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yanhui8558

金虫 (小有名气)

[求助] his标签蛋白纯化,不挂柱已有1人参与

我一直在用大肠杆菌表达一个蛋白激酶,用pet21a载体,用过超声破碎和先溶菌酶处理和超声处理破碎。结果蛋白主要在沉淀中,上清中的量不多但还可以,主要问题是不怎么挂镍柱,用PBS平衡柱子,PH8.0, 30mM咪唑洗杂蛋白,250mM咪唑洗脱,跑蛋白电泳和western都是穿过液和上清条带都差不多,很苦恼,有没有高人指点一下啊。
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ybs007

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silicare(金币+2): 2011-07-14 12:40:55
yanhui8558(金币+1): 2011-07-14 17:01:43
很有可能是你融合的蛋白改变了构象,将6His包裹起来不能与镍柱亲和。由于你用的是pET-21a,貌似只有C端的6His,所以要么更换载体,或者更换其他的纯化标签,比如T7标签。
平生我自知
4楼2011-07-14 10:27:08
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zx1984

木虫 (正式写手)


amisking(金币+1): 鼓励应助 2011-07-11 20:14:00
我用pet28a载体表达蛋白,也用超声破碎和和先溶菌酶处理后超声处理破碎,和你一样的情况,也是不挂镍柱。后来用wash buffer浓度梯度洗也不好。很郁闷。
2楼2011-07-11 19:13:05
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nnxqwei

至尊木虫 (职业作家)

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yanhui8558(金币+1): 2011-07-12 09:35:27
确定纯化条件没有问题的条件下,考虑换一下6His的位置吧,把原来 的N端换到C端!!
3楼2011-07-12 03:21:44
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jyh024

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yanhui8558(金币+2): 2011-07-14 17:02:13
lstt09nk(金币+3): 辛苦,感谢交流,欢迎常来 2011-07-17 20:22:27
The reasons may be:
•  Elution conditions are too mild (histidine-tagged protein still bound):
Elute with an increasing imidazole gradient or decreasing pH to
determine the optimal elution conditions.
• The protein has precipitated in the column: Try detergents or changed
NaCl concentration or elute under denaturing (unfolding) conditions
(use 4–8 M urea or 4–6 M Gua-HCl) to remove precipitated proteins. For
the next experiment, decrease amount of sample, or decrease protein
concentration by eluting with a linear imidazole gradient instead of
imidazole steps.
• Nonspecific hydrophobic or other interaction: Add a nonionic
detergent to the elution buffer (e.g. 0.2% Triton X-100) or change the NaCl
concentration.
• Concentration of imidazole in the sample and/or binding buffer is too
high: The protein is found in the flowthrough material. Decrease the
imidazole concentration.
• Target protein may not be histidine-tagged as expected: Verify DNA
sequence of the gene. Analyze samples taken before and after induction
of expression with, for example, anti-His antibodies in Western blotting.
• Histidine-tag may be insufficiently exposed: The protein is found in the
flowthrough material. Perform purification of unfolded protein in urea or
Gua-HCl as for inclusion bodies.
5楼2011-07-14 16:44:28
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