Stringent Quality Testing

To ensure that we deliver the highest quality products, our recombinant proteins undergo rigorous testing before they reach your hands.

Product Purity and Quantitation Testing table


Acceptance criteria for majority of proteins is greater than 95%
Quantity UV spec, SDS-PAGE
10 and 25 μg sizes are bottled at 0.1 or 0.2 mg/ml 
100 μg and larger sizes are bottled at a lot-specific concentration
Molecular Weight DTT-reduced and non-reduced SDS-PAGE
Mass Spec (for E.coli expressed proteins)
Microbiological Control 0.2 μm filtration prior to bottling
Endotoxin level Endotoxin tested by the LAL (Limulus Amoebocyte Lysate) assay 
Less than 0.1 ng per μg protein or 1 EU per μg protein


Recombinant proteins were run in SDS-PAGE under either DTT-reducing or non-reducing conditions, as indicated, to confirm purity of the recombinant protein was >95%.

Recombinant proteins run on an LC-Agilent 6230 Time-of-Flight Mass Spectrometer. Deconvoluted mass spectrums shown with predicted and observed molecular weights indicated.

Functional Testing

Based on the expected function of the protein, we test our recombinants in bioassays for quality control, to characterize the protein, and measure its activity. These bioassays include: proliferation, chemotaxis, neurite outgrowth, enzymatic activity, cytotoxicity, cytokine production, adhesion, and differentiation assays.

Recombinant Human OMG (Carrier-Free)



Figure A. 300 ng of human OMG, immobilized as a 3 μL droplet on a nitrocellulose-coated plate, completely inhibits neurite outgrowth of E13 chick DRG neurons induced by laminin substrate. Figure B. 3 μL droplet of buffer control (PBS) on a nitrocellulose-coated plate shows no inhibition of neurite outgrowth of E13 chick DRG neurons induced by laminin substrate.

Recombinant Mouse Syndecan-2 (Carrier-Free)



When mouse Syndecan-2 is immobilized at 5 μg/mL, human FGF-basic binds with EC50 of 2-8 ng/mL in a functional ELISA.

Stability Testing

Our recombinants are stability tested at different temperatures and time intervals to determine optimal storage, handling, and shipping conditions. Our testing shows that most of our recombinant proteins are able to withstand room temperature (RT) and 37°C for a week without losing activity. In addition, most recombinants are able to withstand four freeze-thaw cycles without losing activity.

Recombinant proteins were aliquoted in PBS pH 7.2 at 0.2 mg/ml. One aliquot was frozen and thawed four times (4x freeze/thaws), one was kept at RT, and one was kept at 37°C for one week. All samples were tested for bioactivity as compared to a control stored at 4°C.

Competitor and Internal Control Testing

To ensure you have full confidence when using our recombinant proteins, we internally compare new lots with previous lots for consistency. In addition, we also test our products against those available from competitors.

Recombinant Rat EGF (carrier-free)



Recombinant rat EGF induces a cytotoxic effect on human A431 epidermoid carcinoma cell line in a dose- dependent manner. BioLegend’s protein was compared side-by-side to the leading competitor’s equivalent product.

Recombinant Mouse M-CSF


Recombinant mouse M-CSF induces proliferation of M-NFS-60 cells in a dose-dependent manner. A new lot of protein was compared side-by-side to an internal gold standard.