Shop All Protein Conjugates

Fibrinogen From Human Plasma, Alexa Fluor™ 488 Conjugate (Invitrogen™)

Molecular Probes® fibrinogen conjugates are prepared by attaching fluorescent dye molecules to purified human fibrinogen (approximately 15 dye molecules for each fibrinogen molecule), purifying the conjugate to remove unreacted dye, and then lyophilizing for storage.

Fluorescently labeled fibrinogen has proven to be a valuable tool for investigating platelet activation and subsequent fibrinogen binding. For instance, fluorescein-labeled fibrinogen has been used to detect fibrinogen bound to activated platelets by flow cytometry.

Human Fibrinogen Conjugate Specifications:
• Label (Ex/Em): Alexa Fluor® 488 (~495/519 nm)
• Spectrally similar to fluorescein, but the signal is less pH-dependent and more photostable
• Lyophilized product can be dissolved in buffer (e.g., sodium bicarbonate, pH 8.3) for use
• Fluorescence is typically detected using fluorescence microscopy or flow cytometry


Find More Probes for Cell Adhesion and Receptor Binding
Review Probes for Cell Adhesion, Chemotaxis, Multidrug Resistance and Glutathione—Section 15.6 and Probes for Following Receptor Binding and Phagocytosis—Section 16.1 in the Molecular Probes® Handbook for more information on these probes.

For Research Use Only. Not for human or animal therapeutic or diagnostic use.

Epidermal Growth Factor, Tetramethylrhodamine Conjugate (rhodamine EGF) (Invitrogen™)

We offer several conjugates of epidermal growth factor that are useful for the detection of EGF receptor in cells. Fluorescently labeled EGF has enabled scientists to investigate receptor-membrane interactions, study receptor distribution, calculate rate constants for the interaction of EGF with its receptor, and more. The conjugates incorporating fluorescein (FITC), Oregon Green® 514, and tetramethylrhodamine were constructed with the dye directly attached to EGF. The conjugates of EGF with Alexa Fluor® dyes and Texas Red® dye are complexes of the dye–streptavidin molecule and biotinylated EGF. The biotinylated conjugates utilize biotin-XX, which contains a long spacer arm designed to enhance the probe’s affinity for the EGF receptor.

Epidermal Growth Factor Conjugate Specifications:
• EGF molecule: 53 amino acids, MW=6,045 Da
• Label (Ex/Em): Tetramethylrhodamine (~555/580 nm)
• Number of fluorophore molecules on each EGF molecule: 1
• Fluorescence is typically monitored using a flow cytometer, fluorescence microscope, or fluorimeter


Find More Receptor Binding and Phagocytosis Probes
We offer a number of fluorescently labeled probes for studying receptor-mediated endocytosis, membrane markers for endocytosis and exocytosis, and methods for detecting internalized fluorescent ligands. Review Probes for Following Receptor Binding and Phagocytosis—Section 16.1 in the Molecular Probes® Handbook for more information on these products.

For Research Use. Not for human or animal therapeutic or diagnostic use.

Fibrinogen From Human Plasma, Alexa Fluor™ 546 Conjugate (Invitrogen™)

Molecular Probes® fibrinogen conjugates are prepared by attaching fluorescent dye molecules to purified human fibrinogen (approximately 15 dye molecules for each fibrinogen molecule), purifying the conjugate to remove unreacted dye, and then lyophilizing for storage.

Fluorescently labeled fibrinogen has proven to be a valuable tool for investigating platelet activation and subsequent fibrinogen binding. For instance, fluorescein-labeled fibrinogen has been used to detect fibrinogen bound to activated platelets by flow cytometry.

