Recombinant mouse LIF protein (Qk018)


Recombinant mouse LIF (murine leukemia inhibitory factor) protein supports the derivation, propagation and expansion of mouse embryonic stem cells (ESC), and maintenance of pluripotency. Qkine mouse LIF protein is animal and carrier-protein free for highly reproducible results. Bioactivity was tested by colony formation assay and determination of Nanog expression (1).

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Recombinant mouse LIF (leukemia inhibitory factor) increases the robustness of mouse embryonic stem cell culture in feeder or feeder-free chemically defined culture systems. High-quality LIF contributes to successful and reproducible propagation of mouse ES cells.

Summary: Qk018 recombinant mouse LIF (Uniprot: P09056), expressed in E. coli and purified to homogeneity.

Molecular mass: 20 kDa

Form: Protein is provided lyophilized. Animal-free (AOF) and carrier protein-free.

Example data

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

SDS-PAGE shows mouse LIF migrates as a single band at 20 kDa

Purity and bioactivity

For peace of mind that our recombinant mouse LIF 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, UV spectroscopy and endotoxin level testing.

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

Research applications

iPSC/ESC maintenance

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 are 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: mouse LIF (Qk018) migrates as a single band at 20 kDa in non-reducing (NR) and upon reduction (R) with β-mercaptoethanol

Qk018 mouse LIF purity in SDS-PAGE

Purified recombinant protein (3 μg) was resolved using 15% w/v SDS-PAGE in reduced (+β-mercaptoethanol, R) and non-reduced conditions (NR) and stained with Coomassie Brilliant Blue R250. Data from Qk018 batch #104278.

Purity: mass spectrometry analysis

Result: Consistent with the calculated mass. No heterogeneity is present.

Mass spectrometry analysis of mouse LIF shows correct protein identity

Mass spectrometry is used to confirm the identity of the protein and reveal heterogeneity that may not be evident in SDS-PAGE analysis. The results are compared with the calculated mass of the protein with the assumption that all the cysteines are disulfide-linked. Data from Qk018 batch #104278.

Purity: endotoxin level determination

Result: Endotoxin level <0.005 EU/µg 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.

Mouse LIF supports ES cell colony formation

Recombinant mouse LIF (animal-free) supports mouse embryonic stem cell colony formation and has been benchmarked against LIF supplement from Supplier A in chemically-defined feeder-free culture.

Qk018 mouse LIF supports mouse ES cell propagation

Mouse LIF (Qk018) support mouse ES cell propagation in chemically-defined, feeder-free iPSC culture. Cultures are dissociated to a single cell suspension and plated at very low (clonal) density in defined media containing Qk018 mouse LIF or mouse LIF supplement from another supplier (Supplier A). The number of colonies that formed was determined after 4-5 days.

Our thanks to Leitch lab, MRC London Institute of Medical Sciences, Imperial College for mouse ES cell data and discussion.

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  1. Harry Leitch

    Flow cytometry analysis of Nanog-reporter positive mouse ES cells cultured using Qk018 mouse LIF vs. ESGRO

    Harry Leitch

    Flow cytometry was used to compare the percentage of Nanog-reporter positive mouse ES cells cultured in a chemically-defined, feeder-free iPSC culture media containing either Qk018 mouse LIF or ESGRO. Our results show that Nanog expression in mouse ES cells cultured with Qk018 mouse LIF was comparable to, if not potentially better than, ESGRO.

    Harry Leitch (MA MB BChir PhD MRCPCH), MRC London Institute of Medical Sciences, Imperial College.

    (0) (0)

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Please follow the handling guidance for lyophilized cytokines below to minimize loss of protein due to precipitation or adsorption to plastic. We advise storing the recombinant protein at very low pH before dilution in cell culture media or final working solutions. Low pH will also assist in maintaining the correct disulfide structure of the protein by minimizing disulfide bond exchange reactions.

  • Resuspension in physiological buffers may cause precipitation of stock solutions, hence we recommend dissolving our lyophilized cytokines in 10 mM HCl (1:1000 dilution of concentrated HCl) while keeping the protein concentration at 50 µg/ml or above, in order to avoid loss by adsorption to plasticware.
  • To ensure you recover all of the protein, let the sample sit for a few minutes with the solubilization buffer at room temperature and pipette gently up and down (avoid foaming).
  • Rinse the tube with some more 10 mM HCl and pool with the rest.
  • The protein is tolerant of some freeze and thaw cycles, but as always with proteins, it is better to aliquot and store frozen.
  • Our proteins 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 storage.

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 0.11
Recovered concentration: 1.1 mg / ml
Recovery: >100% due to routine over-fill

Recovery from the vial is demonstrated using UV recovery quantitation

Concentration was calculated using extinction coefficient at 280 nm. Example data from Qk018 batch #104278.

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