STRATAGENE Competent Cells User Manual
Competent Cells
How do you choose the
right competent cell?
UNIQUE
SOLUTIONS
HIGH
EFFICIENCY
INNOVATIVE
SPECIALTY CELLS
+
CLONING
COMPETENT CELLS
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2>3
COMPETENT CELLS
Get Your Clone with Our Competent Cells
From the high-efficiency ultracompetent and electroporation-competent cells to the reliable subcloning-grade competent cells,
our competent cells feature the widest range of cloning efficiencies available. Whether you are cloning small amounts of DNA
or doing routine day-to-day cloning, we have the right efficiency and genotype for every application.
Hte Phenotype1/Hee Phenotype
+
Subcloning-Grade Cells
>
_
1 x 106transformants/μg
of supercoiled DNA
+
SUBCLONING-GRADE COMPETENT CELLS
are perfect when you don’t need high
efficiency, but do need consistent results
every day. They are the economical choice for
routine subcloning procedures when DNA is
not limited. The XL1-Blue strain is available
as subcloning-grade competent cells
.
HTE AND HEE PHENOTYPES
enhance competent cell performance. These
phenotypes allow you to efficiently transform large
plasmids and ligated DNA. XL10-Gold®2,
BL21-Gold
and 96Pack® Gold6 cells each contain this novel
phenotype. ElectroTen-Blue
cells contain the Hee phenotype.
3
, BL21-CodonPlus®4, SoloPack® Gold
were developed to
®
electrocompetent
5
Ultracompetent Cells
>
_
5 x 109transformants/μg
of supercoiled DNA
+
ULTRACOMPETENT CELLS
efficiencies available for chemically competent
E. coli. They are perfect for plasmid library
construction, transforming large constructs or
other applications where optimal transformation
efficiency is critical
provide the highest
.
Competent Cells
>
_
1 x 108transformants/μg
of supercoiled DNA
+
COMPETENT CELLS
procedures that do not require supercompetent
efficiencies. At 1 x 10
group of competent cells is the economical
alternative for routine cloning.
are available for cloning
8
transformants/μg, this
Competent Cells
Supercompetent Cells
>
_
1 x 109transformants/μg
of supercoiled DNA
+
SUPERCOMPETENT CELLS
wide variety of strains at efficiencies greater
than 1 x 10
superior-quality cells include the following:
XL1-Blue, XL1-Blue MRF´, XL1- Blue MR,
XL1-Blue MRF´ Kan, SoloPack® Gold and
SURE
9
transformants/μg. These
®
2 supercompetent cells.
are available in a
Electroporation - Competent Cells
>
_
3 x 1010transformants/μg of supercoiled
DNA efficiency for ElectroTen-Blue
+
ELECTROPORATION-COMPETENT CELLS
are simple-to-use. Ease-of-use and high
efficiency make electroporation a popular
method for library construction, cloning large
inserts or cloning limited amounts of DNA. Our
high-performance ElectroTen-Blue
survive electroporation treatment better than
other cells, giving them superior cloning
efficiency for ligated DNA. XL1-Blue
9
®10
, ABLE
®11
, SURE
MRF’
also available as high efficiency ( 1 x 10
transformants/μg of supercoiled DNA)
electroporation-competent cells.
®
cells
®
cells
8
, XL1-Blue
and TG112 cells are
10
>
_
7
The Hte and Hee Phenotypes
Large and Ligated DNA
At Stratagene, we know it is more difficult to introduce large or ligated DNA constructs into
competent cells than supercoiled DNA or small plasmids. We have developed the Hte (high
transformation efficiency) and Hee (high electroporation efficiency) phenotypes to enhance
competent cell performance for your chemical and electroporation transformations. Increased
performance translates into increased success in obtaining representative primary and cDNA
libraries.
High Transformation Efficiency
The XL10-Gold
®
ultracompetent cells were designed to transform
large plasmids and ligated DNA with the highest transformation
efficiency possible, while exhibiting faster growth and larger
colonies. This strain was created by moving the Hte phenotype
into our highest-efficiency strain, XL2-Blue MRF´.
We ran a series of assays to demonstrate the Hte phenotype’s
ability to improve competent cell performance. In the first assay,
500 ng of the pRK2013 plasmid (25kb) was transformed into
XL10-Gold cells, XL2-Blue cells and DH10B cells. The
XL10-Gold cells were 80-fold more efficient than the other cell
lines with this large supercoiled plasmid (Figure 1). In the
second assay, we tested for the ability of XL10-Gold cells to
transform an 8-kb, non-supercoiled DNA molecule, generated
by the ligation-independent cloning technique (LIC). The
XL10-Gold strain proved 27-fold more efficient than the general
cloning host DH5α (data not shown).