Human Fibrinogen Conjugate Specifications:
• Label (Ex/Em): Alexa Fluor® 546 (~558/573 nm)
• Spectrally similar to tetramethylrhodamine (TMR), but is brighter and more photostable
• Lyophilized product can be dissolved in buffer (e.g., sodium bicarbonate, pH 8.3) for use
• Fluorescence is typically detected using fluorescence microscopy or flow cytometry


Find More Probes for Cell Adhesion and Receptor Binding
Review Probes for Cell Adhesion, Chemotaxis, Multidrug Resistance and Glutathione—Section 15.6 and Probes for Following Receptor Binding and Phagocytosis—Section 16.1 in the Molecular Probes® Handbook for more information on these probes.

For Research Use Only. Not for human or animal therapeutic or diagnostic use.

Actin, from rabbit muscle, Alexa Fluor™ 568 conjugate, in solution (Invitrogen™)

The orange-fluorescent Alexa Fluor® 568 actin conjugate is an important tool for investigating cytoskeleton dynamics in-vivo. This fluorescent conjugate is prepared by labeling the amine residues of polymerized F-actin. After labeling, the conjugates are subjected to depolymerization and subsequent polymerization to ensure that the actin conjugates are able to assemble properly. The labeled actin that polymerizes is then separated from remaining monomeric actin by centrifugation, depolymerized and packaged in monomeric form.

Epidermal Growth Factor, Biotinylated, complexed to Alexa Fluor™ 555 Streptavidin (Alexa Fluor™ 555 EGF complex) (Invitrogen™)

We offer several conjugates of epidermal growth factor that are useful for the detection of EGF receptor in cells. Fluorescently labeled EGF has enabled scientists to investigate receptor-membrane interactions, study receptor distribution, calculate rate constants for the interaction of EGF with its receptor, and more. The conjugates incorporating fluorescein (FITC), Oregon Green® 514, and tetramethylrhodamine were constructed with the dye directly attached to EGF. The conjugates of EGF with Alexa Fluor® dyes and Texas Red® dye are complexes of the dye–streptavidin molecule and biotinylated EGF. The biotinylated conjugates utilize biotin-XX, which contains a long spacer arm designed to enhance the probe’s affinity for the EGF receptor.

Epidermal Growth Factor Conjugate Specifications:
• EGF molecule: 53 amino acids, MW=6,045 Da
• Label (Ex/Em): Biotin-XX complexed with Alexa Fluor® 555 streptavidin (~555/565 nm)
• Number of fluorophore molecules on each EGF molecule: ~2–3
• Fluorescence is typically monitored using a flow cytometer, fluorescence microscope, or fluorimeter


Find More Receptor Binding and Phagocytosis Probes
We offer a number of fluorescently labeled probes for studying receptor-mediated endocytosis, membrane markers for endocytosis and exocytosis, and methods for detecting internalized fluorescent ligands. Review Probes for Following Receptor Binding and Phagocytosis—Section 16.1 in the Molecular Probes® Handbook for more information on these products.

For Research Use. Not for human or animal therapeutic or diagnostic use.

Fibrinogen From Human Plasma, Alexa Fluor™ 594 Conjugate (Invitrogen™)

Molecular Probes® fibrinogen conjugates are prepared by attaching fluorescent dye molecules to purified human fibrinogen (approximately 15 dye molecules for each fibrinogen molecule), purifying the conjugate to remove unreacted dye, and then lyophilizing for storage.

Fluorescently labeled fibrinogen has proven to be a valuable tool for investigating platelet activation and subsequent fibrinogen binding. For instance, fluorescein-labeled fibrinogen has been used to detect fibrinogen bound to activated platelets by flow cytometry.

Human Fibrinogen Conjugate Specifications:
• Label (Ex/Em): Alexa Fluor® 594 (~590/617 nm)
• Spectrally similar to Texas Red® dye conjugates, but brighter
• Lyophilized product can be dissolved in buffer (e.g., sodium bicarbonate, pH 8.3) for use
• Fluorescence is typically detected using fluorescence microscopy or flow cytometry


Find More Probes for Cell Adhesion and Receptor Binding
Review Probes for Cell Adhesion, Chemotaxis, Multidrug Resistance and Glutathione—Section 15.6 and Probes for Following Receptor Binding and Phagocytosis—Section 16.1 in the Molecular Probes® Handbook for more information on these probes.

