Stability of G,A triple helices.

AUTOR(ES)

Debin, A

RESUMO

In this work we selected double-stranded DNA sequences capable of forming stable triplexes at 20 or 50 degrees C with corresponding 13mer purine oligonucleotides. This selection was obtained by a double aptamer approach where both the starting sequences of the oligonucleotides and the target DNA duplex were random. The results of selection were confirmed by a cold exchange method and the influence of the position of a 'mismatch' on the stability of the triplex was documented in several cases. The selected sequences obey two rules: (i) they have a high G content; (ii) for a given G content the stability of the resulting triplex is higher if the G residues lie in stretches. The computer simulation of the Mg2+, Na+and Cl-environment around three triplexes by a density scaled Monte Carlo method provides an interpretation of the experimental observations. The Mg2+cations are statistically close to the G N7 and relatively far from the A N7. The presence of an A repels the Mg2+from adjacent G residues. Therefore, the triplexes are stabilized when the Mg2+can form a continuous spine on G N7.

Documentos Relacionados

• Ligand-induced formation of nucleic acid triple helices.
• Parallel and antiparallel A*A-T intramolecular triple helices.
• Kinetic studies on the formation of intermolecular triple helices.
• Crystals of hemagglutinin-neuraminidase of parainfluenza virus contain triple-stranded helices.
• Molecular mechanics calculations of the riboacetal internucleotide linkage in double and triple helices.