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| Diatomaceous Earth-based Midi-prep
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| [ 文章来源: | 文章作者:
| 发布时间:2006-09-26|
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Diatomaceous Earth-based Midi-prepNote: This procedure is the method of choice for isolating double stranded plasmid-based templates for the Sequenase Dye-Labeled Terminator Sequencing Reactions.
A. Materials
Media and reagents are listed here in the maxi-prep section.
B. Methods
- Pick one colony into 3 ml of 2xTY containg the appropriate antibiotic (typically Amp at 25 ug/ml for pUC-based plasmids) and incubate at 37oC with shaking for 8-9 hours.
- Transfer seed culture to 50 ml media and incubate as above for 11-14 hours.
- Harvest cells by transferring into a 50 ml sterile conical tube and spinning at 3000 rpm in GPR tabletop centrifuge for 5 min. Decant supernatant and freeze cell pellet at -70oC for at least 1 hour.
- Resuspend defrosted cells in 2 ml GET/lysozyme (2 mg/ml). Add 4 ml of NaOH/SDS and incubate on ice for 5min.
- Add 4 ml of 3M NaOAc, pH4.8, and incubate on ice for 60min.
- Filter the supernatant through cheesecloth into another 50 ml conical tube and spin at 3000 rpm in the GPR centrifuge for 20min.
- Decant supernatant to 50 ml polypropylene tube and add 20 mg/ml of DNase-free RNaseA. Incubate at 37oC for 30 minutes.
- Add 7 ml (equal volume) of matrix (20mg/ml in guanadine HCl dissolved in 10:1 TE). Mix about 5min. Spin 5min at 3000 rpm in GPR tabletop centrifuge.
- Wash with an equal volume of wash buffer. Spin. Decant supernatant.
- Wash with an equal volume of acetone. Spin. Decant supernatant.
- Dry in vacuum oven (about 15-20min).
- Add 600 ul of 10:1 TE, incubate for 10min at 65oC with intermittent mixing.
- Spin at 8000 for 5min. Decant supernatant to Eppendorf tube.
- Spin again and transfer to Eppendorf tube (about 250 ul).
- Precipitate with 2.5 volumes of ethanol/acetate, rinse with 80% ethanol, and dry in a Speed-vac.
- Resuspend in 40 ul of 10:0.1 TE and assay concentration using 2 ul on an agarose gel. The yield should be ~1 ug/ml of starting cells. Use ~5 ug in the Sequenase Dye-Labeled Terminator Sequencing Reactions.
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