4.2时,带1个单位正电荷;
在4.2至9.8时,静电荷为0;在9.8至10.6时,带一个单位负电荷。
大于10.6时,带2个单位负电荷。
所以,该四肽的等电点是:pI = 1/2 (4.2 + 9.8)= 7.0

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