In-cell approaches in electron paramagnetic resonance spectroscopy to study conformations of DNA G-quadruplexes

............................................................................................. Introduction.......................................................................................... I. Literature overview 1. DNA G-quadruplexes........................................................................... 1.1 Structural characterization................................................................. 1.2 Human telomeric DNA.................................................................... 1.3 Methods to study G-quadruplexes....................................................... 2. Spin-label EPR spectroscopy.................................................................. 2.1 Resonance phenomenon.................................................................. 2.2 Time-domain (pulse) EPR............................................................... 2.2.1 Pulses and pulse sequences........................................................ 2.2.2 Double electron-electron resonance.............................................. 2.3 Nitroxides as spin labels.................................................................. 2.4 EPR on spin labeled DNA............................................................... 2.4.1 Site-directed spin labeling of oligonucleotides................................. 2.4.2 DEER studies of DNA............................................................. 3. In-cell magnetic resonance..................................................................... 3.1 General prerequisites and techniques................................................... 3.2 Chemical reactions and stability of nitroxides in biological systems............... II. Experimental 4. Materials.......................................................................................... 4.1 Chemicals.................................................................................... 4.2 Spin labeled DNA.......................................................................... 4.3 Xenopus laevis oocytes and cell extract................................................. 5. Methods........................................................................................... 5.1 CD spectroscopy........................................................................... 5.2 FRET......................................................................................... 4