title: Progress towards a DNA-based model system for the study of electron spin-spin interactions.
abstract: A DNA-based model system is described for studying electron spin-spin interactions between a paramagnetic metal ion and a nitroxide spin label. The modified base deoxythymidine-EDTA (dT-EDTA) chelates the divalent or trivalent metal ion and produces a new feature in the circular dichroism (CD) spectra that makes it possible to monitor local DNA melting. Based on the results of optical and electron paramagnetic resonance (EPR) experiments, we find that the terminus of the DNA duplex that incorporates dT-EDTA and the spin-label melts at a higher temperature than the rest of the DNA duplex. EPR microwave progressive power saturation experiments performed at 77 K are consistent with the specific binding of Dy(III) at the EDTA site and an intramolecular dipole-dipole interaction between the nitroxide spin-label and the chelated Dy(III). This model system should be suitable for studying the relaxation properties of metal ions by saturation-recovery EPR.
authors.affiliation: Department of Chemistry, The College of New Jersey, PO Box 7718, Ewing, NJ 08628, USA.
authors.forename: Xi Jun
authors.initials: XJ
authors.lastname: Chen
authors.forename: Joseph
authors.initials: J
authors.lastname: Schramm
authors.forename: Christopher
authors.initials: C
authors.lastname: Tuohy
authors.forename: Heather
authors.initials: H
authors.lastname: Skiff
authors.forename: Kathleen
authors.initials: K
authors.lastname: Hummel
authors.forename: Anne R
authors.initials: AR
authors.lastname: Szklarski
authors.forename: Nicholas
authors.initials: N
authors.lastname: Vacirca
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Wolf
authors.forename: Donald J
authors.initials: DJ
authors.lastname: Hirsh
mesh_terms: D002942:Circular Dichroism; D003451:Cryoprotective Agents / Q000737:chemistry; D003497:Cyclic N-Oxides / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D004492:Edetic Acid / Q000031:analogs & derivatives* / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D008872:Microwaves; D008956:Models, Chemical; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D013113:Spin Labels; D013816:Thermodynamics; D013936:Thymidine / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: C523522:1-oxyl-2,2,5,5-tetramethylpyrroline-3-carboxylate; D003451:Cryoprotective Agents; D003497:Cyclic N-Oxides; D009838:Oligodeoxyribonucleotides; D013113:Spin Labels; C523523:deoxythymidine-EDTA; D004247:DNA; D004492:Edetic Acid; D013936:Thymidine