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Electron Spin Relaxation of Photoexcited Porphyrin in Water—Glycerol Glass

Recently, the photoexcited triplet state of porphyrin was proposed as a promising spin-label for pulsed dipolar electron paramagnetic resonance (EPR). Herein, we report the factors that determine the electron spin echo dephasing of the photoexcited porphyrin in a water–glycerol matrix. The electron...

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Autores principales: Sannikova, Natalya, Timofeev, Ivan, Bagryanskaya, Elena, Bowman, Michael, Fedin, Matvey, Krumkacheva, Olesya
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7321249/
https://www.ncbi.nlm.nih.gov/pubmed/32527023
http://dx.doi.org/10.3390/molecules25112677
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author Sannikova, Natalya
Timofeev, Ivan
Bagryanskaya, Elena
Bowman, Michael
Fedin, Matvey
Krumkacheva, Olesya
author_facet Sannikova, Natalya
Timofeev, Ivan
Bagryanskaya, Elena
Bowman, Michael
Fedin, Matvey
Krumkacheva, Olesya
author_sort Sannikova, Natalya
collection PubMed
description Recently, the photoexcited triplet state of porphyrin was proposed as a promising spin-label for pulsed dipolar electron paramagnetic resonance (EPR). Herein, we report the factors that determine the electron spin echo dephasing of the photoexcited porphyrin in a water–glycerol matrix. The electron spin relaxation of a water-soluble porphyrin was measured by Q-band EPR, and the temperature dependence and the effect of solvent deuteration on the relaxation times were studied. The phase memory relaxation rate (1/T(m)) is noticeably affected by solvent nuclei and is substantially faster in protonated solvents than in deuterated solvents. The T(m) is as large as 13–17 μs in deuterated solvent, potentially expanding the range of distances available for measurement by dipole spectroscopy with photoexcited porphyrin. The 1/T(m) depends linearly on the degree of solvent deuteration and can be used to probe the environment of a porphyrin in or near a biopolymer, including the solvent accessibility of porphyrins used in photodynamic therapy. We characterized the noncovalent binding of porphyrin to human serum albumin (HSA) from 1/T(m) and electron spin echo envelope modulation (ESEEM) and found that porphyrin is quite exposed to solvent on the surface of HSA. The 1/T(m) and ESEEM are equally effective and provide complementary methods to determine the solvent accessibility of a porphyrin bound to protein or to determine the location of the porphyrin.
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spelling pubmed-73212492020-07-06 Electron Spin Relaxation of Photoexcited Porphyrin in Water—Glycerol Glass Sannikova, Natalya Timofeev, Ivan Bagryanskaya, Elena Bowman, Michael Fedin, Matvey Krumkacheva, Olesya Molecules Article Recently, the photoexcited triplet state of porphyrin was proposed as a promising spin-label for pulsed dipolar electron paramagnetic resonance (EPR). Herein, we report the factors that determine the electron spin echo dephasing of the photoexcited porphyrin in a water–glycerol matrix. The electron spin relaxation of a water-soluble porphyrin was measured by Q-band EPR, and the temperature dependence and the effect of solvent deuteration on the relaxation times were studied. The phase memory relaxation rate (1/T(m)) is noticeably affected by solvent nuclei and is substantially faster in protonated solvents than in deuterated solvents. The T(m) is as large as 13–17 μs in deuterated solvent, potentially expanding the range of distances available for measurement by dipole spectroscopy with photoexcited porphyrin. The 1/T(m) depends linearly on the degree of solvent deuteration and can be used to probe the environment of a porphyrin in or near a biopolymer, including the solvent accessibility of porphyrins used in photodynamic therapy. We characterized the noncovalent binding of porphyrin to human serum albumin (HSA) from 1/T(m) and electron spin echo envelope modulation (ESEEM) and found that porphyrin is quite exposed to solvent on the surface of HSA. The 1/T(m) and ESEEM are equally effective and provide complementary methods to determine the solvent accessibility of a porphyrin bound to protein or to determine the location of the porphyrin. MDPI 2020-06-09 /pmc/articles/PMC7321249/ /pubmed/32527023 http://dx.doi.org/10.3390/molecules25112677 Text en © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Sannikova, Natalya
Timofeev, Ivan
Bagryanskaya, Elena
Bowman, Michael
Fedin, Matvey
Krumkacheva, Olesya
Electron Spin Relaxation of Photoexcited Porphyrin in Water—Glycerol Glass
title Electron Spin Relaxation of Photoexcited Porphyrin in Water—Glycerol Glass
title_full Electron Spin Relaxation of Photoexcited Porphyrin in Water—Glycerol Glass
title_fullStr Electron Spin Relaxation of Photoexcited Porphyrin in Water—Glycerol Glass
title_full_unstemmed Electron Spin Relaxation of Photoexcited Porphyrin in Water—Glycerol Glass
title_short Electron Spin Relaxation of Photoexcited Porphyrin in Water—Glycerol Glass
title_sort electron spin relaxation of photoexcited porphyrin in water—glycerol glass
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7321249/
https://www.ncbi.nlm.nih.gov/pubmed/32527023
http://dx.doi.org/10.3390/molecules25112677
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