For Research Use Only. Not for human or animal therapeutic or diagnostic use.

Transferrin From Human Serum, Alexa Fluor™ 488 Conjugate (Invitrogen™)

Transferrin is a monomeric serum glycoprotein (~80,000 daltons) that binds to a specific receptor on the surface of vertebrate cells and delivers up to two Fe3+ atoms via receptor-mediated endocytosis—our labeled LDL complexes are useful tools for studying this phenomenon. Once iron-carrying transferrin proteins are inside endosomes, 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. Fluorescent transferrin conjugates can therefore be used with fluorescent LDL to distinguish the lysosomally directed and recycling endosomal pathways.

These experiments are typically performed by adding fluorescently labeled transferrin to cultured cells and analyzing them by microscopy. We offer a biotinylated transferrin conjugate and more than 10 fluorescent versions.

Transferrin Specifications:

Label (Ex/Em): Alexa Fluor® 488 (495/519)

Amount: 15 mg solid (contains 5 mg of transferrin conjugate)

Key Applications of Labeled Transferrin
Some of the many applications for labeled transferrin include:
• Image transferrin receptor dynamics using FRET
• Observe receptor trafficking in live cells by confocal laser-scanning microscopy
• Investigate events occurring during endosomal acidification
• Measure transferrin receptor binding affinity in mammals and parasites

For Research Use Only. Not intended for any animal or human therapeutic or diagnostic use.

Epidermal Growth Factor, Biotinylated, complexed to Alexa Fluor™ 647 Streptavidin (Alexa Fluor™ 647 EGF complex) (Invitrogen™)

We offer several conjugates of epidermal growth factor that are useful for the detection of EGF receptor in cells. Fluorescently labeled EGF has enabled scientists to investigate receptor-membrane interactions, study receptor distribution, calculate rate constants for the interaction of EGF with its receptor, and more. The conjugates incorporating fluorescein (FITC), Oregon Green® 514, and tetramethylrhodamine were constructed with the dye directly attached to EGF. The conjugates of EGF with Alexa Fluor® dyes and Texas Red® dye are complexes of the dye–streptavidin molecule and biotinylated EGF. The biotinylated conjugates utilize biotin-XX, which contains a long spacer arm designed to enhance the probe’s affinity for the EGF receptor.

Epidermal Growth Factor Conjugate Specifications:
• EGF molecule: 53 amino acids, MW=6,045 Da
• Label (Ex/Em): Biotin-XX complexed with Alexa Fluor® 647 streptavidin (~650/665 nm)
• Number of fluorophore molecules on each EGF molecule: ~2–3
• Fluorescence is typically monitored using a flow cytometer, fluorescence microscope, or fluorimeter


Find More Receptor Binding and Phagocytosis Probes
We offer a number of fluorescently labeled probes for studying receptor-mediated endocytosis, membrane markers for endocytosis and exocytosis, and methods for detecting internalized fluorescent ligands. Review Probes for Following Receptor Binding and Phagocytosis—Section 16.1 in the Molecular Probes® Handbook for more information on these products.

For Research Use. Not for human or animal therapeutic or diagnostic use.

Transferrin From Human Serum, Alexa Fluor™ 594 Conjugate (Invitrogen™)

Transferrin is a monomeric serum glycoprotein (~80,000 daltons) that binds to a specific receptor on the surface of vertebrate cells and delivers up to two Fe3+ atoms via receptor-mediated endocytosis—our labeled LDL complexes are useful tools for studying this phenomenon. Once iron-carrying transferrin proteins are inside endosomes, 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. Fluorescent transferrin conjugates can therefore be used with fluorescent LDL to distinguish the lysosomally directed and recycling endosomal pathways.

