title: Room-temperature electron spin relaxation of nitroxides immobilized in trehalose: Effect of substituents adjacent to NO-group.
abstract: Trehalose has been recently promoted as efficient immobilizer of biomolecules for room-temperature EPR studies, including distance measurements between attached nitroxide spin labels. Generally, the structure of nitroxide influences the electron spin relaxation times, being crucial parameters for room-temperature pulse EPR measurements. Therefore, in this work we investigated a series of nitroxides with different substituents adjacent to NO-moiety including spirocyclohexane, spirocyclopentane, tetraethyl and tetramethyl groups. Electron spin relaxation times (T1, Tm) of these radicals immobilized in trehalose were measured at room temperature at X- and Q-bands (9/34GHz). In addition, a comparison was made with the corresponding relaxation times in nitroxide-labeled DNA immobilized in trehalose. In all cases phase memory times Tm were close to 700ns and did not essentially depend on structure of substituents. Comparison of temperature dependences of Tm at T=80-300K shows that the benefit of spirocyclohexane substituents well-known at medium temperatures (∼100-180K) becomes negligible at 300K. Therefore, unless there are specific interactions between spin labels and biomolecules, the room-temperature value of Tm in trehalose is weakly dependent on the structure of substituents adjacent to NO-moiety of nitroxide. The issues of specific interactions and stability of nitroxide labels in biological media might be more important for room temperature pulsed dipolar EPR than differences in intrinsic spin relaxation of radicals.
authors.affiliation: N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS, Lavrentiev ave. 9, Novosibirsk 630090, Russia; Novosibirsk State University, Pirogova str. 2, Novosibirsk 630090, Russia.
authors.forename: Andrey A
authors.initials: AA
authors.lastname: Kuzhelev
authors.affiliation: N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS, Lavrentiev ave. 9, Novosibirsk 630090, Russia; International Tomography Center SB RAS, Institutskaya str. 3a, Novosibirsk 630090, Russia.
authors.forename: Rodion K
authors.initials: RK
authors.lastname: Strizhakov
authors.affiliation: International Tomography Center SB RAS, Institutskaya str. 3a, Novosibirsk 630090, Russia; Novosibirsk State University, Pirogova str. 2, Novosibirsk 630090, Russia.
authors.forename: Olesya A
authors.initials: OA
authors.lastname: Krumkacheva
authors.affiliation: N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS, Lavrentiev ave. 9, Novosibirsk 630090, Russia; Novosibirsk State University, Pirogova str. 2, Novosibirsk 630090, Russia.
authors.forename: Yuliya F
authors.initials: YF
authors.lastname: Polienko
authors.affiliation: N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS, Lavrentiev ave. 9, Novosibirsk 630090, Russia; Novosibirsk State University, Pirogova str. 2, Novosibirsk 630090, Russia.
authors.forename: Denis A
authors.initials: DA
authors.lastname: Morozov
authors.affiliation: Novosibirsk State University, Pirogova str. 2, Novosibirsk 630090, Russia; Institute of Chemical Biology and Fundamental Medicine, SB RAS, Novosibirsk 630090, Russia.
authors.forename: Georgiy Yu
authors.initials: GY
authors.lastname: Shevelev
authors.affiliation: Institute of Chemical Biology and Fundamental Medicine, SB RAS, Novosibirsk 630090, Russia.
authors.forename: Dmitrii V
authors.initials: DV
authors.lastname: Pyshnyi
authors.affiliation: N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS, Lavrentiev ave. 9, Novosibirsk 630090, Russia; Novosibirsk State University, Pirogova str. 2, Novosibirsk 630090, Russia.
authors.forename: Igor A
authors.initials: IA
authors.lastname: Kirilyuk
authors.affiliation: International Tomography Center SB RAS, Institutskaya str. 3a, Novosibirsk 630090, Russia; Novosibirsk State University, Pirogova str. 2, Novosibirsk 630090, Russia. Electronic address: mfedin@tomo.nsc.ru.
authors.forename: Matvey V
authors.initials: MV
authors.lastname: Fedin
authors.affiliation: N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS, Lavrentiev ave. 9, Novosibirsk 630090, Russia; Novosibirsk State University, Pirogova str. 2, Novosibirsk 630090, Russia. Electronic address: egbagryanskaya@nioch.nsc.ru.
authors.forename: Elena G
authors.initials: EG
authors.lastname: Bagryanskaya
mesh_terms: D000327:Adsorption; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D008422:Materials Testing; D009569:Nitric Oxide / Q000737:chemistry*; D013113:Spin Labels; D013696:Temperature; D014199:Trehalose / Q000737:chemistry*
chemical_list: D013113:Spin Labels; D009569:Nitric Oxide; D014199:Trehalose
keywords: Electron spin relaxation; Nitroxides; Pulse dipole EPR; Spin labels; Trehalose