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Brij and Tween are trademarks of ICI Americas, Inc. Coomassie is a trademark of BASF Aktiengesellschaft. Ficoll is a trademark
of Amersham Pharmacia Biotech. StrepTactin is a trademark of Institut für Bioanalytik GmbH. StrepTactin is covered by German
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Criterion™ TGX Stain-Free™ and Criterion Stain Free™ precast gels are covered by U.S. Patent No. 7,569,130.
Purchase of Criterion™ XT Bis-Tris gels, XT MOPS running buffer, XT MES running buffer, XT MOPS buffer kit, and XT MES buffer
kit is accompanied by a limited license under U.S. patents 6,143,154; 6,096,182; 6,059,948; 5,578,180; 5,922,185; 6,162,338;
and 6,783,651 and corresponding foreign patents.
Appendix C: Related Literature .................................................... 45
Appendix D: Ordering Information .................................................. 46
Page 7
1
Criterion™ Precast Gels
1.1 Introduction
Criterion precast gels are an effective system for performing polyacrylamide gel electrophoresis (PAGE).
These 13.3 x 8.7 cm gels are wider and longer than traditional mini format gels, and their innovative,
easy-to-use design produces excellent resolution while accommodating more samples per gel.
Designed for use with the Criterion family of vertical electrophoresis cells, which includes the Criterion
(2-gel capacity) and Criterion™ Dodeca™ (12-gel capacity) cells, Criterion precast gels allow separation of
more samples than mini format gels and provide significant cost and time savings. Some of the unique
features provided are:
n
Integrated buffer chamber that eliminates buffer leaks
n
Capacity for up to 26 samples per gel
n
Compatibility with multichannel pipets (12+2 and 26-well)
n
Outlined and numbered wells that simplify sample loading and identification
n
Patented1 J-foot design that eliminates post-run gel processing steps and improves gel
drying and blotting results
n
Criterion™ TGX Stain-Free™ formulations for rapid gel imaging without staining
Integrated buffer
chamber
Gel type, expiration
date, and catalog
and lot numbers
Criterion precast gels are available in a range of formulations for virtually every electrophoresis
application (Table 1.1). All Criterion gels are composed of polyacrylamide with a bisacrylamide
crosslinker, and they are available in a selection of single percentages and gradients.
Table 1.1. Criterion precast gel formulations.
Application Gel Formulation Sample Buffer Running Buffer
Use each Criterion precast gel as soon as possible after removing it from the storage pouch.
Improper storage of Criterion precast gels can produce numerous artifacts.
n
Store gels flat
n
Avoid prolonged storage at temperatures above those recommended
n
Do not freeze gels
n
If you suspect your gels have been stored improperly, discard them
Do not run more than one gel type in the same apparatus at the same time. Different gel percentages
and formulations have different conductivities and different run times.
Use unstained standards with Criterion TGX Stain-Free and Criterion Stain Free gels, as some
™
prestained standards are not detected by the Gel Doc
EZ imager. To monitor electrophoresis, use
10 µl of a 1:1 mixture of Precision Plus Protein™ unstained and prestained standards.
PowerPac™ Basic or PowerPac HC power supply (or equivalent)
n
Sample buffer
n
Running buffer (460 ml per gel)
2.3 Setting Up and Running Criterion Gels in the Criterion Cell
1. Each Criterion gel is packaged in a plastic storage tray. Remove the cover of the tray by lifting the
corner tab and pulling it diagonally across the package. Remove the gel from the package.
2. Remove the comb and rinse the wells with deionized water (diH2O) or running buffer.
3. Remove the tape from the bottom of the cassette by pulling the tab across the gel.
4. Insert the cassette into one of the slots in the Criterion cell tank so that the integrated upper buffer
chamber faces the center of the cell (A).
5. Fill each integrated upper buffer chamber with 60 ml
running buffer.
6. Fill each half of the lower buffer tank with 400 ml
running buffer to the marked fill line.
A
Integrated upper buffer
chamber
7. Load samples using a syringe or a pipet with
gel-loading tips.
Optional: place a sample loading guide on the
outer edge of the cassette to help align pipet tips
with the wells (this is particularly useful when using
multichannel pipets).
8. Place the lid on the tank, aligning the color-coded
banana plugs with corresponding jacks on the lid.
See Chapters 3–10 for power supply settings.
2.4 Removing the Gel
1. After electrophoresis is complete, turn off the power
supply and disconnect the electrical leads.
2. Remove the lid from the tank and remove the
gel(s) from the cell. Pour off and discard the upper
running buffer.
3. Invert the cassette and place the integral buffer
chamber over the cassette-opening tool built into
the Criterion cell lid (B).
4. Press down firmly to break the seals on both sides of
the cassette. The cassette splits open approximately ¹/3
of the way. Alternatively, open the gel cassette by sliding
the tapered back of the comb into the slits on either
side of the cassette.
5. Pull the two halves of the cassette apart from the top to
completely expose the gel (C).
6. Remove the gel by either floating the gel into a fixing or
staining solution or by carefully lifting the bottom edge
of the gel from the cassette.
Criterion™ precast gels provide versatile systems for the separation of proteins by either molecular
weight (SDS-PAGE) or mass-to-charge ratio (native PAGE). (See Chapter 4 for native PAGE applications
and protocols.) This versatility is possible because Criterion gels are made without SDS, allowing the
sample buffer and running buffer to determine the separation mechanism.
SDS-PAGE relies on a discontinuous buffer system. Two ions differing in electrophoretic mobility form
a moving boundary when voltage is applied. Proteins have an intermediate mobility that causes them
to concentrate, or stack, into a narrow zone at the beginning of electrophoresis. As that zone moves
through the gel, the sieving effect of the polyacrylamide gel matrix causes proteins of different molecular
weights to move at different rates. This stacking effect is responsible for the high resolving power of
SDS-PAGE: the sample is loaded in a relatively broad zone, and the moving boundary concentrates the
proteins into sharp bands prior to separation.
Protein samples for SDS-PAGE are prepared using SDS and usually a thiol reducing agent such as
β-mercaptoethanol or dithiothreitol (DTT). SDS forms complexes with proteins, giving them a rodlike
shape and similar mass-to-charge ratio. The reducing agent disrupts disulfide bonds between and
within proteins, allowing complete denaturation and dissociation. Heat treatment in the presence of
SDS and reducing agent effectively eliminates the effects of native charge and higher order structure on
electrophoretic mobility, so the migration distance depends primarily on molecular weight.
