Support & Resources


CF® Dye & Other Bioconjugates

Biotium offers bioconjugates for a variety of applications, available with our bright & photostable CF® Dyes and other labels. Jump to a section below to learn more:

Apoptotic cell marker
AchR probe labels neuromuscular junctions
Plasma membrane probes & endocytic tracers
Glycoprotein probes, cell surface stains
Fluid phase tracers
For probe synthesis, TUNEL assay, or receptor probes
F-Actin stain for cytoskeleton
Biotinylated probes, labeled streptavidin & biotin
Conjugated with our superior CF® Dyes and other labels


Annexin V is a 36 kDa protein that has high affinity for phosphatidylserine (PS). During apoptosis, PS is translocated from the inner to the outer leaflet of the plasma membrane, where it can be stained by fluorescent conjugates of Annexin V. We offer Annexin V labeled with a wide selection of CF® Dyes and other labels, including Near-IR CF® Dye Annexin V Conjugates. We also offer Annexin V Kits with other apoptotic or necrotic cell stains.

Annexin staining is calcium-dependent, and is traditionally performed in an optimized Annexin Binding Buffer. Annexin conjugates also can be used to stain cells in culture medium without a wash step for real-time apoptosis monitoring. Annexin can be fixed with formaldehyde after staining as long as calcium is included in all buffers. However, Annexin staining cannot be performed on fixed cells or tissues. For fixed cell apoptosis stains, see our TUNEL Assays.

Apoptotic HeLa cells stained with NucView 488 caspase-3 substrate (green) and CF594 Annexin V (red).
NucView 405 CF488A Annexin RedDot
RedDot™ 1 (red) in live HeLa. Apoptotic cells are stained with NucView® 405 (blue) and CF®488A Annexin V (green).

Annexin V Conjugates

Annexin V Conjugates• Wide selection of CF® dyes, R-PE, biotin, and other labels
• 50 ug/mL in 10 mM Tris, 1 mM EDTA, 30 mM NaCl, 1 mg/mL bovine serum albumin, 0.1% sodium azide, pH 7.5
CF® Dye Annexin V Conjugates, Azide Free, Lyophilized• Azide-free for no-wash, real-time live cell imaging in culture medium
• Choice of twelve CF® dyes
Near-IR CF® Dye Annexin V• Lyophilized, preservative-free
• Choice of five near-IR CF® dyes
Annexin V (His Tag)• Recombinant Annexin V with or without His Tag expressed from E.coli
5X Annexin Binding Buffer• Concentrated buffer optimized for Annexin V binding

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Alpha-bungarotoxin is a polypeptide snake toxin that binds to the nicotinic acetylcholine receptor found at the neuromuscular junction with high affinity. Fluorescent alpha-bungarotoxin can be used for labeling of nicotinic acetylcholine receptors at neuromuscular junctions in tissue sections. Alpha-bungarotoxin may also be used for detection of GABA A receptor subsets in cells, or for labeling recombinant proteins that express the alpha-bungarotoxin binding site (BBS) epitope tag.

We offer α-bungarotoxin conjugated to a wide selection of CF® Dyes and other labels, as well as unconjugated α-bungarotoxin.

  • Choose from 9 bright and stable CF® Dye colors or other labels
  • Dye options for super-resolution and 2-photon imaging
Neuromuscular junction endplate in rat skeletal muscle cryosection stained with CF®594 α-bungarotoxin (red). Nuclei are stained with DAPI.
Neuromuscular junction in section of rat skeletal muscle stained with CF®633 α-bungarotoxin (magenta). Nuclei are stained with DAPI (cyan).

α-Bungarotoxin Conjugates

CF® Dye & Other α-Bungarotoxin Conjugates• Choice of popular CF® dye colors or a selection of classic fluorophores
Biotin-XX-α-Bungarotoxin• Biotinylated α bungartoxin
α-Bungarotoxin• Unconjugated α-bungarotoxin, potent inhibitor of the motor endplate acetylcholine receptor

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Cholera Toxin Subunit B Conjugates
Cholera toxin subunit B binds to ganglioside GM1 in lipid rafts on the plasma membrane. Cholera toxin subunit B is reported to be internalized by clathrin-dependent and independent pathways depending on cell type. We offer cholera toxin subunit B conjugated to a selection of CF® Dyes. The conjugates can be used to label lipid rafts on the cell surface, track endocytic vesicles, and as a retrograde neuronal tracer.

