Recombinant protein
FEBICO Heritage & Emerging Applications
Phycoerythrin (R-PE) is a naturally derived protein-based fluorophore, and it outperforms most synthetic dyes in several key respects:
- Brightness: R-PE has one of the highest extinction coefficients and quantum yields of any fluorescent label available. It is approximately 20–30× brighter than FITC under equivalent conditions, which makes it the preferred choice for detecting low-density surface markers or small cell populations.
- Large Stokes shift: The gap between R-PE's excitation (~496/565 nm) and emission (~578 nm) peaks reduces spectral spillover and background noise compared to dyes like FITC where excitation and emission are closer together.
- Natural origin: Unlike synthetic organic dyes, R-PE is a protein produced by living algae. Flogen's R-PE is derived from FEBICO-cultivated marine red algae, giving it a traceable, biological origin that some regulatory and research contexts increasingly value.
- Tandem dye versatility: R-PE's ability to act as a FRET donor makes it the backbone of a wide family of tandem dyes (PE-Cy5, PE-Cy5.5, PE-Cy7, etc.), extending a single 488 nm laser excitation across the entire visible and near-infrared spectrum. Synthetic dyes cannot replicate this energy transfer architecture.
The trade-off versus synthetic dyes is that R-PE is more sensitive to heat and light, requires careful cold-chain storage in liquid format, and is larger (~240 kDa), which can be a consideration in some proximity-based assay designs.
Manufacturing and sourcing
At Flogen, batch consistency is maintained through several interconnected practices:
Proprietary Purification Technology Our state-of-the-art facilities and proprietary purification processes are designed to deliver high-purity biomolecules with repeatable results. For Phycobiliproteins like R-PE, we use defined purity indices, for example, an A565/A280 absorbance ratio greater than 5.0, as a standard quality benchmark for every batch, ensuring each lot meets HPLC-grade purity before release.
Standardized Formulations We offer many of our products, including phycobiliproteins, in lyophilized (freeze-dried) formats. Lyophilization removes variability introduced by liquid storage, eliminates the need for ammonium sulfate precipitates that require dialysis, and produces a stable, homogeneous powder that is easier to characterize and reproduce consistently across batches.
Defined Storage and Stability Standards Each product is manufactured and packaged to meet defined shelf-life criteria. For example, our phycobiliproteins are guaranteed stable for 3 years when stored at 2–8°C, protected from light. This means our quality standards are built into every step from production through delivery.
Certificate of Analysis (COA) Per Batch We provide Technical Data Sheets (TDS), Certificates of Analysis (COA), and MSDS documents for each product, allowing customers to verify lot-specific performance data. You can access these directly through our website under Support → TDS/COA/MSDS.
Decades of Manufacturing Expertise As a specialty manufacturer with decades of experience in microalgae cultivation and bulk protein production, our team has deep process knowledge that supports tight manufacturing controls, from upstream cultivation to final conjugation and packaging.
If you have specific consistency requirements or are evaluating us for further manufacture or OEM purposes, we'd be happy to discuss custom validation protocols. Please feel free to reach out to us at flogensales@febico.com.tw or call +886 2 2655 8198.
Ordering & Documentation
Phycobiliprotein
All three are phycobiliproteins used as fluorescent labels, but they differ in their spectral properties and ideal use cases:
- R-PE (R-Phycoerythrin) has an excitation peak around 496/565 nm and emits at ~578 nm (orange). It is exceptionally bright and well-suited for detection of low-abundance targets. Best used with 488 nm or 532 nm lasers. Ideal for flow cytometry and bead-based assays like Luminex.
- APC (Allophycocyanin) is excited at ~650 nm and emits at ~660 nm (far-red). It pairs with red lasers (633 or 640 nm) and is the preferred choice for multicolor panels where spectral separation from PE-based dyes is needed.
- PerCP (Peridinin-Chlorophyll Protein) excites at 482 nm and emits at ~677 nm (far-red). It is used with 488 nm lasers and occupies a spectral space distinct from PE, making it useful in 3- or 4-color panels on single-laser instruments.
As a general guide: if you are running a single-color or 2-color assay on a blue-laser instrument, R-PE is often the first choice for brightness. For multicolor panels with both blue and red lasers, combining R-PE and APC gives excellent spectral separation. PerCP is valuable when you need a third color on the blue laser alone.
Yes. R-PE (Streptavidin RPE or antibody-conjugated PE) is the standard reporter fluorophore used in Luminex xMAP and similar bead-based multiplex platforms. Its exceptionally high quantum yield means it generates a strong signal even at the low antigen concentrations typical in bead-capture assays. Flogen's R-PE has been validated for use as a reporter in these systems. For Luminex applications we recommend our Streptavidin RPE, which can bind biotinylated detection antibodies directly, or our Lyo SMCC-RPE for customers who prefer to conjugate their own antibodies. Please refer to the individual product TDS for recommended working concentrations.
The purity of R-PE is typically assessed using the A565/A280 absorbance ratio (also called the purity index):
- A565/A280 > 5.0 — This is considered HPLC-grade or high-purity R-PE. This grade is required for antibody conjugation, as contaminating proteins will compete in the labeling reaction and reduce conjugation efficiency and yield.
- A565/A280 4.0–5.0 — Suitable for most direct detection applications in flow cytometry and immunoassays where the protein will be used as-is, not further conjugated.
