Recombinant human FGF2 protein (145 aa)


Qk025 Recombinant human FGF2 protein (145 aa) is a highly bioactive, shortform variant of human fibroblast growth factor 2 protein. Our recombinant FGF2 protein has been extensively optimized for production at high purity in E. coli and purified to homogeneity, providing a reliable option for regulation of ESC maintenance, as well as iPSC/MSC proliferation and differentiation.

Fibroblast growth factor 2 (FGF2) or basic FGF has a broad range of physiological roles including regulation of cell proliferation and differentiation. FGF2 is used to support the maintenance of human embryonic stem cells and proliferation and differentiation of induced pluripotent and mesenchymal stem cells.

Summary: Qk025 mature domain of human FGF2, basic FGF (145aa form comprising residues 144-288, Uniprot: P09038) expressed in E.coli and purified to homogeneity

Molecular mass: ~17 kDa

Form: Protein is provided frozen in PBS (carrier protein-free) at 1 mg/ml

Basic fibroblast growth factor, bFGF, FGF-β, FGF2, Fibroblast growth factor-basic, HBGF-2

1. Ludwig, T. E. et al. Derivation of human embryonic stem cells in defined conditions. Nat. Biotechnol. 24, 185–187 (2006).
2. Ludwig, T. E. et al. Feeder-independent culture of human embryonic stem cells. Nat. Methods 3, 637–646 (2006).
3. Chen, G., Gulbranson, D. R., Yu, P., Hou, Z. & Thomson, J. A. Thermal stability of fibroblast growth factor protein is a determinant factor in regulating self-renewal, differentiation, and reprogramming in human pluripotent stem cells. Stem Cells 30, 623–30 (2012).

Purity and bioactivity

For peace of mind that our recombinant human basic FGF / FGF-2 protein will work exactly the same way every day, from batch to batch and at any scale you need, we conduct extensive purity and bioactivity analysis, including SDS-PAGE, mass spectrometry, reverse phase chromatography, UV spectroscopy and endotoxin level testing.

To confirm the biochemical identity of our bFGF / FGF-2 protein and ensure that its purity meets our rigorous standards, we conduct SDS-PAGE on every protein batch in both reduced and non-reduced conditions and use appropriate loading and high sensitivity stains.

We confirm consistent bioactivity using a FGF-responsive firefly luciferase reporter assay in HEK293T cells. By knowing what the expected activity of the protein is and measuring calibrant alongside each batch of protein, we can use this bioassay to define a complete dose-response curve and check the EC50 value of the preparation.

Find out more about our extensive purity testing in the next tab.

Example data

Protein purity: SDS-PAGE in reduced and non-reduced conditions

Bioactivity: FGF-responsive luciferase reporter assay

Research applications

iPSC/ESC maintenance

iPSC/ESC differentiation

All our proteins are produced in our Cambridge, UK, labs.  We provide detailed quality data for each batch because we believe reliable, high quality cytokines and growth factors are critical for successful stem cell and organoid culture.  Please contact us with questions any time by email or phone +44 (0) 1223 491486 / US toll free 1-866 877 2185.

Order online and upload your PO or pay by credit card,  or email your PO to

We provide bulk orders and stock reservation for sensitive applications, please email us.

Our products are for research use only and not for diagnostic or therapeutic use.  Products are not for resale.

For final purity and activity tests on our proteins, we choose a vial at random and reconstitute as recommended.  Biochemical identity and purity is determined using SDS-PAGE, mass spectrometry and analytical reverse phase chromatography.  Bioactivity is quantified using an appropriate cell-based assay.  As stem cells are sensitive to endotoxin levels, we use a high resolution test to ensure endotoxin levels are at industry leading low levels (<0.01 EU per µg protein).  We also check that the correct amount of protein is recovered from the vial - it might sound basic but if you order 100 µg, we believe you should receive 100 µg so when you use the proteins you can rely on your calculated dilution.

Purity: SDS-PAGE

Result: FGF2 migrates as major band at 17 kDa in non-reducing (-βME) conditions and upon reduction (+βME). The higher molecular mass band at 35 kDa is a dimer that we always see in our highly purified human FGF2, the presence of this does not affect biological activity.

Purified recombinant protein (7 µg) was resolved using 15% w/v SDS-PAGE in reduced (+β-mercaptothanol, R) and non-reduced conditions (NR) and stained with Coomassie Brilliant Blue R250.

Bioactivity: luciferase reporter assay

Purity: mass spec analysis

Result: calculated molecular mass of FGF2 is 16310 Da.  Molecular mass from this analysis is 16310 Da, consistent with the calculated mass.  The calculated molecular mass of dimeric protein is 32620 Da and this is represented in the mass spec with average molecular mass 32617 Da.

MALDI mass spectrometric analysis is used to confirm the molecular mass of the intact protein and to reveal any heterogeneity that would not be evident in SDS-PAGE analysis. The results are compared with calculated mass of the protein with the assumption that all the cysteines are disulphide-linked. The different peaks represent different charge states of the protein.

Purity: endotoxin level determination

Result: Endotoxin level <0.005 EU/ug protein (below level of detection)

Stem cell cultures are sensitive to endotoxins1, which can be present in media, serum and as a contaminant on plasticware.  We optimize our protein production processes to ensure the lowest possible levels of endotoxin contamination.    Our endotoxin pass criteria are set at the industry leading <0.1 EU per ug protein and we aim for <0.01 EU per ug protein.  Endotoxin levels in our proteins are determined by an external expert microbiological testing services provider. 

1. A biological study establishing the endotoxin limit for in vitro proliferation of human mesenchymal stem cells (2017). Yusuke Nomura, Chie Fukui, Yuki Morishita, Yuji Haishima. Regenerative Therapy, 7, 45-51.

Thaw the sample on ice, spin briefly and dilute with PBS as needed.  Our protein are supplied carrier-protein free.  If compatible with your work, add carrier protein of your choice such as BSA, HSA or gelatin to further minimize loss by adsorption.  Spin in a microfuge for 5 minutes at maximum speed, and divide the solution into suitable aliquots and store at -80°C. We recommend that single-use aliquots should be prepared to avoid freeze-thaw cycles.

Every effort is made to ensure samples are sterile however we recommend sterile filtering after dilution in media or the final working solution.

  • The protein is tolerant of some freeze and thaw cycles, but as always with proteins, it is better to aliquot and stored frozen.
  • Our protein are supplied carrier-protein free.  If compatible with your work, add carrier protein of your choice such as BSA, HSA or gelatin to further minimize loss by adsorption.
  • Store in -80°C for long term storage. -20°C for short-term.

We check that the correct amount of protein is recovered from the vial – it might sound basic but if you order 100 µg, we believe you should receive 100 µg so when you use the proteins you can rely on your calculated dilution.

Recovery: protein quantitation

Result: UV spectrum shows full recovery of protein following aliquoting and lyophilization.

Absorbance at 280 nm: average 0.112
Recovered concentration:0.112 cm-1 x 10 /0.98 cm-1 mg ml-1 = 1.1 mg / ml
Recovery: 110% (>100% due to routine 10% over-fill of vials during aliquoting)

The sample was diluted 1:10 in 100 mM sodium phosphate pH 7.4 and the UV spectrum 340-220 nm measured in duplicate. Concentration was calculated using extinction coefficient at 280 nm