electron paramagnetic resonance
Dotaz
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Annals of the New York Academy of Sciences, ISSN 0077-8923 Volume 222, Issue 1, December 1973
1124 stran : ilustrace ; 23 cm
- MeSH
- elektronová paramagnetická rezonance MeSH
- magnetická rezonanční spektroskopie MeSH
- Publikační typ
- kongresy MeSH
- sborníky MeSH
- Konspekt
- Lékařské vědy. Lékařství
- NLK Obory
- radiologie, nukleární medicína a zobrazovací metody
Cytochrome c (cyt c) is one of the most studied conjugated proteins due to its electron-transfer properties and ability to regulate the processes involved in homeostasis or apoptosis. Here we report an electrochemical strategy for investigating the electroactivity of cyt c and its analogs with a disrupted heme moiety, i.e. apocytochrome c (acyt c) and porphyrin cytochrome c (pcyt c). The electrochemical data are supplemented with low-temperature and spin-probe electron paramagnetic resonance (EPR) spectroscopy. The main contribution of this report is a complex evaluation of cyt c reduction and oxidation at the level of surface-localized amino acid residues and the heme moiety in a single electrochemical scan. The electrochemical pattern of cyt c is substantially different to both analogs acyt c and pcyt c, which could be applicable in further studies on the redox properties and structural stability of cytochromes and other hemeproteins.
Singlet oxygen (¹O₂) scavenging activity of plastoquinol in photosystem II (PSII) of higher plants was studied by electron paramagnetic resonance (EPR) spin-trapping technique. It is demonstrated here that illumination of spinach PSII membranes deprived of intrinsic plastoquinone results in ¹O₂ formation, as monitored by TEMPONE EPR signal. Interestingly, the addition of exogenous plastoquinol (PQH₂-1) to PQ-depleted PSII membranes significantly suppressed TEMPONE EPR signal. The presence of exogenous plastoquinols with a different side-chain length (PQH₂-n, n isoprenoid units in the side chain) caused a similar extent of ¹O₂ scavenging activity. These observations reveal that plastoquinol exogenously added to PQ-depleted PSII membranes serves as efficient scavenger of ¹O₂.
- MeSH
- buněčná membrána účinky léků metabolismus MeSH
- elektronová paramagnetická rezonance MeSH
- fotosystém II (proteinový komplex) chemie metabolismus MeSH
- plastochinon analogy a deriváty chemie MeSH
- scavengery volných radikálů farmakologie MeSH
- singletový kyslík chemie MeSH
- spin trapping MeSH
- Spinacia oleracea chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Pressurized hot water extraction (PHWE) was employed to prepare extracts from dried grape skin of two wine grape varieties (St. Laurent and Alibernet) at various temperatures (from 40 up to 120°C) and amounts of sample (0.5, 1.0 and 1.5 g). To assess the antioxidant activity of the extracts, electron paramagnetic resonance (EPR) spectroscopy was applied involving DPPH and ABTS(+) assays. Other extract characteristics including HPLC profile of anthocyanins and total phenolic compound content were obtained as well. PHWE has also been compared with earlier results of extractions of the same grape skin samples with compressed methanol and compressed ethanol under the conditions of pressurized fluid extraction (PFE). From this comparison, PHWE emerges as the more benign and efficient extraction method to recover valuable phenolic antioxidants from grape skins for the prospective use in functional food supplements.
- MeSH
- antioxidancia chemie MeSH
- chemická frakcionace metody MeSH
- elektronová paramagnetická rezonance metody MeSH
- epidermis rostlin chemie MeSH
- rostlinné extrakty chemie MeSH
- spektrofotometrie ultrafialová MeSH
- tlak MeSH
- Vitis chemie MeSH
- voda chemie MeSH
- vysoká teplota MeSH
- vysokoúčinná kapalinová chromatografie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Hydroxyl radical (HO•) production in photosystem II (PSII) was studied by electron paramagnetic resonance (EPR) spin-trapping technique. It is demonstrated here that the exposure of PSII membranes to heat stress (40 °C) results in HO• formation, as monitored by the formation of EMPO-OH adduct EPR signal. The presence of different exogenous halides significantly suppressed the EMPO-OH adduct EPR signal in PSII membranes under heat stress. The addition of exogenous acetate and blocker of chloride channel suppressed the EMPO-OH adduct EPR signal, whereas the blocker of calcium channel did not affect the EMPO-OH adduct EPR signal. Heat-induced hydrogen peroxide (H₂O₂) production was studied by amplex red fluorescent assay. The presence of exogenous halides, acetate and chloride blocker showed the suppression of H₂O₂ production in PSII membranes under heat stress. Based on our results, it is proposed that the formation of HO• under heat stress is linked to uncontrolled accessibility of water to the water-splitting manganese complex caused by the release of chloride ion on the electron donor side of PSII. Uncontrolled water accessibility to the water-splitting manganese complex causes the formation of H₂O₂ due to improper water oxidation, which leads to the formation of HO• via the Fenton reaction under heat stress.
- MeSH
- chloridy metabolismus MeSH
- elektronová paramagnetická rezonance metody MeSH
- fotosystém II (proteinový komplex) chemie metabolismus MeSH
- hydroxylový radikál metabolismus MeSH
- oxidace-redukce MeSH
- peroxid vodíku farmakologie MeSH
- spin trapping metody MeSH
- Spinacia oleracea chemie MeSH
- vytápění MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
