Effect of Temperature on the Electron Paramagnetic Resonance Spectrum of Irradiated Alanine

Vanhaelewyn, Gauthier; Mondelaers, W.; Callens, Freddy

doi:10.2307/3580035

Cited by 21 publications

(20 citation statements)

References 12 publications

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“…The electron paramagnetic resonance (EPR) spectra of alanine powder irradiated at room temperature are dominated by the well known room-temperature-stable alanine radical CH 3 C HCOOH. Upon heating of room-temperature-irradiated alanine powder, a strong decay of the signal is observed, and the features of the spectrum which have recently been ascribed to a second stable radical in alanine irradiated at room temperature become more pronounced, providing an experimental isolation of this second alanine radical (Vanhaelewyn et al, 1999).…”

Section: Effect Of Temperaturementioning

confidence: 89%

Radiolysis of proteins in the solid state: an approach by EPR and product analysis

Terryn

Deridder

Sicard-Roselli

et al. 2005

J Synchrotron Radiat

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Radio-induced modifications in proteins have been studied using several techniques. Electron paramagnetic resonance (EPR) was used to characterize free radicals, and analysis methods (high-performance liquid chromatography, capillary electrophoresis) were employed to visualize final degraded forms. Whereas EPR indicates that perthiyl radicals are formed, analysis does not detect any compound in which such bonds would be broken. Since EPR signals decay with time, it is concluded that rearrangements occur at subsequent steps, in which the solvent used during the analysis might play a role.

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Section: Effect Of Temperaturementioning

confidence: 89%

Radiolysis of proteins in the solid state: an approach by EPR and product analysis

Terryn

Deridder

Sicard-Roselli

et al. 2005

J Synchrotron Radiat

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“…However, Miyagawa and co-workers employing EPR and electron nuclear double resonance (ENDOR) analyses of irradiated alanine crystals , pointed out evidence for at least one additional radical component in the spectra. Callens and co-workers similarly provided evidence for at least one, possibly two, other components using multivariate spectral analysis. − In a series of papers using EPR, ENDOR, ENDOR induced EPR (EIE), and spectral simulations, Sagstuen, Hole, Malinen, and co-workers uniquely characterized the second major component designated R2 and in addition launched convincing evidence of a third (minor) radical component, R3 . − A tentative radical structure was assigned to this third component although no well-defined spectral signature had been observed experimentally . The experimental EPR/ENDOR data enabled precise simulations of the spectra for both the R1 and R2 components.…”

Section: Introductionmentioning

confidence: 99%

“…There is still not sufficient experimental evidence for the actual spectral fingerprint of the R3 radical. During the past decennium, multivariate analyses of series of inherently related data have shown considerable progress, and a variety of methods and algorithms have been established for determining hidden common features or traits in such data series. ,,− Some of these methods can be used to extract pure component spectra and component contribution fractions from spectra of mixtures consisting of several different components, without requiring any prior knowledge of the component spectra or the sample composition.…”

Section: Introductionmentioning

confidence: 99%

In Quest of the Alanine R3 Radical: Multivariate EPR Spectral Analyses of X-Irradiated Alanine in the Solid State

et al. 2017

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The amino acid l-α-alanine is the most commonly used material for solid-state electron paramagnetic resonance (EPR) dosimetry, due to the formation of highly stable radicals upon irradiation, with yields proportional to the radiation dose. Two major alanine radical components designated R1 and R2 have previously been uniquely characterized from EPR and electron-nuclear double resonance (ENDOR) studies as well as from quantum chemical calculations. There is also convincing experimental evidence of a third minor radical component R3, and a tentative radical structure has been suggested, even though no well-defined spectral signature has been observed experimentally. In the present study, temperature dependent EPR spectra of X-ray irradiated polycrystalline alanine were analyzed using five multivariate methods in further attempts to understand the composite nature of the alanine dosimeter EPR spectrum. Principal component analysis (PCA), maximum likelihood common factor analysis (MLCFA), independent component analysis (ICA), self-modeling mixture analysis (SMA), and multivariate curve resolution (MCR) were used to extract pure radical spectra and their fractional contributions from the experimental EPR spectra. All methods yielded spectral estimates resembling the established R1 spectrum. Furthermore, SMA and MCR consistently predicted both the established R2 spectrum and the shape of the R3 spectrum. The predicted shape of the R3 spectrum corresponded well with the proposed tentative spectrum derived from spectrum simulations. Thus, results from two independent multivariate data analysis techniques strongly support the previous evidence that three radicals are indeed present in irradiated alanine samples.

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“…First, the X-band EPR spectrum of an irradiated drug is often composite: several types of radicals can be trapped within the matrix. The different spectra must therefore be separated, which can be achieved by playing on certain parameters such as temperature [10] or the microwave power at the EPR measurement. [1] Secondly, the EPR spectrum obtained is a typical powder one where radicals are randomly orientated.…”

Section: Introductionmentioning

confidence: 99%

The Use of Multi-frequency EPR Techniques to Identify the Radicals Produced in Irradiated β-Blockers

Engalytcheff¹,

Kolberg

Barra

et al. 2004

Free Radical Research

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The identification of radicals trapped in irradiated drugs can be very intricate. A multi-frequency electron paramagnetic resonance (EPR) study is proposed to resolve this problem. The Q-band (ca. 34 GHz) comparison with X-band (ca. 9 GHz) did not show significant differences for the four beta-blockers studied (atenolol, esmolol, nadolol and propranolol). The use of a higher frequency (285 GHz) was required. It enabled us to determine the g-tensor values of the radicals present in atenolol and esmolol, respectively, g1 = 2.0086, g2 = 2.0059 and g3 = 2.0021 and g1 = 2.0066, g2 = 2.0044 and g3 = 2.0021. The latter was assigned as a phenoxyl radical, which can not be the case for the former. Therefore, radicals produced in esmolol may result from a more complex mechanism than the abstraction followed by the diffusion of an H atom inside the solid. In addition, two molecules as similar as atenolol and esmolol hydrochloride do not contain the same radicals after irradiation. These two conclusions drawn from the EPR results on beta-blockers show clearly the importance of continuing the investigations on radiolytic mechanisms in solid-state drugs.

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Effect of Temperature on the Electron Paramagnetic Resonance Spectrum of Irradiated Alanine

Cited by 21 publications

References 12 publications

Radiolysis of proteins in the solid state: an approach by EPR and product analysis

Radiolysis of proteins in the solid state: an approach by EPR and product analysis

In Quest of the Alanine R3 Radical: Multivariate EPR Spectral Analyses of X-Irradiated Alanine in the Solid State

The Use of Multi-frequency EPR Techniques to Identify the Radicals Produced in Irradiated β-Blockers

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