Fluorokines™ Fluorescent-Labeled Recombinant Proteins

Evaluating CAR Expression on CAR-T Cells using Fluorescent-labeled Proteins

 

Fluorokines – Direct Detection of Target Molecules by Flow Cytometry

R&D Systems Fluorokines are fluorescent-labeled recombinant proteins that allow target molecules to be directly stained and detected by flow cytometry. Our catalog includes Fluorokines that are designed for evaluating the expression of specific chimeric antigen receptors on CAR-T or CAR-NK cells, Fluorokines for detecting cells expressing specific immune checkpoint receptors, as well as Fluorokines for assessing SAR-CoV-2 reactive ACE-2+ cells or SARS-CoV-2-related immune responses.

Fluorokines are made by conjugating the bioactive protein to the fluorophore via amine labeling, and the resulting fluorescent-labeled protein is then rigorously tested to ensure consistent labeling of each lot. The entire manufacturing process is controlled to reduce lot-to-lot variability and ensure a consistent F/P ratio. Additionally, the specificity of each protein is quality controlled tested using flow cytometry to confirm that the Fluorokine stains the appropriate target.

 

Benefits of Using Fluorescent-labeled Proteins for Detecting Target Molecules

  • Direct detection. Direct detection of a target molecule with a Fluorokine is highly specific and eliminates background staining that may occur by indirect detection using an epitope-tagged target antigen and a fluorophore-labeled secondary antibody.
  • Reduced Processing Time. Target detection requires only a single processing step as Fluorokines eliminate the need for a secondary antibody.
  • Conjugated to Alexa Fluor® Dyes. Fluorescent-labeled proteins are conjugated to Alexa Fluor dyes, which offer more intense fluorescence than other spectrally similar fluorophore labels and excellent photostability.
  • High Levels of Bioactivity. Fluorescent-labeled proteins are rigorously tested to ensure that they retain the same high level of activity as the unlabeled recombinant protein.
  • High lot-to-lot consistency. Each new lot is tested side-by-side with previous lots and with a master lot to ensure high lot-to-lot consistency.

 

Fluorokines Technique Talk Webinar

Fluorokines for Chimeric Antigen Receptor Detection

The ability to evaluate the expression of a chimeric antigen receptor (CAR) following T cell or natural killer (NK) cell transduction is a critical step in the production of CAR-T or CAR-NK cells for cancer immunotherapy. Using fluorescent-labeled proteins to evaluate CAR expression is highly specific, reduces processing time, and eliminates background staining that may occur by indirect detection of the CAR using an epitope-tagged target antigen and a fluorophore-labeled secondary antibody.

Fluorescent-labeled Proteins for CAR-T or CAR-NK Cell Detection

Alexa Fluor® is a registered trademark of Molecular Probes, Inc., Eugene, OR.