Molecular weight is estimated by plotting the logarithm of protein molecular weight vs. the relative
mobility (R
or by using the point-to-point semilog interpolation method in Quantity One® or Image Lab™ software.
Refer to bulletins 3133 and 3144 for more information.
) of the protein (Rf = distance migrated by the protein/distance migrated by the dye front)
f
3.2 Criterion Gel Selection Guide for SDS-PAGE
A number of Criterion gel types are available for SDS-PAGE (Table 3.1) in both single and gradient
polyacrylamide percentages. Use the protein migration charts and tables to select the gel type that
offers optimum resolution of your sample:
n
Use single-percentage gels to separate bands of similar molecular weight. Optimum
separation occurs in the lower half of the gel, so use a percentage in which the protein
migrates to the lower half of the gel
n
Use gradient gels to separate samples containing a broad range of molecular weights.
Gradient gels allow resolution of both high and low molecular weight bands on the same
gel. Larger pore sizes at the top of the gel permit resolution of larger molecules, and smaller
pore sizes toward the bottom of the gel restrict excessive separation of small molecules
Criterion Stain Free™ Tris-HCl Laemmli gels with trihalo compounds for rapid fluorescence
detection
Bis-Tris Criterion™ XT Bis-Tris Based on a Bis-Tris HCl buffer system (pH 6.4); use these gels with
Criterion XT MES buffer for optimum resolution of small proteins
Bis-Tris Criterion XT Bis-Tris Based on a Bis-Tris HCl buffer system (pH 6.4); use these gels with
Criterion XT MOPS buffer for optimum resolution of midsized proteins
Tris-acetate Criterion XT Tris-acetate Based on a Tris-acetate buffer system (pH 7.0)
3.2.1 Criterion TGX and Criterion TGX Stain-Free Gels
Criterion TGX (Tris-Glycine eXtended shelf life) gels are Laemmli-like gels with a proprietary modification
that extends their shelf life to 12 months and enhances separation characteristics relative to conventional
gel types. The TGX formulation yields Laemmli-like separation patterns with short run times and
exceptionally straight lanes and sharp bands. TGX gels offer excellent staining quality, greater transfer
efficiency, and molecular weight estimation without the need for special, expensive buffers.
These gels are run using standard Laemmli sample buffer and Tris/glycine/SDS running buffer. Two
types of TGX formulations are available:
n
Criterion TGX — Laemmli-like, extended shelf life gels
n
Criterion TGX Stain-Free — Laemmli-like, extended shelf life gels with trihalo compounds
that allow rapid fluorescent detection of proteins with the Criterion Stain Free system,
eliminating staining and destaining steps for faster results (see Chapter 5 for more details)
Gel Composition
Crosslinker 2.6% C
Stacking gel 4% T, 2.6% C
Shelf life ~12 months at 2–8°C; expiration date is printed on each cassette
Gel Percentage Optimum Separation Range
7.5% 40–200 kD
10% 30–150 kD
12% 20 –120 kD
18% 10–50 kD
4–15% 20–250 kD
4–20% 10–200 kD
8–16% 20 –120 kD
10–20% 10–100 kD
Any kD™ 1 10–200 kD
1
Any kD is a unique single-percentage formulation that provides a broad separation range and short running time.
3.2.2 Criterion Tris-HCl and Criterion Stain Free Gels
These Tris-HCl, Laemmli gels use discontinuous glycinate and chloride ion fronts to form moving
boundaries to stack and then separate denatured proteins by size. They are run using standard Laemmli
sample buffer and Tris/glycine/SDS running buffer.
n
Criterion Tris-HCl — Tris-HCl formulation that offer a shelf life of 12 weeks
n
Criterion Stain Free — Tris-HCl gels with unique trihalo compounds that allow rapid
fluorescent detection of proteins with the Criterion Stain Free system, eliminating staining
and destaining steps for faster results (see Chapter 5 for more details)
Gel Composition
Gel buffer 0.375 M Tris-HCl, pH 8.6
Crosslinker 2.6% C
Stacking gel 4% T, 2.6% C
Storage buffer 0.375 M Tris-HCl, pH 8.6
Shelf life ~12 weeks at 2–8°C; expiration date is printed on each cassette
Migration charts for protein standards on Criterion Tris-HCl, Criterion TGX, and TGX Stain-Free gels.
3.2.3 Criterion XT Bis-Tris Gels
Criterion XT Bis-Tris gels are based on a Bis-Tris HCl buffer system (pH 6.4) that uses discontinuous
chloride and MES or MOPS ion fronts to form moving boundaries that stack and separate denatured
proteins by size. This chemistry of XT Bis-Tris gels allows maximum stability and consistent results with
a shelf life of at least 12 months.
Running XT Bis-Tris gels with either XT MES or XT MOPS denaturing running buffer produces different
migration patterns. A combination of these two running buffers and three XT Bis-Tris gels can generate
up to six different migration patterns for small to midsize proteins.
Gel Composition
Gel buffer Bis-Tris HCl, pH 6.4
Crosslinker 5% C
Stacking gel 4% T, 5% C
Storage buffer Bis-Tris HCl, pH 6.4
Shelf life 12 months at ambient temperature; expiration date is printed on each cassette
Gel Percentage Optimum Separation Range
XT MES Buffer XT MOPS Buffer
10% 2.5–200 kD 14–220 kD
12% 1–30 kD 6–66 kD
4–12% 2.5–200 kD 10–300 kD
Migration charts for protein standards on Criterion XT Bis-Tris gels.
3.2.4 Criterion XT Tris-Acetate Gels
Criterion XT Tris-acetate gels are based on a Tris-acetate buffer system (pH 7.0). It uses discontinuous
acetate and Tricine ion fronts to form moving boundaries that stack and separate large denatured
proteins by molecular weight.
Gel Composition
Gel buffer Tris-acetate, pH 7.0
Crosslinker 3.8% C
Stacking gel 4% T, 3.8% C
Storage buffer Tris-acetate, pH 7.0
Shelf life 8 months at 2–8°C; expiration
date is printed on each cassette
Gel Percentage Optimum Separation range
7% 36–200 kD
3–8% 40–400 kD
Migration charts for protein standards
on Criterion XT Tris-Acetate gels.
See Appendix B for buffer formulations. Do not adjust pH.
