Home Physical Sciences Triarylmethyl Radical: EPR Signal to Noise at Frequencies between 250 MHz and 1.5 GHz and Dependence of Relaxation on Radical and Salt Concentration and on Frequency
Article
Licensed
Unlicensed Requires Authentication

Triarylmethyl Radical: EPR Signal to Noise at Frequencies between 250 MHz and 1.5 GHz and Dependence of Relaxation on Radical and Salt Concentration and on Frequency

  • Yilin Shi , Richard W. Quine , George A. Rinard , Laura Buchanan , Sandra S. Eaton , Gareth R. Eaton EMAIL logo , Boris Epel , Simone Wanless Seagle and Howard J. Halpern
Published/Copyright: November 18, 2016
Zeitschrift für Physikalische Chemie
From the journal Zeitschrift für Physikalische Chemie Volume 231 Issue 4

Abstract

In vivo oximetry by pulsed electron paramagnetic resonance is based on measurements of changes in electron spin relaxation rates of probe molecules, such as the triarylmethyl radicals. A series of experiments was performed at frequencies between 250 MHz and 1.5 GHz to assist in the selection of an optimum frequency for oximetry. Electron spin relaxation rates for the triarylmethyl radical OX063 as a function of radical concentration, salt concentration, and resonance frequency were measured by electron spin echo 2-pulse decay and 3-pulse inversion recovery in the frequency range of 250 MHz–1.5 GHz. At constant OX063 concentration, 1/T1 decreases with increasing frequency because the tumbling dependent processes that dominate relaxation at 250 MHz are less effective at higher frequency. 1/T2 also decreases with increasing frequency because 1/T1 is a significant contribution to 1/T2 for trityl radicals in fluid solution. 1/T2–1/T1, the incomplete motional averaging contribution to 1/T2, increases with increasing frequency. At constant frequency, relaxation rates increase with increasing radical concentration due to contributions from collisions that are more effective for 1/T2 than 1/T1. The collisional contribution to relaxation increases as the concentration of counter-ions in solution increases, which is attributed to interactions of cations with the negatively charged radicals that decrease repulsion between trityl radicals. The Signal-to-Noise ratio (S/N) of field-swept echo-detected spectra of OX063 were measured in the frequency range of 400 MHz–1 GHz. S/N values, normalized by √Q, increase as frequency increases. Adding salt to the radical solution decreased S/N because salt lowers the resonator Q. Changing the temperature from 19 to 37°C caused little change in S/N at 700 MHz. Both slower relaxation rates and higher S/N at higher frequencies are advantageous for oximetry. The potential disadvantage of higher frequencies is the decreased depth of penetration into tissue.

Keywords: cross loop resonator; electron spin relaxation; in vivo imaging; tumbling

Dedicated to: Kev Salikhov on the occasion of his 80th birthday.

Acknowledgments

This research was funded in part by NIH P41 EB002034 (HJH, PI), R01 CA098575 (HJH, PI) and R01CA177744 (GRE, PI). Loans of equipment from Bruker BioSpin contributed to the success.

References

1. I. Dhimitruka, A. A. Bobko, T. D. Eubank, D. A. Komarov, V. V. Khramtsov, J. Am. Chem. Soc. 135 (2013) 5904.10.1021/ja401572rSearch in Google Scholar PubMed PubMed Central

2. B. B. Williams, H. J. Halpern, Biol. Magn. Reson. 23 (2005) 283.10.1007/0-387-26741-7_11Search in Google Scholar

3. E. Epel, M. K. Bowman, C. Mailer, H. Halpern, Magn. Reson. Med. 27 (2014) 362.10.1002/mrm.24926Search in Google Scholar PubMed PubMed Central

4. B. Epel, H. Halpern, Methods Enzymol. 564 (2015) 501.10.1016/bs.mie.2015.08.017Search in Google Scholar PubMed PubMed Central

5. L. J. Berliner, In Vivo EPR (ESR): Theory and Application, Kluwer Academic, New York (2003).10.1007/978-1-4615-0061-2Search in Google Scholar

6. A. A. Bobko, I. Dhimitruka, J. L. Zweier, V. V. Khramtsov, J. Am. Chem. Soc. 129 (2007) 7240.10.1021/ja071515uSearch in Google Scholar PubMed

