Long-Mange Distance Measurements on Nucleic Acids in Cells by Pulsed EPM Spectroscopy

摘要

The tertiary structure and conformational dynamics of ribonucleic acids (RNAs) are essential for their function as biological catalysts, regulators, and structural scaffolds. X-ray crystallography, NMR, continuous-wave (cw) EPR, and fluorescence spectroscopies are well-established methods to investigate their structural and dynamic properties. Additionally, over the past few years pulsed electron-electron double-resonance (PELDOR) spectroscopy has been used to determine distances in nucleic acid (NA) molecules in the range of 1.5-7 nm. The method measures the magnetic dipole-dipole interaction between two nitroxide spin labels covalently attached to the oligonucleotide molecule. PELDOR spectroscopy has proven to provide very accurate distances and distance distribution functions for double-labeled oligonucleotides. Thus, we can obtain important information on the tertiary structure as well as on the conformational flexibility of the molecule. The structure and dynamics of NAs depend on environmental factors, such as the concentration of ions, small molecules, molecular crowding, viscosity, and interactions with proteins. Therefore, it is important to investigate whether the in vitro determined NA structure reflects the intracellular (in vivo) conformation.