SYTO Green Fluorescent Nucleic Acid Stains are cell-permeant nucleic acid stains that show a large fluorescence enhancement upon binding nucleic acids. The SYTO dyes can be used to stain RNA and DNA in both live and dead eukaryotic cells, as well as in Gram-positive and Gram-negative bacteria.

The SYTO stains share several important characteristics:
• Permeability to virtually all cell membranes, including mammalian cells and bacteria
• High molar absorptivity, with extinction coefficients >50,000 cm^-1 M^-1 at visible absorption maxima
• Extremely low intrinsic fluorescence, with quantum yields typically <0.01 when not bound to nucleic acids
• Quantum yields that are typically >0.4 when bound to nucleic acids.

SYTO Green-Fluorescent Nucleic Acid Stains excitation/emission:
• SYTO 9—RNA 486/501 nm; DNA 485/498 nm
• SYTO 11—RNA 510/530 nm; DNA 508/527 nm
• SYTO 12—RNA 500/519 nm; DNA 499/522 nm
• SYTO 13—RNA 491/514 nm; DNA 488/509 nm
• SYTO 14—RNA 521/547 nm; DNA 517/549 nm
• SYTO 16—RNA 494/525 nm; DNA 488/518 nm
• SYTO 21—DNA 494/517 nm
• SYTO 24—DNA 490/515 nm
• SYTO BC—RNA 487/504 nm; DNA 485/500 nm
• SYTO RNASelect—RNA 490/530 nm

SYTO dyes differ from each other in one or more characteristics, including cell permeability, fluorescence enhancement upon binding nucleic acids, excitation and emission spectra, DNA/RNA selectivity, and binding affinity. The SYTO dyes are compatible with a variety of fluorescence-based instruments that use laser excitation or a conventional broadband illumination source (e.g., mercury- and xenon-arc lamps). Filter sets that are suitable for imaging cells labeled with fluorescein (FITC), Alexa Fluor 488, or GFP will work well for imaging cells stained with SYTO Green Nucleic Acid Stains.

SYTO nucleic acid stains have been used in diverse applications from staining DNA spotted on microarrays to staining live and fixed cells. The SYTO dyes do not act exclusively as nuclear stains in live cells and should not be equated with DNA-selective compounds such as DAPI (Cat. Nos. D1306, D21490) or Hoechst 33342 (Cat. Nos. H1399, H3570), which stain nuclei in live animal cells. Eukaryotic cells incubated with SYTO dyes generally show cytoplasmic or mitochondrial staining, as well as nuclear staining. The SYTO Green Fluorescent Nucleic Acid Stains have proven valuable in a broad range of research applications as well as used in flow cytometry and fluorescence microscopy.

Specific staining applications for some of the SYTO Green Fluorescent Nucleic Acid Stains:
The SYTO 9 stain has been shown to stain live and dead Gram-positive and Gram-negative bacteria. It is a component of the LIVE/DEAD BacLight Bacterial Viability Kits (Cat. Nos. L7007, L7012, L13152).

The SYTO 11 stain (Cat. No. S7573) has been used in conjunction with time-lapse microscopy to examine the cleavage orientation of dividing cells in the developing cerebral cortex.

The SYTO 13 stain (Cat. No. S7575) has been used in combination with propidium iodide (Cat. Nos. P1304, P3566) to monitor glutamate-induced necrosis in cerebellar granule cells.

The SYTO 14 stain (Cat. No. S7576) binds to cytoplasmic RNA, allowing its use in tracking RNA granule transport in living neurons.

Several reports describe the use of SYTO dyes for detecting apoptosis. A series of SYTO nucleic acid stains was screened for the ability to discriminate between apoptotic and non-apoptotic mouse thymocytes, and the SYTO 16 stain (Cat. no. S7578) was found to be optimal for this application. The SYTO 16 stain has also been used with propidium iodide to differentiate live and dead COS-7 cells with a laser-based scanning cytometer.

The SYTO BC Green Fluorescent Nucleic Acid Stain is a mixture of some of our best SYTO dyes for bacterial staining and is a component of the Bacteria Counting Kit (Cat. No. B7277) for bacterial counting in flow cytometry.

The SYTO RNASelect Green Fluorescent Cell Stain is a cell-permeant nucleic acid stain that selectively stains RNA. Although virtually nonfluorescent in the absence of nucleic acids, the SYTO RNASelect stain exhibits bright green fluorescence when bound to RNA (absorption/emission maxima ∼490/530 nm), but only a weak fluorescent signal when bound to DNA. It has been used for staining RNA cargo in exosomes in both live cell samples and isolated exosomes.

SYTO Green Fluorescent Nucleic Acid Stain Sampler Kit
The SYTO Green Fluorescent Nucleic Acid Stain Sampler Kit #1 contains our collection of cell-permeant, green-fluorescent SYTO nucleic acid stains. Because the dyes may demonstrate different staining behaviors with various tissues and cells, it may be necessary to test the dyes to find the optimal dye for a specific application. The kit contains 50 μL each of SYTO 11–14, 16, 21, and 24 dyes.

Any physiological buffer between pH 7.0–8.0, including PBS, can be used to dilute the SYTO dyes for the staining solution.