TY - JOUR

T1 - Pulse EPR of Triarylmethyl Probes

T2 - A New Approach for the Investigation of Molecular Motions in Soft Matter

AU - Kuzhelev, Andrey A.

AU - Krumkacheva, Olesya A.

AU - Ivanov, Mikhail Yu

AU - Prikhod'Ko, Sergey A.

AU - Adonin, Nicolay Yu

AU - Tormyshev, Victor M.

AU - Bowman, Michael K.

AU - Fedin, Matvey V.

AU - Bagryanskaya, Elena G.

N1 - Publisher Copyright: Copyright © 2018 American Chemical Society.

PY - 2018/9/13

Y1 - 2018/9/13

N2 - 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.

AB - 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.

KW - ELECTRON-SPIN RELAXATION

KW - DISTANCE MEASUREMENTS

KW - TRITYL RADICALS

KW - DIPOLAR SPECTROSCOPY

KW - LIPID-BILAYERS

KW - IONIC LIQUIDS

KW - CW EPR

KW - LABELS

KW - RESONANCE

KW - DYNAMICS

UR - http://www.scopus.com/inward/record.url?scp=85053205753&partnerID=8YFLogxK

U2 - 10.1021/acs.jpcb.8b07714

DO - 10.1021/acs.jpcb.8b07714

M3 - Article

C2 - 30137993

AN - SCOPUS:85053205753

VL - 122

SP - 8624

EP - 8630

JO - Journal of Physical Chemistry B

JF - Journal of Physical Chemistry B

SN - 1520-6106

IS - 36

ER -