Abstract
CW saturation experiments are widely used in ESR studies of relaxation processes in proteins and lipids. We develop the theory of saturation in ESR spectra in terms of its close relation with that of 2D-ELDOR. Our treatment of saturation is then based on the microscopic order macroscopic disorder (MOMD) model and can be used to fit the full CW saturation spectrum, rather than fitting just the peak–peak amplitude as a function of microwave field \(B_1\) as is commonly done. This requires fewer experiments to yield effects on \(T_1\), as well as provides a more extensive dynamic structural picture, for example, for scanning experiments on different protein sites. The code is released as a publicly available software package in Python that can be used to fit CW saturation spectra from biological samples of interest.
Similar content being viewed by others
Data Availability Statement
The data and computer programs that support the findings of this study are available from the corresponding author upon reasonable request.
References
P.P. Borbat, H.S. Mchaourab, J. Freed, J. Am. Chem. Soc. 124, 5304 (2002)
G. Jeschke, Ann. Rev. Phys. Chem. 63, 419 (2012)
P.F. Knowles, D. Marsh, Biochem. J. 274, 625 (1991)
B. Dzikovski, V. Livshits, J.H. Freed, J. Phys. Chem. B 119, 13330 (2015)
C. Altenbach, W. Froncisz, R. Hemker, H. Mchaourab, W.L. Hubbell, Biophys. J. 89, 2103 (2005)
D. Snead, A.L. Lai, R.T. Wragg, D. Parisotto, T. Ramdall, J. Dittman, J.H. Freed, D. Eliezer, Front. Mol. Neurosci. 10, 154 (2017)
E. Meirovitch, A. Nayeem, J.H. Freed, J. Phys. Chem. 88, 3454 (1984)
M.J. Stephen, G.K. Fraenkel, J. Chem. Phys. 32, 1435 (1960)
J.H. Freed, J. Chem. Phys. 43, 2312 (1965)
S.A. Goldman, G.V. Bruno, J.H. Freed, J. Chem. Phys. 59, 3071 (1973)
E. Meirovitch, D. Igner, E. Igner, G. Moro, J.H. Freed, J. Phys. Chem. 77, 3915 (1982)
S. Lee, D. Budil, J.H. Freed, J. Chem. Phys. 101, 5529 (1994)
D. Budil, S. Lee, S. Saxena, J.H. Freed, J. Magn. Reson. A 120, 155 (1996)
J.H. Freed, G.V. Bruno, C. Polnaszek, J. Chem. Phys. 55, 5270 (1971)
J.H. Freed, G.V. Bruno, C.F. Polnaszek, J. Phys. Chem. 75(22), 3385 (1971)
J.H. Freed, J. Phys. Chem. 78(12), 1155 (1974)
J.H. Freed, in Time Domain Electron Spin Resonance, Chap. 2, ed. by L. Kevan, R.N. Schwartz. Theory of ESR Saturation Recovery in Liquids and Related Media, (Wiley, 1979), p. 31
D. Schneider, J.H. Freed, in Lasers, Molecules and Methods, Chap. 10, ed. by Hirschfelder, Wyatt, Coalson. Spin Relaxation and Motional Dynamics, (McGraw-Hill, 1989), p. 431
T.A. Davis, ACM Trans. Math. Softw. 30, 196 (2004)
G. Bruno, Application of the Stochastic Liouville Method in Calculating ESR Lineshapes in the Slow Tumbling Region and an ESR-ELDOR Study of Exchange, PhD Dissertation, Cornell University, Department of Chemistry and Chemical Biology (1973)
G. Moro, J.H. Freed, J. Chem. Phys. 75, 3157 (1981)
I. Kuprov, J. Magn. Reson. 208, 179 (2011)
P. Gupta, Z. Liang, J.H. Freed, J. Chem. Phys. 152, 214112 (2020)
“Scipy v1.6.2 reference guide”. https://docs.scipy.org/doc/scipy/reference/generated/scipy.sparse.linalg.gmres.html. Accessed 20 Apr 2021
D. Schneider, in Spectral decompositions and slow motional lineshape analysis. In: Rocky mountain conference on analytical chemistry (2004)
I. Kuprov, J. Magn. Reson. 270, 124 (2016)
S. Konishi, G. Kitagawa, Information Criteria and Statistical Modeling (Springer, Berlin, 2008)
M. Newville, T. Stensitzki, D.B. Allen, M. Rawlik, A. Ingargiola, A. Nelson, in Lmfit: Non-Linear Least-Square Minimization and Curve-Fitting for Python. Astrophysics Source Code Library, record ascl:1606.014 (2016)
S. Stoll, A. Schweiger, J. Magn. Reson. 178(1), 42 (2006)
B.J. Gaffney, H.M. McConnell, J. Mag. Res. 16, 1 (1974)
B. Dzikovski, D. Tipikin, J.H. Freed, J. Phys. Chem. B 116, 6694 (2012)
S.S. Eaton, G.R. Eaton, in Biological Magnetic Resonance 24/B, Chap. 1, ed. by S.S. Eaton, G.R. Eaton, L. Berliner. Saturation Recovery EPR, (Springer, 2005)
Acknowledgements
This work is supported by Grant no. P41GM103521 (NIGMS/NIH) from the National Institute of General Medical Sciences (NIGMS). We also wish to acknowledge the comments of Siddarth Chandrasekaran and Alex Lai.
Author information
Authors and Affiliations
Corresponding author
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Gupta, P., Dzikovski, B. & Freed, J.H. Theory and Least Squares Fitting of CW ESR Saturation Spectra Using the MOMD Model. Appl Magn Reson 53, 699–715 (2022). https://doi.org/10.1007/s00723-021-01390-7
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00723-021-01390-7