Transferrin Conjugates
Transferrin is a glycoprotein iron carrier that delivers iron to vertebrate cells via receptor-mediated endocytosis. After binding to its receptor on the cell surface, transferrin is rapidly internalized by invagination of clathrin-coated pits. Inside endocytic vesicles, the acidic environment favors dissociation of iron from the transferrin-receptor complex. Following the release of iron, the apotransferrin is recycled to the plasma membrane where it is released from its receptor to scavenge more iron. We offer human transferrin labeled with a selection of our bright and photostable CF® Dyes for imaging of recycling endosomes by microscopy.

HeLa cells were surface labeled with CF™488A cholera toxin B (green) at 4°C, then fixed, permeabilized, and stained with DAPI (blue).
U87-MG cells were incubated with CF®680R transferrin (red), CF®488A dextran (green), and Hoechst 33342 (blue) for 30 minutes at 37°C, washed and imaged.

Cholera Toxin & Transferrin Conjugates

CF® Dye Cholera Toxin• Binds lipid rafts, can be used as endocytosis probe or neuronal retrograde tracer
• Available with a large choice CF® dye colors
CF® Dye Human Transferrin• Trace recycling endosomes
• Available with a selection of popular CF® dye colors

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Lectins are carbohydrate binding proteins that recognized specific sugar moieties on cell surface glycoproteins. Concanavalin A (Con A) and wheat germ agglutinin (WGA) can be used to selectively stain the cell surface of live cells, and withstand fixation and permeabilization. When cells are fixed and permeabilized before staining, fluorescent lectins stain both cell surface and organelles in the secretory pathway. WGA also is a live cell Gram stain for bacteria, while Concanavalin A and WGA conjugates can be used to stain cell wall and bud scars in yeast. See our Microbiology Technology Page for more information.

Other lectins may be used markers for specific cell types. For example, Lycopersicon esculentum (Tomato) lectin (LEL, TL) is a known marker for blood vessels and microglial cells, while Ulex europaeus agglutinin I (UEA I) is a marker for endothelial cells and incompletely differentiated gastrin cells.

View Biotium’s full selection of lectin CF® Dye conjugates below.

Live HeLa cells stained with CF®594 ConA (red) and Hoechst 33342 (blue).
S. cerevisiae stained with CF®594 Con A (red) and CF®488A WGA (green).
E. coli and Salmonella co-culture stained with DAPI (blue) and CF®633 WGA (red).
Staining of rat brain cryosection with CF®488A LEL, TL.

Lectin Conjugates

CF® Dye Concanavalin A (Con A)• Cell surface stain for yeast, fungi, and mammalian cells
• Selectively binds to a-mannopyranosyl and a-glucopyranosy residues
• Available with a wide selection of CF® Dyes
CF® Dye Wheat Germ Agglutinin (WGA)• Cell surface stain for mammalian cells and gram+ bacteria
• Also stains yeast bud scars
• Has high affinity for sialic acid and N-acetylglucosamine
• Choose from a wide selection of CF® Dyes or HRP
CF® Dye Peanut Lectin (PNA) from Arachis hypogaea• Specific for terminal β-galactose and binds preferentially to galactosyl (β-1,3) N-acetylgalactosamine
• Choice of 4 CF® dye colors
CF® Dye Lycopersicon Esculentum (Tomato) Lectin (LEL, TL)• Marker for blood vessels and microglial cells
• Binds to [GlcNAc] 1,3-N-acetylglucosamine, glycophorin, and Tamm-Horsfall glycoprotein
• Used to study tumor angiogenesis or tracing neovascular development in xenograft models
• Choice of 5 CF® Dyes or biotin
CF® Dye Ulex Europaeus Agglutinin I (UEA I)• Marker for human endothelial cells and incompletely differentiated gastrin cells
• Binds to glycoproteins and glycolipids containing α-linked fucose residues
• Choice of 5 CF® Dyes or biotin
CF® Dye Phaseolus Vulgaris Leucoagglutinin (PHA-L)• Used to stimulate lymphocyte and T cell proliferation
• Choice of 5 CF® Dyes or biotin
CF® Dye Datura Stramonium Lectin (DSL)• Binds to (beta-1,4) linked N-acetylglucosamine oligomers
• Choice of 5 CF® Dyes or biotin

