Nguyen T. Thuong

Solid-phase preparation of 5′,3′-heterobifunctional oligodeoxyribonucleotides using modified solid supports

Abstract The solid-phase preparation of oligodeoxyribonucleotides attached to intercalator or reactive groups through their 5′- and (or) 3′-ends is reported. These syntheses implicate the introduction of suitable masked functional groups at the 5′-end of the oligonucleotide by the intermediate of their phosphoramidite derivatives or at the 3′-end of the oligonucleotide using modified solid supports. After full deblocking, the functional groups (phosphate, thiophosphate, primary amine or thiol) can be reacted with the suitable reactive group involved in the chosen ligand. These methods allow the preparation of heterobifunctional derivatized oligodeoxyribonucleotides.

Solid phase synthesis of oligo-α- and oligo-β-deoxynucleotidescovalently linked to an acridine

Abstract Oligo-α- and oligo-β-deoxynucleotides covalently linked at their 5′- end to an intercalating agent are synthesized on an automatic solid-phase DNA synthesizer. The acridine group was introduced with the acridine-phosphoramidite 5 , easily obtained from 2-methoxy-6-chloro-9-(ω-hydroxypentylamino)acridine 4 and 2-cyanoetyl N,N,N′,N′-tetraisopropyl-phosphoro-diamidite. The oligomers from the matrix were cleaved and unblocked in one step by sodium hydroxide.

Synthesis, purification and characterization of two peptide-oligonucleotide conjugates as potential artificial nucleases

Abstract Two peptide-oligonucleotide conjugates 10a and 10b, containing as their peptide moiety the active site mimic of ribonuclease A (HGH motif) and the Cu (II) complexing metallopeptide (GGH motif) respectively, have been synthesized by original on-line solid phase synthesis using pentafluorophenyl active esters and Boc-His(Tos)-OH. Mild basic conditions for the final deprotection and reversed-phase purification afforded the pure hybrid molecules in good yields. The conjugates have been characterized by matrix-assisted laser desorption ionization time-of-flight mass spectrometry.

Solid-phase synthesis of modified oligodeoxyribonucleotides with an acridine derivative or a thiophosphate group at their 3' end

Abstract Use of a derivatized support involving the 2,2′-diethyldithio-group 7 allows the automated synthesis of oligodeoxyribonucleotide bearing acridine derivative (via nucleoside-3′-acridinylphosphoramidite 3 ) or 3′phosphorothioate group (including the sulfurization step for attachment of the first nucleoside to the support).

On-line solid phase synthesis of oligonucleotide-peptide hybrids using silica supports

A procedure for the preparation of oligonucleotide-peptide hybrid molecules by means of automated synthesis is described. The conjugates have been assembled on silica supports including CPG (Controlled Pore Glass) and Fractosil supports. The novel Ne-lysine protecting group, 1-(4,4-dimethyl-2,6-dioxocyclohex-1-ylidene) ethyl (Dde) was used.

Synthese et reactivite d'oligothymidylates substitues par un agent intercalant et un groupe thiophosphate

Abstract An acridine dye derivative and a thiophosphate group have been covalently tethered to both ends of oligothymidylates. The sulphur atom of the thiophosphate anion reacts specifically with electrophilic agents, thereby allowing a variety of other chemical species to be attached to the modified oligonucleotides.

Synthesis and structural studies of a self-complementary decadeoxynucleotide d(AATTGCAATT) I. - Synthesis and chemical characterization of the decanucleotide

The synthesis of the self-complementary decadeoxynucleotide d(AATTGCAATT) is described. The phosphotriester method has been used with several modifications. Protected nucleotides have been prepared in a one-step reaction involving a new monofunctional phosphorylating agent: p-chlorophenyl-beta-cyanoethyl phosphate. Triethylammonium salts of mononucleoside 3-phosphodiesters were obtained either by decyanoethylation of the triesters or, in the case of thymine, by a one-step reaction starting from 5-0-methoxytritylthymidine and the mixture pyridine-para-chlorophenyl-methyl-phosphorobromidate. The usual coupling reactions were then used to prepare the decadeoxynucleotide in large quantities.

Interaction of Hoechst 33258 with a DNA triple helix

The interaction of Hoechst 33258 molecule, a minor groove binding drug, with T-A-T triple helix and A-T double helix was studied using circular dichroism spectroscopy and thermal denaturation. The triple helix consisted of an oligonucleotide (dA)12-x-(dT)12-x-(dT)12, where x is a hexa-ethylene glycol chain bridged between the 3 phosphate of one strand and the 5 phosphate of the following strand. This oligonucleotide is able to fold back on itself to form a very stable triplex. Circular dichroism spectroscopy demonstrates that Hoechst 33258 can bind to the triple helical structure. Spectral analysis shows that the bound drug exhibits a conformation and an environment slightly different in double-stranded and in triple-stranded structure. The affinity to the triple stranded structure is found smaller than to the double stranded one. Thermal denaturation experiments demonstrate that Hoechst 33258 destabilizes the triplex whereas it stabilizes the duplex.

Spectroscopic studies of (m5dC-dG)3: thermal stability of B- and Z-forms.

The hexanucleoside pentaphosphate d(m5CpGpm5CpGpm5CpG) has been studied in solution by ultra-violet absorption, circular dichroism and 31P nuclear magnetic resonance under various experimental conditions. In 0.2 M NaClO4 at low temperature, an hexamer duplex is formed which has a B or B-like conformation. As the salt concentration is increased, a transition from a B-form to the Z-form occurs and is complete in 3 M NaClO4. In 3 M NaClO4, the behavior of the Z double helix is complex as a function of temperature. The variation of the circular dichroism at 295 nm is biphasic. A first transition occurs over a large range of temperature and corresponds to a conformational change due to a non-cooperative intramolecular process. Ultra-violet absorption and 31P nuclear magnetic resonance show that the new conformation arising from a distortion of the backbone is not similar to that observed in low salt conditions (B-form). At high hexanucleotide concentration, aggregates are formed. The second transition is cooperative and corresponds to the melting of a double stranded helix into single strands.

Synthesis of Oligonucleotides Covalently Linked to Intercalating Agents and to Reactive Groups

Abstract The use of modified supports involving 2,2′-dithiodiethanol allows solid-phase synthesis of oligonucleotides derivatized at their 3′ end with an acridine or a phenanthroline derivative or with phosphate, thiophosphate and amino group.