@phdthesis{Dickerhoff2017,
  author    = {Jonathan Dickerhoff},
  title     = {Nucleotide Analogues as Powerful Tools in Exploring G-Quadruplex Folding},
  journal    = {Nukleotidanaloga als effektive Werkzeuge zur Untersuchung der G-Quadruplexfaltung},
  url       = {https://nbn-resolving.org/urn:nbn:de:gbv:9-002788-2},
  year      = {2017},
  abstract  = {The four stranded G-quadruplexes are important secondary structures of nucleic acids formed by guanosine-rich sequences. Besides the application as scaffold for technological applications, they are involved in many cellular processes such as gene regulation, replication, or maintenance of chromosomal ends. Characteristically, a large diversity of quadruplex structures is observed, whereas the correlation between sequence and structure is still not fully understood. In this thesis, the effects of modified nucleotides on G-quadruplexes were analyzed using NMR-spectroscopy to gain insight into driving forces determining the folding process. Contrary to DNA quadruplexes, the folding landscape of RNA structures is mostly restricted to parallel topologies. Therefore, ribose moieties were introduced into DNA sequences to isolate the effect of the additional hydroxy group. In this way, sequential CHO hydrogen bonds between the 2\′-OH and the H8 of the 3\′-neighbored anti conformer were identified and subsequently detected within RNA structures. In a second part, 2\′-fluoro-2\′-deoxyribose was incorporated at positions with guanosine in unfavored syn orientation. Instead of a changed global fold, the direction of the hydrogen bond network in the modified tetrad was reversed. This first example of tetrad inversion within a unimolecular quadruplex yielded a unique (3+1)-hybrid topology with only homopolar stacking interactions. Additionally, the effect was reproduced for another sequence and high-resolution structures were determined. Unfavored interactions between the 2\′-fluorine and the narrow groove of the quadruplex were identified as a reason for different sugar conformations and consequent structural rearrangements.},
  language  = {en}
}