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Thiazole Red Homodimer (TOTO®-3), 1 mM in DMSO

Thiazole red homodimer (TRhD), also known as TOTO®-3, is a cell-impermeant, high-affinity, far-red fluorogenic nucleic acid stain.

Product Attributes

Apoptosis/viability marker

Dead cell stain

For live or fixed cells

For fixed cells/tissue sections, For live/intact cells

Detection method/readout

Fluorescence microscopy, Flow cytometry

Probe cellular localization

Nucleus & cytoplasm

Assay type/options

No-wash staining, Real-time imaging

Cell permeability

Membrane impermeant




642/661 nm (with DNA)

Catalog #
200 uL
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Product Description

Thiazole Red Homodimer (TRhD), also known as TOTO®-3, is a cell-impermeant, high-affinity nucleic acid stain based upon a symmetric cyanine dye dimer. The dye is essentially non-fluorescent in the absence of nucleic acids, but exhibits bright far-red fluorescence when bound to nucleic acids. TRhD is also used as a nuclear counterstain and dead cell indicator.

  • Dimeric nucleic acid stain
  • Cell-impermeant
  • λExEm (with DNA) = 642/661 nm
  • Supplied at 1 mM in DMSO
  • C53H62I4N6S2
  • MW: 1355

See the table below for other chemical equivalents of Thermo Fisher Scientific’s branded dead-cell selective nucleic acid dyes.


Equivalent to

Color (Ex/Em)

Catalog No.

Oxazole Blue, 1 mM in DMSO PO-PRO™-1 Blue (434/457 nm) 40091
Oxazole Blue Homodimer, 1 mM in DMSO POPO™-1 Blue (433/457 nm) 40093
Oxazole Yellow, 1 mM in DMSO YO-PRO®-1 Green (491/506 nm) 40089
Oxazole Yellow Homodimer, 1 mM in DMSO YOYO®-1 Green (491/508 nm) 40090
TO Iodide, 1 mM in DMSO TO-PRO®-1 Green (515/531 nm) 40088
Thiazole Orange Homodimer, 1 mM in DMSO TOTO®-1 Green (514/531 nm) 40079
Oxazole Red, 1 mM in DMSO YO-PRO®-3 Far-red (613/629 nm) 40105
Oxazole Red Homodimer, 1 mM in DMSO YOYO®-3 Far-red (612/631 nm) 40106
Thiazole Red, 1 mM in DMSO TO-PRO®-3 Far-red (642/657 nm) 40087
Thiazole Red Homodimer, 1 mM in DMSO TOTO®-3 Far-red (642/661 nm) 40080
YOYO, YO-PRO, POPO, PO-PRO, TOTO, and TO-PRO are trademarks and registered trademarks of Thermo Fisher Scientific.

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