EPR and ENDOR study of radiation-induced radical formation in purines: sodium inosine crystals X-irradiated at 10 K

X-irradiated single crystals of sodium inosine (Na(+)*Inosine(-)*2.5H(2)O), in which the hypoxanthine base is present as the N1-deprotonated anion, were investigated using K-band (24 GHz) electron paramagnetic resonance (EPR), electron-nuclear double resonance (ENDOR), and ENDOR induced EPR (EIE) techniques at 10 K. At least five different radicals were present immediately after irradiation at 10 K. R1, which decayed upon warming the crystals to 50 K, was identified as the electron-loss product of the parent N1-deprotonated hypoxanthine base. Hyperfine couplings to HC8 and HC2 were fully characterized with ENDOR spectroscopy, and the identification was supported by DFT calculations. R2, which also decayed on warming to 50 K, exhibited nearly equal couplings to HC2 and HC8. Taken in combination with an extensive set of DFT calculations, the experimental results indicate that R2 is the (doubly negative) product of electron-gain by the initially anionic N1-deprotonated hypoxanthine parent. R3, which exhibited hyperfine coupling only to HC8 could not be identified. R4, which persisted on annealing to 260 K, exhibited one large alpha-proton hyperfine coupling which was fully characterized by ENDOR. Based on DFT calculations and the experimental data, R4 was identified as the product of net H-abstraction from C5'. The remaining HC5' was the source of the measured alpha-proton coupling. R5, present at low temperature and the only observable radical after warming the crystals to room temperature, was identified as the C8-H addition radical. The alpha-coupling to HC2 and beta-couplings to the pair of C8 methlyene protons were fully characterized by ENDOR.     

Syntheses and Structural Characterization of 1-（4-Phenyl-2-thiazolyl）-3-（4-methylphenyl）-5-（2-furyl）-4,5-dihydro-（1H）-pyrazole and 1-（4-（4-Fluoro）phenyl-2-thiazolyl）-3-（4-methyl-phenyl）-5-（2-furyl）-4,5-dihydro-（1H）-pyrazole

The title compounds were synthesized and characterized by IR,1H-NMR,Mass and elementary analysis and single-crystal X-ray diffraction.In 1a,intermolecular C-H…π interactions produce a three-dimensional network.In 1b,intermolecular C-H…O hydrogen bonds generate an R22(22) ring.The hydrogen bonding is supported by C-H…π interactions.     

Determination of pKa values of nonsteroidal antiinflammatory drug‐oxicams by RP–HPLC and their analysis in pharmaceutical dosage forms

In this study, pK_a values were determined by using the dependence of the capacity factor on the pH of the mobile phase for four ionizable substances, namely, tenoxicam, piroxicam, meloxicam, and naproxen (I.S.). The effect of the mobile phase composition on the ionization constant was studied by measuring the pK_a at different ACN concentrations, ranging from 30 to 40%. The adequate condition for the chromatographic determination of these compounds in pharmaceutical dosage forms was established based on the different retention behaviors of the species. An octadecylsilica Nucleosil C18 column (150×4.6 mm, 5 μm) was used for all the determinations. The chromatographic separation of oxicams was carried out using acetonitrile (ACN)/water at 35% v/v, containing 65 mM phosphoric acid and UV detection at a wavelength of 355 nm. The method developed was successfully applied to the simultaneous determination of these drug compounds in laboratory‐prepared mixtures and their commercial pharmaceutical dosage forms. Each analysis requires no longer than 12 min.     

B2O3 reinforced polylactic acid/thermoplastic polyethylene glycol shape memory composites

Recently, there has been a great demand for boron-containing compounds (BCCs) with unique biological properties. The demand for the use of these compounds not alone but as additives in composite materials is increasing day by day. In this study, the effect of adding B₂O₃ compound to the blend of PLA and PEG polymers, which is an important biocompatible shape memory polymer, was investigated. In order to examine the effect of increasing B₂O₃ additive on the thermal properties of PLA-PEG blend, it was determined by using a Differential Scanning Calorimetry (DSC) and thermogravimetric analyzer (TGA), and it was seen that while the melting temperature of PEG decreased, the melting temperature of PLA increased. In addition, when the thermal stability of the composites was examined, increasing of thermal stability was observed with the addition of B₂O₃ and a three-step degradation occurred. It was determined that the B₂O₃/PLA-PEG composite was homogeneous by taking X-ray measurements and SEM measurements. The antimicrobial property of the PLA-PEG blend improved with the increasing B₂O₃ contribution were observed from the antimicrobial activity measurements of the composite against 4 different bacteria. However, it was determined that the PLA-PEG blend preserved its shape memory effect with increasing diboron trioxide contribution.