RELATIVE TRANSFORMATION EFFICIENCY
01020304050607080
pRK2013
(25kb)
pUC18
(2.7kb)
DH10B Cells XL2-Blue Cells XL10®-Gold Cells
High Electroporation Efficiency
The Hee (high electroporation efficiency) phenotype improves
the survival rate of electroporated cells, resulting in a significant
increase in transformation efficiencies. The theoretical efficiency
E. coli
with which
11
colony-forming units (cfu) per microgram of supercoiled
3 x 10
cells become transformed is approximately
pUC plasmid DNA. To date, the actual values from the highest-
9
efficiency hosts have ranged from 5 x 10
10
mations to 1 x 10
cfu for electroporation procedures. Data sug-
for chemical transfor-
ests this difference is partly due to harsh electroporation condi-
tions that reduce the number of survivng cells taking up the
®
plasmid DNA. Our ElectroTen-Blue
cells, with an average efficiency of ≥3.0 x 10
Electroporation-Competent
10
(Figure 2) and
the Hee phenotype significantly increase your ability to trans-
form large or ligated DNA, obtain representative primary
libraries, and ensure success in any cloning project.
ElectroTen-Blue®Cells vs the Competition
(Ligated DNA Constructs)
4.50E+07
4.00E+07
3.50E+07
3.00E+07
2.50E+07
2.00E+07
1.50E+07
1.00E+07
cfu/ μg ligated DN A
5.00E+06
0.00E+00
Competitor I Competitor B Competitor S ElectroTen-Blue
Cells
®
FIGURE 1
XL10-GOLD
EFFICIENCIES
mid (25 kb) was transformed into 100 μl of
pRK2013 plasmid is used to compensate for the lower transformation efficiency. Aliquots
of each transformation were selected on the appropriate antibiotic-agar plates and the low-
est efficiency was set to one to calculate relative transformation efficiency.
®
CELLS TRANSFORM LARGE DNA AT HIGHER
100 pg of the pUC18 plasmid (2.7 kb) or 500 ng of the pRK2013 plas-
E. coli
competent cells. 500 ng of the
FIGURE 2
ELECTROTEN-BLUE
ElectroTen-Blue®Electroporation-Competent Cells consistently outperform “highest
efficiency” electroporation-competent cells from other suppliers. The pBluescript
vector was ligated to a 0.8-kb orange fluorescent protein (OFP) fragment and
electroporated following manufacturing guidelines.
®
CELLS AND LIGATED DNA
www.stratagene.com
®
cloning
4>5
HIGHEST
PERFORMANCE
5 x 10
9
XL10-Gold®Kan
cells
5 x 10
9
XL10-Gold
®
cells
COMPETENT CELLS >DIFFICULT CLONING
XL10-Gold® Ultracompetent Cells
Highest Efficiency Chemically Competent Cells
XL10-Gold®ultracompetent cells provide the highest chemical transformation efficiencies of
large plasmids and ligated DNA. The XL10-Gold strain allows cloning of methylated DNA and
produces high-quality miniprep DNA. Plasmid libraries constructed in this strain are more representative because XL10-Gold cells decrease the bias against large inserts.
Large DNA
XL10-Gold
®
cells are the only chemically competent cells that
allow you to efficiently transform large DNA molecules, including
expression vectors and genomic DNA. XL10-Gold ultracompe-
tent cells are the host cells of choice when you need the highest
transformation efficiencies for large constructs.
Optimal Plasmid Libraries
XL10-Gold ultracompetent cells are ideal for plasmid library con-
struction. Ligated plasmid DNA generally transforms with signifi-
cantly lower efficiency than supercoiled plasmids and larger
plasmids will transform less efficiently than the smaller plasmids.
The bias against large DNA molecules impacts the construction
of plasmid libraries and reduces the probability of finding full-
length cDNA clones. In addition, larger plasmid library vectors,
such as two-hybrid vectors and eukaryotic expression vectors,
RELATIVE TRANSFORMATION EFFICIENCY
0 5 10 15 20 25
potentially increase this size bias. XL10-Gold cells decrease
this size bias and produce more colonies for a more
representative library.
To demonstrate the ability of XL10-Gold cells to produce the
largest number of colonies, we transformed them with several
plasmid cDNA libraries. The libraries were transformed into
other cloning hosts and the resulting colonies were counted.