- A565/A280 < 4.0 — Indicates the presence of non-fluorescent protein impurities. Not recommended for conjugation and may increase background noise in sensitive assays.
All Flogen R-PE products include the A565/A280 ratio on their Certificate of Analysis. If you are planning to perform your own conjugation, please specify this when requesting a quote so we can ensure the correct purity grade is supplied.
SMCC (succinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate) is a heterobifunctional crosslinker that creates a stable covalent bond between a protein and a thiol-bearing molecule such as a reduced antibody. In our Lyo SMCC-RPE and Lyo SMCC-APC products, the SMCC linker has already been attached to the phycobiliprotein, so you simply need to reduce your antibody (to expose free thiol groups) and mix — saving significant preparation time.
The choice between the two comes down to your instrument configuration and panel design:
- Lyo SMCC-RPE — Use when your instrument has a 488 nm or 532 nm laser and you want maximum brightness for detecting low-abundance targets. Best for blue- or green-laser based cytometers.
- Lyo SMCC-APC — Use when your instrument has a red laser (633/640 nm) or when you need spectral separation from PE-based channels in a multicolor panel. APC's far-red emission (~660 nm) is ideal for panels already using PE, FITC, or PerCP on the blue laser.
If you are designing a multicolor antibody panel and need both colors, you can conjugate separate antibodies to each, giving you two distinct detection channels from a single conjugation workflow.
1. Direct Multiplexing (Spectral Separation)Because different phycobiliproteins have widely separated emission peaks, they can be used simultaneously without their signals overlapping. A typical 3-color multiplex panel might use:PE for the orange channel ($575$ nm)APC for the red channel ($660$ nm)PerCP for the far-red channel ($677$ nm)
2. Tandem Dyes (The "Antenna" Effect)The most powerful use of phycobiliproteins in multiplexing is as donor molecules in tandem dyes. Scientists chemically link a phycobiliprotein (like PE) to a smaller organic cyanine dye (like Cy7).
How it works: The PE acts as an antenna, absorbing light at 488 nm and transferring that energy to the Cy7, which then emits light at a much longer wavelength (780 nm).The Result: You can use one single laser (e.g., the Blue 488 nm laser) to excite four different antibodies, each emitting a different color (PE, PE-Cy5, PE-Cy5.5, and PE-Cy7). This exponentially increases the number of targets you can measure at once.
3. Bead-Based Multiplexing (Luminex®)In bead-based assays, phycobiliproteins (usually R-PE) serve as the reporter dye.The system uses tiny beads dyed with different internal ratios of red and infrared dyes to identify the "target" (e.g., Bead #25 is for IL-6, Bead #42 is for TNF-alpha).R-PE is then used to label the detection antibody. Because PE is so bright, it can detect even a few molecules of the target protein captured on the bead surface, allowing for high-sensitivity multiplexing of up to 500 different analytes in one small well.
Streptavidin Conjugate
All three serve the same detection function (binding biotinylated targets) but differ in their fluorescent labels, excitation requirements, and emission wavelengths. The right choice depends on your instrument's laser configuration and your panel design:
- Streptavidin RPE (SAPE) — Excitation: 496, 546, 565 nm / Emission: 578 nm (orange). Compatible with 488 nm or 532 nm (blue/green) lasers. R-PE is exceptionally bright and is the standard reporter for Luminex bead-based assays. Choose this when brightness is the priority or when your assay uses a blue/green laser system.
- Streptavidin APC — Excitation: 650 nm / Emission: 660 nm (far-red). Compatible with red lasers (633 or 640 nm). Our Streptavidin APC is produced using cross-linked APC (cl-APC), which is chemically stabilized to prevent subunit dissociation at low concentrations — a key advantage for sensitivity in demanding assays. Choose this when your instrument has a red laser and you need spectral separation from PE- or FITC-based channels.
- Streptavidin FITC — Excitation: 488 nm / Emission: 520 nm (green). Compatible with 488 nm (blue) lasers. FITC is a smaller synthetic dye with a well-established history in flow cytometry and IHC. It is cost-efficient and suitable for straightforward single- or two-color experiments. Choose this when cost efficiency is important or when working on instruments without red laser capability and PE is already occupied in your panel.
As a general rule for multicolor flow cytometry panels: Streptavidin FITC and Streptavidin RPE can both be excited by the blue laser but occupy clearly separated emission channels (520 nm vs. 578 nm), making them compatible in the same panel. Adding Streptavidin APC on the red laser gives you a clean third detection channel.
Flogen's streptavidin conjugates have been validated across the following platforms:
- Flow cytometry: for detecting biotinylated primary or secondary antibodies on cell surfaces or intracellular targets
- Bead-based multiplex assays: including Luminex xMAP® and Illumina VeraCode®, where SAPE serves as the standard reporter fluorophore
- Microarray platforms: including Affymetrix GeneChip®, where SAPE is used to stain biotin-labeled cRNA after hybridization
- Immunohistochemistry (IHC): for fluorescent tissue staining using biotinylated detection antibodies
- Microplate-based immunoassays (ELISA-type): for fluorescent signal readout in plate-based formats
- Fluorescence immunoassays (FIA): across research and diagnostic workflows
All three conjugates — Streptavidin RPE, Streptavidin APC, and Streptavidin FITC — undergo biotin-binding activity checks and fluorescent intensity verification as part of Flogen's standard QC process.