Tris/glycine/SDS (1x) 25 mM Tris, 192 mM glycine, 0.1% SDS
(pH 8.3) Dilute 100 ml 10x stock (catalog #161-0732) with 900 ml diH2O
XT MES (pH 6.4) Dilute 50 ml 20x stock (catalog #161-0789) with 950 ml diH2O
XT MOPS (pH 6.9) Dilute 50 ml 20x stock (catalog #161-0788) with 950 ml diH2O
XT Tricine (pH 8.2) Dilute 50 ml 20x stock (catalog #161-0790) with 950 ml diH2O
3.3.2 Sample Buffers
Laemmli 62.5 mM Tris-HCl, pH 6.8, 2% SDS, 25% glycerol, 0.01% (catalog #161-0737)
bromophenol blue, 5% β-mercaptoethanol or 100 mM DTT (added fresh)
XT Use XT sample buffer (catalog #161-0791) and XT reducing agent
(catalog #161-0792)
3.4 Sample Preparation
1. Determine the appropriate concentration of sample to load (depends on the load volume and the
detection method used; see Chapter 12 for approximate stain sensitivities).
2. Dilute the sample with at least an equivalent volume of sample buffer with added reducing agent.
For nonreducing conditions, omit the reducing agent.
TGX and Tris-HCl Gels XT Gels (Bis-Tris and Tris-Acetate)
Run conditions and times are approximate. Conditions may vary depending on water and buffer
conductivity, which vary from one lab setting to the next. Multiply current by the number of gels run.
Table 3.3. Running conditions for SDS-PAGE with Criterion gels in the Criterion cell. Do not run different gel
formulations at the same time.
TGX Tris-HCl Bis-Tris Tris-Acetate
Running buffer Tris/glycine/SDS Tris/glycine/SDS XT MOPS XT MES XT Tricine
Standard Conditions
Power conditions 200 V constant 200 V constant 200 V constant 200 V constant 150 V constant
Expected current (per gel)
Initial 55–80 mA 90–120 mA 165–175 mA 185–200 mA 170–180 mA
Final 33– 43 mA 35–55 mA 60–70 mA 90–110 mA 85–95 mA
In native PAGE, proteins are prepared in nonreducing, nondenaturing sample buffer, which maintains
native structure and mass-to-charge ratios. Separation is also performed in the absence of SDS and
reducing agents. Though native PAGE uses the same moving boundary described for SDS-PAGE
(see Section 3.1), protein mobility depends on a number of factors besides molecular weight, including
the shape and charge of the protein. Protein-protein interactions may be retained during native PAGE,
so some proteins may separate as multisubunit complexes. Consequently, native PAGE is not suitable
for molecular weight determination.
The nonreducing and nondenaturing environment of native PAGE allows protein separation with
retention of biological activity. Because native structure is retained, native PAGE can allow resolution of
proteins with the same molecular weight.
4.2 Criterion™ Gel Selection Guide for Native PAGE
Table 4.1. Criterion precast gels for SDS-PAGE.
Gel Formulation Gels Description
Laemmli-like Criterion™ TGX™ Laemmli-like, extended shelf life gels
Criterion™ TGX Stain-Free™ Laemmli-like, extended shelf life gels with trihalo compounds for rapid
fluorescence detection
Criterion Stain Free™ Tris-HCl Laemmli gels with trihalo compounds for rapid fluorescence
detection
Tris-acetate Criterion™ XT Tris-acetate Based on a Tris-acetate buffer system (pH 7.0)
4.2.1 Criterion TGX and Criterion TGX Stain-Free Gels
Criterion TGX (Tris-Glycine eXtended shelf life) gels are Tris-HCl, Laemmli-like gels with a proprietary
modification that extends their shelf life to 12 months and enhances separation characteristics relative to
conventional gel types. The TGX formulation yields Laemmli-like separation patterns with exceptionally
straight lanes and sharp bands and has excellent staining quality and transfer efficiency.
These gels are run using native sample buffer and Tris/glycine running buffer.
Two types of TGX formulations are available:
n
Criterion TGX — Laemmli-like gels with the TGX formulation
n
Criterion TGX Stain-Free — Laemmli-like, extended shelf life gels that include unique trihalo
compounds that allow rapid fluorescent detection of proteins with the Criterion Stain Free
system, eliminating staining and destaining steps for faster results (see Chapter 5 for more
details)
Shelf life ~12 months at 2–8°C; expiration date is printed on each cassette
4.2.2 Criterion Tris-HCl and Criterion Stain Free Gels
These Tris-HCl Laemmli gels are run using native sample buffer and Tris/glycine running buffer.
n
Criterion Tris-HCl — Tris-HCl, Laemmli-like formulation that offer a shelf life of 12 weeks
n
Criterion Stain Free — Tris-HCl, Laemmli-like gels with unique trihalo compounds that allow
rapid uorescent detection of proteins with the Criterion Stain Free system, eliminating
staining and destaining steps for faster results (see Chapter 5 for more details)
Gel Composition
Gel buffer 0.375 M Tris-HCl, pH 8.6
Crosslinker 2.6% C
Stacking gel 4% T, 2.6% C
Storage buffer 0.375 M Tris-HCl, pH 8.6
Shelf life ~12 weeks at 2–8°C; expiration date is printed on each cassette
4.2.3 Criterion XT Tris-Acetate Gels
Criterion XT Tris-acetate gels can also be used to separate proteins by their charge-to-mass ratio
(under native PAGE conditions). Separation by native PAGE with XT Tris-acetate gels uses discontinuous
acetate and Tricine ion fronts to form moving boundaries to stack and separate proteins by both size
and charge.
Gel Composition
Gel buffer Tris-acetate, pH 7.0
Crosslinker 3.8% C
Stacking gel 4% T, 3.8% C
Storage buffer Tris-acetate, pH 7.0
Shelf life 8 months at 2–8°C; expiration
date is printed on each cassette
4.3 Native PAGE Buffers
See Appendix B for buffer formulations. Do not adjust pH unless instructed to do so.
