Synthesis, characterizations and applications of C2'-modified oligonucleotide analogues
Notice bibliographique
Résumé
During the past two decades, oligonucleotide analogues have drawn considerable attention as potential therapeutic and diagnostic agents. Gene silencing through "RNA interference" (siRNA) or the more mature "antisense" technology (AONs) have proven to be powerful tools for studying gene functions. Chemical modifications of these compounds are generally required to improve their "drug-like" properties such as potency, selectivity and delivery, particularly in the development of oligonucleotide-based therapeutics. Aptamers are another emerging class of oligonucleotide therapeutics and diagnostics. This thesis focuses on oligonucleotides containing 1-(2-deoxy-2-alpha-C-hydroxymethyl-beta- D-ribofuranosyl)thymine (2'-alpha-hm-dT, abbreviated as "H") and 2'-deoxy-2'-fluoroarabinonucleotides (2'F-araN), and their applications. A major component of this work focused on the synthesis of 2'-alpha-hm-dT (H) and the first investigation of oligoribonucleotides containing this nucleoside analogue. Specifically, 2'-CH2O-phosphoramidite and 3'-O-phosphoramidite derivatives of H were synthesized and incorporated into both 2',5'-RNA and RNA chains. Incorporation of 3',5'-linked H units into a DNA, 2',5'-RNA or RNA strand led to significant destabilization of duplexes formed with unmodified RNA targets. 2',5'-Linked H units into 2',5'-RNA or RNA caused significantly less destabilization, and in fact, they were shown to stabilize the loop structure of some RNA hairpins. These results were rationalized in terms of the "compact" and "extended" conformations of nucleotides. A series of branched RNAs (Y-shaped) related to yeast pre-mRNA splicing intermediates were synthesized incorporating both natural (i.e., ribose) and nonnatural (i.e., H, and acyclic nucleoside) branch points in order to examine the effect of sugar conformation and phosphodiester configuration on yeast debranching enzyme (yDBR) hydrolytic efficiency. The results indicate that 2'-phosphodiester scission with yDBR occurs only with a ribose-phosphate backbone at the branch point, whereas some of the H-containing branched RNAs were found to competitively inhibit yDBR hydrolytic activity. This thesis also examines the stabilization of DNA guanine-quadruplexes (G-quadruplexes) by replacing the deoxyribose sugar by a 2-deoxy-2-fluoroarabinose. The effect of this substitution was assessed in the well-known thrombin-binding DNA aptamer d(G2T2G2TGTG2T 2G2), the telomeric DNA d(G4T4G 4) sequence and a phosphorothioate octanucleotide PS-d(T2G 4T2), all of which are known to fold into G-quadruplex structures. Stabilization of the G-quadruplexes was possible provided that the arabinose sugar was introduced at guanosine residues adopting an anti N-glycosidic bond conformation. Some of the arabinose modified thrombin-binding aptamers not only exhibited superior thermal stability and nuclease resistance, but also maintained high thrombin binding affinity. Finally, this thesis examines the ability of DNA polymerases to recognize and utilize 2'-deoxy-2'-fluoro-beta-D-arabinonucleoside 5'-triphosphates (2'F-araNTPs) as building blocks for the synthesis of 2'-deoxy-2'-fluoro-beta- D-arabinonucleic acids (2'F-ANA). The results obtained indicate that a few DNA polymerases can synthesize 2'F-ANA and 2'F-ANA-DNA chimeras on a DNA template. Conversely, certain enzymes were shown to catalyze 2'F-ANA template-directed DNA synthesis. While it was not possible to synthesize 2'F-ANA strands on a 2'F-ANA template, it is possible for some DNA polymerases to catalyze the formation of multiple 2'F-ANA:2'F-ANA base pairs within a DNA-FANA chimeric duplex. These results suggest that it should be possible to evolve FANA-modified aptamers via SELEX.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 0,001 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».