Name: Theophyllin HSA Biotin Conjugate
Brand: Molecular Depot
SKU: B2021538
Price: 995.00 USD
Availability: InStock

<h2>What are protein conjugates in this category?</h2>
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Protein Conjugates are recombinant target proteins, such as receptors or other binding partners, labeled with biotin through site-specific Avi-tag enzymatic biotinylation or fused to an antibody Fc region, giving the protein a defined chemical handle for capture on a streptavidin-coated surface or purification via Protein A/G resin. This differs from Immunoglobulin Conjugates, where the conjugated molecule is an antibody itself; here, the protein being studied is the one carrying the conjugate, supporting applications like screening for binding partners or building a defined capture surface around your specific target.
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<h2 dir="ltr">What you will find:</h2>
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Enzyme-Linked Reporting Probes: High-purity target proteins conjugated to horseradish peroxidase or alkaline phosphatase for powerful chemiluminescent and colorimetric detection.
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Biotinylated Capture Complexes: Specialized macromolecular configurations engineered to exploit ultra-high-affinity streptavidin systems for sensitive target isolation and signal enhancement.
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Secondary Detection Systems: Calibrated protein links prepared to bind primary target molecules reliably, ensuring clear baseline identification in multi-tier immunoassay setups.
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<h2>How to choose protein conjugates</h2>
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Choose Avi-tag biotinylation for uniform, site-specific protein orientation
Avi-tag biotinylation enzymatically attaches a single biotin molecule to one lysine residue within a short, defined peptide sequence, producing a homogeneous product with consistent orientation when bound to a streptavidin-coated surface, unlike chemical biotinylation, which can label multiple, less predictable sites.
Choose an Fc-fusion conjugate for Protein A/G-based purification and capture
An Fc-fusion conjugate, with the Fc region of an antibody (commonly human IgG1) fused to your target protein, can be purified and captured using Protein A or Protein G resin, leveraging the same chemistry used elsewhere in antibody purification workflows.
Confirm whether bioactivity is preserved in the conjugated form
A biotinylated or Fc-fusion conjugate should report bioactivity similar to its unlabeled counterpart, and checking conjugate-specific binding or activity data, rather than assuming it matches the unlabeled parent protein, helps confirm the conjugation hasn't disrupted the protein's natural function.
Decide whether you need a combined multi-tag construct
Some protein conjugates combine an Fc-fusion region, an Avi-tag for biotinylation, and an additional purification tag like polyhistidine in a single construct, supporting multiple downstream uses, such as purification, capture, and detection, from one product.
Confirm degree of biotinylation if precise stoichiometry matters
Biotinylation is typically confirmed to a specific minimum percentage, such as 90% or higher, and checking this confirmed degree of labeling matters for applications sensitive to the exact biotin-to-protein ratio, such as some quantitative binding assays.
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<h2>Specifications context</h2>
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Avi-tag biotinylated proteins are typically confirmed to be at least 90% biotinylated, with the biotin attached to a single lysine residue within the Avi-tag peptide sequence, providing enhanced control over protein orientation in binding assays compared with chemical biotinylation approaches. As of 2026, biotinylated and Fc-fusion protein conjugates remain widely used tools for screening protein-protein interactions and antibody or small molecule libraries, leveraging the predictable, well-characterized attachment chemistry these conjugate formats provide.
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Protein Conjugates

Molecular Depot

Key Specifications

Theophyllin HSA Biotin Conjugate

Theophyllin HSA Biotin Conjugate (B2021538) from Molecular Depot couples theophylline, a methylxanthine bronchodilator, to biotinylated human serum albumin (HSA). Supplied as 1 mg of solution, it is used to capture theophylline on streptavidin surfaces for ELISA, lateral-flow and biosensor assays. Available from MBP, a registered vendor at leading US research institutions.