Running buffer (1x) 25 mM Tris, 192 mM glycine
Dilute 100 ml 10x stock (catalog #161-0734) with 900 ml diH2O
Sample buffer 62.5 mM Tris-HCl, pH 6.8, 25% glycerol, 0.01% bromophenol blue
(catalog #161-0738)
In the absence of SDS, the net charge of a polypeptide is determined by its amino acid composition and
the pH of the sample buffer. Only polypeptides with a net negative charge migrate into Criterion gels
under native conditions. Most polypeptides have an acidic or slightly basic pI (~3–8). These proteins can
be separated using the following standard protocol:
1. Determine the protein concentration and load volume of your sample based on the detection
method used (see Chapter 12 for approximate stain sensitivities).
2. Dilute the sample in twice the volume of native sample buffer (DO NOT HEAT SAMPLES).
For example, combine: 5 μl sample
10 μl native sample buffer (catalog #161-0738)
15 μl total volume
Strongly basic proteins (pl >8.5) have a net positive charge and will not enter a Criterion gel under native
conditions. To allow polypeptides with a net positive charge to migrate into a native Criterion gel, change
the polarity of the electrodes by reversing the color-coded jacks when connecting to the power supply.
4.5 Running Conditions
Running conditions for native PAGE are similar to the standard running conditions used for SDS-PAGE
(see Section 3.5). If high temperature is a concern, run native PAGE at lower voltage; at lower voltages, runs
require more time to complete.
Table 4.1. Running conditions for native PAGE for Criterion gels in the Criterion cell.
The Criterion Stain Free system, which comprises the Gel Doc™ EZ imager, Image Lab™ software,
and Criterion™ TGX Stain-Free™ and Criterion Stain Free precast gels, eliminates the time-consuming
staining and destaining steps required by other protein detection methods. Criterion TGX (Tris-Glycine
eXtended shelf life) Stain-Free gels include a proprietary modification that extends their shelf life to
12 months and enhances separation characteristics relative to conventional gel types. Criterion TGX
Stain-Free and Criterion Stain Free gels also include unique trihalo compounds that allow rapid
fluorescent detection of proteins with the Gel Doc EZ imager — without staining.
The trihalo compounds in the gels react with tryptophan residues in a UV-induced reaction to
produce fluorescence, which can be easily detected by the Gel Doc EZ imager within gels or on lowfluorescence PVDF membranes. Activation of the trihalo compounds in the gels adds 58 Da moieties
to available tryptophan residues and is required for protein visualization. Proteins that do not contain
tryptophan residues cannot be detected using this system. The sensitivity of the Criterion Stain Free
system is comparable to staining with Coomassie Brilliant Blue for proteins with a tryptophan content
>1.5%; sensitivity superior to Coomassie staining is possible for proteins with a tryptophan content >3%.
Molecular weights of proteins are estimated by a regression method using Image Lab software. The
software generates a standard curve using the molecular weight and relative mobility (R
proteins (Rf = distance migrated by the protein/distance migrated by the dye front). The standard curve
is then used to estimate the molecular weights of sample proteins.
Benefits of the Criterion Stain Free system include:
n
Elimination of staining and destaining steps for faster results
n
Automated gel imaging and analysis
n
No background variability within a gel or between gels (as is often seen with standard
Coomassie staining)
n
Reduced organic waste by not requiring acetic acid and methanol for staining or destaining
n
Visualization of transferred (blotted) proteins on low-fluorescence PVDF membranes
5.3 Electrophoresis with Criterion TGX Stain-Free Gels
Criterion TGX Stain-Free gels (and Criterion Stain Free gels) are made and packaged without SDS, so
they can be used for both SDS and native PAGE applications. To perform electrophoresis with these
gels, prepare the sample and running buffers, set up the Criterion cell, and perform the run as directed
in Chapters 2–4.
Use unstained standards with Criterion TGX Stain-Free and Criterion Stain Free gels,
as some prestained standards are not detected by Stain-Free technology.
To monitor electrophoresis, use 10 µl of a 1:1 mixture of Precision Plus Protein
™
unstained
and Precision Plus Protein All Blue protein standards.
5.4 Using the Gel Doc EZ Imager
Image Criterion TGX Stain-Free and Criterion Stain Free gels and blots in the Gel Doc EZ imager.
The imager activates the reaction between the proteins and trihalo compounds in the gel to enable
visualization.
n
Immediately place the gel in the tray of the imager; no fixation or rinsing steps are required.
Prolonged rinsing may diminish image quality and lead to gel deformation
n
If desired, stain the gel with any TGX-compatible stains after imaging. Certain stains, if used
prior to imaging, eliminate detection capability
Refer to the Gel Doc EZ Stain-Free Sample Tray Instruction Manual (bulletin 10019634) for detailed
instructions.
Criterion™ Tris-Tricine/peptide gels are optimized for separating peptides and proteins with molecular
weight <10,000. Peptide-SDS complexes move more slowly through these gels, allowing the faster SDS
micelles that normally interfere with peptide separations to separate completely from peptides. This
enables resolution of distinct peptide bands.
6.2 Criterion Tris-Tricine/Peptide Gels
6.2.1 Gel Composition
Gel buffer 1.0 M Tris-HCl, pH 8.45
Crosslinker 2.6% C
Stacking gel 4% T, 2.6% C
Storage buffer 1.0 M Tris-HCl, pH 8.45
Shelf life ~12 weeks at 2–8°C; expiration date is printed on each cassette
6.2.2 Gel Selection Guide
Criterion Tris-Tricine/peptide gels are available in either a single percentage or a linear gradient format.
Gel Percentage Optimum Separation Range
16.5% 1.5–30 kD
10–20% 1–40 kD
6.3 Tris-Tricine/Peptide Buffers
See Appendix B for buffer formulations. Do not adjust pH unless instructed to do so.
Running buffer (1x) 100 mM Tris, 100 mM Tricine, 0.1% SDS
Dilute 100 ml 10x stock (catalog #161-0744) with 900 ml diH2O
Sample buffer 200 mM Tris-HCl, pH 6.8, 2% SDS, 40% glycerol, 0.04% Coomassie
(catalog #161-0739) Brilliant Blue G-250, 2% β-mercaptoethanol or 100 mM DTT (added fresh)
1. Determine the appropriate concentration of sample to load (depends on the load volume and the
detection method used; see Chapter 12 for approximate stain sensitivities).
2. Dilute the sample with at least an equivalent volume of sample buffer (catalog #161-0739) and
reducing agent (β-mercaptoethanol, for example). Heat the diluted sample at 90–95°C for 5 min,
or at 70°C for 10 min.
