SYTO

• from Molecular Probes now owned by Invitrogen
• series of blue-, green-, orange and red-fluorescent dyes

SYTO dyes are close to sybr green (they stain nucleic acid and are membrane permeant), but differ in some important point :

- SYTO dyes stain ds nucleic acid but are saturating at low concentration unlike Sybr green

- SYTO dyes require high-power diode to be efficiency excited (Found on Rotor-gene Q for exemple)

- SYTO dyes are known to be less inhibiting than sybr green in real time quantitative PCR

Because those dyes can easily saturate ds nucleic acid, they are very accurate for high resolution melting curve (HRM), which is used to detect single nucleotide mutation.

SYTO dyes are cyanine dyes. Nucleic acid interaction with those type dyes is complex and may be affected by a lot of factors : electrostatic, hydrophobic, and steric interactions. Cyanine dye binding appears to be cooperative, which it can explain their efficiency to saturate ds nucleic acid at low concentration.