Application of magnetic field over-modulation for improved EPR linewidth measurements using probes with Lorentzian lineshape

Yuanmu Deng, Ramasamy P. Pandian, Rizwan Ahmad, Periannan Kuppusamy, Jay L. Zweier

Research output: Contribution to journalArticle

Abstract

Magnetic field modulation in CW electron paramagnetic resonance (EPR) is used for signal detection. However, it can also distort signal lineshape. In experiments where the linewidth information is of particular importance, small modulation amplitude is usually used to limit the lineshape distortion. The use of small modulation amplitude, however, results in low signal-to-noise ratio and therefore affects the precision of linewidth measurements. Recently, a new spectral simulation model has been developed enabling accurate fitting of modulation-broadened EPR spectra in liquids. Since the use of large modulation amplitude (over-modulation) can significantly enhance the EPR signal, the precision of linewidth measurements is therefore greatly improved. We investigated the over-modulation technique in EPR oximetry experiments using the oxygen-sensing probe lithium octa-n-butoxy-substitued naphthalocyanine (LiNc-BuO). Modulation amplitudes 2-18 times the intrinsic linewidth of the probe were applied to increase the spectral signal-to-noise ratio. The intrinsic linewidth of the probe at different oxygen concentrations was accurately extracted through curve fitting from the enhanced spectra. Thus, we demonstrated that the over-modulation model is also applicable to particulate oxygen-sensing probes such as LiNc-BuO and that the lineshape broadening induced by oxygen is separable from that induced by over-modulation. Therefore, the over-modulation technique can be used to enhance sensitivity and improve linewidth measurements for EPR oximetry with particulate oxygen-sensing probes with Lorentzian lineshape. It should be particularly useful for in vivo oxygen measurements, in which direct linewidth measurements may not be feasible due to inadequate signal-to-noise ratio.

Original languageEnglish (US)
Pages (from-to)254-261
Number of pages8
JournalJournal of Magnetic Resonance
Volume181
Issue number2
DOIs
StatePublished - Aug 2006
Externally publishedYes

Fingerprint

Electron Spin Resonance Spectroscopy
Magnetic Fields
Linewidth
Paramagnetic resonance
electron paramagnetic resonance
Modulation
Magnetic fields
Oxygen
Amplitude modulation
modulation
probes
Signal-To-Noise Ratio
magnetic fields
oxygen
oximetry
Oximetry
Signal to noise ratio
signal to noise ratios
particulates
Lithium

Keywords

  • EPR
  • EPR oximetry
  • Free radical
  • Magnetic field modulation
  • Over-modulation
  • Simulation

ASJC Scopus subject areas

  • Molecular Biology
  • Physical and Theoretical Chemistry
  • Spectroscopy
  • Radiology Nuclear Medicine and imaging
  • Condensed Matter Physics

Cite this

Application of magnetic field over-modulation for improved EPR linewidth measurements using probes with Lorentzian lineshape. / Deng, Yuanmu; Pandian, Ramasamy P.; Ahmad, Rizwan; Kuppusamy, Periannan; Zweier, Jay L.

In: Journal of Magnetic Resonance, Vol. 181, No. 2, 08.2006, p. 254-261.

Research output: Contribution to journalArticle

Deng, Yuanmu ; Pandian, Ramasamy P. ; Ahmad, Rizwan ; Kuppusamy, Periannan ; Zweier, Jay L. / Application of magnetic field over-modulation for improved EPR linewidth measurements using probes with Lorentzian lineshape. In: Journal of Magnetic Resonance. 2006 ; Vol. 181, No. 2. pp. 254-261.
@article{a119f2b7c93f4594bfb14b83e4097bf0,
title = "Application of magnetic field over-modulation for improved EPR linewidth measurements using probes with Lorentzian lineshape",
abstract = "Magnetic field modulation in CW electron paramagnetic resonance (EPR) is used for signal detection. However, it can also distort signal lineshape. In experiments where the linewidth information is of particular importance, small modulation amplitude is usually used to limit the lineshape distortion. The use of small modulation amplitude, however, results in low signal-to-noise ratio and therefore affects the precision of linewidth measurements. Recently, a new spectral simulation model has been developed enabling accurate fitting of modulation-broadened EPR spectra in liquids. Since the use of large modulation amplitude (over-modulation) can significantly enhance the EPR signal, the precision of linewidth measurements is therefore greatly improved. We investigated the over-modulation technique in EPR oximetry experiments using the oxygen-sensing probe lithium octa-n-butoxy-substitued naphthalocyanine (LiNc-BuO). Modulation amplitudes 2-18 times the intrinsic linewidth of the probe were applied to increase the spectral signal-to-noise ratio. The intrinsic linewidth of the probe at different oxygen concentrations was accurately extracted through curve fitting from the enhanced spectra. Thus, we demonstrated that the over-modulation model is also applicable to particulate oxygen-sensing probes such as LiNc-BuO and that the lineshape broadening induced by oxygen is separable from that induced by over-modulation. Therefore, the over-modulation technique can be used to enhance sensitivity and improve linewidth measurements for EPR oximetry with particulate oxygen-sensing probes with Lorentzian lineshape. It should be particularly useful for in vivo oxygen measurements, in which direct linewidth measurements may not be feasible due to inadequate signal-to-noise ratio.",
keywords = "EPR, EPR oximetry, Free radical, Magnetic field modulation, Over-modulation, Simulation",
author = "Yuanmu Deng and Pandian, {Ramasamy P.} and Rizwan Ahmad and Periannan Kuppusamy and Zweier, {Jay L.}",
year = "2006",
month = "8",
doi = "10.1016/j.jmr.2006.05.010",
language = "English (US)",
volume = "181",
pages = "254--261",
journal = "Journal of Magnetic Resonance",
issn = "1090-7807",
publisher = "Academic Press Inc.",
number = "2",

