Oligonucleotide-oligospermine conjugates (zip nucleic acids): a convenient means of finely tuning hybridization temperatures.
Synthesis of oligonucleotide probes and control of their hybridization temperature are key aspects of polymerase chain reaction (PCR)-based detection of genetic sequences. A straightforward means to approach the last goal is to decrease the repulsion between the polyanionic probe and target strands. To this end, we have developed a versatile automated synthesis of oligonucleotide-oligospermine derivatives that gave fast access to a large variety of compounds. Plots of their hybridization temperatures T(m) vs overall charge provided a measure of the impact of interstrand phosphate repulsion (and of spermine-mediated attraction) on the main driving force of duplex formation, i.e., base pairing. It showed that stabilization brought about by excess cationic charges can be of larger absolute magnitude than interstrand repulsion, even in high salt media. Base sequence and conjugation site (3' or 5') hardly influenced the effect of spermine on T(m). In typical PCR probe conditions, the T(m) increased linearly with the number of grafted spermines (e.g., 6.2 degrees C per spermine for a decanucleotide probe). The large data set of T(m) vs number of spermines and oligonucleotide length allowed us to empirically derive a simple mathematical relation that is accurately predicting the T(m) of any oligonucleotide-oligospermine derivative. Zip nucleic acids (ZNA) are thus providing an interesting alternative to locked nucleic acids (LNA) or minor groove binders (MGB) for raising the stability of 8-12-mer oligonucleotides up to ca. 70 degrees C, the level required for quantitative PCR experiments.
Noir
Régis
R
Laboratoire de Chimie Génétique associé CNRS et Université de Strasbourg, Faculté de Pharmacie, 67401 Illkirch, France.
Kotera
Mitsuharu
M
Pons
Bénédicte
B
Remy
Jean-Serge
JS
Behr
Jean-Paul
JP
D007477:Ions / Q000737:chemistry; D015335:Molecular Probes / Q000737:chemistry*; D015394:Molecular Structure; D009696:Nucleic Acids / Q000737:chemistry*; D009841:Oligonucleotides / Q000138:chemical synthesis / Q000737:chemistry*; D013096:Spermine / Q000737:chemistry*; D013696:Temperature
D007477:Ions; D015335:Molecular Probes; D009696:Nucleic Acids; D009841:Oligonucleotides; D013096:Spermine