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TAMRA (carboxytetramethylrhodamine) exists as 5- and 6-derivatives, or as a mixture of both isomers. It is the most commonly used rhodamine dye in oligonucleotide based applications. The fluorescent properties of TAMRA are sometimes used in non-radioactive sequencing, and in situ hybridisation studies, however TAMRA is more often as a quencher in Real-Time PCR applications based on FRET.
The light-absorbing properties of TAMRA, and spectral overlap with several commonly used fluorophores - including FAM, HEX, TET and JOE, make it useful as a quencher for the design of dual-labelled probes. The usefulness of TAMRA is, however, limited because of its broad emission spectrum, which reduces its capabilities in multiplexing. Its intrinsic fluorescence contributes to the background signal, potentially reducing the sensitivity of assays based on TAMRA. Despite these limitations, TAMRA has been used extensively in the design of probe-based assays, perhaps most notably in Taqman probes for Real-Time PCR.
TAMRA is not sufficiently stable to strong bases; the molecule degrades in the presence of ammonium hydroxide, hence TAMRA-labelled oligos must be synthesised using mild deprotection monomers. Subsequent deprotection of the oligo is achieved with t-butylamine/methanol/ water (1:1:2) for 2.5h at 70˚C. Although there is still a small amount of TAMRA degradation, this is easily removed during purification. Alternatively, amino-modified oligos can be post-synthetically labelled using a suitable TAMRA NHS ester.
We provide a number of solid support and phosphoramidite options for direct TAMRA labelling internally, or at the 3’ or 5’ end of oligonucleotides.
| LK0251 | TAMRA NHS Ester in DMSO |
| LK2143 | TAMRA-dT-CE Phosphoramidite |
| LK2434 | 3'-TAMRA CPG S |
| LK2435 | 3'-TAMRA CPG L |
Dilution volumes (in ml) are for 0.1M solutions in 10% THF in anhydrous acetonitrile. Adjust accordingly for other concentrations. For µmol pack sizes, products should be diluted as 100µmol/ml to achieve 0.1M, regardless of molecular weight.
Item |
Mol. Formula |
Mol. Wt. |
Unit Wt. |
250mg |
500mg |
1g |
| LK0251 | C29H25N3O7 | 527.53 | 412.44 | - | - | - |
| LK2143 | C73H83N8O13P | 1311.48 | 870.85 | 1.91 | 3.81 | 7.62 |
| LK2434/5 | - | - | 623.60 | - | - | - |
TAMRA-labelled oligonucleotides require milder deprotection conditions: use tbutylamine/methanol/water (1:1:2).1 Therefore, use Ac-dC and dmf-dG when synthesising the oligo being labelled. Standard ammonium hydroxide deprotection significantly degrades TAMRA. Post-synthetic labelling using TAMRA NHS Ester (LK0251) is discussed below.
TAMRA-dT-CE Phosphoramidite (LK2143) is dissolved in 10% THF in anhydrous acetonitrile (LK4059) to standard concentrations. Allow 15min for the product to completely dissolve.
LK2143 – A 6min coupling time is recommended.
LK2143 – Deprotection is carried out using tbutylamine/methanol/water (1:1:2) for 2.5h at 70˚C.
LK2434/5 – Typical protocol is as follows:
Note that the TAMRA label degrades during deprotection and these degraded oligos are not removed during Poly-Pak™ purification.
Typical protocol is as follows:
As noted above, TAMRA-labelled oligos will not survive standard deprotection conditions. Therefore, if such conditions are necessary, LK0251 can be used to label the oligonucleotide post-synthetically. This is provided as a 0.17M solution in DMSO. A synthesised amino-modified oligonucleotide is then conjugated to TAMRA using the NHS ester in sodium carbonate/bicarbonate buffer (0.1M, pH=9). A typical protocol for the conjugation of an amino-modified oligo (synthesised at 0.2μmol scale) is as follows:
Absorbance Max./nm |
Emission Max./nm |
Colour |
|
| TAMRA | 565 | 580 | Pink |
All products are stored dry in a freezer at –10 to –30°C, protected from light. Labelled oligos are stored in the dark. LK2143 is stable in solution for 24h.
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