Háskóli ÍslandsUniversity of IcelandGophane, Dnyaneshwar B.Endeward, BurkhardPrisner, Thomas F.Sigurdsson, Snorri2020-08-102020-08-102014-10-08Gophane, D.B., Endeward, B., Prisner, T.F. and Sigurdsson, S.T. (2014), Conformationally Restricted Isoindoline‐Derived Spin Labels in Duplex DNA: Distances and Rotational Flexibility by Pulsed Electron–Electron Double Resonance Spectroscopy. Chem. Eur. J., 20: 15913-15919. doi:10.1002/chem.2014037260947-65391521-3765 (eISSN)https://hdl.handle.net/20.500.11815/1953Post-print (lokagerð höfundar)Three structurally related isoindoline-derived spin labels that have different mobilities were incorporated into duplex DNA to systematically study the effect of motion on orientation-dependent pulsed electron-electron double resonance (PELDOR) measurements. To that end, a new nitroxide spin label, U-ExIm, was synthesized and incorporated into DNA oligonucleotides. U-ExIm is the first example of a conformationally unambiguous spin label for nucleic acids, in which the nitroxide N-O bond lies on the same axis as the three single bonds used to attach the otherwise rigid isoindoline- based spin label to a uridine base. Continuous-wave (CW) EPR measurements of U-ExIm confirm a very high rotational mobility of the spin label in duplex DNA relative to the structurally related spin label U-Im, which has restricted mobility due to an intramolecular hydrogen bond. The Xband CW-EPR spectra of U-ExIm can be used to identify mismatches in duplex DNA. PELDOR distance measurements between pairs of the spin labels U-Im, OxU, and U-ExIm in duplex DNA showed a strong angular dependence for U-Im, a medium dependence for OxU, and no orientation effect for U-ExIm. Thus, precise distances can be extracted from U-ExIm without having to take orientational effects into account.15913-15919eninfo:eu-repo/semantics/openAccessEPR SpectroscopyNucleic acidsPELDORDEERAminoxyl radicalLitrófsgreiningKjarnsýrurinfo:eu-repo/semantics/articleChemistry - A European Journal10.1002/chem.201403726