7. L. Yong, J. Harbridge, R. W. Quine, G. A. Rinard, S. S. Eaton, G. R. Eaton, C. Mailer, E. Barth, H. J. Halpern, J. Magn. Reson. 152 (2001) 156.10.1006/jmre.2001.2379Search in Google Scholar PubMed

8. H. J. Halpern, D. P. Spencer, J. van Polen, M. K. Bowman, A. C. Nelson, E. M. Dowey, B. A. Teicher, Rev. Sci. Instrum. 60 (1989) 1040.10.1063/1.1140314Search in Google Scholar

9. H. J. Halpern, M. K. Bowman, in EPR Imaging and In Vivo EPR, G. R. Eaton et al., Eds., CRC Press, Boca Raton (1991), ch. 6.Search in Google Scholar

10. A. Kuzhelev, D. Trukhin, O. Krumkacheva, R. Strizhakov, O. Rogozhnikova, T. Troitskaya, M. Fedin, V. Tormyshev, E. Bagryanskaya, J. Phys. Chem. B 119 (2015) 13630.10.1021/acs.jpcb.5b03027Search in Google Scholar PubMed PubMed Central

11. R. W. Quine, G. A. Rinard, Y. Shi, L. A. Buchanan, J. R. Biller, S. S. Eaton, G. R. Eaton, Magn. Reson. B, Magn. Reson. Engineering accepted for publication (2016).Search in Google Scholar

12. R. W. Quine, G. A. Rinard, B. T. Ghim, S. S. Eaton, G. R. Eaton, Rev. Sci. Instrum. 67 (1996) 2514.10.1063/1.1147206Search in Google Scholar

13. R. Owenius, G. R. Eaton, S. S. Eaton, J. Magn. Reson. 172 (2005) 168.10.1016/j.jmr.2004.10.007Search in Google Scholar

14. M. K. Bowman, C. Mailer, H. J. Halpern, J. Magn. Reson. 172 (2005) 254.10.1016/j.jmr.2004.10.010Search in Google Scholar

15. S. N. Trukhan, V. F. Yudanov, O. Rogozhnikova, D. Trukhin, M. K. Bowman, M. D. Krzyaniak, H. Chen, O. N. Martyanov, J. Magn. Reson. 233 (2013) 29.10.1016/j.jmr.2013.04.017Search in Google Scholar

16. G. A. Rinard, R. W. Quine, S. S. Eaton, G. R. Eaton, Biol. Magn. Reson. 21 (2004) 115.10.1007/978-1-4419-8951-2_3Search in Google Scholar

17. G. A. Rinard, S. S. Eaton, G. R. Eaton, C. P. Poole, Jr., H. A. Farach, Handbook of Electron Spin Resonance 2 (1999) 1.10.1007/978-1-4612-1486-1_1Search in Google Scholar

18. D. H. Gadani, V. A. Rana, S. P. Bhatnagar, A. N. Prajapati, A.D. Vyas, Indian J. Pure Appl. Phys. 50 (2012) 405.Search in Google Scholar

19. P. A. Bottomley, E. R. Andrew, Phys. Biol. Med. 23 (1978) 630.10.1088/0031-9155/23/4/006Search in Google Scholar

20. D. I. Hoult, P. C. Lauterbur, J. Magn. Reson. 34 (1979) 425.10.1016/0022-2364(79)90019-2Search in Google Scholar

21. T. W. Redpath, J. M. S. Hutchison, Magn. Reson. Imag. 2 (1984) 295.10.1016/0730-725X(84)90195-4Search in Google Scholar

22. P. Roschmann, Med. Phys. 14 (1987) 922.10.1118/1.595995Search in Google Scholar PubMed

23. I. Marin-Montesinos, J. C. Paniagua, M. Vilaseca, A. Urtizberea, F. Luis, M. Feliz, F. Lin, S. Van Doorslaer, M. Pons, Phys. Chem. Chem. Phys. 17 (2015) 5785.10.1039/C4CP05225KSearch in Google Scholar PubMed

24. S. Chandresekhar, Rev. Modern Phys. 15 (1943) 1.10.1103/RevModPhys.15.1Search in Google Scholar

Supplemental Material:

The online version of this article (DOI: 10.1515/zpch-2016-0813) offers supplementary material, available to authorized users.

