Annals of the New York Academy of Sciences, ISSN 0077-8923 Volume 222, Issue 1, December 1973
1124 stran : ilustrace ; 23 cm
- MeSH
- Electron Spin Resonance Spectroscopy MeSH
- Magnetic Resonance Spectroscopy MeSH
- Publication type
- Congress MeSH
- Collected Work MeSH
- Conspectus
- Lékařské vědy. Lékařství
- NML Fields
- 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
- Cell Membrane drug effects metabolism MeSH
- Electron Spin Resonance Spectroscopy MeSH
- Photosystem II Protein Complex chemistry metabolism MeSH
- Plastoquinone analogs & derivatives chemistry MeSH
- Free Radical Scavengers pharmacology MeSH
- Singlet Oxygen chemistry MeSH
- Spin Trapping MeSH
- Spinacia oleracea chemistry MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't 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
- Antioxidants chemistry MeSH
- Chemical Fractionation methods MeSH
- Electron Spin Resonance Spectroscopy methods MeSH
- Plant Epidermis chemistry MeSH
- Plant Extracts chemistry MeSH
- Spectrophotometry, Ultraviolet MeSH
- Pressure MeSH
- Vitis chemistry MeSH
- Water chemistry MeSH
- Hot Temperature MeSH
- Chromatography, High Pressure Liquid MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't 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
- Chlorides metabolism MeSH
- Electron Spin Resonance Spectroscopy methods MeSH
- Photosystem II Protein Complex chemistry metabolism MeSH
- Hydroxyl Radical metabolism MeSH
- Oxidation-Reduction MeSH
- Hydrogen Peroxide pharmacology MeSH
- Spin Trapping methods MeSH
- Spinacia oleracea chemistry MeSH
- Heating MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
