NorthernLights™ Fluorescent Secondary Antibodies & Streptavidin Conjugates

NorthernLights™ fluorescent secondary antibodies and streptavidin conjugates are bright and resistant to photobleaching. We are currently offering secondary antibodies recognizing mouse, rat, goat, sheep, and rabbit IgG as well as chicken IgY. These reagents are available with three distinct excitation and emission maxima, making them ideal for multi-color fluorescence microscopy (Figure 1). Their spectral properties are similar to several frequently used fluorochromes and can be used with common filter sets and/or lasers (see the table below).

NorthernLights™ Highlights

  • Bright
  • Photostable: Resistant to photobleaching
  • Comparable spectral properties to many common fluorochromes limiting the need for additional instrumentation
  • Specific antibodies deliver low background and high signal-to-noise ratio
  • Stable in alcohols and xylene
  • Suitable for fluorescence microscopy and flow cytometry


Streptavidin, a protein of 55,000 Daltons, can bind 4 moles of biotin per mole of protein. The complex formed between streptavidin-biotin is stable over a wide range of pH and temperatures. Streptavidin lacks carbohydrate residues present in the avidin molecule reducing non-specific interactions with surface molecules. The dissociation constant for biotin is approximately 10-15 M. Streptavidin conjugated NorthernLights Fluorochromes are an excellent choice for visualization of proteins detected using biotinylated antibodies.

NorthernLights Secondary Reagents Cat. # Abs/Em Maxima Laser (Ex) Fluorochromes with Comparable Spectrums (Abs/Em)
NL-493 anti-Sheep IgG NL012 493/514
Click to view Graph
Argon (488) FITC (492/520)
Cy™2 (489/506)
Alexa Fluor® 488 (494/519)
NL-493 anti-Rabbit IgG NL006
NL-493 anti-Mouse IgG NL009
NL-493 anti-Rat IgG NL015
NL-493 anti-Goat IgG NL003
NL-493 Streptavidin NL997
NL-493 anti-Chicken IgY NL018
NL-557 anti-Sheep IgG NL010 557/574
Click to view Graph
Krypton (568)
HeNe (543)
Phycoerythrin (565/575)
Rhodamine Red™ X (570/590)
Cy™3 (548/562)
NL-557 anti-Rabbit IgG NL004
NL-557 anti-Mouse IgG NL007
NL-557 anti-Rat IgG NL013
NL-557 anti-Goat IgG NL001
NL-557 Streptavidin NL999
NL-557 anti-Chicken IgY NL016
NL-637 anti-Sheep IgG NL011 637/658
Click to View Graph
HeNe (633) Allophycocyanin (645-660)
Alexa Fluor® 647 (650-668)
Cy™5 (650/670)
NL-637 anti-Rabbit IgG NL005
NL-637 anti-Mouse IgG NL008
NL-637 anti-Rat IgG NL014
NL-637 anti-Goat IgG NL002
NL-637 Streptavidin NL998
NL-637 anti-Chicken IgY NL017
Click for larger image
Figure 1. Rat cortical stem cell differentiation was monitored using multi-color immunocytochemistry. Neural progenitors were labeled with R&D Systems goat anti-rat nestin polyclonal antibody (Catalog # AF2736) and stained with R&D Systems donkey anti-goat NorthernLights-493 secondary antibody (Catalog # NL003; green). Differentiated neurons were labeled with R&D Systems neuron-specific mouse anti-beta-III tubulin monoclonal antibody (TuJ-1; Catalog # MAB1195) and stained using R&D Systems donkey anti-mouse NorthernLights-557 secondary antibody (Catalog # NL007; red). Nuclei were stained with DAPI (blue).
Alexa Fluor is a registered trademark of Invitrogen.
Rhodamine Red is a trademark of Invitrogen.
Cy is a trademark of GE Healthcare.