Harry Hahn hhahn at
Fri Sep 16 12:23:05 EST 1994

In article <stauth-160994084243 at>,
stauth at (Darren Stauth) wrote:

> I've been having problems recently in making competent cells with high
> enough efficiency (>100,000,000 cfu/ug) needed to transform TA clones. 
> Does anyone have a good protocol for making high efficiency competent

This is a protocol originally adapted from Chung and Miller, NAR 16:3580.
I routinely get efficiencies around 10^8.

- Grow cells to early log phase (0.3-0.6 A600)
- Pellet cells and discard supernatant
- Resuspend in TSB, 1/10 of original culture volume
- Add glycerol to 15% if freezing and store at -70°C
- Use 100 microliters cells to 10 microliters or less of DNA to transform

Medium (LB, 2xYT, etc) containing
   10% PEG 3350
   5 % DMSO
   10 mM MgCl2
   10 mM MgSO4

Good luck,
Harry Hahn / hhahn at / har'ry (har'e) v.t. harass; ravage.

More information about the Methods mailing list