Isoelectric focusing (IEF) separates proteins by their net charge rather than molecular weight. Criterion™
IEF gels are cast with Bio-Rad’s Bio-Lyte® ampholytes, amphoteric molecules that generate a pH
gradient across the gels. Proteins migrate to their isoelectric point (pI), the pH at which the protein
has no net charge. Criterion IEF gels contain no denaturing agents, so IEF is performed under native
conditions.
7.2 Criterion IEF Gels
7.2.1 Gel Composition
Gel buffer 2% ampholyte, pH 3–10 or 5–8
Crosslinker 3.0% C
Stacking gel None
Storage buffer diH2O
Shelf life ~24 weeks at 2–8°C; expiration date is printed on each cassette
7.2.2 Gel Selection Guide
IEF gel pH Range
5–8 5–8.0
3–10 4–8 .5
7.3 IEF Buffers
See Appendix B for buffer formulations. Do not adjust pH unless instructed to do so.
Running buffers:
IEF cathode buffer (1x) 20 mM lysine (free base), 20 mM arginine (free base)
Dilute 100 ml 10x stock (catalog #161-0762) with 900 ml diH2O
IEF anode buffer (1x) 7 mM phosphoric acid
Dilute 100 ml 10x stock (catalog #161-0761) with 900 ml diH2O
Criterion™ zymogram gels are used to test for proteolytic activity. Gels are cast with gelatin or casein,
which acts as a substrate for proteases that are separated in the gel under nonreducing conditions.
Proteases are detected by first renaturing the enzymes and then allowing them to break down the
substrate. Zymogram gels are stained with Coomassie Brilliant Blue R-250 stain, which stains the
substrate while leaving clear areas around active proteases.
8.2 Criterion Zymogram Gels
8.2.1 Gel Composition
Gel buffer 0.375 M Tris-HCl, pH 8.6
Crosslinker 2.6% C
Stacking gel 4% T, 2.6% C
Storage buffer 0.375 M Tris-HCl, pH 8.6, 0.2% NaN
Shelf life ~8 weeks at 2–8°C; expiration date is printed on each cassette
8.2.2 Gel Selection Guide
Zymogram Gel Optimum Separation Range
10% with gelatin 30–150 kD
12.5% with casein 20–120 kD
3
8.3 Zymogram Buffers
See Appendix B for buffer formulations. Do not adjust pH unless instructed to do so.
Running buffer (1x) 25 mM Tris, 192 mM glycine, 0.1% SDS
Dilute 100 ml 10x stock (catalog #161-0732) with 900 ml diH2O
Sample buffer 62.5 mM Tris-HCl, pH 6.8, 4% SDS, 25% glycerol, 0.01% Coomassie
(catalog #161-0764) Brilliant Blue G-250
1. Determine the appropriate protein concentration of your sample based on the detection method
and load volume used. (See Chapter 12 for approximate stain sensitivities.)
2. Dilute 1 part sample with 1 part sample buffer. Do not heat the samples.
Criterion™ TBE gels are used to separate small double-stranded DNA (dsDNA) fragments, particularly
PCR products. DNA molecules have nearly uniform mass-to-charge ratios, allowing nondenaturing
nucleic acid PAGE to separate dsDNA by mass using a continuous TBE buffer system.
9.2 Criterion TBE Gels
9.2.1 Gel Composition
Gel buffer 89 mM Tris, 89 mM boric acid, 2 mM EDTA, pH 8.3
Crosslinker 3.3% C
Stacking gel 4% T, 3.3% C
Storage buffer 89 mM Tris, 89 mM boric acid, 2 mM EDTA
Shelf life ~12 weeks at 2–8°C; expiration date is printed on each cassette
9.2.2 Gel Selection Guide
Gel Percentage Optimum Separation Range
5% 200–2,000 bp
10% 50–1,500 bp
15% 20–1,000 bp
4–20% 10–2,000 bp
9.3 Nondenaturing Nucleic Acid PAGE Buffers
See Appendix B for buffer formulations. Do not adjust pH unless directed to do so.
Running buffer (1x) 89 mM Tris, 89 mM boric acid, 2 mM EDTA
Dilute 100 ml 10x stock (catalog #161-0733) with 900 ml diH2O
Determine the DNA concentration of your sample based on the detection method used. (See Chapter
12 for approximate stain sensitivities.) Dilute 4 parts sample with 1 part sample buffer.
9.5 Running Conditions
Table 9.1. Running conditions for nondenaturing nucleic acid PAGE with Criterion gels in the Criterion cell.
Criterion™ TBE-urea gels are used for separation of small RNA and single-stranded DNA (ssDNA)
fragments. Applications include oligonucleotide analysis, RNase protection assays, and northern
blotting.
10.2 Criterion TBE-Urea Gels
10.2.1 Gel Composition
Gel buffer 89 mM Tris, 89 mM boric acid, 2 mM EDTA, 7 M urea, pH 8.3
Crosslinker 3.3% C
Stacking gel 4% T, 3.3% C
Storage buffer 89 mM Tris, 89 mM boric acid, 2 mM EDTA, pH 8.3
Shelf life ~8 weeks at 2–8°C; expiration date is printed on each cassette
10.2.2 Gel Selection Guide
Gel Percentage Optimum Separation Range
5% 50–1,000 nt
10% 25–300 nt
15% 10–50 nt
10.3 TBE-Urea Buffers
See Appendix B for buffer formulations. Do not adjust pH unless directed to do so.
Running buffer (1x) 89 mM Tris, 89 mM boric acid, 2 mM EDTA
Dilute 100 ml 10x stock (catalog #161-0733) with 900 ml diH2O
Sample buffer (5x) 89 mM Tris, 89 mM boric acid, 2 mM EDTA, pH 8.0, 12% Ficoll,
(catalog #161-0768) 0.01% bromophenol blue, 0.02% xylene cyanole FF, 7 M urea
10.4 Sample Preparation
Determine the desired ssDNA or RNA concentration for your sample based on the detection method
used. Dilute 4 parts sample with 1 part sample buffer.
Criterion™ precast gels are available for second-dimension PAGE in 2-D electrophoresis workflows.
The IPG-well gels accommodate 11 cm IPG strips. Criterion™ Any kD™ gels are particularly well suited
for 2-D electrophoresis applications.
