EPR and ENDOR Studies of Single Crystals of α-Glycine X-ray Irradiated at 295 K

and, Audun Sanderud; Sagstuen, Einar

doi:10.1021/jp982932j

Cited by 38 publications

(51 citation statements)

References 36 publications

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“…For instance, it was found that soft x-ray irradiation of several amino acids under ultrahigh vacuum (UHV) conditions leads to a decomposition of the molecules via several pathways, including dehydrogenation, decarboxylation, deamination, and dehydration. [14][15][16][17][18][19][20] So far, little is known on the radiation-induced processes in mixed glycine-water ice films. Only very recently, Lattelais et al 21 reported on the effect of soft x-ray irradiation of glycine diluted into water ice at 30 K. On the basis of the x-ray absorption spectroscopy examinations, it was found that water neither protects nor enhances the glycine photodecomposition.…”

Section: Introductionmentioning

confidence: 99%

Synchrotron x-ray photoemission study of soft x-ray processed ultrathin glycine-water ice films

Tzvetkov

Netzer

2011

The Journal of Chemical Physics

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Ultrathin glycine-water ice films have been prepared in ultrahigh vacuum by condensation of H(2)O and glycine at 90 K on single crystalline alumina surfaces and processed by soft x-ray (610 eV) exposure for up to 60 min. The physicochemical changes in the films were monitored using synchrotron x-ray photoemission spectroscopy. Two films with different amounts of H(2)O have been considered in order to evaluate the influence of the water ice content on the radiation-induced effects. The analysis of C1s, N1s, and O1s spectral regions together with the changes in the valence band spectra indicates that amino acid degradation occurs fast mainly via decarboxylation and deamination of pristine molecules. Enrichment of the x-ray exposed surfaces with fragments with carbon atoms without strong electronegative substituents (C-C and C-H) is documented as well. In the thinner glycine-water ice film (six layers of glycine + six layers of water) the 3D ice suffers strongly from the x-rays and is largely removed from the sample. The rate of photodecomposition of glycine in this film is about 30% higher than for glycine in the thicker film (6 layers of glycine + 60 layers of water). The photoemission results suggest that the destruction of amino acid molecules is caused by the direct interaction with the radiation and that no chemical attack of glycine by the species released by water radiolysis is detected.

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Section: Introductionmentioning

confidence: 99%

Synchrotron x-ray photoemission study of soft x-ray processed ultrathin glycine-water ice films

Tzvetkov

Netzer

2011

The Journal of Chemical Physics

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“…The main reason for diffi culties in the interpretation of the results is the contribution of several components with different shapes but similar stability. Therefore, the experimental spectra were confronted with simulated signals based on the ENDOR data published by Sanderud and Sagstuen [21]. The EPR spectrum of a single crystal of glycine presented in their work is analogous to that shown in this paper.…”

Section: Glycine (G)mentioning

confidence: 64%

“…Despite many years of research, this well-resolved experimental spectrum has not been completely deconvoluted yet [21][22][23][24]. The main reason for diffi culties in the interpretation of the results is the contribution of several components with different shapes but similar stability.…”

Section: Glycine (G)mentioning

confidence: 99%

Radicals initiated by gamma rays in selected amino acids and collagen

et al. 2019

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Calf skin collagen and three amino acids essential for its structure, namely glycine, L-proline and 4-hydroxyl-L-proline, were irradiated with gamma rays up to a dose of 10 kGy. Conversion of radicals over time or after thermal annealing to selected temperatures was monitored by X-band electron paramagnetic resonance (EPR) spectroscopy. Some experimental spectra were compared with signals simulated based on literature data from the electron nuclear double resonance (ENDOR) studies. The following phenomena were confirmed in the tested amino acids: abstraction of hydrogen atom (glycine, proline, hydroxyproline, collagen), deamination (glycine, hydroxyproline), decarboxylation (hydroxyproline). Chain scission at glycine residues, radiation-induced decomposition of side groups and oxidative degradation were observed in irradiated collagen. The decay of radicals in collagen saturated with water occurred at lower temperatures than in macromolecules having only structural water. The paramagnetic centres were the most stable in an oxygen-free atmosphere (vacuum). Radical processes deteriorated the structure of collagen; hence, radiation sterilization of skin grafts requires careful pros and cons analysis.

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“…This crystalline amino acid is a benchmark system to study the damaging effects of radiation on proteins. 18 It has attracted experimental [19][20][21][22][23][24][25] as well as theoretical 16,17,[26][27][28] attention. Several approaches to simulate the molecular environment were evaluated 16 and it was established that at least a cluster or a periodic approach is crucial for a correct description of the structure and conformation of the glycine radical.…”

Section: Introductionmentioning

confidence: 99%

Cluster or periodic, static or dynamic—the challenge of calculating the g tensor of the solid-state glycine radical

Pauwels

Asher

Kaupp

et al. 2011

Phys. Chem. Chem. Phys.

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The calculation of the g tensor of the main + NH 3 -CH-COO À radiation-induced radical in solid-state a-glycine presents a real challenge to computational methods. Density functional calculations of this spectroscopic property struggle with its small anisotropy and the zwitterionic nature of the amino acids in the crystal of this seemingly simple system. Here, several factors influencing the calculated g tensor are examined by comparing with experimental data. The extent of the molecular environment is varied in both a cluster and a periodic approach and dynamic calculations are performed to account for temperature effects. The latter does not necessarily lead to a better agreement with experiment than a static calculation. Application of a periodic approach is straightforward, but an all-electron scheme clearly is favorable. In a cluster approach, the selected basis set and density functional are of less importance, provided a hybrid functional is used to prevent cluster boundary effects. The applied spin-orbit coupling operators and proper treatment of the gauge origin of the magnetic vector potential also seem to be less critical than in other, similar molecular systems. But a careful selection of the cluster size proves to be essential for this glycine radical system. The calculated g tensor varies significantly with increasing cluster size, yielding only a good agreement with experiment when 5-7 glycine molecules in the immediate environment of the central glycine radical are incorporated. Further expansion of the cluster size can even lead to an essentially incorrect description of the radical in the condensed phase, indicating that bigger clusters can become unbalanced.

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EPR and ENDOR Studies of Single Crystals of α-Glycine X-ray Irradiated at 295 K

Cited by 38 publications

References 36 publications

Synchrotron x-ray photoemission study of soft x-ray processed ultrathin glycine-water ice films

Synchrotron x-ray photoemission study of soft x-ray processed ultrathin glycine-water ice films

Radicals initiated by gamma rays in selected amino acids and collagen

Cluster or periodic, static or dynamic—the challenge of calculating the g tensor of the solid-state glycine radical

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