This miniprep protocol works with the new Qiagen buffers. It is supposed to give a yield of around 100ng/ul concentration for p15A plasmids.
My protocol:
0. streak cells from glycerol stock on a new plate
1. start a new culture from the plate with 8ml LB
2. spin down overnight culture for 10 min at 4000rpm
3. decant the supernatant and put the tube upside down for 5 min to get rid of remaining supernatant
4. resuspend cells by 250ul P1+RNase(100ug/mL), sit on room temperature for 30min (reactivate RNase, might not be necessary)
5. put the P2 in 42C water bath for 10 min to re-dissolve NaOH and SDS (critical!)
6. add 250ul P2, mix well, then add 350ul N3, mix well by upside and down tubes
7. spin down pellets for 15min at 21600rcf
8. transfer supernatant to miniprep column(~750ul)
9. spin down for 1min at 17900rcf,decant the liquid
10. add 750ul PE buffer, spin down and decant the liquid
11. spin down again to get rid of extra PE, transfer the column to the 1.7ml epperdorf tube
12. add 30ul H2O(we have DNase/RNase free H2O in the lab), sit on table for 1min, then spin down the plasmids