Protein Species Source Tag Fluorescent Label Catalog # Bioactivity
BCMA Human NS0 Fc Alexa Fluor® 488 AFG193 Binds anti-BCMA monoclonal antibody conjugated beads
Alexa Fluor® 647 AFR193
Atto 488 ATJ193
Atto 647N ATM193
CD19 Human CHO Fc Alexa Fluor® 488 AFG9269 Binds anti-CD19 monoclonal antibody conjugated beads
Alexa Fluor® 647 AFR9269
Atto 488 ATJ9269
Atto 647N ATM9269
CD30/TNFRSF8 Human HEK293 Fc Alexa Fluor® 488 AFG11155 Binds HEK293 human embryonic kidney cells transfected with human CD30 Ligand
Alexa Fluor® 647 AFR11155
CD40/TNFRSF5 Human NS0 Fc, His Alexa Fluor® 488 AFG1493 Binds anti-CD40/TNFRSF5 antibody conjugated beads
Alexa Fluor® 647 AFR1493
CD300e Human HEK293 Fc Alexa Fluor® 488 AFG10479 Binds anti-CD300e monoclonal antibody conjugated beads
Alexa Fluor® 647 AFR10479
EMMPRIN/CD147 Human NS0 Fc Alexa Fluor® 488 AFG972 Binds anti-EMMPRIN/CD147 monoclonal antibody conjugated beads
Alexa Fluor® 647 AFR972
EGF R Human NS0 Fc Alexa Fluor® 488 AFG344 Binds anti-EGF R monoclonal antibody conjugated beads
Alexa Fluor® 647 AFR344
ErbB2/Her2 Human NS0 Fc Alexa Fluor® 488 AFG1129 Binds anti-ErbB2/Her2 monoclonal antibody conjugated beads
Alexa Fluor® 647 AFR1129
Glypican 3 Human NS0 His Alexa Fluor® 488 AFG2119 Binds anti-Glypican 3 antibody conjugated beads
Alexa Fluor® 647 AFR2119
Mesothelin Human NS0 His Alexa Fluor® 488 AFG3265 Binds anti-Mesothelin monoclonal antibody conjugated beads
Alexa Fluor® 647 AFR3265
MUC-1 Human HEK293 Fc Alexa Fluor® 488 AFG10332 Binds anti-MUC-1 monoclonal antibody conjugated beads
Alexa Fluor® 647 AFR10332
OX40 Human NS0 Fc Alexa Fluor® 488 AFG3388 Binds anti-OX40 monoclonal antibody conjugated beads
Alexa Fluor® 647 AFR3388
PD-1 Human NS0 Fc Alexa Fluor® 488 AFG1086 Binds anti-PD-1 monoclonal antibody conjugated beads
Alexa Fluor® 647 AFR1086
Siglec-2 / CD22 Human NS0 Fc Alexa Fluor® 488 AFG1968 Binds anti-Siglec-2 / CD22 monoclonal antibody conjugated beads
Alexa Fluor® 647 AFR1968
Atto 488 ATJ1968
Atto 647N ATM1968
Siglec-3 / CD33 Human NS0 Fc Alexa Fluor® 488 AFG1137 Binds anti-Siglec-3 / CD33 monoclonal antibody conjugated beads
Alexa Fluor® 647 AFR1137
Atto 488 ATJ1137
Atto 647N ATM1137
TSLPR Human NS0 Fc Alexa Fluor® 488 AFG981 Binds anti-TSLPR monoclonal antibody conjugated beads
Alexa Fluor® 647 AFR981

As directly detecting a CAR with a labeled target antigen is currently the method of choice for evaluating CAR expression, we are diligently working to expand our selection of Fluorokines for CAR-T and CAR-NK cell research. As an alternative method, we also offer Avi-tag biotinylated proteins, which can be detected using fluorochrome-labeled streptavidin. Additionally, if you are unable to find either the fluorescent-labeled or biotinylated protein that you need on our website, our Custom Protein Services team can work with you to create a customized protein solution to meet your specific research needs.

Utilizing Fluorokines Fluorescent-labeled Proteins to Detect CAR-T Cells

Graphic showing that a chimeric antigen receptor (CAR) on CAR-T cells can bind to either its target antigen expressed on a tumor cell or to a purified fluorescent-labeled protein, which allows the percentage of T cells expressing the CAR to be evaluated

Demonstration of the Utility of a Fluorokine for Evaluating CAR Expression. (A) CAR-T cell therapy is based on the principle that T cells removed from a patient or donor can be genetically engineered to express a specific chimeric antigen receptor (CAR). Once these CAR-T cells are infused back into the patient, the CAR will bind to its specific target antigen on the surface of the patient's tumor cells, activating the T cells, and allowing them to attack and destroy the tumor cells. (B) The ability to evaluate CAR expression following T cell transduction is an important step in the production of CAR-T cells. T cells expressing the CAR can be directly stained using a Fluorokine (target antigen) and the percentage of CAR-expressing cells can be determined by flow cytometry. (C) CD4+CD8+ T cells were transduced with a hCD19-CAR (left) or not transduced (right) and then cultured for 11 days. Cells were stained with a PE-Cy7-CD4 and Recombinant Human CD19 Fc Chimera Atto 488 Protein (Catalog # ATJ9269), and detected by flow cytometry.

Specificity, Bioactivity, and Lot-to-Lot Consistency Testing of R&D Systems Fluorokines for CAR-T Cell Research

Flow cytometry data showing staining of CD19-CAR-T cells by Recombinant Human CD19 Fc Chimera Atto 488, with CD4+CD8+ T cells that were not transduced with a hCD19-CAR serving as a negative control

Bioactivity assay data showing binding of different concentrations of three different lots of Recombinant Human BCMA Fc Chimera Atto 647N or the unlabeled Recombinant Human BCMA Fc Chimera protein to Recombinant Human APRIL. The data demonstrates consistent bioactivity between the fluorescent-labeled and unlabeled proteins and lot-to-lot consistency in the bioactivity of the different lots of the fluorescent-labeled protein.

