Secondary Antibodies and Reagents

Our secondary reagents are designed to complement our large selection of primary antibodies and are available with a variety of conjugates. Find freedom in your experimental design with our secondary reagents validated for a range of methods, including flow cytometry, microscopy, western blotting, and ELISAs.

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Learn More About Streptavidin


Amplification Techniques and Streptavidin Conjugates


Streptavidin is a protein that binds to biotin with one of the strongest non-covalent interactions known in nature. We provide a wide array of streptavidin conjugates to fluorophores or enzymes, allowing them to be utilized as a secondary labeling method to detect biotinylated molecules in common research applications.

Biotin anti-mouse IL-10 + Brilliant Violet 421™ Streptavidin

Immortalized mouse bone marrow-derived macrophages, treated with LPS (100 ng/mL for 24 h), were stained with Alexa Fluor® 594 Wheat Germ Agglutinin (red) and biotin anti-mouse IL-10 (clone JES5-16E3), followed by Brilliant Violet 421™ Streptavidin (light blue). Data provided by James Harris, Trinity College, Dublin.

Biotin anti-mouse CD56 + Brilliant Violet 421™ Streptavidin

Human NK cell line NK92 fixed and stained with biotin anti-CD56 (clone HCD56) and Brilliant Violet 421™Streptavidin (blue), phalloidin Alexa Fluor® 568 (red), and anti-perforin FITC (green). The first image is the DIC view (far left). The final image (far right) shows the merged fluorescence of the three stains. Data provided by Emily Mace and Jordan Orange, Children's Hospital of Philadelphia.

HLA-A2/peptide Tetramer + PE Streptavidin or Brilliant Violet 421™ Streptavidin

Human PBMCs were stained with PerCP anti-human CD8 and labeled with NLVPMVATV-loaded human HLA-A2 tetramer bound to PE StreptavidinBrilliant Violet 421™ Streptavidin, or Pacific Blue™ Streptavidin. The data shows positive staining with a wide range of tetramer dilutions for PE and BV421™. Data provided by Rick Willis and John Altman, Emory/Yerkes.


Streptavidin Conjugates and Effects on Molecular Weight


The streptavidin molecule alone weighs 52 kD. When streptavidin is conjugated to a fluorophore the molecular weight of the entire label is altered. Use our chart below for quick reference to see the total molecular weight after conjugation. 

Streptavidin Conjugate Molecular Weight
Format MW (kD)*
Unconjugated Streptavidin 52
Alexa Fluor® 488 60
Alexa Fluor® 594 60
Alexa Fluor® 647 60
APC 320
APC/Cy7 350
Brilliant Violet™ 421 340
Brilliant Violet™ 510 340
Brilliant Violet™ 570 340
Brilliant Violet™ 605 340
Brilliant Violet™ 650 340
Brilliant Violet™ 711 340
Brilliant Violet™ 785 340
Cy3 60
Cy5 60
Dylight™ 488 60
Dylight™ 594 60
Dylight™ 649 60
PE 360
PE/Cy5 480
PE/Cy7 360
PE/Dazzle™ 594 540
PerCP 120
PerCP/Cy5.5 110
*These molecular weights are based on the averages of the lots produced. To obtain lot-specific molecular weights, contact Technical Service.

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