M15(pREP4)热激感受态细胞

M15(pREP4)：                                                   100μl/支

pUC19 (control vector，10pg/μl):                           10μl

保存条件(保质期)：                                   -80℃（6个月） 

M15(pREP4)热激感受态细胞基因型

F-, Φ80ΔlacM15, thi, lac-, mtl-, recA+, KmR

产品说明

M15(pREP4)蛋白表达菌株含有pREP4质粒，该质粒通过p15A复制子启动复制，可以与许多原核表达质粒共存于同一大肠杆菌细胞中；同时该质粒携带lac I基因，可高效表达lac 抑制蛋白，在IPTG诱导前可抑制目标蛋白的本底表达，特别适合毒性基因的表达。M15(pREP4)菌株是PQE系列质粒的配套菌株，特别适合PQE系列质粒或由E.coli T5 启动子诱导表达的质粒的蛋白表达。pREP4质粒赋予该菌株卡那霉素抗性。生物生产的M15(pREP4)感受态细胞经特殊工艺制作，pUC19质粒检测转化效率达2×10⁸cfu/μg DNA。

M15(pREP4)热激感受态细胞操作方法

1. M15(pREP4)感受态细胞从-80℃拿出，迅速插入冰中，5分钟后待菌块融化，加入目的质粒并用手拨打EP管底混匀，冰中静置25分钟。

2. 42℃水浴热激45秒，迅速放回冰上并静置2分钟，晃动会降低转化效率。

3. 向离心管中加入700 μl不含抗生素的无菌培养基 (LB)，混匀后37℃，200 rpm复苏60分钟。

4. 5000 rpm离心一分钟收菌，留取50 μl左右上清轻轻吹打重悬菌块并涂布到含相应抗生素的LB培养基上（若质粒浓度较高，也可稀释后涂板，务必保证能在平板上挑到单克隆菌落）。

5. 将平板倒置放于37℃培养箱过夜培养，M15(pREP4)菌株在平板或液体培养基中生长时，需在培养基中加入终浓度为35ug/ml的卡那霉素。

Sample Induction Protocol (for reference only )

1. Inoculate a single colony from a freshly streaked plate into 3ml 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. (0.6 recommended; about 2.5h).

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 2-4 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 also accep- table). 

IPTG配制：

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. 

M15(pREP4)热激感受态细胞注意事项

1. 感受态细胞*在冰中缓慢融化，插入冰中8分钟内加入目标DNA，不可在冰中放置时间过长，长时间存放会降低转化效率。

2. M15(pREP4)菌株在平板或液体培养基中生长时，需在培养基中加入终浓度为35ug/ml的卡那霉素。

3. 转化高浓度的质粒可相应减少最终用于涂板的菌量。

4. 为获得需要量的蛋白，*诱导时间，温度，IPTG浓度需实验者优化。