SYTO

SYTO is a family of fluorescent nucleic acid stains used in life sciences research. Developed by Molecular Probes and now marketed by Thermo Fisher Scientific, these dyes permeate cell membranes and bind to nucleic acids, enabling visualization of nuclei and other nucleic acid-containing structures in living and fixed samples. The dyes vary in spectral properties, with multiple members emitting green, yellow, orange, or red light, allowing multicolor experiments in a single specimen.

Applications: SYTO dyes are commonly used for fluorescence microscopy, flow cytometry, and plate-based assays to label cells, assess cell counts, monitor nucleic acid content, or differentiate cell populations in mixed samples. They are often used in combination with other fluorophores to enable viability assays or to distinguish live from dead cells, depending on the dye and protocol.

Mechanism and considerations: SYTO dyes work by binding to nucleic acids with different affinities and selectivities. They are generally membrane-permeant, enabling staining of live cells, but staining conditions (concentration, incubation time) affect signal and viability. Some dyes can contribute to background fluorescence, and spectral overlap with other fluorophores must be considered in multicolor experiments. Proper controls and calibration are recommended.

History and corporate background: Molecular Probes introduced the first SYTO dyes in the 1990s. The company was acquired by Invitrogen, which later became part of Thermo Fisher Scientific, and the SYTO line remains widely used in research and diagnostics.