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).
Recombinant mouse LIF protein (Qk018)
£58.00 – £928.00
- Purity & bioactivity data
- Customer & collaborator data
- Resuspension & storage
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.
Result: mouse LIF (Qk018) migrates as a single band at 20 kDa in non-reducing (NR) and upon reduction (R) with β-mercaptoethanol
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 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.
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.
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.
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
Concentration was calculated using extinction coefficient at 280 nm. Example data from Qk018 batch #104278.