Amino-Modifier C6 dT is a convenient phosphoramidite reagent used to introduce an amino group from dT in oligo synthesis. Amino-Modifier C6 dT is added during a normal oligo synthesis. The TFA protecting group is removed during standard ammonium hydroxide deprotection. Sequence modifiers are designed for use in automated synthesis. The amino-modified dT can be coupled directly to a molecule by a standard peptide coupling or via the intermediate N-hydroxysuccinimide (NHS) ester. The amino-modifier dT can be added in place of a dT residue during oligonucleotide synthesis. The primary amine on the C6 analogues is separated from the oligonucleotide by a spacer arm with a total of 7 -10 atoms and can be labelled or attached to a detcatable tag such as a fluorescent dye or an enzyme.