PubMed · 4297216
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D H Eargle. 1968. Electron paramagnetic resonance.. https://doi.org/10.1021/ac60261a009
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The effects of hyaluronan and its degradation products on irradiation-induced lipid peroxidation were investigated. Liposomal skin lipid models with increasing complexity were used. Hyaluronan and its fragments were able to reduce the amount of lipid peroxidation secondary products quantified by the thiobarbituric acid (TBA) assay. The qualitative changes were studied by mass spectrometry. To elucidate the nature of free radical involvement electron paramagnetic resonance (EPR) studies were carried out. The influence of hyaluronan and its fragments on the concentration of hydroxyl radicals generated by the Fenton system was examined using the spin trapping technique. Moreover, the mucopolysaccharide's ability to react with stable radicals was checked. The quantification assay of 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH) showed no concentration changes of the stable radical caused by hyaluronan. Hyaluronan was found to exhibit prooxidative effects in the Fenton assay in a concentration dependent manner. A transition metal chelation was proposed as a mechanism of this behavior. Considering human skin and its constant exposure to UV light and oxygen and an increased pool of iron in irradiated skin the administration of hyaluronan or its fragments in cosmetic formulations or sunscreens could be helpful for the protection of the human skin.
A rapid increase in RNA structural studies has been seen in the past few years, in part due to the interest in the multitude of cellular functions performed by RNA. Electron paramagnetic resonance spectroscopy is a useful technique for studying biopolymer structure under physiologically relevant conditions. We present herein the use of pulsed electron double resonance for the determination of a 35 +/- 2 A distance between two spin label nitroxides that were linked to specific positions within an RNA.
Phosphoinositide (PI) 3-kinases catalyze the phosphorylation of the D3 position of the inositol ring of PI, and its phosphorylated derivatives and play important roles in many intracellular signal transducing pathways. Class IA PI3-kinases contain distinct regulatory (p85) and catalytic (p110) subunits. p110 is stabilized and inhibited by constitutive association with p85, and is disinhibited when the SH2 domains of p85 bind to tyrosyl-phosphorylated proteins. Because the two subunits do not dissociate, disinhibition of p110 presumably occurs by an allosteric mechanism. To explore the means by which p85 regulates the activity of p110, structures of the inter-SH2 domain of p85 were determined with and without phosphopeptide by using a combination of site directed spin labeling EPR and homology modeling and molecular dynamics. The inter-SH2 domain is assigned as a rigid anti-parallel coiled-coil whose primary function is to bind p110, facilitating inhibition of p110 by the N-terminal SH2 domain of p85.