Tet (Figure 1) is a tetrachloro derivative of fluorescein. This dye is often used in real-time PCR assays, especially for multiplexing with FAM and Hex. TET-labeled oligonucleotides are also useful as primers for DNA sequencing or genotyping (microsatellite/STR analysis).
Figure 1. Structure of 5'-Tet (R = sequence).
metabion offers the Tet modification in its DNA and RNA portfolio: