A Guide to Determining Protein Stability

Proteins play the most critical role in immunoassays. They act as the detection antigen or antibody that assay developers use to determine whether a disease state is present. Preserving these proteins is essential in determining accurate results. Surmodics™ IVD’s dried protein stabilizers and blockers are designed to preserve the conformation and activity of dried proteins coated on a wide range of surfaces, keeping antibodies and antigens at peak performance for long durations. At the same time, the blocking mechanisms in these reagents reduce non-specific binding of interfering proteins to maximize assay sensitivity.

Additionally, assay developers require in-solution protein stability for immunoassay applications. Conjugate stabilizers preserve activity of the enzyme (HRP or AP) and the antibody or antigen of the conjugate complex. This allows for the storage of conjugated proteins at lower use concentrations to facilitate optimization during assay development and manufacturing.

Surmodics IVD’s StabilZyme™ family provides unparalleled long-term stability of protein conjugates at working strength concentrations. Our formulations for HRP conjugates, AP conjugates and general protein applications ensure that assay developers have a complete set of tools to address the labile nature of each protein of interest. These reagents immediately improve protein stability assay performance and manufacturability by maintaining protein activity and longer shelf life.

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Factors that affect Protein Stability

It is generally believed that the structure of a protein and its environmental conditions determine protein stability. External factors such as temperature, pH and the presence of salts, metal ions or other contaminants may denature a protein. Proteins may also denature when absorbed to the side of a laboratory vessel. It is imperative the proteins are stored and used in an environment that stabilizes their native structure.

Proteins are used and stored in dry form as well as in-solution. Drying and freezing processes can result in denaturation of proteins if proper stabilization conditions are not utilized at crucial stages of preparation, storage and handling.

All the above factors profoundly affect the stability of protein and ultimately alter its functions and properties. This is dangerous as it can lead to precipitation, degradation, and denaturation that will render the protein useless.

Why is it important to understand protein stability?

Proteins are used extensively in numerous industrial and research applications. The stability of proteins is one the most critical factors when building protein-based assays. Thus, it is vital to have a clear understanding of protein stability as it plays a significant part on the protein of interest. The main goal of many in vitro diagnostic assays is to create a favorable support environment where protein samples can effortlessly retain their native states. When the proteins of interest take up the non-native congregating structures, they lose their normal function. Protein stability is essential for purifying, expressing, and storing proteins. It is also crucial in functional studies where native and recombinant proteins are being used.

Assays such as ELISA’s use proteins (e.g., antigens and antibodies) immobilized to a solid support along with detection proteins labeled with chromogenic or fluorescent molecules or conjugated with other biomolecules, such as horseradish peroxidase (HRP) or alkaline phosphatase (AP). Different types of proteins, enzymes and cells need proper strategies for handling and storage to maintain maximum functionality for diagnostic applications.

Having the necessary tools to preserve protein stability is essential. That’s where Surmodics IVD comes in. Our dried protein stabilizers and blockers and in-solution protein stabilizers have helped hundreds of assay developers preserve the stability of their proteins and overall immunoassays.

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Reagents for Dried Protein Stability

Surmodics IVD’s dried protein stabilizers and blockers (immunoassay stabilizers) offer assay developers unmatched stabilization of dried proteins and blocking efficacy in a one-step process to streamline manufacturing of immunoassays. We offer three distinct reagents for dried protein stability, StabilCoat™, StabilGuard™ and StabilBlock™. These reagents are the industry’s gold standard for stability and blocking efficacy. The result is immediate improvement of assay performance in a one-step process for streamlined manufacturing.

There are several technical advantages when using our dried protein stabilizers and blocker. When looking at their stability capability, all three of these dried protein stabilizers extended the shelf life of dried proteins on various surfaces, including polystyrene plates, latex beads, magnetics particles and nitrocellulose membranes. Additionally, they help to increase assay sensitivity. Furthermore, they offer assay developers increased signal-to-noise ratios across the assay range and are also provided in multiple formulations to optimize lower detection limits. These reagents also help to reduce background noise by eliminating non-specific binding from the sample matrix and other assay components.