Analysis of the Specificity, Bioactivity, and Lot-to-Lot Consistency of Recombinant Human BCMA/TNFRSF17 Fc Chimera Atto 647N Protein. Fluorescent beads conjugated to an anti-Human BCMA Monoclonal Antibody were stained with (A) Recombinant Human BCMA/TNFRSF17 Fc Chimera Atto 647N Protein (Catalog # ATM193) or (B) unstained and detected by flow cytometry. (C) Recombinant Human APRIL/TNFSF13 (Catalog # 5860-AP) was immobilized at 0.1 ug/mL, 100 ul/well, and the indicated concentrations of three independent lots of Recombinant Human BCMA Fc Chimera Atto 647N (Catalog # ATM193; red, green, orange lines) or unlabeled Recombinant Human BCMA Fc Chimera (Catalog # 193-BC; blue line) were added. The data demonstrates consistent bioactivity between the fluorescent-labeled and unlabeled proteins and lot-to-lot consistency in the bioactivity of the three different lots of the fluorescent-labeled protein.

Flow cytometry data showing staining of anti-BCMA-conjugated beads with Recombinant Human BCMA/TNFRSF17 Fc Chimera Atto 488 Protein, with unstained anti-BCMA-conjugated beads serving as a negative control.

Detection of CD19-CAR-T Cells with Recombinant Human CD19 Fc Chimera Atto 647N Protein. CD4+CD8+ T cells were either (A) transduced with a hCD19-CAR or (B) not transduced, and then cultured for 11 days. Cells were stained with a PE-Cy7-CD4 and Recombinant Human CD19 Fc Chimera Atto 647N Protein (Catalog # ATM9269) and detected by flow cytometry.

Fluorokines are Compatible with Antibody Panels for Multi-Color Flow Cytometry

Flow cytometry data showing staining of anti-BCMA-conjugated beads with Recombinant Human BCMA/TNFRSF17 Fc Chimera Atto 488 Protein, with unstained anti-BCMA-conjugated beads serving as a negative control.

Fluorokines can be used with Fluorochrome-conjugated Antibodies to Characterize CD19-CAR-T Cells by Multi-Color Flow Cytometry. CD4+CD8+ T cells transduced with a hCD19-CAR were stained with the following panel of monoclonal antibodies: Alexa Fluor® 700-conjugated Mouse Anti-Human CD14 (Catalog # FAB3832N), PerCP-conjugated Mouse Anti-Human CD45 (Catalog # FAB1430C), PE-conjugated Rabbit Anti-Human CD56/NCAM-1 (Catalog # FAB24086P), Alexa Fluor® 405-conjugated Mouse Anti-Human CD8 (Catalog # FAB1509V), PE-Cy7-CD4, and Alexa Fluor® 594-conjugated Mouse Anti-Human CD62L/L-Selectin (Catalog # FAB9787T), along with the Fluorokine, Recombinant Human CD19 Fc Chimera Atto 647N Protein (Catalog # ATM9269). Cells were initially gated on singlets and live cells.

What Are CAR-T Cell Therapies?

Learn about the types of cancer being treated with CAR-T cell therapy and how CAR-T cell therapy works.

CAR-T cell therapies are being increasingly investigated and used for treating hematologic cancers, including acute lymphocytic leukemia (ALL), acute myeloid leukemia (AML), lymphoma, and multiple myeloma (MM).1 This type of cell therapy utilizes T cells removed from a patient or a donor and genetically engineers the cells to express a chimeric antigen receptor (CAR). The CAR is a synthetic T cell receptor consisting of an extracellular antibody-derived single chain variable fragment (scFv) that binds to a specific target antigen, linked to one or more intracellular signaling sequences that promote T cell activation following scFv binding. Once the CAR-modified T cells are expanded, they are then infused back into the patient, where they bind to their specific antigen on the surface of the patient’s tumor cells and become activated, allowing them to attack and destroy the tumor cells. The ability to evaluate the expression of the CAR following retroviral or lentiviral transduction of the patient’s T cells is an important step for understanding the dose of CAR+T cells that is being transferred back into the patient. Proteins labeled with a fluorescent dye allow target cells expressing the corresponding CAR to be directly stained and detected by flow cytometry.

