NMR characterisation of a triple stranded complex formed by homo-purine and homo-pyrimidine DNA strands at 1:1 molar ratio and acidic pH.
AUTOR(ES)
Bhaumik, S R
RESUMO
Homo-purine (d-TGAGGAAAGAAGGT) and homo-pyrimidine (d-CTCCTTTCTTCC) oligomers have been designed such that they are complementary in parallel orientation. When mixed in a 1:1 molar ratio, the system adopts an antiparallel duplex at neutral pH with three mismatched base pairs. On lowering the pH below 5.5, a new complex is formed. The NMR results show the coexistence of a intermolecular pyrimidine.purine:pyrimidine DNA triplex and a single stranded oligopurine at this pH. The triplex is stabilized by five T.A:T, four C+.G:C and two mismatched triads, namely, C+.G-T and T.A-C. This triplex is further stabilized by a Hoogsteen C+.G base-pair on one end. Temperature dependence of the imino proton resonances reveals that the triplex dissociates directly into single strands around 55 degrees C, without duplex intermediates. Parallel duplexes are not formed under any of the conditions employed in this study.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=307352Documentos Relacionados
- Complexes formed by (pyrimidine)n . (purine)n DNAs on lowering the pH are three-stranded.
- A novel palindromic triple-stranded structure formed by homopyrimidine dodecamer d-CTTCTCCTCTTC and homopurine hexamer d-GAAGAG.
- Poly(pyrimidine) . poly(purine) synthetic DNAs containing 5-methylcytosine form stable triplexes at neutral pH.
- Spectroscopic and calorimetric investigation on the DNA triplex formed by d(CTCTTCTTTCTTTTCTTTCTTCTC) and d(GAGAAGAAAGA) at acidic pH.
- Polypurine/polypyrimidine hairpins form a triple helix structure at low pH.