pH-Independent triplex formation: hairpin DNA containing isoguanine or 9-deaza-9-propynylguanine in place of protonated cytosine

Autor(en): Seela, Frank
Shaikh, Khalil I.
Stichwörter: 2'-DEOXYISOGUANOSINE; CHAIN ORIENTATION; Chemistry; Chemistry, Organic; ENZYMATIC INCORPORATION; GC BASE-PAIRS; HELIX FORMATION; NONNATURAL DEOXYRIBONUCLEOSIDE; OLIGONUCLEOTIDES; PARALLEL; RECOGNITION; STABILITY
Erscheinungsdatum: 2006
Herausgeber: ROYAL SOC CHEMISTRY
Journal: ORGANIC & BIOMOLECULAR CHEMISTRY
Volumen: 4
Ausgabe: 21
Startseite: 3993
Seitenende: 4004
Zusammenfassung: 
Triplex-forming oligonucleotides (TFOs) containing 2'-deoxyisoguanosine ( 1), 7-bromo-7-deaza-2'-deoxyisoguanosine ( 2) as well as the propynylated 9-deazaguanine N-7-(2'-deoxyribonucleoside) 3b were prepared. For this the phosphoramidites 9a, b of the nucleoside 1 and, the phosphoramidites 19, 20 of compound 3b were synthesized. They were employed in solid-phase oligonucleotide synthesis to yield the protected 31-mer oligonucleotides. The deblocking of the allyl-protected oligonucleotides containing 1 was carried out by Pd(0)[PPh3](4) - PPh3 followed by 25% aq. NH3. Formation of the 31-mer single-stranded intramolecular triplexes was studied by UV-melting curve analysis. In the single-stranded 31-mer oligonucleotides the protonated dC in the dCH(+) - dG - dC base triad was replaced by 2'-deoxyisoguanosine ( 1), 7-bromo-7-deaza-2'-deoxyisoguanosine ( 2) and, 9-deaza-9-propynylguanine N7-(2'-deoxyribonucleoside) ( 3b). The replacement of protonated dC by compounds 1 and 3b resulted in intramolecular triplexes which are formed pH-independently and are stable under neutral conditions. These triplexes contain ``purine'' nucleosides in the third pyrimidine rich strand of the oligonucleotide hairpin.
ISSN: 14770520
DOI: 10.1039/b610930f

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