基因型

F-ompT hsdSB(rB-mB-) gal dcm(DE3) pRARE(argU, argW, ilex, glyT, leuW, proL) (CamR)

產品說明

Rosetta(DE3)菌株具有氯霉素抗性，補充大腸桿菌缺乏的6 種稀有密碼子(AUA, AGG, AGA, CUA, CCC, GGA)對應的tRNA，提高外源基因，尤其是真核基因在原核系統中的表達水平，該菌株染色體整合了λ噬菌體DE3區 (DE3區含有T7噬菌體RNA聚合酶)，同時表達T7 RNA聚合酶和大腸桿菌RNA聚合酶，可用于pET系列，pGEX，pMAL等質粒的蛋白表達。Rosetta(DE3)感受態細胞由特殊工藝制作，pUC19質粒檢測轉化效率高達108 cfu/μg DNA。

操作方法

1. Rosetta(DE3)感受態細胞從-80℃拿出，迅速插入冰中，5分鐘后待菌塊融化，加入目的DNA（質粒或連接產物）并用手撥打EP管底輕輕混勻(避免用槍吸打)，冰中靜置25分鐘。

2. 42℃水浴熱激45秒，迅速放回冰上并靜置2分鐘，晃動會降低轉化效率。

3. 向離心管中加入700μl不含抗生素的無菌培養基 (2YT或LB)，混勻后37℃，200rpm復蘇60分鐘。

4. 5000rpm離心一分鐘收菌，留取100μl左右上清輕輕吹打重懸菌塊并涂布到含相應抗生素的2YT 或LB培養基上。

5.將平板倒置放于37℃培養箱過夜培養。

Sample Induction Protocol (for reference only )

1.   Inoculate a single colony from a freshly streaked plate into 5 ml of LB medium containing the appropriate antibiotic for the plasmid and host strain.

2.   Incubate with shaking at 200 rpm at 37℃ overnight.  

3.   Inoculate 50 ml of LB medium containing the appropriate antibiotic with 0.5 ml of the overnight culture prepared in step 2(use the 500 ml triangular flask as the container would be better).

4.   Incubate with shaking at 150 rpm at 37℃ until the OD 600 reaches 0.5-0.8.

5.   (Optional)Pipet 1ml of  the cultures into clean microcentrifuge tubes and  place the tubes on ice until  needed  for gel analysis or storage at  -20℃. These will serve as the non-induced control samples.      

6.   Add IPTG to a final concentration of 1 mM.  Optimal time for induction of the target protein may vary from 2-16 hours, depending on the protein.

7.   Incubate with shaking at 120 rpm at 37℃ for 3-4 hours. To determine the optimal time for induction of the target protein, it is recommended that a time course experiment be performed varying the induction from 2-16 hours.

8.   Place the culture on ice for 10 minutes. Harvest cells by centrifugation at 5,000×g for 10 minutes at 4℃.

9.   Remove the supernatant and store the cell pellet at -20℃ (storage at lower temperatures is alsoacceptable).

IPTG

Prepare a 1 M solution of IPTG (Isopropyl-β-D-thiogalactoside; Isopropyl-β-D-thiogalactopyranoside) by

dissolving 2.38 g of IPTG in dd water and adjust the final volume to 10 ml. Filter sterilize before use.

氯霉素

Chloramphenicol  34 mg/ml in ethanol. Store at -20℃. Use at 34 μg/ml.

注意事項

1. 感受態細胞最好在冰中緩慢融化，插入冰中8分鐘內加入目標DNA，不可在冰中放置時間過長，長時間存放會降低轉化效率。

2. 混入質粒時應輕柔操作。

3. 轉化高濃度的質粒可相應減少最終用于涂板的菌量。

4. 誘導時，IPTG濃度可選(0.1-2mM均可)。

5. 為獲得需要量的蛋白，最佳誘導時間，溫度，IPTG濃度需實驗者優化。