The transition from first- to second-dimension gel electrophoresis involves:
n
Equilibration of the resolved IPG strips in a reducing buffer containing SDS
n
Placing the IPG strip on top of the second-dimension gel
11.2 Equilibration
Equilibration ensures that proteins in the IPG strips are coated with SDS and that cysteines are reduced
and alkylated. Use the equilibration protocols (bulletin 4110009) and buffers in the ReadyPrep™ 2-D
starter kit (catalog #163-2105), or other protocols and buffers used with Tris-HCl gels.
11.3 Agarose Overlay
Place the equilibrated IPG strip into the IPG well of the Criterion gel and overlay it with molten agarose to
ensure good contact between the strip and gel.
0.003% bromophenol blue (catalog #161-0404) in 1x Tris/glycine/SDS running buffer.
(Alternatively, use ReadyPrep overlay agarose, catalog #163-2111)
n
Criterion™ XT gels: prepare 0.5% low-melt agarose (catalog #161-3111), 0.001%
bromophenol blue (catalog #161-0404) in appropriate 1x XT running buffer
1. Following equilibration, place the IPG strip, gel side up, on the back plate of the Criterion gel, above
the IPG well. The “+” and pH range on the IPG strip should be on the left.
2. Using forceps, push the strip into the IPG well, taking care to not trap air bubbles under the strip.
Push on the backing of the strip, not on the gel.
3. Using a disposable pipet, add overlay agarose to the IPG well. Fill the well to the top of the inner
plate. Dispense rapidly, as overlay agarose solidifies quickly. To avoid bubbles, tilt the cassette
slightly to allow bubbles to escape. Push gently on the plastic backing of the strip to free any
trapped bubbles.
11.4 Second-Dimension Electrophoresis
Place the cassettes into the Criterion cell and start the run using the run conditions for SDS-PAGE.
Use the migration of the bromophenol blue in the overlay agarose to monitor the progress of the run.
Following electrophoresis, either stain the gel or use the Criterion Stain Free™ system to visualize
proteins in the gel.
n
Refer to Table 12.1 for a comparison of total protein stains
n
For Criterion™ TGX Stain-Free™ and Criterion Stain Free™ gels, immediately place the gel on
the tray of the Gel Doc™ EZ imager; no additional fixation or rinsing steps are required.
If desired, stain with any compatible stains (Table 12.1) following imaging. Some stains, if
used prior to imaging, can impair imaging quality
Table 12.1. Total protein gel stains for use with Criterion gels.
Stain
Criterion Gels
Coomassie
R-250
™
Bio-Safe
Coomassie
Zinc stain
1
Sensitivity
(Lower
Limit)
36 –47 ng~0.5Laboratory
8–28 ng~0.5Nonhazardous43 070 51
6–12 ng~0.2High contrast, fast,
Optimum
Protein Load
(µg/Band)
Advantages
standard
reversible
Disadvantages
Requires
methanol
destaining
Negative SDSPAGE stain, must
be photographed
Imaging
Photography
with white light
or transmission
densitometry
4006082
literature
Manual
Consult
Silver
Stain Plus
Silver stain0.6–1. 2 n g~0.01Stains complex
Dodeca
silver stain kit
Oriole
fluorescent
gel stain
1
Do not use zinc stain or Oriole fluorescent gel stain to stain native gels.
™
kit
™
™
1
0.6–1.2 n g~0.01Sensitive, robust,
mass spectrometry
compatible
proteins (glyco- or
lipoproteins)
0. 5–1.2 n g~0 .1Convenient
staining for a large
number of gels
Fluorescence
visualization
with UV transillumination
LIT4 42
LIT34
4110 15 0
10017295
Page 37
Instruction Manual and Application Guide
Stain
SYPRO
Ruby protein
gel stain
Flamingo
fluorescent gel
stain
Criterion TGX Stain-Free and Criterion Stain Free Gels
Stain Free
imaging
™
Sensitivity
(Lower
Limit)
1–10 ng~ 0.1Broad dynamic
0.25– 0.5 ng~0.02Broad dynamic
2–28 ng~0.5Rapid (<5 min),
Optimum
Protein Load
(µg/Band)
Advantages
range
range, mass
spectrometry
compatible
compatible with
blotting and mass
spectrometry,
simple protocol
with no additional
reagents
Disadvantages
Requires laseror LED-based
imaging
instrument for
maximum
sensitivity
Requires
tryptophan
residues in
proteins for
detection
Imaging
Fluorescence
visualization
with UV,
LED, or laser
scanning
Fluorescence
visualization
using Criterion
Stain Free
imaging system
Manual
400 6173
10003321
10014472
12.2 Peptide Gel Staining
Peptides and small proteins are prone to diffusion and loss during staining. The following protocol
includes a fixing step prior to staining to prevent sample loss and is suitable for detection of bands as
low as 10–20 ng.
Fixative solution 40% methanol, 10% acetic acid
Stain solution 0.025% (w/v) Coomassie Blue G-250, 10% acetic acid
Destain solution 10% acetic acid
Place gels in fixative solution and equilibrate for 30 min. Stain gels with stain solution for 1 hr. Stain
should be used only once; reuse may result in loss of sensitivity. Destain gels three times for 15 min or
until the desired background is achieved. Some peptides may not be completely fixed and may diffuse
out of the gels if fixing and staining times are greatly exceeded.
12.3 IEF Gel Staining
Samples on IEF gels can be detected using multiple methods. Use Table 12.2 as a guide to selecting an
appropriate staining method.
Table 12.2. IEF gel detection methods.
Method
Silver Stain Plus kit0.6–1.2 ng~0.01Sensitive, robust, mass
Prior to staining zymogram gels, sample proteases must first be renatured and allowed to break down
the substrate contained in the gel. The following protocol provides basic guidelines for detection.
Optimal results should be determined empirically.
Renaturing solution 2.5% Triton X-100
Development solution 50 mM Tris, 200 mM NaCl, 5 mM CaCl2 (anhydrous), 0.02% Brij-35
Adjust to pH 7.5
Place gels in renaturing solution for 30 min at room temperature. Incubate gels in development solution
at 37ºC for a minimum of 4 hr. Highest sensitivity is typically achieved with overnight incubation.
Optimum conditions should be determined empirically. Stain gels with staining solution for at least 1 hr
at room temperature. Destain until clear bands appear against the blue background (~30–60 min).
12.5 TBE Gel Staining
Use Table 12.3 as a guide to selecting an appropriate staining method.
Table 12.3. TBE gel detection methods.
