Vznik a stabilita DNA minivlásenek

Bušková, Hana

The secondary structure of DNA is variable and depends on the sequence of nu- cleotides in a strand. While DNA can form duplexes, formations of three, four, or even a single strand have been observed in vivo and in vitro as well. In this thesis, we study the effect of small changes of oligonucleotide sequences on the stability of hairpins formed by DNA heptamers by 1 H nuclear magnetic resonance (NMR) spectroscopy. Suitable DNA sequences were selected based on symmetry rules and stability prediction by near- est neighbor model. Two-dimensional 1 H -1 H NOESY spectra were used to assign the 1 H resonances of aromatic hydrogens. Variable-temperature 1D spectra served for ob- taining melting curves, from which the thermodynamic properties of the hairpins were determined. The presence of hairpins in the solutions was confirmed by the character of the NOESY spectra, independence of melting temperature on oligonucleotide concen- tration, and comparison of competing melting-curve models of duplex and hairpin. Our results point out the importance of the order of the stem base pairs and contribute to the description of the extraordinary stability of DNA mini-hairpins. 1

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