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Dextrans are water soluble branched-chain polysaccharides. Fluorescently labeled dextrans are used as markers for trafficking of fluid phase endocytic cargo to lysosomes. They are also used as tracers for epithelial and endothelial permeability. They can also be used as microinjected tracers for neuronal morphology. CF® Dye Dextrans are available with a variety of dye colors and molecular weights ranging from 10,000 to 250,000.

Note: While formaldehyde fixation preserves the localization of dextrans in endosomes, the labeling generally cannot tolerate detergent permeabilization, likely because the dextran molecules remain in the fluid phase and do not associate closely enough with cellular proteins to become cross-linked by fixative.

CF® Dye Bovine Serum Albumin (BSA) also can be used as a tracer for protein uptake and permeability.

CF® Dye Hydrazides are water soluble dyes that can be used as microinjected cytoplasmic tracers or fluid-phase markers. Hydrazides also can be used for labeling aldehyde or ketone groups, such as carbohydrate molecules after peroxidation with periodate. However, for this application we recommend using CF® Dye aminooxy forms, which are more reactive toward these groups than hydrazide forms. For 2D-DIGE platform, we recommend CFDI hydrazides. Also see our full selection of polar tracer dyes.

Live HeLa cells incubated with CF®568 Dextran 10,000 MW (red), showing accumulation of the probe in endosomes.

CF® Dye Dextrans

CF® Dye Dextran, 3500 MWUV-excitable CF®350
CF® Dye Dextran, 10,000 MWAvailable with a wide selection of CF® Dye colors
CF® Dye Dextran, 40,000 MWGreen fluorescent CF®488A,
near-IR CF®680, CF®750 or CF®770
CF® Dye Dextran, 70,000 MWBlue fluorescent CF®350,
Green fluorescent CF®488A,
Far-red fluorescent CF®633,
near-IR CF®680, CF®750 or CF®770
CF® Dye Dextran, 150,000 MWGreen fluorescent CF®488A,
near-IR CF®680, CF®750 or CF®770
CF® Dye Dextran, 250,000 MWGreen fluorescent CF®488A,
near-IR CF®680, CF®750 or CF®770
Don’t see the color you’re looking for? Contact us and let us know, we regularly add new conjugates to our catalog on request.


CF® Dye BSAGreen fluorescent CF®488A, red fluorescent CF®594, far-red fluorescent CF®640R, or near-IR fluorescent CF®680

CF® Dye Hydrazides

CF® Dye Hydrazide• Fixable polar tracers
• Wide selection of bright, photostable, and highly soluble CF® dye colors

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Labeled Nucleotides

Labeled nucleotides can be used to synthesize labeled DNA probes for in situ hybridization and nucleic acid blotting applications. Labeled dUTP also can be used for TUNEL assay (also see our CF® Dye TUNEL Assay Kits). We also offer nucleotides linked to other fluorophores and biotin. Aminoallyl nucleotides can be used to introduce free amine groups into probes for subsequent labeling with reactive dyes or biotin.

Bromine and digoxygenin (DIG) labeled nucleotides can be detected using specific antibodies. Bromo-deoxyuridine (BrdU) can be used to monitor DNA synthesis in cells (see our anti-BrdU antibodies).

Labeled cAMP

Fluorescently-labeled cAMP analogs have been imaged bound to the cAMP receptor on the surface of Dictyostelium cells.

Interphase profiling of human chromosome 1 using a selection of Biotium’s dUTP conjugates. Image courtesy of Ramesh Babu, InteGen LLC. See the highlighted citation to learn more about this image.