Commonly Targeted Antigens for CAR-T Cell Therapy

CAR-T cells expressing CARs specific for different surface molecules, including CD19 and BCMA, have been generated and are being evaluated as anti-cancer therapies. CD19 is an antigen that is widely expressed on B cell-derived cancers and is one of the most popular targets for CAR-T cell therapies.1 Two anti-CD19-CAR-T cell therapies have been approved by the U.S. Food and Drug Administration (FDA). Tisagenlecleucel (KYMRIAH) was approved in August 2017 for treating relapsed or refractory B cell precursor acute lymphoblastic leukemia (ALL), and axicabtagene ciloleucel (Yescarta) was approved in October 2017 for treating adult patients with relapsed or refractory diffuse large B cell lymphoma (DLBCL). Although remarkable clinical remission has been observed using anti-CD19 CAR-T cells, relapses have also occurred due to either the escape and proliferation of CD19-tumor cells, or factors that may contribute to the loss of CAR-T cells or CAR-T cell function, including a loss of CAR-T cell persistence, activation-induced cell death or senescence, or an immunosuppressive tumor microenvironment.2 Dual targeting strategies are being pursued to try to overcome these obstacles.

The second most-targeted tumor antigen for CAR-T cell therapy is B-cell maturation antigen (BCMA).1 BCMA is involved in regulating B cell maturation and differentiation into plasma cells and is typically expressed at higher levels on malignant plasma cells than on normal plasma cells. 3, 4 Anti-BCMA CAR-T cell therapy is currently being pursued for the treatment of multiple myeloma and has thus far shown promising results.3, 4 Other top targets being investigated in clinical trials for CAR-T cell therapies include GD2, EGF R, HER2, Mesothelin, CD20, CD22, CD30, CD33, CD123, Glypican-3, and NKG2D.1

References
  • 1. Yu, J.X. et al. (2019) Nat. Rev. Drug Discov. 18:821.
  • 2. Hay, K.A. & C.J. Turtle (2017) Drugs 77:237.
  • 3. Mikkilineni, L. & J.N. Kochenderfer (2017) Blood 130:2594.
  • 4. D’Agostino, M. & N. Raje (2020) Leukemia 34:21.

Fluorokines for Immune Checkpoint Ligands

Immune checkpoint molecules deliver signals that control the activities of different immune cell types and represent some of the most promising targets for immuno-oncology research. Utilize our new Alexa Fluor®-labeled immune checkpoint ligands to easily sort or detect cells expressing specific immune checkpoint receptors. Fluorescent-labeled immune checkpoint ligands bind to cells expressing their corresponding receptors in a highly specific manner, allowing the direct detection of these cells by flow cytometry.

Alexa Fluor®-labeled Immune Checkpoint Ligands

Alexa Fluor® is a registered trademark of Molecular Probes, Inc., Eugene, OR.

Protein Species Source Tag Fluorescent Label Catalog # Bioactivity
B7-1/CD80 Human HEK293 His Alexa Fluor® 488 AFG9050 Binds anti-B7-1 monoclonal antibody conjugated beads
Alexa Fluor® 647 AFR9050
CHO Fc Alexa Fluor® 488 AFG10133
Alexa Fluor® 647 AFR10133
B7-2/CD86 Human CHO Fc Alexa Fluor® 488 AFG7625 Binds to anti-B7-2/CD86 antibody conjugated beads
Alexa Fluor® 647 AFR7625
HEK293 His Alexa Fluor® 647 AFR9090 Binds to anti-B7-2/CD86 monoclonal antibody conjugated beads
B7-H2 Human NS0 Fc Alexa Fluor® 488 AFG165 Binds anti-B7-H2 antibody conjugated beads
Alexa Fluor® 647 AFR165
CD155/PVR Human NS0 His Alexa Fluor® 488 AFG2530 Binds anti-CD155/PVR monoclonal antibody conjugated beads
Alexa Fluor® 647 AFR2530
GITR Ligand/TNFSF18 Human CHO GCN4-IZ, HA Alexa Fluor® 488 AFG6987 Binds anti-GITR Ligand monoclonal antibody conjugated beads
Alexa Fluor® 647 AFR6987
HVEM/TNFRSF14 Human HEK293 Fc Alexa Fluor® 488 AFG11177 Binds anti-HVEM/TNFRSF14 antibody conjugated beads
Alexa Fluor® 647 AFR11177
PD-L1/B7-H1 Human HEK293 His Alexa Fluor® 488 AFG9049 Binds anti-PD-L1/B7-H1 monoclonal antibody conjugated beads
Alexa Fluor® 647 AFR9049
PD-L2/B7-DC Human NS0 Fc Alexa Fluor® 488 AFG1224 Binds anti-PD-L2/B7-DC monoclonal antibody conjugated beads
Alexa Fluor® 647 AFR1224

