FREQUENTLY ASKED TECHNICAL QUESTION
QUESTION: Can Etheno-dA be substituted for dA in a sequencing or PCR primer . What is the best method for cleavage/deprotection of oligos containing Etheno-dA. What are the excitation/emmision wavelengths for oligos containing etheno-dA.?
RESPONSE:Due to the structure of the 1, N6 etheno structure etheno dA will not base-pair with T or dU. For this reason oligonucleotides with etheno-dA in the middle or 3'-end will not act as PCR or sequencing primers. However if located at or near the 5''-end etheno-dA can be incorporated one or more times and still act as an effective sequencing or PCR primer (1).
Etheno-dA is somewhat labile to NH4OH so it is best to use base labile protecting groups such as Pac dA, isopropyl-Pac-dG and Ac-dC and either deprotect with K2CO3:MeOH, 4 hr. at RT. or NH4OH 4 hr. at RT.. If using standard protecting groups use mild deprotection conditions (0.4 M Methanolic NaOH; MeOH:H2O, 4:1) 17 hr. at room temperature.
|
Excitation |
Emission |
Ribo etheno-A |
345 nm |
455 nm |
Oligo-etheno-dA |
270 nm |
410 nm |
|
300 nm |
410 nm |
REFERENCE(S):
1. Srivastava, S.C., et.al., (1994), Nucleic Acids Research, 22, 1296-1304.
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