}

TY - JOUR

T1 - Application of magnetic field over-modulation for improved EPR linewidth measurements using probes with Lorentzian lineshape

AU - Deng, Yuanmu

AU - Pandian, Ramasamy P.

AU - Ahmad, Rizwan

AU - Kuppusamy, Periannan

AU - Zweier, Jay L.

PY - 2006/8

Y1 - 2006/8

N2 - Magnetic field modulation in CW electron paramagnetic resonance (EPR) is used for signal detection. However, it can also distort signal lineshape. In experiments where the linewidth information is of particular importance, small modulation amplitude is usually used to limit the lineshape distortion. The use of small modulation amplitude, however, results in low signal-to-noise ratio and therefore affects the precision of linewidth measurements. Recently, a new spectral simulation model has been developed enabling accurate fitting of modulation-broadened EPR spectra in liquids. Since the use of large modulation amplitude (over-modulation) can significantly enhance the EPR signal, the precision of linewidth measurements is therefore greatly improved. We investigated the over-modulation technique in EPR oximetry experiments using the oxygen-sensing probe lithium octa-n-butoxy-substitued naphthalocyanine (LiNc-BuO). Modulation amplitudes 2-18 times the intrinsic linewidth of the probe were applied to increase the spectral signal-to-noise ratio. The intrinsic linewidth of the probe at different oxygen concentrations was accurately extracted through curve fitting from the enhanced spectra. Thus, we demonstrated that the over-modulation model is also applicable to particulate oxygen-sensing probes such as LiNc-BuO and that the lineshape broadening induced by oxygen is separable from that induced by over-modulation. Therefore, the over-modulation technique can be used to enhance sensitivity and improve linewidth measurements for EPR oximetry with particulate oxygen-sensing probes with Lorentzian lineshape. It should be particularly useful for in vivo oxygen measurements, in which direct linewidth measurements may not be feasible due to inadequate signal-to-noise ratio.

AB - Magnetic field modulation in CW electron paramagnetic resonance (EPR) is used for signal detection. However, it can also distort signal lineshape. In experiments where the linewidth information is of particular importance, small modulation amplitude is usually used to limit the lineshape distortion. The use of small modulation amplitude, however, results in low signal-to-noise ratio and therefore affects the precision of linewidth measurements. Recently, a new spectral simulation model has been developed enabling accurate fitting of modulation-broadened EPR spectra in liquids. Since the use of large modulation amplitude (over-modulation) can significantly enhance the EPR signal, the precision of linewidth measurements is therefore greatly improved. We investigated the over-modulation technique in EPR oximetry experiments using the oxygen-sensing probe lithium octa-n-butoxy-substitued naphthalocyanine (LiNc-BuO). Modulation amplitudes 2-18 times the intrinsic linewidth of the probe were applied to increase the spectral signal-to-noise ratio. The intrinsic linewidth of the probe at different oxygen concentrations was accurately extracted through curve fitting from the enhanced spectra. Thus, we demonstrated that the over-modulation model is also applicable to particulate oxygen-sensing probes such as LiNc-BuO and that the lineshape broadening induced by oxygen is separable from that induced by over-modulation. Therefore, the over-modulation technique can be used to enhance sensitivity and improve linewidth measurements for EPR oximetry with particulate oxygen-sensing probes with Lorentzian lineshape. It should be particularly useful for in vivo oxygen measurements, in which direct linewidth measurements may not be feasible due to inadequate signal-to-noise ratio.

KW - EPR

KW - EPR oximetry

KW - Free radical

KW - Magnetic field modulation

KW - Over-modulation

KW - Simulation

UR - http://www.scopus.com/inward/record.url?scp=33746568908&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33746568908&partnerID=8YFLogxK

U2 - 10.1016/j.jmr.2006.05.010

DO - 10.1016/j.jmr.2006.05.010

M3 - Article

C2 - 16759891

AN - SCOPUS:33746568908

VL - 181

SP - 254

EP - 261

JO - Journal of Magnetic Resonance

JF - Journal of Magnetic Resonance

SN - 1090-7807

IS - 2

ER -