Biotin (also known as vitamin H) is a non-aromatic heterocyclic compound with a 4-carboxybutyl tail. A variety of derivatives of biotin are available in which the biotin moiety is connected (through the 4-carboxybutyl group) to a linker molecule that can be attached directly to an oligonucleotide.

Biotin-labeled oligonucleotides can be used to link the oligonucleotide to streptavidin-protein conjugates, streptavidin affinity columns, or labeled streptavidin. Biolegio offers three different biotin labels.
The biotin moiety can be attached to the oligo through an 8-atom spacer (Biotin-ON), a 15-atom spacer (Biotin-TEG), or a thymidine residue (Biotin-dT). Biotin can be attached to the 5' end, the 3' end, or can be used internally within a sequence. Attachment of a biotin molecule to the 3' terminus can also be used to prevent 3' exonuclease digestion and 3' extension during amplification reactions. The Biotin used for 3'- labeling is a C3 Biotin or a 3'-Biotin-TEG
For internal labeling Biotin-dT is used (a biotin-modified thymidine residue that can be used internally in place of thymidine).
The biotin is linked to the dT via a 10-atom spacer arm.

If the Biotin should be removed from the DNA after capturing the biotin labeled DNA with streptavidin beads or attaching the modified DNA to a surface, the use of Biotin-PC is recommended. The Biotin can be cleaved from the DNA molecule by illuminating with a handheld UV light source.

Due to the low coupling efficiency of Biotin, purification of biotin labeled oligos is highly recommended.

Biotin dT (5' - internal)

Biotin ON (5' - internal)

Biotin TEG (5' - internal)

Biotin (5')

Biotin PC (5')