Cross-Linked Allophycocyanin (cl-APC)| High-Purity Fluorescent Label for Flow Cytometry & Immunoassays

In cl-APC, the protein subunits are covalently cross-linked using a controlled chemical process, locking the trimeric structure in place regardless of dilution. The result is an APC format that maintains full fluorescent brightness and spectral integrity even after a 60× dilution from its stock concentration, a critical performance advantage for demanding applications in flow cytometry, diagnostic reagent manufacturing, and tandem dye production.

Flogen cl-APC is produced at ultra-high concentration (21.4 mg/mL, exceeding the industry standard of ≥10 mg/mL) and manufactured at scale up to 100 g per batch, making it the choice for industrial and commercial customers requiring a reliable, high-volume supply of premium APC raw material.

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Structural Stability at Low Concentrations — The Core Advantage The defining property of cl-APC is that its trimeric structure remains intact even at the very low working concentrations used in real-world assays. Standard APC dissociates under these conditions, producing a dimmer, less consistent signal. cl-APC maintains its structural integrity and fluorescence performance after a verified 60× dilution, giving you assay results that are both brighter and more reproducible than standard APC.

Cross-Link Rate Exceeds Industry Benchmark Flogen cl-APC achieves a cross-link rate of 1.30, against an industry specification threshold of ≥ 1.2. A higher cross-link rate correlates with greater resistance to subunit dissociation, providing an additional performance margin over minimally compliant material from other suppliers.

Ultra-High Concentration — More Than Twice the Industry Standard Flogen cl-APC is concentrated to 21.4 mg/mL, compared to the typical commercial specification of ≥10 mg/mL. This ultra-high concentration stock means you work with smaller volumes in your formulation process, reducing buffer dilution effects and providing greater flexibility in reagent design. It also simplifies logistics — more active material per vial, fewer shipments.

High Spectral Purity Verified by UV-Vis Every lot is characterized by UV-Vis spectroscopy and released against defined purity criteria: A650/A280 ≥ 5.0 and A650/A620 ≥ 1.5. Lot values consistently exceed these specifications (5.14 and 1.56 respectively), confirming a high proportion of intact, fluorescently active protein relative to non-fluorescent contaminants.

Industrial-Scale Production Capacity With a manufacturing capacity of up to 100 g per batch, Flogen is one of the few suppliers capable of supporting industrial-scale cl-APC demand reliably. This makes us a suitable long-term raw material partner for diagnostic kit manufacturers, reagent companies, and tandem dye producers who cannot afford supply interruptions.

Lot-to-Lot Consistency for Commercial Operations All critical quality attributes — concentration, cross-link rate, purity ratios, and spectral properties — are monitored across every production batch. Our manufacturing process is designed to produce the same material every time, reducing the re-validation burden when transitioning between lots in regulated or semi-regulated manufacturing environments.

Ideal Raw Material for Streptavidin and Antibody Conjugation cl-APC's structural stability makes it a superior raw material for conjugation compared to standard APC. Because the trimer does not dissociate during the conjugation process or at the working concentrations of the final conjugate, your cl-APC antibody or streptavidin conjugate will deliver brighter and more consistent signal than the equivalent standard APC conjugate — particularly at the low concentrations used in flow cytometry.

Tandem Dye Manufacturing (APC-Cy5.5, APC-Cy7, APC-R700) cl-APC is the superior raw material for producing APC-based tandem fluorophores. In tandem dye configurations, APC acts as the FRET donor and must maintain its trimeric structure throughout both the conjugation process and the final use conditions. Standard APC that dissociates during tandem production or at assay working concentrations produces inconsistent FRET efficiency and dimmer far-red/near-infrared signal. cl-APC locks the trimer in place, ensuring predictable FRET performance and brighter, more consistent tandem dye lots — a critical quality parameter for diagnostic manufacturers.

Streptavidin cl-APC Conjugate Production cl-APC is the raw material used in Flogen's own Streptavidin APC (Cat. No. 4SA). For OEM customers who perform their own conjugation, cl-APC provides a stable, high-purity APC substrate for producing streptavidin, antibody, or other protein conjugates for bead-based multiplex assays (Luminex xMAP®), flow cytometry, and fluorescence immunoassays. The stability advantage of cl-APC is fully preserved in the final conjugate.

Diagnostic Reagent and Kit Manufacturing For IVD manufacturers and commercial kit producers, cl-APC provides the supply reliability, lot-to-lot consistency, and structural performance required for regulated product development. The combination of 100 g/batch production capacity, defined release specifications, and COA documentation for every lot supports both internal quality systems and regulatory submissions. Custom pack sizes and documentation packages are available on request.

Immunohistochemistry (IHC) — Fluorescence cl-APC conjugated to detection antibodies or streptavidin performs well in fluorescence IHC applications, particularly for low-abundance target detection in tissue sections where maximal signal-to-noise is essential. Its far-red emission (662 nm) is cleanly separated from DAPI, FITC, and most green/yellow fluorophores, enabling unambiguous co-localization analysis in multiplexed tissue panels