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Abstract
From the very first discovery of biological iron-sulfur clusters with EPR, the spectroscopy has been used to study not only purified proteins but also complex systems such as respiratory complexes, membrane particles and, later, whole cells. In recent times, the emphasis of iron-sulfur biochemistry has moved from characterization of individual proteins to the systems biology of iron-sulfur biosynthesis, regulation, degradation, and implications for human health. Although this move would suggest a blossoming of System-EPR as a specific, non-invasive monitor of Fe/S (dys)homeostasis in whole cells, a review of the literature reveals limited success possibly due to technical difficulties in adherence to EPR spectroscopic and biochemical standards. In an attempt to boost application of System-EPR the required boundary conditions and their practical applications are explicitly and comprehensively formulated.
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Affiliation(s)
- Wilfred R Hagen
- Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629HZ, Delft, The Netherlands.
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Tadyszak K, Boś-Liedke A, Jurga J, Baranowski M, Mrówczyński R, Chlewicki W, Jurga S, Czechowski T. Overmodulation of projections as signal-to-noise enhancement method in EPR imaging. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2016; 54:136-142. [PMID: 26364566 DOI: 10.1002/mrc.4330] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 07/08/2015] [Accepted: 08/04/2015] [Indexed: 06/05/2023]
Abstract
A study concerning the image quality in electron paramagnetic resonance imaging in two-dimensional spatial experiments is presented. The aim of the measurements was to improve the signal-to-noise ratio (SNR) of the projections and the reconstructed image by applying modulation amplitude higher than the radical electron paramagnetic resonance linewidth. Data were gathered by applying four constant modulation amplitudes, where one was below 1/3 (Amod = 0.04 mT) of the radical linewidth (ΔBpp = 0.14 mT). Three other modulation amplitude values were used in this experiment, leading to undermodulated (Amod < 1/3 ΔBpp), partially overmodulated (Amod ~ 1/3 ΔBpp) and fully overmodulated (Amod > > 1/3 ΔBpp) projections. The advantages of an applied overmodulation condition were demonstrated in the study performed on a phantom containing four shapes of 1.25 mM water solution of 2, 2, 6, 6-tetramethyl-1-piperidinyloxyl. It was shown that even when the overmodulated reference spectrum was used in the deconvolution procedure, as well as the projection itself, the phantom shapes reconstructed as images directly correspond to those obtained in undermodulation conditions. It was shown that the best SNR of the reconstructed images is expected for the modulation amplitude close to 1/3 of the projection linewidth, which is defined as the distance from the first maximum to the last minimum of the gradient-broadened spectrum. For higher modulation amplitude, the SNR of the reconstructed image is decreased, even if the SNR of the measured projection is increased.
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Affiliation(s)
- Krzysztof Tadyszak
- NanoBioMedical Centre, Adam Mickiewicz University, ul. Umultowska 85, 61614, Poznań, Poland
| | - Agnieszka Boś-Liedke
- NanoBioMedical Centre, Adam Mickiewicz University, ul. Umultowska 85, 61614, Poznań, Poland
- Department of Medical Physics, Faculty of Physics, Adam Mickiewicz University, ul. Umultowska 85, 61614, Poznań, Poland
| | - Jan Jurga
- Laboratory of EPR Tomography, Poznań University of Technology, ul. Piotrowo 3, 60965, Poznań, Poland
- noviLET, ul. Naramowicka 232, PL, 61611, Poznań, Poland
| | - Mikołaj Baranowski
- Department of Physics, Faculty of Physics, Adam Mickiewicz University, ul. Umultowska 85, PL, 61614, Poznań, Poland
- noviLET, ul. Naramowicka 232, PL, 61611, Poznań, Poland
| | - Radosław Mrówczyński
- NanoBioMedical Centre, Adam Mickiewicz University, ul. Umultowska 85, 61614, Poznań, Poland
| | - Wojciech Chlewicki
- Faculty of Electrical Engineering, West Pomeranian University of Technology, al. Piastów 17, 70-310, Szczecin, Poland
- noviLET, ul. Naramowicka 232, PL, 61611, Poznań, Poland
| | - Stefan Jurga
- NanoBioMedical Centre, Adam Mickiewicz University, ul. Umultowska 85, 61614, Poznań, Poland
- Department of Macromolecular Physics, Faculty of Physics, Adam Mickiewicz University, ul. Romana Maya 1, 61371, Poznań, Poland
| | - Tomasz Czechowski
- NanoBioMedical Centre, Adam Mickiewicz University, ul. Umultowska 85, 61614, Poznań, Poland
- Laboratory of EPR Tomography, Poznań University of Technology, ul. Piotrowo 3, 60965, Poznań, Poland
- noviLET, ul. Naramowicka 232, PL, 61611, Poznań, Poland
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Golub F, Potter LC, Ash JN, Blank A, Ahmad R. Estimation of spin-echo relaxation time. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 237:17-22. [PMID: 24125956 DOI: 10.1016/j.jmr.2013.09.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2013] [Revised: 09/05/2013] [Accepted: 09/08/2013] [Indexed: 06/02/2023]
