On September 9 Anna-Lena Johanna Segler will defend her doctoral thesis titled: Synthesis of DNA and RNA containing rigid spin- and fluorescent labels for studies by EPR and fluorescence spectroscopies. The defence will be held at the National Museum Of Iceland - Lecture hall and starts at 10:00.
Dr. Stefán Jónsson, Manager at Alvotech
Dr. Claudia Höbartner, Professor at the Faculty of Chemistry and Pharmacy, University of Würzburg, Germany
Advisor: Dr. Snorri Þór Sigurðsson, Professor at the Faculty of Physical Sciences, University of Iceland
Dr. Óttar Rolfsson, Professor at the Faculty of Medicine, University of Iceland
Dr. Guðmundur G. Haraldsson, Professor at the Faculty of Physical Sciences, University of Iceland
Dr. Benjamín Ragnar Sveinbjörnsson, Assistant Professor at the Faculty of Physical Sciences, University of Iceland
Chair of Ceremony: Dr. Einar Örn Sveinbjörnsson, Professor and the Head of the Faculty of Physical Sciences, University of Iceland
To gain information about the function of nucleic acids, their structure and dynamics need to be investigated. Electron paramagnetic resonance (EPR)- and fluorescence spectroscopies are highly sensitive and valuable techniques to study nucleic acids. These methods require incorporation of spin- and fluorescent labels prior to measurements. This doctoral dissertation focuses on the synthesis of rigid spin- and fluorescent labels and their incorporation into DNA and RNA for the study of structure and dynamics of nucleic acids by EPR- and fluorescence spectroscopies.
The first part of the thesis describes a protecting group strategy to address a long-standing problem associated with spin-labeling by chemical synthesis of nucleic acids, namely reduction of nitroxides during solid-phase synthesis. A benzoyl group was used to protect the nitroxide by reducing the nitroxide to the corresponding hydroxylamine, followed by benzoylation. The method was used to incorporate the rigid spin label Çm into RNA with quantitative spin-labeling efficiency. This protecting-group strategy can be used as a general method to incorporate nitroxide spin-labels into nucleic acids by the phosphoramidite approach.
The second part of this thesis focuses on labeling of specific nucleic acids with rigid spin- and fluorescent labels, namely Ç, Çm and Çmf. The rigid spin labels Ç and Çm were incorporated into DNA and RNA, respectively, for measurements in the research group of Prof. Thomas F. Prisner at the Goethe University in Frankfurt, by pulsed electron-electron double resonance (PELDOR) spectroscopy. Furthermore, Çmf, the fluorescent derivative of Çm, was incorporated into various RNAs to investigate them by fluorescence spectroscopy, by the research group of Prof. Josef Wachtveitl at the Goethe University in Frankfurt.
The third part of the thesis describes the design and synthesis of the new rigid spin labels Ċ and Ċm for DNA and RNA, respectively, that are carbazole-derived nitroxides and analogues of cytidine. Crystal structure analysis indicated that Ċ and Ċm are more rigid than the rigid spin labels Ç and Çm. Ċ and Ċm were incorporated into several oligonucleotides and shown to be non-perturbing of duplex structure. These new rigid spin labels are promising candidates for future studies of DNA and RNA structures and dynamics by pulsed EPR methods.
About the doctoral candidate:
Anna-Lena was born in Rendsburg, Germany in 1990 but moved to Iceland with her family in 1998. She completed her BS in Chemistry at the University of Iceland in 2016. Anna-Lena began her MS in chemistry at the University of Iceland in 2016 but switched to the PhD program in 2017.