These experiments are typically performed by adding fluorescently labeled transferrin to cultured cells and analyzing them by microscopy. We offer a biotinylated transferrin conjugate and more than 10 fluorescent versions.

Transferrin Specifications:

Label (Ex/Em): Alexa Fluor® 594 (590/617)

Amount: 15 mg solid (contains 5 mg of transferrin conjugate)

Key Applications of Labeled Transferrin
Some of the many applications for labeled transferrin include:
• Image transferrin receptor dynamics using FRET
• Observe receptor trafficking in live cells by confocal laser-scanning microscopy
• Investigate events occurring during endosomal acidification
• Measure transferrin receptor binding affinity in mammals and parasites

For Research Use Only. Not intended for any animal or human therapeutic or diagnostic use.

α-Bungarotoxin (from Bungarus multicinctus) (Invitrogen™)

α-Bungarotoxin, a 74-amino acid peptide extracted from Bungarus multicinctus venom, binds with high affinity as a competitive antagonist to nicotinic acetylcholine receptors (nAChRs) of neuromuscular junctions.

Vybrant™ Alexa Fluor™ 488 Lipid Raft Labeling Kit (Invitrogen™)

Vybrant Lipid Raft Labeling Kits are designed to provide convenient, reliable and extremely bright fluorescent labeling of lipid rafts in live cells. Kits include cholera toxin subunit B (CT-B) labeled with either the green-fluorescent Alexa Fluor 488, the orange-fluorescent Alexa Fluor 555 or the red-fluorescent Alexa Fluor 594 dye, as well as an antibody that specifically recognizes CT-B. A 10X solution of phosphate-buffered saline (10X PBS), pH 7.2, and detailed instructions are also included in the kits.

Transferrin From Human Serum, Alexa Fluor™ 633 Conjugate (Invitrogen™)

Transferrin is a monomeric serum glycoprotein (~80,000 daltons) that binds to a specific receptor on the surface of vertebrate cells and delivers up to two Fe3+ atoms via receptor-mediated endocytosis—our labeled LDL complexes are useful tools for studying this phenomenon. Once iron-carrying transferrin proteins are inside endosomes, 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. Fluorescent transferrin conjugates can therefore be used with fluorescent LDL to distinguish the lysosomally directed and recycling endosomal pathways.

These experiments are typically performed by adding fluorescently labeled transferrin to cultured cells and analyzing them by microscopy. We offer a biotinylated transferrin conjugate and more than 10 fluorescent versions.

Transferrin Specifications:

Label (Ex/Em): Alexa Fluor® 633 (632/650)

Amount: 15 mg solid (contains 5 mg of transferrin conjugate)

Key Applications of Labeled Transferrin
Some of the many applications for labeled transferrin include:
• Image transferrin receptor dynamics using FRET
• Observe receptor trafficking in live cells by confocal laser-scanning microscopy
• Investigate events occurring during endosomal acidification
• Measure transferrin receptor binding affinity in mammals and parasites

For Research Use Only. Not intended for any animal or human therapeutic or diagnostic use.

Cholera Toxin Subunit B (Recombinant), Biotin-XX Conjugate (Invitrogen™)

Molecular Probes® cholera toxin conjugates are made from a recombinant version of the B subunit only. This allows us to provide a very high-purity product that is completely free of the toxic A subunit. Cholera toxin B subunit (CT-B) attaches to cells by binding to ganglioside GM1, making it a powerful tool for retrograde labeling of neurons. This tracer has been used in a variety of applications, including tracing of rat forebrain afferents, projections of the parabrachial region, and neurons of the urinary bladder wall. When used in neuronal tracing applications, CT-B is typically introduced by pressure injection or by iontophoretic injection into neural tissue.

