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The radiation-induced crosslinking and grafting of two aryloxy-substituted elastomeric polyphosphazenes have been carried out by both gamma and electron beam irradiation. The classic Charlesby–Pinner [1] plus a simpler approach were used to determine the G(X) values for the crosslinked elastomeric polymers. The apparent G(X) value for the same polymer depended on whether the gamma-ray or the E-beam results were used. The presence of 8.5% repeat units with allylic groups in the side chain increased the G(X) value by an order of magnitude when the irradiation was performed under vacuum with the gamma source. The extent of acrylic acid grafting was also higher for the polymer containing the allylic group. Nearly all the grafted polyphosphazene films were insoluble in THF, a good solvent for the ungrafted samples. 相似文献
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Chromatographia - Three groups of metabolites were analyzed in extracts of rat hepatocytes by an HPLC method: (i) nucleotides (ATP, ADP, AMP, GTP, GDP, UTP, UDP, IMP, UMP), (ii) nucleosides and... 相似文献
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Annika Höhn Petra Hartmann Veronika Gebhart Johanna Sonntag Tilman Grune Tobias Jung 《Photochemistry and photobiology》2015,91(4):887-894
In this study, the athermal effects of water‐filtered infrared A (wIRA)‐irradiation (780–1400 nm) on human dermal fibroblasts were investigated. For this purpose, cells were exposed to wIRA‐irradiation (178 mW cm?2 for 1 h), while a sophisticated experimental setup prevented warming of the samples exceeding 0.1°C. The investigated parameters were the formation of reactive oxygen species (ROS), mitochondrial membrane potential and superoxide release, protein oxidation, proliferation rate, as well as intracellular Ca2+‐release in single cells, most of them quantified via fluorescence microscopy and fluorimetric techniques. The existence of actual athermal wIRA‐effects is still intensively discussed, since their detection requires a careful experimental setup and both efficient and powerful temperature regulation of the exposed samples. Here, we can definitively show that some of the supposed athermal wIRA‐effects may be rather artifacts, since wIRA did not reveal any impact on the above mentioned parameters—as long as the temperature of the exposed cells was carefully maintained. Though, we were able to identify an athermal DNA‐protective wIRA‐effect, since the induced DNA damage (quantified via 8‐Oxo‐G‐formation) was significantly decreased after a subsequent UVB‐exposure. These results suggest that many of the supposed athermal wIRA‐effects can be induced by pure warming of the samples, independent from any wIRA‐irradiation. 相似文献
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A. Werner T. Grune W. Siems W. Schneider H. Shimasaki H. Esterbauer G. Gerber 《Chromatographia》1989,28(1-2):65-68
Summary The analysis of two metabolite groups, nucleotides and aldehydes, is necessary for assessment of oxygen radical metabolism during hypoxia and reoxygenation.Nucleotides and their derivatives were determined by HPLC using gradient elution with 10 mM NH4H2PO4 buffer containing 2 mM t-butylammoniumphosphate and acetonitrile.Aldehydes occuring after lipid peroxidation were analyzed by derivatisation to dinitrophenylhydrazones followed by TLC and HPLC separation with methanol/water on an ODS column. 相似文献
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Abstract This work focuses on the application of a multifunctional phosphazene monomer, 2,2,4,4,6,6-hexakis(2-hydroxyethyl methacrylate)-cyclotriphosphazene (6-Hema) for enhancement of the sensitivity of polyphosphazenes to both 60Co and E-beam radiation. Specifically, elastomeric and glassy phosphazene polymer films treated with 6-Hema were irradiated under vacuum, and the gel content was determined. The Charlesby-Pinner approach was used to compare the radiation sensitivities of these films. This served as the basis for eventually preparing SiO2 wafers with thin films of the glassy polyphosphazenes mixed with or overcoated by the 6-Hema monomer. The SiO2 wafers prepared with the most sensitive polymer/monomer system were patterned with an ERC electron beam accelerator/scanning electron microscope computer-driven instrument. It was determined that these negative resist films were 1-2 orders of magnitude more sensitive to radiation than the polymers without the monomer. 相似文献
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A double detection system for the determination of adenine metabolism in biological tissues using isocratic ion-pair reversed-phase chromatography is presented. Two isocratic ion-pair separations were used: (i) 10 mM NH4H2PO4, 2 mM tetrabutylammonium phosphate (PIC reagent A) and 18% acetonitrile for the determination of nucleotides and (ii) 50 mM KH2PO4, 1 mM PIC reagent A and 1% acetonitrile for the determination of monophosphorylated nucleotides, nucleosides and nucleobases. The parallel detection of ultraviolet absorbance at 254 nm and the radioactivity of separated purine compounds allows the detection of pool sizes and of the specific radioactivities in tracer kinetic experiments. The high-performance liquid chromatography methods were applied to the determination of flux rates during adenine nucleotide metabolism in suspensions of Ehrlich mouse ascites tumour cells. The pathways of adenine metabolism in cells during the proliferation and plateau phases of tumour growth were compared. 相似文献
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T Grune W Siems G Gerber Y V Tikhonov A M Pimenov R T Toguzov 《Journal of chromatography. A》1991,563(1):53-61
The pool of purine compounds was analysed in liver, skeletal muscle and blood of mice during the growth of Ehrlich ascites tumour cells. Three fast isocratic high-performance liquid chromatographic methods were used. (1) Determination of nucleotides by an isocratic ion-pair reversed-phase chromatography with a 10 mM ammonium phosphate buffer containing acetonitrile and tetrabutylammonium phosphate. (2) Separation of nucleosides and nucleobases in cell extracts by a reversed-phase system with methanol and 50 mM potassium phosphate buffer as eluent. (3) Nucleosides and nucleobases in body fluids were analysed by a reversed-phase system with 10 mM potassium phosphate containing methanol. These methods allow the rapid determination of purine compounds in small biological samples from various cell types and body fluids, with high accuracy and sensitivity. The pool of cellular nucleotides increased during the exponential phase of tumour growth. Adenosine accumulated significantly in all tissues in the stationary phase of tumour growth. 相似文献