Fluorescent Secondary Antibodies

fluorescent anti-rabbit & anti-mouse secondary conjugates

Active Motif's fluorescent secondary antibody conjugates provide you with an array of choices for immunofluorescent detection of primary antibodies. Our secondary antibodies are conjugated to a number of high-quality dyes, including the Chromeo™ line of fluorescent dyes. We also offer ATTO dye conjugates that have been maximally cross-adsorbed against IgG's of a variety of species to eliminate background caused by non-specific binding. Chromeo 488, Chromeo 505, Chromeo 494 and the ATTO STED dyes have been certified by Leica Microsystems for STimulated Emission Depletion (STED) microscopy, allowing a spatial resolution of 50 - 70 nm.

HeLa cells stained by alpha-Tubulin mAb with ATTO 647N (STED/GSD) Fluorescent Secondary Antibody and Histone H3 trimethyl Lys4 with Chromeo 488 Fluorescent Secondary Antibody using both confocal and STED microscopy

Figure 1: Active Motif's primary antibodies and fluorescent secondary antibodies in confocal and STED microscopy.
HeLa cells were stained with alpha Tubulin mouse mAb (Clone 5-B-1-2) and ATTO 647N (STED/GSD) Goat anti-mouse IgG (Catalog No. 15038). Histone H3 was stained with Histone H3 trimethyl Lys4 rabbit polyclonal antibody (Catalog No. 39159) and the Chromeo 488 Goat anti-rabbit IgG (Catalog No. 15041) secondary antibody. The confocal (left) and STED (right) images are courtesy of Leica Microsystems, Germany.

Chromeo 488, Chromeo 505, Chromeo 546, ATTO 532 (GSD), ATTO 647N (STED/GSD) and the Rhodamine 6G (GSD) secondary antibody conjugates are recommended by Leica Microsystems for high-resolution GSDIM microscopy, using the novel SR GSD microscope. With this novel high resolution technique a resolution of about 20 nm can be achieved.

Click on antibody conjugate below to see its complete information. To see all of our primary antibodies, please go to the Primary Antibodies page. Or, to find the antibodies you're looking for using a variety of specific search criteria, use the Search box and/or apply the various Filters in the left column.


Chromeo™ Dyes are bright fluorescent labels that replace Alexa Fluor*, DyLight* or Cy*-dyes. They are compatible with most excitation sources including diode lasers, LEDs, tungsten lamps and xenon arc lamps. The dyes have been conjugated to high-quality secondary antibodies by an optimized conjugation method, including subsequent purification from interfering substances.

Chromeo™ Dye Secondary Antibody Conjugate advantages

  • High intensity
  • Specificity under various fixation conditions
  • Photostability – the combination with MAX Stain™ reagents provides optimal fluorescent stability for multiple exposures and increased exposure time
  • Low background

Fluorescent Chromeo Dyes Secondary Antibody Conjugates enable sensitive and specific detection in fluorescence microscopy, high content screening, ELISA, FRET applications or flow cytometry. To ensure that you get the best results possible, we highly recommend that you use our secondary antibody conjugates together with our MAX Stain™ Immunofluorescence Tools, as those components have been formulated to optimize the performance of the Chromeo™ Dyes.

To receive more detailed information and application data about individual Chromeo dyes, simply click on the name of the Chromeo dye of your choice in the table below. To see a larger spectra image, click on the spectrum of your choice.