Method
Ethidium bromide50 ngClassic fluorescent DNA stainCarcinogenic
Silver stain1–2 ngMore sensitive than ethidium bromideRequires multiple steps
Western blotting is an electrophoretic technique used to move proteins from a gel onto a solid support
such as a nitrocellulose or PVDF membrane. The membrane can be used for immunological or
biochemical analyses or demonstration of protein-protein or protein-ligand interactions. Below are
guidelines for western blotting of Criterion™ precast gels onto nitrocellulose or PVDF membranes using
either wet or semi-dry transfer techniques.
Assess transfer efficiency using a total protein blot stain such as SYPRO Ruby stain (see Table 12.1).
With Criterion
PVDF membranes may also be assessed using the Gel Doc™ EZ imager (see Chapter 5; activate the gel
before blotting).
™
TGX Stain-Free™ and Criterion Stain Free™ gels, transfer efficiency to low-fluorescence
13.2 Transfer
13.2.1 Transfer Buffers
See Appendix B for buffer formulations. Do not adjust pH unless directed to do so.
Towbin buffer (1x) 25 mM Tris, 192 mM glycine, 20% (v/v) methanol (pH 8.3)
Dilute 100 ml 10x stock (catalog #161-0734) with 400 ml diH2O.
Add 200 ml methanol, then adjust volume to 1 L with diH2O.
Add SDS to 0.1% to promote transfer of high molecular weight proteins.
13.2.2 Wet Transfer Using the Criterion Blotter
1. Equilibrate the gels and membranes (for example, in Towbin buffer) for 15 min prior to blot assembly.
2. Assemble the transfer apparatus:
a) Fill the tank with transfer buffer to ~50% of the fill volume and place a magnetic stir bar inside
the tank.
b) Place the ice block in the pocket in the back of the cell. Flip down the lever to hold the ice
block. Alternatively, connect the optional cooling coil to an appropriate recirculating water chiller
and place it in the grooves in the back of the tank.
3. Assemble the cassette:
a) Pour chilled transfer buffer into each compartment of the assembly tray, and then place the
membrane (nitrocellulose, PVDF) into the front (small) compartment of the tray to soak.
Wet PVDF membranes in methanol before soaking in transfer buffer.
b) Open the cassette and place it in the back (large) compartment of the tray so the red plate
with the handle is vertical (anode) and the black plate (cathode) is horizontal and submerged in
transfer buffer.
c) Assemble the sandwich as shown, placing the gel closest to the black side of the cassette and
the membrane closest to the red plate. Use a blot roller to remove air trapped between the
layers of the blot assembly.
Foam pad
Filter paper
Membrane
Gel
Filter paper
Foam pad
Assembly of the gel blot sandwich with the Criterion blotter.
4. Place the assembled cassette into the groove in the tank, aligning the red side of the card with the
red electrode. Make sure the magnetic stirbar is free to move. Repeat steps 2–4 for a second blot.
5. Add the remaining transfer buffer to the fill level marked on the tank, place the tank on a stir plate,
and begin stirring to maintain even buffer temperature and ion concentration during the transfer.
6. Connect the Criterion blotter to a PowerPac™ HC power supply and begin transfer.
For many proteins, excellent transfer efficiency is obtained in 30 min at a constant voltage of 100 V. For
best results, optimize conditions for proteins of interest. Large proteins (>150 kD) may take 60 min, while
smaller proteins (<30 kD) may transfer in 20 min. Refer to the Criterion Blotter Instruction Manual (bulletin
4006190) or the Protein Blotting Guide (bulletin 2895) for additional information.
®
13.2.3 Transfer Using the Trans-Blot
Turbo™ System
1. Open the transfer pack and assemble the components on the cassette in the order shown. For best
results, use the roller to remove any air trapped between the layers. If using a single mini or midi
sandwich, place the sandwich in the middle of the cassette bottom. With two mini gels, place the
sandwiches on a midi stack with the foot of each gel facing the center of the stack.
2. Place the lid on the cassette and lock the lid in place by turning the knob clockwise, using the
symbols on the lid as a guide. Slide the cassette into the appropriate bay of the Trans-Blot Turbo cell.
Each cassette and bay can hold up to two mini gels or one midi gel (Table 13.1).
3. Start the transfer. With the cassette in the cell, press TURBO and select the gel type. Press A:RUN
or B:RUN to begin the transfer. Press LIST to select a Bio-Rad optimized protocol (Table 13.2) or a
user-defined protocol. Press NEW to create and run a new protocol.
4. When transfer completes, RUN COMPLETE appears. Pull the cassette straight out of the slot and
unlock the lid. Disassemble the blotting sandwich.
Assembly of the gel blot sandwich with the Trans-Blot Turbo system.
Table 13.1. Placement of cassettes in the Trans-Blot Turbo cell.
AcceptableUnacceptable
Option 1Option 2Option 1Option 2
Upper bay (A)1 mini gel2 mini gels -or- 1 midi gel1 mini gel2 mini gels -or- 1 midi gel
-a nd/or-- and/or--and--and-
Lower bay (B)1 mini gel2 mini gels -or- 1 midi gel2 mini gels -or- 1 midi gel1 mini gel
Table 13.2. Trans-Blot Turbo transfer protocols.
Protocol Name
STA ND AR D SDAny30Up to 1.0 A, 25 V constantUp to 1.0 A, 25 V constant
1.5 MM GELAny102.5 A constant, up to 25 V1.3 A constant, up to 25 V
HIGH MW>15 0102.5 A constant, up to 25 V1.3 A constant, up to 25 V
LOW MW<3052.5 A constant, up to 25 V1.3 A constant, up to 25 V
MIXED MW5 –15072.5 A constant, up to 25 V1.3 A constant, up to 25 V
1 Mini TGX5–15032.5 A constant, up to 25 VN /A
MW, kDTime, Min
1 Mini Gel
2 Mini Gels or 1 Midi Gel
Refer to the Trans-Blot Turbo Instruction Manual (bulletin 10020688) for complete instructions or the
Protein Blotting Guide (bulletin 2895) for additional information.
13.2.4 Semi-Dry Transfer Using the Trans-Blot® SD Cell
1. Equilibrate the gels and membranes (for example, in transfer buffer; see Appendix B for buffer
recipes) for 20 min prior to blot assembly.
2. Assemble the blot for transfer using the Trans-Blot SD semi-dry transfer system.
3. Connect the Trans-Blot SD cell to a PowerPac HC
power supply and begin transfer at 10–15 V.
