<> "The repository administrator has not yet configured an RDF license."^^ . <> . . "Modified Oligonucleotides : Investigations and Applications of the Diels-Alderase Ribozyme"^^ . "The hypothesis of the origin of life was fundamentally changed by the discovery of catalytic RNA. The fascinating fact that RNA can function as a catalyst in the formation of carbon-carbon bonds, thereby creating enantiomeric centers and thus potential building blocks for life-sustaining structures, is of great importance to those who wish to understand biocatalytic processes. Ribozymes are generally identified by in vitro selection. Such an artificial ribozyme was utilized for the work presented in this dissertation; specifically, the Diels-Alderase ribozyme was the focus of the investigation. This ribozyme catalyzes a Diels-Alder reaction between anthracene and maleimide. The work presented herein revolved around modifications of oligonucleotides on different levels. Modification of RNA with organic moieties is indispensable for effective in vitro selection of such ribozymes. This thesis consists of three parts. In the first, new pathways were established for the synthesis of modified guanosine monophosphates (GMPs). The ability of the enzyme T7 RNA polymerase to incorporate these modified GMPs during transcription priming coined the term initiator nucleotides. The syntheses of a substituted anthracene and aldehyde-modified initiator nucleotides connected with a flexible polyethylene glycol linker were realized in just three synthetic steps. The incorporation of the initiator nucleotides into short RNA transcripts was investigated, as well as their incorporation into an RNA library with a randomized region eligible for in vitro selection. Excellent incorporation rates up to 77% were obtained for the transcription into the RNA library. The reactivity of thereby modified RNA molecules was subsequently studied in chemical reactions. Whereas the anthracene derivative could be reacted in a Diels-Alder reaction, the aldehyde led to full conversion in the reaction with hydrazides. In the second part of this thesis, the effect of divalent metal ions on the folding and stability of the Diels-Alderase ribozyme was studied in UV thermal denaturation experiments. Low concentrations of Mg2+ cations led to secondary structure stabilization of up to 85°C. Thermal denaturation studies of the wild-type ribozyme and comparison to mutants complement other ongoing investigations of the complex interplay of non-standard base pairs and triples in the ribozyme structure. While the wild-type ribozyme exhibited a significant stabilization in the presence of Mg2+ cations, a comparable stabilization of the mutants could not be observed. In accordance with the findings in other studies, the best interpretation of this effect on stability was that the mutants, despite their ability to form a pseudoknot structure, could not undergo further compaction. In the third part of this thesis, the Diels-Alderase ribozyme, which causes a remarkable acceleration of the Diels-Alder reaction rate, was successfully used as a catalyst for fluorescently labeling oligonucleotides in cis and in trans. Investigations of the substrate specificity of the ribozyme revealed that only fluorescent maleimide dyes with five carbon atoms next to the dye were accepted as substrates. This distinct feature was utilized as a bioorthogonal labeling strategy for the Diels-Alder bioconjugation of anthracene-modified oligonucleotides with equimolar proportions of fluorescent dyes. A new dual orthogonal labeling strategy was achieved by using an iodoacetamide dye for the thiol modification and a maleimide dye for the anthracene modification within the same DNA strand. For the anthracene modification, the Diels-Alderase ribozyme was employed as a catalyst."^^ . "2011" . . . . . . . . "Florentine"^^ . "Wahl"^^ . "Florentine Wahl"^^ . . . . . . "Modified Oligonucleotides : Investigations and Applications of the Diels-Alderase Ribozyme (PDF)"^^ . . . "Thesis_Florentine_Wahl.pdf"^^ . . . "Modified Oligonucleotides : Investigations and Applications of the Diels-Alderase Ribozyme (Other)"^^ . . . . . . "indexcodes.txt"^^ . . . "Modified Oligonucleotides : Investigations and Applications of the Diels-Alderase Ribozyme (Other)"^^ . . . . . . "lightbox.jpg"^^ . . . "Modified Oligonucleotides : Investigations and Applications of the Diels-Alderase Ribozyme (Other)"^^ . . . . . . "preview.jpg"^^ . . . "Modified Oligonucleotides : Investigations and Applications of the Diels-Alderase Ribozyme (Other)"^^ . . . . . . "medium.jpg"^^ . . . "Modified Oligonucleotides : Investigations and Applications of the Diels-Alderase Ribozyme (Other)"^^ . . . . . . "small.jpg"^^ . . "HTML Summary of #11762 \n\nModified Oligonucleotides : Investigations and Applications of the Diels-Alderase Ribozyme\n\n" . "text/html" . . . "570 Biowissenschaften, Biologie"@de . "570 Life sciences"@en . .