Şemsettin Osmanoğlu

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.

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.

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.

Radiation damage produced in powder of α-(methylamino)isobutyric acid, α -aminoisobutyric acid methyl ester hydrochloride and diethylmalonic acid

The electron paramagnetic resonance spectra of γ-irradiated powders of α-(methylamino)isobutyric acid – CH3NHC(CH3)2COOH, α -aminoisobutyric acid methyl ester hydrochloride – NH2(CH3)2CCOOCH3 HCl, and diethylmalonic acid – (CH3CH2)2C(COOH)2 have been investigated at room temperature. It has been found that γ -irradiation produces the (CH3)2C˙COOH radical in the first, the (CH3)2C˙COOCH3 radical in the second and the (CH3CH2)2C˙COOH radical in the third compound. The spectra were computer-simulated. The g values and the hyperfine coupling constants of the unpaired electron with the environmental methyl, methylene protons and OH proton were determined. The results were found to be in good agreement with the existing literature data and theoretical predictions.

The effect of gamma radiation of amino acid derivatives in the solid state: an EPR study

The spectroscopic features of free radicals produced in gamma irradiation of the N-methyl-dl – alanine, N,N – dimethyl glycine hydrochloride and d – (+) – galactosamine hydrochloride were investigated at room temperature at the dose 15 kGy using EPR technique. The paramagnetic species observed in these compounds were identified as CH3ĊHCOOH, ĊHOH(CHOH)3NH2(CH)2O, and (CH3)2NĊHCOOH.HCl, respectively. A comparison with a new paramagnetic species recently observed and characterized in irradiated amino acids indicates that the new radical presented here has a similar structure. In this paper, we have also studied the stability of these compounds at room temperature after irradiation.

Radiation effect studies on some glycine derivatives in solid state

ABSTRACT Five glycyl derivatives, glycyl-L-histidine, L-alanyl-glycine, glycine hydrochloride, gly-gly hydrochloride and, gly-gly-glycine in powder form were exposed to 20 kGy doses of 60Co gamma radiation to study the effects of ionizing radiation. In these compounds, the paramagnetic centers formed after irradiation were attributed to the R─NHCH─ĊO−OH, ĊH2CHNH, H2NCH2ĊO−OHHCl, NH2ĊHCONHCH2COOHHCl and HNCH2ĊO−OH radicals, respectively. The effect of gamma irradiation to the radical structures and time stability of the radicals were investigated by EPR spectroscopy. The spectra were computer simulated and the hyperfine coupling constants were determined.

Conformational, IR, NMR, and EPR analysis of ifosfamide by density functional theory calculation

The optimized molecular structure, vibrational frequencies, 1H and 13C NMR chemical shifts, and EPR hyperfine splittings of 3-(2-chloroethyl)-2-[(2-chloroethyl)amino]tetrahydro-2H-1,3,2-oxazaphosphorine-2-oxide (ifosfamide) have been investigated using density functional theory (B3LYP) method with 6-31+G(d, p) basis set for the first time. The calculated optimized geometric parameters (bond lengths and bond angles), vibrational frequencies, NMR chemical shifts, and EPR hyperfine splittings were seen to be in a well agreement with the corresponding experimental data. The experimental EPR spectrum of the molecule was recorded after γ-irradiation. From the comparison of the calculated and experimental results the formed radical was attributed to a carbon atom-centered radical occurred upon the loss of a chlorine atom due to breakage of the weak C–Cl bonds. So we mentioned that the free electron is transferred to a carbon atom through intramolecular rearrangement while the molecular charge changes to neutral situation, giving NHĊαH2CßH2 radical.Graphical Abstract

Electron Paramagnetic Resonance of Some γ-Irradiated Amino Acid Derivatives

γ -Irradiated powders of N-acetyl-L-arginine, Nα -carbamyl-L-arginine, N-glycyl-L-leucine and glycyl-L-alanine were investigated at room temperature by electron paramagnetic resonance. The observed species in N-acetyl-L-arginine and Nα -carbamyl-L-arginine were attributed to the CH2CHNHCNHNH2 radical, and those in N-glycyl-L-leucine and glycyl-L-alanine powders to (CH3)2CCH2 and CH3CHCOOH radicals.

EPR of Gamma Irradiated Single Crystal of 2,2-Dimethyl Succinic Acid

We have observed the radical CHCH2 in the EPR spectra of α-irradiated single crystal of 2,2- dimethyl succinic acid.