Pulse EPR of Triarylmethyl Probes: A New Approach for the Investigation of Molecular Motions in Soft Matter

Andrey A. Kuzhelev, Olesya A. Krumkacheva, Mikhail Yu Ivanov, Sergey A. Prikhod'Ko, Nicolay Yu Adonin, Victor M. Tormyshev, Michael K. Bowman, Matvey V. Fedin, Elena G. Bagryanskaya

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

Triarylmethyl (TAM) radicals have become widely used free radicals in the past few years. Their electron spins have long relaxation times and narrow electron paramagnetic resonance (EPR) lines, which make them an important class of probes and tags in biological applications and materials science. In this work, we propose a new approach to characterize librations by means of TAM radicals. The temperature dependence of motional parameter 〈α2〉τc, where 〈α2〉 is the mean-squared amplitude of librations and τc is their characteristic time, is obtained by comparison of the 1/Tm phase-relaxation rates at X- and Q-band EPR frequencies. We study three soft matrixes, viz., glassy trehalose and two ionic liquids, using TAMs with optimized relaxation properties OX063D and a dodeca-n-butyl homologue of Finland trityl (DBT). The motional parameters 〈α2〉τc obtained using TAMs are in excellent agreement with those obtained by means of nitroxide radicals. At the same time, the new TAM-based approach has (1) greater sensitivity due to the narrower EPR spectrum and (2) greater measuring accuracy and broader temperature range due to longer relaxation times. The developed approach may be fruitfully implemented to probe low-temperature molecular motions of TAM-labeled biopolymers, membrane systems, polymers, molecules in glassy media, and ionic liquids.

Original languageEnglish
Pages (from-to)8624-8630
Number of pages7
JournalJournal of Physical Chemistry B
Volume122
Issue number36
DOIs
Publication statusPublished - 13 Sep 2018

Keywords

  • ELECTRON-SPIN RELAXATION
  • DISTANCE MEASUREMENTS
  • TRITYL RADICALS
  • DIPOLAR SPECTROSCOPY
  • LIPID-BILAYERS
  • IONIC LIQUIDS
  • CW EPR
  • LABELS
  • RESONANCE
  • DYNAMICS

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