Analysis of the Specificity of the Recombinant Human PD-L1/B7-H1 and B7-1/CD80 His-tag Alexa Fluor® 647 Proteins

Flow cytometry data showing staining of anti-BCMA-conjugated beads with Recombinant Human BCMA/TNFRSF17 Fc Chimera Atto 488 Protein, with unstained anti-BCMA-conjugated beads serving as a negative control.

Analysis of the Specificity of the Recombinant Human PD-L1/B7-H1 and B7-1/CD80 His-tag Alexa Fluor® 647 Proteins. (A) Streptavidin-coated beads conjugated to Biotinylated Anti-Human PD-L1/B7-H1 Monoclonal Antibody were stained with the indicated concentrations of Recombinant Human PD-L1/B7-H1 His-tag Alexa Fluor® 647 Protein (Catalog # AFR9049). (B) Streptavidin-coated beads conjugated to Biotinylated Anti-Human B7-1/CD80 Monoclonal Antibody (Catalog # BAM1402) were stained with the indicated concentrations of Recombinant Human B7-1/CD80 His-tag Alexa Fluor® 647 Protein (Catalog # AFR9050).

Fluorokines for SARS-CoV-2 Spike Proteins

The SARS-CoV-2 Spike protein is a key factor regulating viral attachment and fusion of the viral and host cell membranes, and therefore, it is a primary target for therapeutic research. To help facilitate this research, Bio-Techne now offers a wide selection of Alexa Fluor®-labeled, bioactive SARS-CoV-2 Spike proteins, including the full ectodomain SARS-CoV-2 Spike protein, the Spike protein receptor binding domain (RBD), and Alexa Fluor-labeled alpha, beta, gamma, delta, kappa, and omicron Spike protein variants. These proteins can be used to directly detect SARS-CoV-2 reactive ACE-2+ cells or to investigate SARS-CoV-2-related immune responses. All fluorescent-labeled Spike proteins are tested to ensure that they detect ACE-2 by flow cytometry.

Alexa Fluor®-labeled SARS-CoV-2 Spike Proteins

Alexa Fluor® is a registered trademark of Molecular Probes, Inc., Eugene, OR.

