Are you ready to make the switch to BioLegend’s recombinant proteins? Now’s your chance to win a Nintendo Switch!


Why Switch?

  • We manufacture over 700 bioactive recombinant proteins at our headquarters in San Diego, CA.
  • We provide purified human, mouse, and rat recombinant proteins, including cytokines, chemokines, and growth factors.
  • Every lot of our proteins undergoes rigorous quality testing and bioassay validation.
  • We price our recombinants effectively to help maximize your budget.

If you’ve made the switch to BioLegend recombinant proteins, you can submit your entry to win a Nintendo Switch.


Fill out a short survey and you will be entered into a raffle to win one of the three Nintendo Switches. Drawings will be held at the end of June, July, and August.


  • One entry per order.
  • Order must contain carrier-free or animal-free bioactive recombinant protein to be eligible.
  • Orders must be placed (or have been placed) between April 15, 2019 and August 31, 2019.  
  • Void where prohibited. It is the responsibility of the submitter to adhere to their institution's policies and guidelines.
  • Available to direct-end users in USA, Canada, UK, Ireland, Germany, Austria, Switzerland, France, Belgium, Netherlands, and Luxembourg. End-users in China, Japan, and Australia are eligible if they place a qualifying order through our exclusive distributors: Dakewe Biotech Co. (China), Tomy Digital Biology Co., Ltd. (Japan), Australian Biosearch (Australia).
  • Not to be combined with other offers or promotions.
  • Offer ends August 31, 2019.

Prior to performing bioassay validation and stability testing, we test each recombinant protein for product purity and quantification. In the table below you can find examples of the attributes tested, the test performed, and some acceptance criteria used to ensure that our customers are confident they are receiving the highest quality reagents.

Parameter Testing


SDS-PAGE, FPLC, (>95%)



Molecular Weight

DTT-reduced and non-reduced SDS-PAGE

Microbiological Control

0.2 μm Filtration

Endotoxin Level

LAL Assay (<0.1 ng/μg protein or <1 EU/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.

Each lot of our bioassay-validated recombinant proteins undergoes quality testing by functional assay to ensure the protein exhibits appropriate activity within a biologically relevant system. In this way, we ensure our proteins will perform within your experimental system. Some applications we test our proteins for include:

  • Activation
  • Binding
  • Chemotaxis
  • Cytokine Production
  • Cytotoxicity
  • Differentiation
  • Expansion
  • Growth
  • In vivo Assays
  • Inhibition
  • Polarization
  • Proliferation
  • Signaling
  • Standard Cell Culture
  • And many more...

Inhibition Assay


Recombinant Human TGF-β1

Proliferation of HT-2 cells induced by mouse IL-4 is inhibited by human TGF-β1.

We offer the majority of our recombinant proteins in a convenient, ready-to-use liquid format, which have a comparable shelf-life to lyophilized proteins.


Advantages of Liquid Recombinant Proteins:


  • Ready-to-use
  • No buffer preparation
  • No pH adjustment
  • No filtration
  • Reduced chance for contamination
  • No risk of protein aggregation during reconstitution


We perform extensive stability testing to ensure that each of our proteins is stable in a liquid format when handled and stored properly. In most cases, our liquid format recombinant proteins exhibit superior in-use shelf life when compared with competitor lyophilized proteins. If extended storage is desired, our proteins typically possess comparable long-term stability to competitors when stored at -80°C.


BioLegend (Liquid)

Competitor A (After Reconstitution)

Competitor B (After Reconstitution)


12 months

3 - 12 months

3 months


6 months

3 - 12 months

3 months


1-3 months

1 week

1 month

Stability Testing

Each recombinant protein released undergoes extensive stability testing to ensure product performance over the reagent’s entire shelf life.

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.

Long-Term Stability Testing

We periodically retest our recombinant proteins at later time points and have shown that some recombinant proteins retain their activity even after 10 years in storage at -80°C.

Recombinant proteins stored at -80°C for 10 years were tested for bioactivity as compared to a fresh competitor  lyophilized protein.

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