TO-PRO-3 stain is an excellent far red-fluorescent nuclear and chromosome counterstain that is impermeant to live cells but penetrates compromised membranes characteristic of dead cells, making it a useful indicator of dead cells within a population. The carbocyanine-based dye exhibits far-red fluorescence with excitation at 642 nm and emission at 661 nm. The long-wavelength fluorescence of TO-PRO-3 stain is well separated from that of commonly used fluorophores imaged in the DAPI and FITC channels.
Long-wavelength light–absorbing dyes such as TO-PRO-3 stain have the advantage that their fluorescence is usually not obscured by tissue autofluorescence. TO-PRO-3 stain has very strong binding affinity for dsDNA, with dissociation constants in the micromolar range. It gives strong and selective staining of the nucleus in cultured cells and in paraffin sections.
TO-PRO-3 stain is among the most sensitive probes for nucleic acid detection, and in addition to cell staining it can be used for staining nucleic acids on solid supports and pre-staining samples for gel or capillary electrophoresis.
TO-PRO-3 stain dashboard
TO-PRO-3 stain products
We offer TO-PRO-3 stain as an iodine salt in DMSO. TO-PRO-3 stain is also included in the SelectFX Nuclear Labeling Kit, which provides four spectrally distinct fluorescent dyes for staining nuclei in fixed-cell preparations.
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Fluorescence immunostaining of a fixed co-culture of murine neurons and dendritic cells. Fluorescence immunostaining of a fixed co-culture of murine neurons and dendritic cells. Neurons were labeled with an antibody directed against neurofilament triplet H (NFH) protein and visualized using red-fluorescent tetramethylrhodamine goat anti–mouse IgG. Dendritic cells were labeled with a biotin conjugate of a primary antibody directed against the integrin CD11c and visualized using green-fluorescent Alexa Fluor 488 streptavidin (S11223, S32354). Nuclei were stained with blue-fluorescent TO-PRO-3. Image submitted by Gauthier Dorban, Institute of Human Histology, University of Liège, Belgium.
High-performance nucleic acid stains
Unlike our range of nuclear counterstains, SYTO dyes do not act exclusively as nuclear stains in live cells and should not be equated with DNA-selective compounds (such as DAPI) which stain nuclei in live animal cells. Eukaryotic cells incubated with SYTO dyes generally show cytoplasmic or mitochondrial staining, as well as nuclear staining.
Nuclear counterstains provide highly selective nuclear staining with little or no cytoplasmic labeling and a choice of colors for multiplexing with other labels. Additionally, some of the stains can also be used in cell cycle analyses using high-content imaging and flow cytometry.
A fixed, permeabilized, and labeled muntjac skin fibroblast. Mitochondria were labeled with mouse anti–OxPhos Complex V inhibitor protein antibody and visualized using orange-fluorescent Alexa Fluor 555 goat anti–mouse IgGantibody. F-actin was labeled with green-fluorescent Alexa Fluor 488 phalloidin, and the nucleus was stained with TO-PRO-3 iodide (pseudocolored magenta).
Molecular Probes Handbook
The significantly revised 11th Edition is the most complete fluorescence labeling and detection reference available. The Molecular Probes Handbook can help you achieve the best experimental results for your fluorescence labeling and detection experiments. View the handbook online or order your own copy.
Antifade reagents suppress photobleaching and preserve the signals of your fluorescently labeled target molecules. They offer excellent compatibility with a multitude of dyes across the spectrum, making them especially valuable tools for multicolor applications. For added convenience, some formulations include the nuclear counterstain DAPI, eliminating the need for a separate counterstaining step.
Cell stain tool
Stain your own cell by using our simulation tool to develop reproducible results with many of our signature fluorescent dyes. Develop your multiplexing strategy for antibody probes, reactive dyes, and counterstains to create your perfectly labeled fluorescent cell.
Plot and compare spectra and check the spectral compatibility for common fluorophores including all of the fluorescent probes from Thermo Fisher Scientific. The Fluorescence SpectraViewer tool is formatted for both microscope imaging and flow cytometry applications.
For Research Use Only. Not for use in diagnostic procedures.