werner@aecom.YU.EDU (Craig Werner) (06/07/87)
I never thought the following would make a difference, but in fact it makes a 20-fold improvement. The SOC medium (SOB + glucose) that is added to allow the cells to recover and express resistance is very important, or the pH thereof is. If you just mix it, the pH is about 7.2. One time I pH'd it to 7.4 ala Maniatis and the transformation frequency plumetted. So I looked up the paper. Hanahan's SOC was kept between pH 6.9 and 7.0. I then did the same. The result: 20-fold enhancement over pH 7.2, about 100-fold over the disastrous 7.4. It just goes to show. Even if the cells take up DNA, if they proceed to die, you get poor results. -- Craig Werner (MD/PhD '91) !philabs!aecom!werner (1935-14E Eastchester Rd., Bronx NY 10461, 212-931-2517) "If I don't see you soon, I'll see you later."e