Cholera Toxin Subunit B Specifications:
• Label (Ex/Em): Biotin-XX
• At neutral pH, the 11.4 kDa B subunit exists as a 57 kDa pentamer
• Lyophilized product can be dissolved in buffer (e.g., PBS) for use


Cholera Toxin Subunit B for Studying Lipid Rafts
More recently, researchers have found that CT-B can be used as a marker for lipid rafts, which are membrane microdomains enriched in cholesterol and sphingolipids thought to be important in cell signaling. For lipid raft staining, cells are first incubated with fluorescent CT-B. Then, an anti–CT-B antibody is added to crosslink the CT-B in the lipid rafts into distinct patches on the plasma membrane. These patches are easily visualized by fluorescence microscopy. In addition to individual fluorescent CT-B conjugates, we also offer Vybrant® Lipid Raft Labeling Kits that contain the Alexa Fluor® 488, Alexa Fluor® 555, or Alexa Fluor® 594 dye conjugates of CT-B, an anti–CT-B antibody, and a detailed protocol for labeling and preparing cells for fluorescence microscopy.

Find More CT-B Conjugates
We offer various CT-B conjugates. Review Protein Conjugates—Section 14.7 in the Molecular Probes® Handbook for more information on these tracers.

For Research Use Only. Not for human or animal therapeutic or diagnostic use.

Pierce™ Alkaline Phosphatase, Biotinylated (Thermo Scientific™)

Thermo Scientific Pierce Biotinylated Proteins include biotin-labeled proteins (BSA), enzymes (HRP, AP) and fluorophores (FITC) for use as controls or signal amplification in IHC via avidin-biotin complex (ABC) techniques.

Biotinylated AP is most commonly used in immunohistochemistry (IHC) to amplify the signal of biotinylated primary antibodies using the ABC staining method.

Biotinylated enzymes—biotin-labeled horseradish peroxidase (B-HRP), alkaline phosphatase (B-AP) and beta-galactosidase (B-bGal) for use in avidin-biotin complex (ABC) staining

Biotin, also known as vitamin H, is a small molecule (MW 244.3) that is present in tiny amounts in all living cells and is critical for a number of biological processes. The valeric acid side chain of the biotin molecule can be derivatized in order to incorporate various reactive groups that are used to attach biotin to other molecules. In the context of immunohistochemistry (IHC), biotin is conjugated to antibodies or to the enzyme reporters used to detect target antigens.

Related Products
Pierce™ Bovine Serum Albumin, Biotinylated
Pierce™ Horseradish Peroxidase, Biotinylated
Pierce™ Biotin-Fluorescein Conjugate
Pierce™ Biotin

Transferrin From Human Serum, Alexa Fluor™ 680 Conjugate (Invitrogen™)

Transferrin is a monomeric serum glycoprotein (~80,000 daltons) that binds to a specific receptor on the surface of vertebrate cells and delivers up to two Fe3+ atoms via receptor-mediated endocytosis—our labeled LDL complexes are useful tools for studying this phenomenon. Once iron-carrying transferrin proteins are inside endosomes, 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. Fluorescent transferrin conjugates can therefore be used with fluorescent LDL to distinguish the lysosomally directed and recycling endosomal pathways.

These experiments are typically performed by adding fluorescently labeled transferrin to cultured cells and analyzing them by microscopy. We offer a biotinylated transferrin conjugate and more than 10 fluorescent versions.

Transferrin Specifications:

Label (Ex/Em): Alexa Fluor® 680 (679/702)

Amount: 15 mg solid (contains 5 mg of transferrin conjugate)

Key Applications of Labeled Transferrin
Some of the many applications for labeled transferrin include:
• Image transferrin receptor dynamics using FRET
• Observe receptor trafficking in live cells by confocal laser-scanning microscopy
• Investigate events occurring during endosomal acidification
• Measure transferrin receptor binding affinity in mammals and parasites

For Research Use Only. Not intended for any animal or human therapeutic or diagnostic use.