SYBR Green I is an asymmetrical cyanine dye, which is used to detect nucleic acids. It consists of a N-alkylated benzothiazolium or benzoxazolium ring system, that is joined by a monomethine bridge to a pyridinium or quinolinium ring system. SYBR Green I binds to the minor groove of dsDNA and is excited at a wavelength of 480 nm. It has a peak fluorescence emission of 520 nm.

Precasting SYBR Green I Gels:Precast nondenaturing polyacrylamide or agarose gels with SYBR Green I staining solution, which is diluted from the SYBR Green I stock reagent 1:10,000 prior to pouring the gel. The DNA detection limit for gels precast with SYBR Green I stain may be slightly higher (on the order of 30 to 40 pg/band) than for gels stained after electrophoresis (less than 20 pg/band), and the migration rate of DNA fragments in SYBR Green I gels may be significantly slower than the migration rate of the same fragments in a gel containing no dye.