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yanhui8558金蟲 (小有名氣)
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[求助]
his標(biāo)簽蛋白純化,不掛柱 已有1人參與
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我一直在用大腸桿菌表達(dá)一個蛋白激酶,用pet21a載體,用過超聲破碎和先溶菌酶處理和超聲處理破碎。結(jié)果蛋白主要在沉淀中,上清中的量不多但還可以,主要問題是不怎么掛鎳柱,用PBS平衡柱子,PH8.0, 30mM咪唑洗雜蛋白,250mM咪唑洗脫,跑蛋白電泳和western都是穿過液和上清條帶都差不多,很苦惱, 有沒有高人指點一下啊。 |
蛋白質(zhì)生物學(xué)實驗經(jīng)驗 |
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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. |
木蟲 (正式寫手)
至尊木蟲 (職業(yè)作家)

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金蟲 (小有名氣)
金蟲 (小有名氣)
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一方面提高可溶性的,對誘導(dǎo)條件進(jìn)行摸索,如溫度,誘導(dǎo)劑濃度。還可以嘗試改變一下表達(dá)載體。另一方面進(jìn)行純化時,可以改變his tag的位置,也可以適當(dāng)提高樹脂的量,或者增大菌體量試一試。若是一點也純化不出來,很有可能是his tag 被包埋在蛋白空間結(jié)構(gòu)中,那建議還是利用變復(fù)性吧! |
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