For most proteins transferred from Criterion precast
gels, optimum transfer efficiency is obtained in
30 min; smaller proteins (<30 kD) may transfer more
quickly, while proteins >150 kD may show increased
transfer efficiencies at up to 60 min. Run times longer
than 60 min are NOT recommended for semi-dry
transfers.
Refer to the Trans-Blot SD Instruction Manual (bulletin
1703940) or the Protein Blotting Guide (bulletin 2895)
for additional information.
(–)
Filter paper
Gel
Membrane
Filter paper
13.3 Total Protein Blot Stains
Total protein staining of a membrane provides
an image of the complete protein pattern, which
is required for the full characterization of specific
antigens detected in complex protein mixtures.
Gels shrink during staining, so comparison of an
immunologically probed membrane to a stained gel is
not practical. Instead, the exact location of a specifc
antigen is determined by comparing two blotted
membranes: one that has been probed with an
antibody and the other stained for total protein.
Table 13.1. Total protein blot stains.
Method
SYPRO Ruby
protein blot stain
Sensitivity
2–8 ng~0.2Compatible with
Protein
Load
(μg/Band)
Advantages
mass spectrometry,
Edman-based
sequencing,
and standard
immunological
procedures
(+)
Assembly of the gel blot sandwich with the
Trans-Blot SD cell.
Disadvantages
Multi-step protocol;
requires UV, LED,
or laser imaging for
maximum sensitivity
Imaging
Fluorescence
visualization
with UV, LED
epi-illumination or
laser scanning
Colloidal gold stain1 ng~ 0.1Highly sensitive,
single-step protocol
Anionic dyes
(amido black,
Coomassie R-250,
Ponceau S, Fast
Green FCF)
Photography with
epi-illumination
or reflectance
densitometry
Page 43
Instruction Manual and Application Guide
To visualize total protein on blots using the Gel Doc EZ imager, refer to Section 5.4.
13.4 Immunodetection
After transfer, blots are ready for downstream processing. While all protein and antibody combinations
are different and may require optimization, a general protocol for the immunodetection of a large
number of protein and antibody combinations is provided (see Appendix B for buffer formulations).
1. Immediately after transfer, place the membrane into Tris-buffered saline with Tween 20 (TTBS)
containing blocking agent (for example, 3% BSA, 5% nonfat dry milk, 1% casein, or 1% gelatin).
Incubate at room temperature with agitation for 1 hr.
2. Dilute the primary antibody in blocking solution (suggested dilution is specified by the manufacturer).
Incubate the blot in the primary antibody solution at room temperature and with agitation for 1 hr.
3. Wash the blot with TTBS as directed in the instructions for the detection method to be used (for
example, 5 times, 5 min each at room temperature).
4. Dilute the secondary antibody into TTBS as specified by the manufacturer. Incubate the blot in the
secondary antibody solution at room temperature with agitation for 1 hr.
5. Wash the blot with TTBS for 5 min at room temperature with agitation. Pour off the wash solution
and repeat 5 times.
6. Follow the directions for the detection kit used to develop the blot. For the Immun-Star™ WesternC™
chemiluminescence kit (catalog #170-5070), mix 3 ml luminol/enhancer with 3 ml peroxide solution
to make a 1x working solution for a 7 x 8.5 cm membrane. Incubate the membrane in the solution
for 3–5 min. Prior to imaging, drain the excess substrate and place the membrane in a protective
sleeve (such as plastic wrap) to prevent drying.
Table 14.1. Troubleshooting electrophoresis and detection with Criterion™ gels. For more troubleshooting tips, refer to the
Criterion cell, Criterion blotter, and Trans-Blot® SD cell instruction manuals, or contact Technical Support.
General Troubleshooting Tips
Current is zero or less than
expected, and samples do not
migrate into gel
Troubleshooting
ProblemCauseSolution
Tape at bottom of cassette not removed Remove tape
Insufficient buffer in integral buffer
chamber
Fill buffer chamber with running buffer
Insufficient buffer in lower buffer
chamber
Electrical disconnectionCheck electrodes and connections
Gels run faster than expectedRunning buffer too concentrated or
incorrect
Gel temperature too highDo not exceed recommended running
Bands “smile” across gel: band
pattern curves upward at both
sides of the gel
Bands “smile” or “frown” within gel
lanes
Bands are skewed or distorted;
lateral band spreading
Excessive heating of gelCheck buffer composition
Insufficient bufferFill both halves of lower buffer tank with
Protein load too highLoad less protein
Sample or buffer preparation issuesMinimize salts, detergents, and solvents
Incorrect running conditionsSet correct voltage
Too much salt in samplesRemove salt from samples (dialysis,
Insufficient or wrong sample bufferCheck buffer composition and dilution
Sample precipitationSelectively remove predominant proteins in
Insoluble materials (for example, cell
membranes) in samples
Fill both halves of lower buffer tank with
400 ml running buffer when running two
gels
Check buffer composition
conditions
Do not exceed recommended running
conditions
400 ml running buffer when running two
gels
in sample preparation and sample loading
buffers
precipitation, or other method)
instructions
sample
Dilute sample in sample buffer
Centrifuge samples to remove particulates
prior to sample loading
10x SDS-PAGE (1 L) 250 mM Tris, 1.92 M glycine, 1% SDS, pH 8.3
(catalog #161-0732)
Tris base 30.3 g
Glycine 144.1 g
SDS 10 g
diH2O to 1 L
Do not adjust the pH (~pH 8.3)
10x Native PAGE (1 L) 250 mM Tris, 1.92 M glycine, pH 8.3
(catalog #161-0734)
Tris base 30.3 g
Glycine 144.1 g
diH2O to 1 L
Do not adjust the pH (~pH 8.3)
10x Tris-Tricine (1 L) 1 M Tris, 1 M Tricine, 1% SDS, pH 8.3
(catalog #161-0744)
Tris base 121.1 g
Tricine 179.2 g
SDS 10 g
diH2O to 1 L Do not adjust the pH (~pH 8.3)
10x TBE (1 L) 890 mM Tris, 890 mM boric acid, 20 mM EDTA
(catalog #161-0741)
Tris base 107.8 g
Boric acid 55.0 g
EDTA 5.8 g
diH2O to 1 L Do not adjust the pH (~pH 8.3)