Labeled Nucleotides

CF® Dye Nucleotides• dUTP, dCTP, UTP, and other nucleotides
• For probe labeling, TUNEL assay with labeled dUTP, and other applications
• Available with a large choice of CF® dye colors
Other Fluorescent Nucleotides• dUTP and other nucleotides with classic fluorescent dyes
Biotinylated Nucleotides• Biotinylated nucleotides for RNA or DNA probe synthesis with a variety of linker lengths
Bromine & DIG Labeled Nucleotides• BrdU, DIG-dUTP, and other nucleotides for detection with specific antibodies
Aminoallyl Nucleotides• For generating amine-functionalized probes for subsequent labeling with amine-reactive dyes or biotin
Labeled cAMP analogs• cAMP receptor probes
• Available with CF® dyes, other fluorophores, or biotin

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Phalloidin is a toxin isolated from the Amanita phalloides mushroom. It is a bicyclic peptide that binds specifically to F-actin. Fluorescently labeled phalloidins stain F-actin at nanomolar concentrations. Unlike antibodies, the binding of phalloidin is not species-specific, and non-specific staining is negligible. Biotium offers Phalloidin Conjugates with a wide selection of CF® Dyes as well as traditional dyes and biotin.

Phalloidin conjugates are not cell-permeable, and are typically used to stain fixed and permeabilized cells. However, they also can be loaded into live cells via cationic liposomes. For live cell cytoskeletal staining, we also offer ViaFluor® Live Cell Microtubule Stains.

HeLa cells stained with rabbit anti-COXIV and CF®555 goat anti-rabbit (mitochondria, red), mouse anti-Golgin 97 and CF®488A goat anti-mouse (Golgi apparatus, green), and far-red CF®640R phalloidin (actin filaments, pseudocolored cyan).

Phalloidin Conjugates

Phalloidin Conjugates• Wide selection of CF® dyes, classic fluorophores, and biotin
• Low cost trial sizes available for CF® dye phalloidins

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Streptavidin is a bacterial protein with four biotin binding sites that binds biotin with extremely high affinity. Streptavidin conjugates are used in many applications to detect biotinylated antibodies or other targets, or to prepare multivalent complexes of biotinylated molecules. Our streptavidin conjugates are high quality streptavidin labeled with a wide selection CF® Dyes and other labels. Also see our Monoclonal Anti-Biotin Conjugates.

Streptavidin Conjugates

Streptavidin Conjugates• High affinity biotin-binding protein
• Wide selection of CF® dyes and other labels

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We provide a wide variety of biotin bioconjugates for detection with streptavidin conjugates or anti-biotin antibodies (see above). Also see primary and secondary antibodies available as biotin conjugates. We also offer the Biotin SE Protein Labeling Kit and Mix-n-Stain™ Biotin Antibody Labeling Kit, so you can label your own conjugates.

We also offer fluorescent biotins and biocytin. Potential applications of fluorescent biotin include detection of biotin binding sites and the degree of biotinylation of proteins, and for the measurement of avidin and streptavidin in crude biological samples. Biocytin is biotin with a fixable amine group. Fluorescent biocytin can be used as a polar tracer by microinjection to study the morphology of cells. See our full selection of polar tracers.

Biotin Conjugates

Biotin-XX-α-Bungarotoxin• Motor endplate acetylcholine receptor probe for neuromuscular junctions
Biotin-Annexin V• Phosphatidylserine-binding protein for labeling apoptotic cells
Biotin-XX-Phalloidin• F-actin probe for fixed cells
Biotin Nucleotides• Selection of nucleotides for probe synthesis or TUNEL assay
Biotin-DHPE• Biotinylated phospholipid
Biotin-cAMP• Biotinylated cAMP receptor probe
Biotin-cGMP• Biotinylated cGMP receptor probe
Biotin NTA• For sensitive detection of His-tagged proteins
CF® Dye Biotin• Fluorescent biotin
• Available with red fluorescent CF®568 or far-red fluorescent CF®633 or CF®640R
CF® Dye Biocytin• Fixable biotin polar tracer
• Available with green fluorescent CF®488A, red fluorescent CF®568, deep-red fluorescent CF®594, or far-red fluorescent CF®640R
Other Fluorescent Biotin• Biotin & biocytin coupled to FITC, rhodamine, AM3-25 membrane dye, and others

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