Variant Description Source Label Catalog #
SARS-CoV-2 Val16-Lys1211  HEK293 Alexa Fluor® 488 AFG10561
Alexa Fluor® 647 AFR10561
SARS-CoV-2 Spike RBD
Arg319-Phe541
HEK293 Alexa Fluor® 488 AFG10500
Alexa Fluor® 647 AFR10500
Alpha B.1.1.7 Val16-Lys1211
H69del, V70del, Y145del, N501Y, A570D, D614G, P681H, T716I, S982A, D1118H
HEK293 Alexa Fluor® 488 AFG10796
Alexa Fluor® 647 AFR10796
Beta B.1.351 Val16-Lys1211
D80A, D215G, L242del, A243del, L244del, K417N, E484K, N501Y, D614G, A701V
HEK293 Alexa Fluor® 488 AFG10786
Alexa Fluor® 647 AFR10786
Gamma P.1 Val16-Lys1211
L18F, T20N, P26S, D138Y, R190S, K417T, E484K, N501Y, D614G, H655Y, T1027I, V1176F
HEK293 Alexa Fluor® 488 AFG10795
Alexa Fluor® 647 AFR10795
Delta B.1.617.2 Val16-Lys1211
T19R, G142D, E156G, F157del, R158del, L452R, T478K, D614G, P681R, D950N
HEK293 Alexa Fluor® 488 AFG10878
Alexa Fluor® 647 AFR10878
B.1.617.2 RBD Arg319-Phe541          L452R, T478K HEK293 Alexa Fluor® 488 AFG10876
Alexa Fluor® 647 AFR10876
Kappa B.1.617.1 Val16-Lys1211
G142D, E154K, L452R, E484Q, D614G, P681R, Q1071H
HEK293 Alexa Fluor® 488 AFG10861
Alexa Fluor® 647 AFR10861
Omicron B.1.1.529 Val16-Lys1211
A76V, H69del, V70del, T95I, G142D, V143del, Y144del, Y145del, N211del, L212I, ins214EPE, G339D, S371L, S373P, S375F, K417N, N440K, G446S, S477N, T478K, E484A, Q493R, G496S, Q498R, N501Y, Y505H, T547K, D614G, H655Y, N679K, P681H, N764K, D796Y, N856K, Q954H, N969K, L981F
HEK293 Alexa Fluor® 488 AFG11060
HEK293 Alexa Fluor® 647 AFR11060
HEK293 Alexa Fluor® 488 AFG11061
HEK293 Alexa Fluor® 647 AFR11061
B.1.1.529 RBD Arg319-Phe541
G339D, S371L, S373P, S375F, K417N, N440K, G446S, S477N, T478K, E484A, Q493R, G496S, Q498R, N501Y, Y505H
HEK293 Alexa Fluor® 488 AFG11056
HEK293 Alexa Fluor® 647 AFR11056
B.1.1.529 BA.2 Val16-Lys1211
T19I, L24del, P25del, Pro26del, A27S,  G142D, V213G, G339D, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, S477N, T478K, E484A, Q493R, Q498R, N501Y, Y505H, D614G, H655Y, N679K, P681H, N764K, D796Y, Q954H, N969K
HEK293 Alexa Fluor® 488 AFG11109
HEK293 Alexa Fluor® 647 AFR11109
B.1.1.529 BA.2 RBD Arg319-Phe541
G339D, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, S477N, T478K, E484A, Q493R, Q498R, N501Y, Y505H 
HEK293 Alexa Fluor® 488 AFG11094
HEK293 Alexa Fluor® 647 AFR11094
ACE-2 Gln18-Ser740/His NS0 Alexa Fluor® 488 AFG933
Alexa Fluor® 647 AFR933

Assessing ACE-2+ Cells Using Recombinant SARS-CoV-2 Spike (GCN4-IZ) His-tag Alexa Fluor® 488 Protein

Flow cytometry data showing staining of anti-BCMA-conjugated beads with Recombinant Human BCMA/TNFRSF17 Fc Chimera Atto 488 Protein, with unstained anti-BCMA-conjugated beads serving as a negative control.

Alexa Fluor® Spike Proteins Detect ACE-2 Expression on HEK293 Cells. HEK293 cells transfected with human ACE-2 were stained with (A) 1 ug/mL (100 uL/well) Recombinant SARS-CoV-2 Spike (GCN4-IZ) His-tag Alexa Fluor® 488 Protein (Catalog # AFG10561) or (B) unstained. Nearly all cells were positive for ACE-2 expression compared to the unstained control.

Custom Protein Services

If you are unable to find the fluorescent-labeled protein that you need on our website, contact our Custom Protein Services team. They will work with you to create a customized protein solution to meet your specific research needs.

 

Bulk Proteins

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Fluorokine Related Research Areas

Acute Lymphoblastic Leukemia

B Cells

B Cell Markers

Lymphoma

Hematologic Cancers

Multiple Myeloma

Video Transcript

R&D Systems fluorescent-labeled proteins allow for specific detection of a chimeric antigen receptor on cells by flow cytometry. Once genetic engineering is performed instructing the cells to express a specific CAR, the cells are cultured allowing for the expression of the CAR on the cell surface. A fluorescently labeled protein that binds to the CAR can be used to determine the cells that are positive by flow cytometry. R&D Systems fluorescent proteins are made by conjugating a fluorescent dye to a bioactive recombinant protein. These proteins are purified and QC tested to ensure bioactivity and lot-to-lot consistency. Advantages of using fluorescently labeled proteins include reduced processing time, no secondary antibody step, and reduced potential for variability and unwanted background staining. Streamline your car expression workflows with R&D Systems, the number one most trusted brand in recombinant proteins.