Biotin-dT can replace dT residues within the oligonucleotide sequence. 5'-Biotin phosphoramidite can be added ONLY ONCE to the 5'-terminus of an oligonucleotide. However, the DMT group on the biotin can be used in RP cartridge and HPLC purification techniques. PC Biotin is a photocleavable 5'-biotin phosphoramidite. BiotinTEG CPG and Protected BiotinLC Serinol CPG are designed for the direct synthesis of oligonucleotides containing biotin at the 3' terminus.
Desthiobiotin is a biotin analogue that exhibits lower binding to biotin-binding proteins such as streptavidin. This biotin analogue is lacking the sulfur group from the molecule and has a dissociation constant (Kd) several orders of magnitude less than biotin/streptavidin. As a result, biomolecules containing desthiobiotin are dissociated from streptavidin simply in the presence of buffered solutions of biotin. We offer desthiobiotinTEG phosphoramidite and the corresponding CPG.
Coupling: 2 minute coupling time recommended
Deprotection: 5'-Biotin is slow to detritylate. If the final DMT-group is to be removed on the synthesizer, we recommend a second deblocking step. If the final DMT-group is left on to aid in cartridge purification, we recommend that the oligo is left in contact with the TFA solution for 10 minutes.
No. However, this can be produced on the synthesizer by adding to the 5'- terminus first 5'-thiol-modifier C6 S-S (10-1936) followed by BioTEG phosphoramidite (10-1955). This should generate a biotinylated primer with a long spacer arm containing the disulfide linkage which can be cleaved later with DTT.||
A colorimetric assay for biotin can be quite effective. The color results from the reaction of biotin with p-dimethylaminocinnamaldehyde in the presence of sulfuric acid.1. Spot 0.2 A260 units of biotinylated oligonucleotide on a silica gel TLC plate.2. Dry the plate.]3. Spray with a solution of 2% p-dimethylaminocinnamaldehyde (Sigma), 2% conc. sulfuric acid in ethanol.4. Heat the plate and the presence of biotin will be indicated by the formation of a pink spot.Since the intensity of the biotin spot is quite low, it is prudent to compare with an unlabelled oligonucleotide similarly treated.
Modification reagents based on a 1,2-diol, e.g., BioTEG, DNP phosphoramidites, or a 1,3-diol, e.g., fluorescein, biotin phosphoramidites, can be added several times at the 5'-terminus since they contain an alcohol group capable of further addition with phosphoramidites. Can this alcohol also be a substrate for T4 polynucleotide kinase for 32P labelling of these modified oligonucleotides? Surprisingly, the answer is yes. Teoule and coworkers have shown(1) that oligos labelled at the 5'-terminus are substrates for kinase. Interestingly, the oligos modified with reagents based on 1,2-diols are labelled to 50%, indicating that only one diastereomer is labelled, while those modified with 1,3-diol reagents are labelled to 100%.||REFERENCE(S): (1) M.L. Fontanel, H. Bazin, and R. Teoule, Analytical Biochemistry, 1993, 214, 338-340. ||