STRATAGENE XL1-Blue MRF User Manual

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Made in USA

200230

Catalog Number

XL1-Blue MRF’ Supercompetent Cells

Product Name

XL1-Blue MRF' supercompetent cells (yellow tubes), 5 × 200 µl
pUC18 control plasmid (0.1 ng/µl in TE buffer), 10 µl
β-Mercaptoethanol (1.42 M), 25 µl

Materials Provided

Todd Parsons

Certified By

Tricia Molina

Quality Controlled By

Shipped on dry ice.

Shipping Conditions

Competent cells must be placed immediately at the bottom of a -80°C freezer directly from the dry ice shipping container. Do not
store the cells in liquid nitrogen. Competent cells are sensitive to even small variations in temperature. Transferring tubes from one
freezer to another may result in a loss of efficiency.

Storage Conditions

≥1.0 × 109 cfu/µg pUC18 DNA

Guaranteed Efficiency

Transformations are performed both with and without plasmid DNA using 100-µl aliquots of cells and 100 pg of pUC18 control
DNA following the protocol outlined below. Following transformation, 2.5-µl samples of the culture are plated in duplicate on LB
agar plates with 100 µg/ml ampicillin. The plates are incubated at 37°C overnight and the efficiency is calculated based on the
average number of colonies per plate.

Test Conditions

Δ(mcrA)183 Δ(mcrCB-hsdSMR-mrr)173 endA1 supE44 thi-1 recA1 gyrA96 relA1 lac [F´ proAB lacIqZΔM15 Tn10 (Tetr)]. (Genes
listed signify mutant alleles. Genes on the F´ episome, however, are wild-type unless indicated otherwise.)

The XL1-Blue MRF´ (Minus Restriction) strain is a restriction minus (McrA-, McrCB-, McrF-, Mrr-, HsdR-) derivative of Stratagene’
s XL1-Blue strain. XL1-Blue MRF´ cells are deficient in all known restriction systems [Δ(mcrA)183, Δ(mcrCB-hsdSMR-mrr)173],
and are endonuclease (endA), and recombination (recA) deficient. The hsdR mutation prevents the cleavage of cloned DNA by the
EcoK endonuclease system, and the recA mutation helps ensure insert stability. The endA mutation greatly improves the quality of
miniprep DNA. The lacIqZΔM15 gene on the F´ episome allows blue-white screening for recombinant plasmids.

Genotype and Background

XL1-Blue MRF' cells are resistant to tetracycline.

Antibiotic Resistance

1. Pre-chill two 14-ml BD Falcon polypropylene round-bottom tubes on ice. (One tube is for the experimental
transformation and one tube is for the pUC18 control.) Preheat SOC medium to 42°C.

2. Thaw the cells on ice. When thawed, gently mix and aliquot 100 µl of cells into each of the two pre-chilled tubes.

3. Add 1.7 µl of the β-mercaptoethanol provided with this kit to each aliquot of cells.

4. Swirl the tubes gently. Incubate the cells on ice for 10 minutes, swirling gently every 2 minutes.

5. Add 0.1-50 ng of the experimental DNA to one aliquot of cells and add 1 µl of the pUC18 control DNA to the other
aliquot. Swirl the tubes gently.

6. Incubate the tubes on ice for 30 minutes.

7. Heat-pulse the tubes in a 42°C water bath for 45 seconds. The duration of the heat pulse is critical.

8. Incubate the tubes on ice for 2 minutes.

9. Add 0.9 ml of preheated (42°C) SOC medium and incubate the tubes at 37°C for 1 hour with shaking at 225-250 rpm.

10. Plate ≤200 µl of the transformation mixture on LB agar plates containing the appropriate antibiotic (and containing
IPTG and X-gal if color screening is desired). For the pUC18 control transformation, plate 2.5 µl of the
transformation mixture on LB-ampicillin agar plates.

11. Incubate the plates at 37°C overnight. If performing blue-white color screening, incubate the plates at 37°C for at least
17 hours to allow color development (color can be enhanced by subsequent incubation of the plates for 2 hours at 4°C).

12. For the pUC18 control, expect 250 colonies (≥1 × 109 cfu/µg pUC18 DNA). For the experimental DNA, the number of
colonies will vary according to the size and form of the transforming DNA, with larger and non-supercoiled DNA
producing fewer colonies.

Transformation Protocol

Blue-white color screening for recombinant plasmids is available when transforming this host strain (containing the lacIqZDM15
gene on the F´ episome) with a plasmid that provides α-complementation (e.g. the Stratagene pBluescript II vector). When lacZ
expression is induced by IPTG in the presence of the chromogenic substrate X-gal, colonies containing plasmids with inserts will be
white, while colonies containing plasmids without inserts will be blue. If an insert is suspected to be toxic, plate the cells on media
without X-gal and IPTG. Color screening will be eliminated, but lower levels of the potentially toxic protein will be expressed in the
absence of IPTG.