Compared to the other hosts, XL10-Gold cells produced the
most colonies, with 25-fold higher efficiency (Figure 3).
pUC18
pCMV-Script
Library
pAD-GAL4
Library
DH10B Cells XL2-Blue Cells XL10-Gold Cells
FIGURE 3
XL10-GOLD®CELLS DEMONSTRATE SUPERIOR TRANSFORMATION OF
LARGE DNA
and DH10B cells. XL10-Gold cells reduce bias against transformation of large DNA compared
to these other cells. 30 ng of the pCMV-Script vector (4.2 kb) or the pAD-GAL4 vector
(7.2 kb) were ligated to 10 ng cDNA for construction of a plasmid library. Of the 15-μl ligation
reactions, 1-μl aliquots were used to transform 100 μl of DH10B, XL2-Blue or XL10-Gold
competent cells. Supercoiled pUC18 plasmid was used for the transformation control.
Relative transformation efficiency comparison between XL10-Gold, XL2-Blue
Newly Improved Electro-Ten Blue®Cells
ELECTROPORATION
1 x 10
10
SURE
®
electroporationcompetent
cells
3 x 10
10
ElectroTen-Blue
®
electroporationcompetent
cells
1 x 10
10
XL1-Blue MRF'
electroporationcompetent
cells
1 x 10
10
XL1-Blue
electroporationcompetent
cells
>_
>_
>_
>_
>_
>_
1 x 10
10
TG1
electroporationcompetent
cells
1 x 10
10
ABLE
®
electroporationcompetent
cells
Highest Efficiency Electroporation-Competent Cells
Stratagene’s ElectroTen-Blue®electrocompetent cells offer the highest available transformation
10
efficiencies of ≥3.0 X 10
and the Hee phenotype make ElectroTen-Blue cells ideal for your most demanding cloning projects.
cfu/μg of supercoiled pUC DNA (Figure 4). High efficiency, ease-of-use,
Easily Transform Large and Ligated DNA
®
ElectroTen-Blue
electrocompetent cells exhibit the high efficiency
electroporation (Hee) phenotype. This phenotype improves the survival
rate of cells, increasing cloning efficiency of large plasmids and ligated
DNA. Derived from XL1-Blue cells, ElectroTen-Blue cells possess all of
the same cloning features such as T1 phage-resistance, and RecA and
EndA negative phenotypes, with the addition of 3-fold higher efficiency
over our previous electrocompetent cell line (Figure 5). These cells are
perfect when you have limited amounts of DNA or when generating
cDNA, genomic, and subtractive libraries. Use this strain when your
experiment must work the first time!
Spend Less Time Preparing Electroporation-Ready DNA
Before electroporation, ligated DNA to be transformed must be purified
to remove DNA ligase, a potential inhibitor of electroporation. Our
™
StrataClean
resin dramatically simplifies this process. Because of its
high affinity for proteins, StrataClean resin removes protein contamina-
tion with extraction complete in only 5 minutes. Use StrataClean resin for
all of your electroporation experiments, a well-established alternative to
phenol extractions and time-consuming ethanol precipitations. This resin
®
is included in our ElectroTen-Blue
electroporation competent cell kit.
Your Favorite Competent Cells
Our most popular strains are available as electroporation-
competent cells. These include our XL1-Blue, XL1-Blue MRF’, SURE
®
and TG1 cells.
ABLE
cfu/ μg supercoiled DNA
4.5 x 10
4.0 x 10
3.5 x 10
3.0 x 10
2.5 x 10
2.0 x 10
1.5 x 10
1.0 x 10
5.0 x 10
10
10
10
10
10
10
10
10
9
Competitor 1 Competitor 2 Competitor 3 ElectroTen-Blue
ElectroporationCompetent Cells
®
®
,
10
6.0 x 10
10
5.0 x 10
10
4.0 x 10
10
3.0 x 10
cfu/ μg DNA
10
2.0 x 10
10
1.0 x 10
Lot 1 Lot 2 Lot 3 Lot 4 Lot 5 Lot 6 Lot 7 Lot 8 Lot 9
ElectroTen-Blue® Electroporation-Competent Cells
FIGURE 4 FIGURE 5
ELECTROTEN-BLUE
SUPERCOILED pUC DNA
ElectroTen-Blue®Electrocompetent Cells consistently outperform
“highest efficiency” electroporation-competent cells from other
®
CELLS VS. THE COMPETITION USING
suppliers. Supercoiled pUC was electroporated following
manufacturer’s instructions.
LOT-TO-LOT EFFICIENCY
We compared transformation efficiencies across several lots of
ElectroTen-Blue
®
Electroporation-Competent Cells. Consistent lot-to-lot
results ensure success in all of your cloning projects.
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