Murat Aydın

EPR Study of Gamma Induced Radicals in Amino and Iminodiacetic Acid Derivatives

In this study, electron paramagnetic resonance spectroscopy was used to investigate free radicals formed in gamma irradiated L-glutamine hydrochloride, iminodiacetic acid hydrochloride and N-(2-hyroxyethyl) iminodiacetic acid powders. The free radicals produced in L-glutamine hydrochloride powders were attributed to the CH2 ˙ CHCOOH radical; and those in iminodiacetic acid hydrochloride and N-(2-hyroxyethyl) iminodiacetic acid powders to the HNCHCH2(COOH)2 and HOCH2CH2N ˙ CHCH2(COOH)2, respectively. The g-values of the radicals and the hyperfine structure constants of the free electron with the environmental protons and 14 N nucleus were determined. The samples were not displayed before they were not irradiated. The free radicals were found stable at room temperature for more than six months. Some spectroscopic properties and suggestions concerning possible structure of the radicals are discussed in this paper.

EPR studies of gamma-irradiated L-alanine ethyl ester hydrochloride, L-arginine and alanyl-L-glutamine

Abstract γ-Irradiated powders of L-alanine ethyl ester hydrochloride (LAES), L-arginine (LA) and alanyl-L-glutamine (ALG) were investigated at room temperature by electron paramagnetic resonance (EPR). The observed species in LAES and LA are attributed to the CH3CHCOOC2H5 and CH2CHNHCNHNH2 radicals, respectively. In the case of ALG, the EPR signal is attributed to the CH2CNHCOOH. Hyperfine structure constants and g-values are determined for these three radicals. It is found that these results are in good agreement with those of previous experimental and theoretical studies. The unirradiated samples were found to display no EPR signal.

Structure and behaviour of the free radicals generated in gamma irradiated amino acid and iminodiacetic acid derivatives

An EPR study has been carried out to investigate the structure and behaviour of the free radical formed γ-irradiated l-alaninamide hydrochloride, dl-glutamic acid monohydrate and N-(2-carboxyethyl) iminodiacetic acid powders at room temperature. The observed paramagnetic species have been attributed to the CH(3)ĊHCONH(2), HOOCCH(2)CH(2)ĊHCOOH and HOOCCH(2)CH(2)NĊHCH(2)(COOH)(2) radicals, respectively. Some spectroscopic properties and suggestions concerning possible structure of the radicals were also discussed in this study.

Electron paramagnetic resonance characterization of gamma irradiation damage centers in powder of L-(+)-tartaric acid, N-acetyl-L-alanine and 1-methyl-L-histidine

The electron paramagnetic resonance (EPR) of γ-irradiated powders of l-(+)-tartaric acid, N-acetyl-l-alanine and 1-methyl-l-histidine were investigated at room temperature. Radiation damage centers are attributed to HOOCCH(OH)Ċ(OH)COOH, CH3ĊHCOOH and ‒CH2ĊHCOOH radicals. The spectra were computer-simulated. Hyperfine structure constants and g-values were determined for these three radicals. The unirradiated samples showed no EPR signal. Some spectroscopic properties and suggestions concerning the possible structure of the radicals are discussed in this paper.

Electron paramagnetic resonance of rγ-irradiated glycyl-L-glutamine monohydrate, iminodiacetic acid and methyliminodiacetic acid

The electron paramagnetic resonances of rγ-irradiated powders of glycyl-L-glutamine monohydrate, iminodiacetic acid and methyliminodiacetic acid were investigated at room temperature. The observed species in glycyl-L-glutamine monohydrate powders were attributed to the CH2C˙NHCOOH radical; and those in iminodiacetic acid and methyliminodiacetic acid powders to the HNC˙HCH2(COOH)2 and H3CNC˙HCH2(COOH)2 radicals respectively. The spectra were computer simulated and the g values of the radicals and the hyperfine structure constants of the unpaired electron with nearby protons and 14N nucleus were determined. The results were found to be in good agreement with the existing literature data.

Radiation effect studies in single crystal of Trifluoroacetyl-α-Aminoisobutyric acid

In this study, electron paramagnetic resonance of γ-irradiated single crystals of N-Trifluoroacetyl-α-amino isobutyric acid (F3Ac-Aib-OH) was investigated at room temperature and analyzed for different orientations of the crystal in the magnetic field. The paramagnetic species in N-Trifluoroacetyl-α-aminoisobutyric acid was attributed to the ĊF2-R radical (R= CONHC(CH3)COOH). Hyperfine coupling constants and g value were also determined. In addition, the single crystal of F3Ac-Aib-OH was UV-irradiated and paramagnetic species formed was studied at room temperature. The effects of gamma irradiation on fluoroamino acid and stability were discussed.

Identification of free radicals induced by gamma irradiation in amino acid derivatives

Powders of N- acetyl- L- leucine and N- methyl- L- glutamic acid were gamma irradiated and the free radicals formed were investigated at room temperature by electron paramagnetic resonance technique. The free radicals formed in compounds were attributed to the (CH3)2CCH2CH(NHCOCH3)COOH and HOOCCH2CH2C (NHCH3)COOH radicals respectively. Both radicals are very stable and we could observe them for five months without almost intensity diminution at room temperature. The g values of the radicals and the hyperfine structure constants of the free electron with nearby protons and 14N nucleus were determined. The results were found to be in good agreement with the existing literature data.

Study of the structure of free radicals in gamma - irradiated amino acid derivatives

Electron paramagnetic resonance spectroscopy has been used for the study of the free radicals produced in the powders of L-arginine monohydrochloride, ala-ala and DL-β-leucine gamma-irradiated at room temperature. The structures of the radicals formed in compounds were determined as NH2(NH)NHCHCH2CH2CH(NH2)COOH, CH3CHCOOH and (CH3)2CCH(NH2)CH2COOH respectively. The paramagnetic species were found to be stable at room temperature more than three months. It was determined that unpaired electron interacted with nearby protons and 14N nucleus in these radicals. The g values of the radicals and the hyperfine structure constants of the free electron were also measured. These results were compared with the earlier studies in amino acid and derivatives radicals and discussed.

Electron paramagnetic resonance and FT-IR spectroscopic studies of DL-2-aminoadipic acid and ammonium acetate powders

Exposure of powder forms of DL-2-aminoadipic acid and ammonium acetate to gamma radiation results in the formation of free radicals detected by the electron paramagnetic resonance spectroscopy at room temperature. In these compounds, the observed paramagnetic species were attributed to the HOOCCH2CH2CH2CHCOOH and CH2COONH4 radicals, respectively. The g values and the hyperfine coupling constants of the unpaired electron with the environmental protons were determined for these two radicals. In work, the observed paramagnetic species were found to be stable at room temperature for more than two months. Also, these compounds were characterised by FT-IR and UV–VIS. Their thermal stabilities were determined by TGA and DTA measurements. Thermal analyses were shown to be unstable of the HOOCCH2CH2CH2CH(NH2)COOH and CH3COONH4 against thermo-oxidative decomposition.

EPR of γ-irradiated single crystal of iminodiacetic acid

The electron paramagnetic resonance of γ-irradiated single crystal of iminodiacetic acid, HN(CH2COOH)2, has been observed and analyzed for different orientations of the crystal in the magnetic field. The radicals produced by γ-irradiation have been investigated at room temperature. The radiation damage centers produced in the crystals were attributed to the HNC˙HCH2(COOH)2 radical. The g values and hyperfine coupling constants of the unpaired electron with the environmental α-proton, methylene protons, NH proton and 14N nucleus were determined. The results were found to be in agreement with hyperfine coupling and are discussed.