Blue-White Color Screening

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Use of 14-ml BD Falcon polypropylene round-bottom tubes: It is important that 14-ml BD Falcon polypropylene round-bottom
tubes (BD Biosciences Catalog #352059) are used for the transformation protocol, since other tubes may be degraded by
β-mercaptoethanol. In addition, the duration of the heat pulse has been optimized using these tubes.
Aliquoting Cells: Keep the cells on ice at all times during aliquoting. It is essential that the polypropylene tubes are placed on ice
before the cells are thawed and that the cells are aliquoted directly into pre-chilled tubes. It is also important to use the volume of
cells indicated in step 2 of the Transformation Protocol. Decreasing the volume will reduce efficiency.
Use of β-Mercaptoethanol (β-ME): β-ME has been shown to increase transformation efficiency. The β-ME mixture provided is
diluted and ready to use. A fresh 1:10 dilution (from a 14.2 M stock) may be used; however, Stratagene cannot guarantee results with
β-ME from other sources.
Quantity and Volume of DNA: The greatest efficiency is obtained from the transformation of 1 µl of 0.1 ng/µl supercoiled pUC18
DNA per 100 µl of cells. A greater number of colonies may be obtained by transforming up to 50 ng DNA, although the resulting
efficiency (cfu/µg) may be lower. The volume of the DNA solution added to the reaction may be increased to up to 10% of the
reaction volume, but the transformation efficiency may be reduced.
Heat Pulse Duration and Temperature: Optimal transformation efficiency is observed when cells are heat-pulsed at 42°C for
45-50 seconds. Efficiency decreases sharply when cells are heat-pulsed for <45 seconds or for >60 seconds. Do not exceed 42°C.
Plating the Transformation Mixture: If plating <100 µl of cells, pipet the cells into a 200-µl pool of SOC medium and then spread
the mixture with a sterile spreader. If plating ≥100 µl, the cells can be spread on the plates directly. Tilt and tap the spreader to
remove the last drop of cells. If desired, cells may be concentrated prior to plating by centrifugation at
1000 rpm for 10 minutes followed by resuspension in 200 µl of SOC medium.

Critical Success Factors and
Troubleshooting

SOB Medium (per Liter)

20.0 g of tryptone

5.0 g of yeast extract

0.5 g of NaCl
Add deionized H2O to a final volume of 1 liter and then autoclave
Add 10 ml of filter-sterilized 1 M MgCl2 and 10 ml of filter-sterilized 1 M MgSO4 prior to use

SOC Medium (per 100 ml)

Prepare immediately before use

2 ml of filter-sterilized 20% (w/v) glucose or 1 ml of filter-sterilized 2 M glucose
SOB medium (autoclaved) to a final volume of 100 ml

LB Agar (per Liter)

10 g of NaCl
10 g of tryptone
5 g of yeast extract
20 g of agar
Add deionized H2O to a final volume of 1 liter

Adjust pH to 7.0 with 5 N NaOH and then autoclave
Pour into petri dishes (~25 ml/100-mm plate)

LB-Ampicillin Agar (per Liter)

1 liter of LB agar, autoclaved and cooled to 55°C
Add 10 ml of 10 mg/ml filter-sterilized ampicillin
Pour into petri dishes (~25 ml/100-mm plate)

Plates for Blue-White Color Screening

Prepare the LB agar and when adding the antibiotic, also add 5-bromo-4-chloro-3-inodlyl-β-D-galactopyranoside (X-gal) to a final
concentration of 80 µg/ml [prepared in dimethylformamide (DMF)] and isopropyl-1-thio-β-D-galactopyranoside (IPTG) to a final
concentration of 20 mM (prepared in sterile dH2O). Alternatively, 100 µl of 10 mM IPTG and 100 µl of 2% X-gal may be spread on

solidified LB agar plates 30 minutes prior to plating the transformations. (For consistent color development across the plate, pipet the
X-gal and the IPTG into a 100-µl pool of SOC medium and then spread the mixture across the plate. Do not mix the IPTG and the
X-gal before pipetting them into the pool of SOC medium because these chemicals may precipitate.)

Preparation of Media and
Reagents

This warranty limits our liability to replacement of this product. No other warranties of any kind, express or implied, including,
without limitation, implied warranties of merchantability or fitness for a particular purpose, are provided by Agilent. Agilent shall
have no liability for any direct, indirect, consequential, or incidental damages arising out of the use, the results of use, or the inability
to use this product.

Limited Product Warranty

For in vitro use only. This certificate is a declaration of analysis at the time of manufacture.