Received: 2016-6-11
Accepted: 2016-10-20
Published Online: 2016-11-18
Published in Print: 2017-4-1

©2017 Walter de Gruyter GmbH, Berlin/Boston

Articles in the same Issue

  1. Frontmatter
  2. Preface
  3. Basic and Combination Cross-Features in X- and Q-band HYSCORE of the 15N Labeled Bacteriochlorophyll a Cation Radical
  4. An EPR Study of Small Magnetic Nanoparticles
  5. Magnetic Resonance Study of the Spin-1/2 Quantum Magnet BaAg2Cu[VO4]2
  6. Triarylmethyl Radicals: An EPR Study of 13C Hyperfine Coupling Constants
  7. Natural Abundance Nitrogen-15 NMR in Thermotropic Liquid Crystals With Cyano-Group
  8. Surface Hydroxyl OH Defects of η-Al2O3 and χ-Al2O3 by Solid State NMR, XRD, and DFT Calculations
  9. THz ESR study of Spinel Compound GeCo2O4
  10. Self-Association of Glycyrrhizic Acid. NMR Study
  11. A Site-Specific Study of the Magnetic Field-Dependent Proton Spin Relaxation of an Iridium N-Heterocyclic Carbene Complex
  12. Multifrequency Multiresonance EPR Investigation of Halogen-bonded Complexes Involving Neutral Nitroxide Radicals
  13. Electron Paramagnetic Resonance and DFT Analysis of the Effects of Bulky Perfluoroalkyl Substituents on a Vanadyl Perfluoro Phthalocyanine
  14. Coordination of the Mn4+-Center in Layered Li[Co0.98Mn0.02]O2 Cathode Materials for Lithium-Ion Batteries
  15. Triarylmethyl Radical: EPR Signal to Noise at Frequencies between 250 MHz and 1.5 GHz and Dependence of Relaxation on Radical and Salt Concentration and on Frequency
https://doi.org/10.1515/zpch-2016-0813
Keywords for this article
cross loop resonator; electron spin relaxation; in vivo imaging; tumbling

Articles in the same Issue

  1. Frontmatter
  2. Preface
  3. Basic and Combination Cross-Features in X- and Q-band HYSCORE of the 15N Labeled Bacteriochlorophyll a Cation Radical
  4. An EPR Study of Small Magnetic Nanoparticles
  5. Magnetic Resonance Study of the Spin-1/2 Quantum Magnet BaAg2Cu[VO4]2
  6. Triarylmethyl Radicals: An EPR Study of 13C Hyperfine Coupling Constants
  7. Natural Abundance Nitrogen-15 NMR in Thermotropic Liquid Crystals With Cyano-Group
  8. Surface Hydroxyl OH Defects of η-Al2O3 and χ-Al2O3 by Solid State NMR, XRD, and DFT Calculations
  9. THz ESR study of Spinel Compound GeCo2O4
  10. Self-Association of Glycyrrhizic Acid. NMR Study
  11. A Site-Specific Study of the Magnetic Field-Dependent Proton Spin Relaxation of an Iridium N-Heterocyclic Carbene Complex
  12. Multifrequency Multiresonance EPR Investigation of Halogen-bonded Complexes Involving Neutral Nitroxide Radicals
  13. Electron Paramagnetic Resonance and DFT Analysis of the Effects of Bulky Perfluoroalkyl Substituents on a Vanadyl Perfluoro Phthalocyanine
  14. Coordination of the Mn4+-Center in Layered Li[Co0.98Mn0.02]O2 Cathode Materials for Lithium-Ion Batteries
  15. Triarylmethyl Radical: EPR Signal to Noise at Frequencies between 250 MHz and 1.5 GHz and Dependence of Relaxation on Radical and Salt Concentration and on Frequency
Sign up now to receive a 20% welcome discount
Institutional Access
How does access work?
Have an idea on how to improve our website?
Please write us.
© 2025 De Gruyter Brill
Downloaded on 9.12.2025 from https://www.degruyterbrill.com/document/doi/10.1515/zpch-2016-0813/html
Scroll to top button