Ok, from now on, I will not write more about what I did, but what I thought.
Now, I finally realized how important different strains are. Recently, I extracted plasmids once and once again, for later digestion and ligation. But I couldn’t extract them well even in case of kit using. Then by accident, I found that some E. coli strains (like JM and BL21) need to dispose the too much proteins especially the DNase, for such strains may product more which may lead to a result of plasmid DNA degradation; other strains (like DH5α) need not.
I remembered when my tutor gave me the vector plasmids, he made me to transfer the pure plasmid into competent E. coli, and then he added: “you may notice the strain, even though the competent cell are all E. coli, the different strains have different features.”
Then I only knew that DH5α is more efficient to express toxin proteins, but now I deepened my understanding.
Last time I transferred the plasmids into strain BL21, and later I always failed on plasmid extraction. Now I know why—BL21 expressed more DNase so that my plasmids got protein contaminated and degraded itself.
At lab, I have learned more delicate things which are not printed on books.
I remembered when my tutor gave me the vector plasmids, he made me to transfer the pure plasmid into competent E. coli, and then he added: “you may notice the strain, even though the competent cell are all E. coli, the different strains have different features.”
Then I only knew that DH5α is more efficient to express toxin proteins, but now I deepened my understanding.
Last time I transferred the plasmids into strain BL21, and later I always failed on plasmid extraction. Now I know why—BL21 expressed more DNase so that my plasmids got protein contaminated and degraded itself.
At lab, I have learned more delicate things which are not printed on books.