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Blocker BSA Blocking Buffers

Solutions of bovine serum albumin to reduce background in immunoassays.

Blocker BSA Blocking Buffers

Thermo Scientific Blocker BSA Blocking Buffers are ready-to-use, 10X PBS or TBS solutions of bovine serum albumin protein for blocking steps in Western blot, ELISA, IHC and nucleic acid detection methods.

These blocking buffers are 10% (w/v) solutions of high-quality BSA that are useful for saturating excess protein-binding sites on membranes and microplates in immunoassays. Blocker BSA Buffers are most frequently diluted 10-fold (to 1% BSA) for initial testing, but other buffer concentrations can be beneficial for specific systems. Blocker BSA is usually more effective than nonfat milk blocking buffers for biotin-avidin systems because it contains a single purified protein that is devoid endogenous biotin.


  • Purified protein – 10% solutions of high-quality bovine serum albumin; a single purified protein provides fewer chances of cross-reaction with assay components than serum or milk solutions
  • Convenient – concentrated formulation saves storage space and can be diluted easily to obtain optimal blocking results for specific applications
  • Easy to use – no waiting for powder to dissolve with this ready-to-dilute liquid concentrate
  • Flexible – available in PBS and TBS formulations to suit a variety of applications

Product Details:

The purpose of the blocking step in an assay is to improve assay sensitivity by reducing background interference. However, unforeseen cross-reaction of detection reagents with blocking buffers is itself a cause of high background and low signal-to-noise ratios in assay systems. Because individual blocking buffers are not compatible with every system, a variety of blockers in both Tris-buffered saline (TBS) and phosphate-buffered saline (PBS) are available. The best blocking buffer for a specific experiment will bind to all potential sites of nonspecific interaction, eliminating background without altering or obscuring the epitope for antibody binding.

To optimize the blocking step for a particular immunoassay, empirical testing is essential. Using inadequate amounts of blocker will result in excessive background. Using an excessive blocker concentration can mask antibody-antigen interactions or inhibit the marker enzyme. For best results when developing a new immunoassay, test several different blocking agents for the highest signal-to-noise ratio in the assay. There is no single blocking agent that is ideal for every occasion because many factors can influence nonspecific binding, including various protein interactions unique to a specific assay system.


  1. Alegria-Schaffer, A., et al. (2009). Performing and optimizing Western blots with an emphasis on chemiluminescent detection. Methods Enzymol. 463:573-99.

Related Resources:

Blocking buffers for Western blot and ELISA -- technical guide
Blocking strategies for immunohistochemistry -- technical guide

Related Products:

All Blocking Buffers

Ordering Information
Product # Description Pkg. Size Instructions MSDS CofA Price
37520 Blocker BSA in TBS (10X)
Formulation: 10% (w/v) bovine serum albumin in Tris-buffered saline, pH 7.4, with Kathon preservative
Sufficient For: 40 blots or microplates at 1% and 30mL each
125mL MSDS for product #37520 Blocker BSA in TBS (10X) Certificate of Analysis for product #37520 Blocker BSA in TBS (10X) $130.00

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37525 Blocker BSA in PBS (10X)
Formulation: 10% (w/v) bovine serum albumin in phosphate-buffered saline, pH 7.4, with Kathon preservative
Sufficient For: 65 blots or microplates at 1% and 30mL each
200mL Product Instructions for product #37525 Blocker BSA in PBS (10X) MSDS for product #37525 Blocker BSA in PBS (10X) Certificate of Analysis for product #37525 Blocker BSA in PBS (10X) $140.00

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Instructions | MSDS | CofA
Product Instructions | MSDS | CofA  

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