Radicals in 5-methylcytosine induced by ionizing radiation. Electron magnetic resonance for structural and mechanistic analyses.

Single crystals of 5-methylcytosine hemihydrate and 5-methylcytosine hydrochloride were X-irradiated and studied at 10 K and at higher temperatures using X- and K-band EPR, ENDOR and EIE spectroscopy. In the hemihydrate crystals, four radicals were identified at 10 K, one of them being the recently reported N1-deprotonated one-electron oxidation product (Krivokapić et al., J.

Primary oxidation products of 5-methylcytosine: methyl dynamics and environmental influences.

The primary oxidation product in X-irradiated single crystals of 5-methylcytosine hemihydrate and 5-methylcytosine hydrochloride has been studied at 10 K, using electron paramagnetic resonance (EPR), electron-nuclear double resonance (ENDOR), and ENDOR-induced EPR (EIE) spectroscopies. The radical is characterized by large couplings to the methyl protons and appears to be deprotonated at N1 in both crystal systems. In the hydrochloride crystal the methyl group is completely frozen at 10 K, whereas in the hemihydrate crystal it undergoes tunneling rotation.

Percutaneous biopsy of cavernous sinus tumour via the foramen ovale.

Background: Tumours involving the cavernous sinus may be challenging to neurosurgeons and neuro-oncologists to treat. Operation may be hazardous for lesions in this area, radical resection is seldom obtained, and other treatments are often needed. Different types of tumour occur at this location.

Ionization energies of the nucleotides.

The vertical ionization energies of the four nucleotides have been computed. Geometries have been chosen to mimic orientations as they appear in B-DNA. The negative charge on the phosphate was neutralized by protonation, and also by the inclusion of counterions.

Free radical conformations and conversions in X-irradiated single crystals of L-cysteic acid by electron magnetic resonance and density functional theory studies.

Single crystals of L-cysteic acid monohydrate were X-irradiated and studied at 295 K using EPR, ENDOR, and EIE techniques. Three spectroscopically different radicals were observed. These were a deamination radical reduction product (R1), and two oxidation products formed by hydrogen abstraction (radicals R2, R3).

Single crystals of L-O-serine phosphate X-irradiated at low temperatures: EPR, ENDOR, EIE, and DFT studies.

Single crystals of the phosphorylated amino acid L-O-serine phosphate were X-irradiated and studied at 10 K and at 77 K using EPR, ENDOR, and EIE techniques. Two radicals, R1(10 K) and R1(77 K), were detected and characterized as two different geometrical conformations of the protonated reduction product >CH-C(OH)(2). R1(10 K) is only observed after irradiation at 10 K, and upon heating to 40 K, R1(10 K) transforms rapidly and irreversibly into R1(77 K).