Recombinant zebrafish FGF2 protein (Qk002)


Recombinant zebrafish FGF2 protein (bFGF) is a 17 kDa biologically active domain of zebrafish fibroblast growth factor 2 protein, expressed in E. coli and purified to homogeneity. Our recombinant FGF2 protein is trusted by the Cambridge Stem Cell Institute, UK  to support the maintenance and differentiation of their stem cell cultures.

Qk002 Recombinant zebrafish FGF2 protein

Fibroblast growth factor 2 (FGF2) – also known as basic fibroblast growth factor (bFGF) – 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.

Recombinant zebrafish fibroblast growth factor 2 has been used extensively to support the maintenance of human stem cells1-3. This version of recombinant zebrafish FGF2 is used by the core facility at the Cambridge Stem Cell Institute, UK and historically by many of the stem cell groups based at University of Cambridge.

Summary: Mature domain of zebrafish Danio rerio FGF2/bFGF (residues 2-154, Uniprot: B3DGE3) expressed in E.coli and purified to homogeneity as described in Ludwig et al.2.

Form: Protein is provided in PBS without carrier protein at 2 mg/ml.

Molecular mass: ~17 kDa

Purity and bioactivity

For peace of mind that our recombinant zebrafish FGF2 protein (also known as bFGF) 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, reversed-phase chromatography, UV spectroscopy and endotoxin level testing.

To confirm the biochemical identity of our recombinant zebrafish FGF2 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 an 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 for each preparation of our recombinant zebrafish FGF2 protein.

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

Example data

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

Recombinant zebrafish FGF2 protein purity in SDS-PAGE

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 at 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 reversed-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 zebrafish FGF2 protein, the presence of this does not affect biological activity.

Recombinant zebrafish FGF2 protein purity in SDS-PAGE

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 17036 Da. Molecular mass from this analysis is 17035 Da, consistent with the calculated mass. The calculated molecular mass of dimeric protein is 34064 Da and this is represented in the mass spec with average molecular mass 34062 Da.

Recombinant zebrafish FGF2 protein has the expected molecular mass in MALDI mass spectrometry analysis

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 disulfide-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.

Share your thoughts!

Let us know what you think...

What others are saying

  1. Stem cell researcher, University of Oxford, UK

    FGF2 for pancreatic cancer sphere systems

    Stem cell researcher, University of Oxford, UK

    We have also used the FGF2 for pancreatic cancer sphere systems and it seems to support the growth of the cells as we would expect. University of Oxford, UK.

    (0) (0)

    Something wrong with this post? Thanks for letting us know. If you can point us in the right direction...




Your personal data will be used to support your experience throughout this website, to manage access to your account, and for other purposes described in our privacy policy.

Continue as a Guest

Don't have an account? Sign Up

Thaw the sample on ice, spin briefly and dilute with PBS as needed. Our proteins are supplied carrier protein-free. If compatible with your work, add a 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, 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.

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 that 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 0.093
Recovered concentration: 0.093 cm-1 x 20 / 0.935 cm-1 mg ml-1 = 1.99 mg / ml

Recovery of recombinant zebrafish FGF2 protein

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.

Go to Top