IEF and 2-D Protein Standards



Isoelectric focusing (IEF) protein molecular weight standards are a mixture of native proteins with isoelectric points (pI) ranging from 4.45 to 9.6, providing reproducible pI calibration in native PAGE or agarose IEF gels. 2-D SDS-PA

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IEF Standards

Isoelectric focusing (IEF) protein standards allow dependable and reproducible pI calibration in native polyacrylamide or agarose IEF gels. Our IEF protein standards are a mixture of nine native proteins with pI ranging from 4.45 to 9.6. Five of the nine proteins are naturally colored to aid in monitoring the focusing. These standards are provided in a stable aqueous solution, and need no reconstitution or dilution prior to use.

Constituent Proteins of IEF Standards*

Protein Color pl
1. Cytochrome c Red 9.6
2. Lentil lectin (3 bands) 7.8, 8.0, 8.2
3. Human hemoglobin C Red 7.5
4. Human hemoglobin A Red 7.1
5. Equine myoglobin (2 bands) Brown 6.8, 7.0
6. Human carbonic anhydrase 6.5
7. Bovine carbonic anhydrase 6.0
8. β-Lactoglobulin B 5.1
9. Phycocyanin (3 bands) Blue 4.45, 4.65, 4.75

* Because the IEF protein standards are in native form, they cannot be used with reducing or denaturing agents such as urea, β-mercaptoethanol, or dithiothreitol. For calibration of IEF tube gels containing urea, use 2-D SDS-PAGE standards.

2-D SDS-PAGE Standards

These unique protein standards provide calibrated references for the pI and molecular weight of proteins in 2-D SDS-PAGE applications. They consist of seven reduced, denatured proteins that can be visualized with silver or Coomassie Blue staining. No dilution is required.

Constituent Proteins of 2–D SDS-PAGE Standards

Protein pl MW
1. Hen egg white conalbumin  6.0, 6.3, 6.6 76,000
2. BSA  5.4, 5.5, 5.6 (empirically determined) 66,000
3. Bovine muscle actin 5.0, 5.1 (empirically determined) 43,000
4. Rabbit muscle GAPDH
8.3, 8.5 36,000
5. Bovine carbonic anhydrase  5.9, 6.0 31,000
6. Soybean trypsin inhibitor  4.5 21,500
7. Equine myoglobin
7.0 17,500

Precision Plus Protein™ Standard Plugs

Precision Plus Protein Standards are available cast into 1 mm thick agarose plugs for easy storage, handling, and loading. They come in easy-to-use snap-off molds in packs of 24 (one application per plug), allowing quick and clean loading of molecular weight standards on any gel. These plugs can be used on vertical 2-D gels with no reference well.

These plug protein standards are unstained. Loading concentrations have been optimized for staining with SYPRO Ruby, Silver Stain Plus™, or Bio-Safe™ Coomassie Blue.

Features and Benefits of Precision Plus Protein Standard Plugs

  • Precast for ease of use — just snap, twist, and load the plug onto a gel
  • Absolute molecular weight accuracy, confirmed by mass spectrometry
  • Ideal ten-band range from 10 kD to 250 kD, with 3 high-intensity reference bands (25 kD, 50 kD, and 75 kD) for instant gel orientation
  • Molecular weights that never change, so band sizes are easy to remember
  • High r2 value, >0.995, allowing accurate molecular weight determination
  • Known concentration of protein in each band, allowing quantitation capability
  • Strep-tag amino acid sequence for detection and molecular weight determination on western blots



MW size range
Varies by standard
Stain type
Number of applications
Depends on staining method
IEF: 250 µl; 2D: 500 µl
Shelf life
12 months at –20°C




Use the filters below to refine results!

(Discontinued) IEF Standards
250 μl, pI range: 4.45–9.6, phycocyanin, β-lactoglobulin B, bovine and human CA, equine myoglobin, human hemoglobin A and C, lentil lectin, and cyt C
500 μl, 17,500–76,000 MW range, pI 4.5–8.5, unstained mixture of myoglobin, trypsin inhibitor, CA, GAPDH, actin, BSA, and conalbumin
Pkg of 24, 1 mm thick agarose plugs containing ten Strep-tagged, recombinant proteins (10–250 kD), including three reference bands



Number Description Options
The Little Book of Standards, Rev D
Protein Standards for Electrophoresis and Blotting Brochure, Rev D
Protein Standards Application Guide, Rev G
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Instruction Manual, IEF Standards, Rev F
Instruction Manual, 2-D SDS-PAGE Standards, Rev A
Instruction Manual, Precision Plus Protein™ Standard Plugs, Unstained, Rev C