Dye Absorption Emission Spectra ε L/(mol-cm) Stokes shift
Chromeo™ 488 498 nm 524 nm Chromeo 488 Fluorescent Dye Spectra 73,000 26 nm
Chromeo™ 494 489 nm 624 nm Chromeo 494 Fluorescent Dye Spectra 55,000 135 nm
Chromeo™ 505 514 nm 530 nm Chromeo 505 Fluorescent Dye Spectra 70,000 16 nm
Chromeo™ 546 550 nm 567 nm Chromeo 546 Fluorescent Dye Spectra 98,800 17 nm
Chromeo™ 642 647 nm 666 nm Chromeo 642 Fluorescent Dye Spectra 180,000 19 nm
ATTO 647N (STED) 644 nm 669 nm ATTO 647N (STED) Fluorescent Dye Spectra 150,000 25 nm
ATTO 655 (STED) 663 nm 684 nm ATTO 655 (STED) Fluorescent Dye Spectra 125,000 21 nm
ATTO 532 (GSD) 534 nm 560 nm ATTO 532 (GSD) Fluorescent Dye Spectra 115,000 26 nm
Rhodamine 6G (GSD) 508 nm 558 nm Rhodamine 6G (GSD) Fluorescent Dye Spectra 116,000 50 nm
Table 1: Properties of Active Motif's Fluorescent Antibody Conjugates.

Next to the spectral properties of the dye and the quality of the secondary antibody, the quality of a fluorescent conjugate is influenced by the dye-to protein ratio, the conjugation method and its purity. All Active Motif Secondary Antibody Conjugates have been prepared by an optimized conjugation protocol making the fluorescent secondaries brighter and lowering the fluorescent background. Active Motif antibody conjugates have been tested in various applications including flow cytometry and fluorescent microscopy where they have shown to work with high efficiency and specificity under multiple fixation conditions.

Active Motif Fluorescent Secondary advantages

  • Unrivaled fluorescent intensity
  • Low background
  • Limited photobleaching
  • High Specificity
  • Flexibility
HeLa cells stained by alpha-Tubulin mAb and Chromeo 642 Fluorescent Secondary Antibody
Figure 1: Chromeo 642 staining in HeLa cells.

HeLa cells were stained with alpha Tubulin mouse mAb (Clone 5-B-1-2) and Chromeo 642 Goat anti-mouse IgG (Catalog No. 15034). The nuclei have been counterstained with DAPI.

STED microscopy images of cells stained by Nuclear pore protein-1 antibody with Chromeo 488 Goat anti-mouse IgG, and vimentin antibody with Chromeo 488 Goat anti-rabbit IgG
Figure 2: Chromeo 488 antibody conjugates in STED microscopy.

Nuclear pore protein-1 (NUP-1) was stained with a primary monoclonal mouse antibody and with Chromeo 488 Goat anti-mouse IgG (Catalog No. 15031) secondary antibody (left). Vimentin was stained with a primary polyclonal rabbit antibody and with Chromeo 488 Goat anti-rabbit IgG (Catalog No. 15041) secondary antibody (right). These STED images are courtesy of Leica Microsystems, Germany.

Enlarged image of alpha Tubulin mAb and Chromeo 546 Fluorescent Secondary Antibody immunofluorescent staining
Figure 3: Tubulin staining in HeLa cells, analyzed by confocal microscopy using the 544 nm line of the HeNe laser.

HeLa cells were stained with alpha Tubulin mouse mAb (Clone 5-B-1-2) and Chromeo 546 Goat anti-mouse IgG (Catalog No. 15033).

The Fluorescent Secondary Antibodies have been cited in the following publications:

Contents & Storage

The Chromeo™ conjugates are supplied as 1 mg of antibody at a concentration of 2 mg/ml. The ATTO and the Rhodamine 6G conjugates are supplied in 200 or 35 µl aliquots in PBS. For short-term storage, the conjugated antibody should be stored at 4°C protected from light. For longer-term storage, aliquot the antibody and store at -20°C. Avoid subjecting the antibody to repeated freeze-thaw cycles. These products are guaranteed for 6 months from the date of arrival.

To ensure photostability of Chromeo 488 under all experimental conditions, one aliquot of MAXfluor™ Mounting Medium for use in fluorescence microscopy is supplied with Chromeo 488 conjugates. This will provide optimal fluorescence stability and anti-fading during long-term storage of your mounted slides. MAXfluor Mounting medium should be stored at 4°C.

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