Abstract
In spin-echo-based EPR oximetry, traditional methods to estimate the T2 relaxation time, which encodes the oxygen concentration of the sample, include fitting an exponential to the peaks or the integrated areas of multiple noisy echoes. These methods are suboptimal and result in a loss of estimation precision for a given acquisition time. Here, we present the maximum likelihood estimate (MLE) of T2 from spin-echo data. The MLE provides, for the data considered, approximately 3-fold time savings over echo-integration and more than 40-fold time savings over peak-picking. A one-dimensional line search results in simple computation of the MLE. It is observed that, perhaps counter-intuitively, prior knowledge of the lineshape does not yield additional reduction of estimation error variance at practical noise levels. The result also illuminates the near optimal performance of T2 estimation via principal components calculated by a singular value decomposition. The proposed method is illustrated by application to simulated and experimental EPR data.
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Affiliation(s)
- F Golub
- Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH 43210, USA
| | - L C Potter
- Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH 43210, USA; Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA
| | - J N Ash
- Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH 43210, USA
| | - A Blank
- Schulich Faculty of Chemistry, Technion - Israel Institute of Technology, Haifa 32000, Israel
| | - R Ahmad
- Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH 43210, USA; Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA.
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Palmer J, Potter L, Johnson D, Zweier J, Ahmad R. Dual-scan acquisition for accelerated continuous-wave EPR oximetry. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2012; 222:53-58. [PMID: 22820009 PMCID: PMC3423522 DOI: 10.1016/j.jmr.2012.05.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Revised: 05/11/2012] [Accepted: 05/26/2012] [Indexed: 06/01/2023]
Abstract
Statistical analysis reveals that, given a fixed acquisition time, linewidth (and thus pO(2)) can be more precisely determined from multiple scans with different modulation amplitudes and sweep widths than from a single-scan. For a Lorentzian lineshape and an unknown but spatially uniform modulation amplitude, the analysis suggests the use of two scans, each occupying half of the total acquisition time. We term this mode of scanning as dual-scan acquisition. For unknown linewidths in a range [Γ(min), Γ(max)], practical guidelines are provided for selecting the modulation amplitude and sweep width for each dual-scan component. Following these guidelines can allow for a 3-4 times reduction in spectroscopic acquisition time versus an optimized single-scan, without requiring hardware modifications. Findings are experimentally verified using L-band spectroscopy with an oxygen-sensitive particulate probe.
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Affiliation(s)
- J. Palmer
- Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH 43210, USA
| | - L.C. Potter
- Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH 43210, USA
| | - D.H. Johnson
- Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA
| | - J.L. Zweier
- Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA
| | - R. Ahmad
- Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA
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Ahmad R, Potter LC, Khramtsov VV. Spectral modeling for accelerated pH spectroscopy using EPR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2012; 218:86-92. [PMID: 22578559 PMCID: PMC3351691 DOI: 10.1016/j.jmr.2012.03.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Revised: 03/01/2012] [Accepted: 03/02/2012] [Indexed: 05/31/2023]
Abstract
A data modeling and processing method for electron paramagnetic resonance (EPR)-based pH spectroscopy is presented. The proposed method models the EPR spectrum of a pH-sensitive probe in both protonated and unprotonated forms. Under slow-exchange conditions, the EPR spectrum of a sample with an unknown pH value can be accurately represented by a weighted sum of the two models, with the pH value completely determined by their relative weights. Unlike traditional pH spectroscopy, which relies on locating resonance peaks, the proposed modeling-based approach utilizes the information from the entire scan and hence leads to more accurate estimation of pH for a given acquisition time. By employing the proposed methodology, we expect a reduction in the pH estimation error by more than a factor of three, which represents an order of magnitude reduction in acquisition time compared to the traditional method.
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Affiliation(s)
- R Ahmad
- Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA.
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