Biotin and desthiobiotin are the most widely used capture labels in oligonucleotide workflows. Biotin provides extremely strong streptavidin binding for durable capture and immobilization, while desthiobiotin is preferred when reversible capture and recovery are required.
In these systems the oligonucleotide carries a biotin affinity label, while streptavidin functions as the protein binding partner used for capture, purification, or immobilization.
| Feature |
Details |
| Main interaction |
Biotin / desthiobiotin – streptavidin binding |
| Typical installs |
5′ biotin, 3′ biotin, internal biotin, long-spacer biotin, desthiobiotin |
| Typical uses |
Pull-down assays, purification, capture, immobilization |
| Design note |
Spacer choice can materially improve streptavidin accessibility |
Biotin remains the most widely used affinity label for oligonucleotide conjugation because of the exceptionally strong interaction between biotin and streptavidin (Kd ≈ 10⁻¹⁵ M). Multiple biotin architectures are available depending on the intended assay workflow, including terminal biotin labeling, internal biotin incorporation, dual-biotin capture formats, and photocleavable biotin systems. Spacer-containing variants such as Biotin-TEG are often selected to improve steric accessibility when oligonucleotides are immobilized on streptavidin matrices.
Common Biotin Oligonucleotide Modifications
| Biotin Modification |
Typical Position |
Application |
When to Select |
| 5′ Biotin |
5′ terminus |
Capture probes, pull-down assays |
Most common configuration for immobilization or streptavidin capture. |
| 3′ Biotin |
3′ terminus |
Hybridization probes, capture assays |
Use when the 5′ end must remain free or functionally available. |
| Biotin dT |
Internal thymidine |
Hybridization probes, detection systems |
Provides an internal label while preserving both termini. |
| Dual Biotin |
5′ and 3′ termini |
High-strength capture |
Improves immobilization stability on streptavidin-coated surfaces. |
| PC-Biotin |
Terminal or internal |
Controlled release after capture |
Useful when captured complexes must be released by light activation. |
| Internal Biotin (Azide) |
Internal modification |
Click chemistry conjugation |
Allows modular post-synthesis installation via CuAAC or SPAAC workflows. |
| 5′ Biotin (Azide) |
5′ terminus |
Click conjugation workflows |
Used when biotin must be installed through bioorthogonal ligation after oligo synthesis. |
| Biotin-TEG |
Terminal modification |
Capture assays |
TEG spacer improves accessibility to streptavidin and reduces steric interference. |
Desthiobiotin Oligonucleotide Labels
Desthiobiotin is a reversible analog of biotin commonly used in affinity capture workflows. While desthiobiotin binds streptavidin strongly, the interaction is weaker than the classical biotin–streptavidin interaction and can be displaced using free biotin. This property allows capture and controlled elution of oligonucleotide–protein complexes.
| Modification |
Typical Position |
Application |
Key Advantage |
| 5′ Desthiobiotin |
5′ terminus |
Reversible streptavidin capture |
Allows elution of complexes with excess biotin. |
| 3′ Desthiobiotin |
3′ terminus |
Affinity purification probes |
Maintains reversible binding for downstream recovery. |
| Internal Desthiobiotin |
Internal nucleotide |
RNA–protein interaction studies |
Maintains probe accessibility during capture. |