A versatile method for the preparation of conjugates of peptides with DNA/PNA/analog by employing chemo-selective click reaction in water

Novel strategies for the site-specific covalent labelling of nucleic acids

To broaden the scope of applications in DNA nano- and biotechnology, material science, diagnostics and molecular recognition the functionalization of DNA is of utmost importance. In the last decade many new methods have been developed to achieve this goal. Apart from the direct chemical synthesis of modified DNA by automated phosphoramidite chemistry incorporation of labelled triphosphates and the post-synthetic labelling approach evolved as valuable methods. New bioorthogonal reactions as Diels-Alder, click and Staudinger ligations pushed forward the post-synthetic approach as new insights into DNA polymerase substrate specificity allowed generation and amplification of labelled DNA strands. These novel developments are summarized herein.

Rapid and efficient DNA strand cross-linking by click chemistry

Click chemistry has been used to covalently cross-link complementary DNA strands between bases to form very stable duplexes. Several alkyne- and azide-modified uracil monomers were used to evaluate the effect of the linkers on the efficiency of the click reaction. All cross-linked duplexes had much higher thermal stabilities than non-cross-linked ones, with increases in melting temperature of up to 30 degrees C. In some cases, the conversion was near-quantitative, and the reaction was complete in 5 min.

Lipid-conjugated oligonucleotides via "click chemistry" efficiently inhibit hepatitis C virus translation

Conjugation of a lipid moiety via "click chemistry" potentiates the cellular uptake of oligonucleotides and allows their intracellular delivery. These nontoxic lipid conjugates efficiently inhibit hepatitis C virus internal ribosome entry site (IRES)-mediated translation in human hepatic Huh7 cells. The biological activity of the lipid-conjugated oligonucleotides is not affected by the presence of serum.

Synthesis of organometallic PNA oligomers by click chemistry

The facile side-specific insertion, on the solid phase, of one or two ferrocene moieties into peptide nucleic acid (PNA) oligomers by click chemistry is presented.

Triazole-linked dumbbell oligodeoxynucleotides with NF-kappaB binding ability as potential decoy molecules

Triazole-cross-linked oligodeoxynucleotides were synthesized with use of the Cu(I) catalyzed alkyne-azide cycloaddition (CuAAC) with oligodeoxynucleotides possessing N-3-(azidoethyl)thymidine and N-3-(propargyl)thymidine at the 3'- and 5'-termini. The newly synthesized oligodeoxynucleotides were thermally stable and their global structures retained those of non-cross-linked oligodeoxynucleotides. The newly synthesized dumbbell oligodeoxynucleotides showed excellent stability against snake venom phosphodiesterase (3'-exonuclease) and high thermal stability, which are necessary for decoy molecules to achieve biological responses leading to alteration of gene expression. Moreover, dumbbell oligodeoxynucleotides have the ability to bind to NF-kappaB p50 homodimer within a similar range to that of a control double-stranded decoy oligodeoxynucleotide. This strategy allows us to prepare triazole-linked dumbbell oligodeoxynucleotides with a range of loop lengths, and we found that the greater the number of the thymidine residues constituting the loop region, the higher the binding affinity of the dumbbell oligodeoxynucleotides to the nuclear factor kappaB. This means that a protein binding ability of the dumbbell oligodeoxynucleotides could be modulated by altering the loop size. This study clearly shows that cross-linking by the triazole structure does not prevent the dumbbell oligodeoxynucleotides from binding to the nuclear factor kappaB transcription factor. Therefore, the results obtained conclusively demonstrate that the triazole cross-linked dumbbell oligodeoxynucleotides could be proposed as powerful decoy molecules.