Surmodics IVD’s Dried Protein Stabilizers:

Assay developers need numerous blocking mechanisms while selecting the antibody titration during assay optimization. Surmodics IVD’s dried protein stabilizers and blockers provide alternative blocking mechanisms to achieve the best signal-to-noise ratios for each assay.

With the introduction of StabilBlock, Surmodics now offers the best available reagent for reducing non-specific binding to boost immunoassay signal-to-noise ratios.

  • StabilCoat Immunoassay Stabilizer
    • Product Code: SC01
    • StabilCoat Immunoassay Stabilizer increases signal-to-noise ratios of assays through effective blocking of the plate while maximizing the binding capacity of the antigen/antibody epitopes.
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  • StabilGuard Immunoassay Stabilizer
    • Product Code: SG01
    • StabilGuard (BSA free) Immunoassay Stabilizers increase signal-to-noise ratios of assays through effective blocking of the plate while maximizing the binding capacity of the antigen/antibody epitopes.
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  • StabilBlock Immunoassay Stabilizer
    • Product Code: ST01
    • StabilBlock Immunoassay Stabilizer gives assay developers the best possible tool to lower non-specific binding and maximize the signal-to-noise ratios of immunoassays.
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Reagents for In-Solution Protein Stability:

Surmodics IVD’s in-solution protein stabilizers (conjugate stabilizers) offer assay developers the gold standard for stability of protein conjugates at working strength concentration for ELISA/EIA, ELISpot, RIA and immunoblot/western blot applications. Our StabilZyme HRP, StabilZyme Protein-Free and StabilZyme NOBLE stabilizers provide the assay developer a complete set of tools to stabilize different HRP conjugates for long term, in-solution stability.

There are several technical advantages when using our in-solution protein stabilizers. When looking at their protein stabilizing capability, these reagents extend the shelf life of antibodies, antigens and other proteins at working strength concentrations and offer retained activity of enzymes in solution for up to two years.

In addition, our StabilZyme in-solution protein stabilizers offer outstanding assay compatibility. Furthermore, we offer multiple formulations with different stabilizing mechanisms to satisfy different enzyme/protein requirements. This includes Protein-free and BSA-free formulations to satisfy the background requirements for specific assay systems. In addition, these reagents stabilize enzymes and control materials in a variety of assays including ELISA/EIA, ELISpot, RIA, immunoblots and microarrays applications.

Surmodics IVD’s In-Solution Protein Stabilizers:

  • StabilZyme HRP Stabilizer:
    • Product Code: SZ02
    • StabilZyme HRP Conjugate Stabilizer is specifically optimized for the HRP enzyme and is the gold standard for in-solution conjugate stability.
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  • StabilZyme SELECT Stabilizer:
    • Product Code: SZ03
    • StabilZyme SELECT Stabilizer is a general purpose in-solution protein stabilizer that can be used for HRP conjugates, standards and controls in immunoassay applications.
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  • StabilZyme NOBLE Stabilizer:
    • Product Code: SZ04
    • StabilZyme NOBLE Stabilizer eliminates protein interference and cross-reactivity that can result from the use of BSA in an assay system
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  • StabilZyme Protein-Free:
    • Product Code: SZPF
    • StabilZyme Protein-Free Stabilizer eliminates interference and cross-reactivity caused by proteins, delivering optimal performance for even the most sensitive immunoassays.
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  • StabilZyme AP Stabilizer
    • Product Code: SA01
    • StabilZyme AP Stabilizer specifically optimizes the AP enzyme and is the gold standard for in-solution conjugate stability.
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  • StabilZyme Protein-Free AP Stabilizer
    • Product Code: SAPF
    • StabilZyme Protein-Free AP Stabilizer eliminates interference and cross-reactivity caused by proteins, delivering optimal performance for even the most sensitive immunoassays.
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