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Blocking Agents

Non-Animal Blocking Agents

A major drawback of animal protein blocking solutions, such as BSA, casein and milk powders, is that they are derived from animal sources. The presence of animal proteins can often lead to high non-specific backgrounds as antigens and antibodies, generated in animals, interact with the “blocking” animal proteins.

Nap-Blocker™ Non-animal blocking protein preparation

For improved assay sensitivity, minimal non-specific binding, and a high signal-to-background ratio. NAP-BLOCKER™ ensures no crossreaction with your animal source antigens and antibodies, due to being 100% free of animal proteins. NAP-BLOCKER™ is easy to use and generates high publication quality blots.

The absence of protein eliminates problems associated with traditional protein based blockers, such as crossreactivity and interference from glycosylated proteins.

Eliminates any concern associated with regulatory compliance issues where use of animal source components are restricted. Furthermore, Protein-Free™ Blocking Buffer is compatible with antibodies and avidin/biotin based systems and results in high signal to background ratios.

For user’s convenience Protein-Free Blocking Buffers are supplied in widely used TBS (Tris-buffered saline at pH 7.5) and PBS buffers (phosphate-buffered saline at pH 7.5) as well as in separate formulations containing Tween®

20 for improving blocking efficiencies. FEATURES • Protein free blocking agent

• Eliminate cross reactivity with animal source antibodies • High signal to background ratios

• Four convenient formats, with and without detergent • Ready-to-use


• Suitable for Western blot and ELISA applications PART NO.


Figure 7: Comparison of NAP-BLOCKER™ and milk powder. Protein lysates were transferred to PVDF membranes and blocked for 90 minutes as indicated. The membranes were probed for actin and subsequently exposed to film for 20 minutes.

NAP-BLOCKER™ is free from biotin and other cross-reacting agents present in most of the animal source blocking agents.

NAP-BLOCKER™ ensures uniform blocking without non-specific binding. It is simple to use with improved results compared to milk powder preparations.

NAP-BLOCKER™ is supplied as a pre-made [2X] solution; simply dilute with any buffer and block nitrocellulose or PVDF membranes. Alternatively, NAP-BLOCKER™ is supplied in PBS or TBS buffers.


• Non-animal protein blocking agent • 2X concentrated solution

• Uniform blocking with reduced background staining APPLICATIONS

• For Western blots, dot blots, ELISA and assay development PART NO.


786-190 786-190P 786-190T



Protein-Free™ Eliminates protein related cross-activity

Protein-Free Blocking Buffer does not contain protein; it is a proprietary formulation of non-protein agents that eliminates nonspecific binding sites in ELISA, blotting, immunohistochemistry and other applications.


2 x 500ml 2 x 500ml 2 x 500ml

786-664 786-665 786-662 786-663

Protein-Free Blocking Buffer-PBS Protein-Free Blocking Buffer-PBST Protein-Free Blocking Buffer-TBS Protein-Free Blocking Buffer-TBST


500ml 500ml 500ml 500ml

Non-Sera Animal Protein Blocking Agents

FISH-Blocker™ Uses fish proteins to eliminate cross reactivity

FISH-Blocker™ is a blocking agent that uses a fish protein as the primary blocking agent. The use of a fish protein, a non-mammalian protein, eliminates or minimizes the interaction of antibodies raised in mammals. FISH-Blocker™ is one of the best blocking agents for immunoassays and it offers an alternative to milk-based blocking agents, minimizing the risk of non-specific binding of antibodies during the immunodetection process and lowering the background.


• A non-mammalian protein to elimate non-specific binding • High signal to background ratio • Ready-to-use


• Suitable for Western blot and ELISA applications PART NO.


786-675 786-674

FISH-Blocker™ in PBS FISH-Blocker™ in TBS


500ml 500ml

Astral Scientific Product Guide August 2015

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