The Experts below are selected from a list of 324642 Experts worldwide ranked by ideXlab platform
Myran C. Sauer - One of the best experts on this subject based on the ideXlab platform.
-
Hole Scavenging and Photo-Stimulated Recombination of Electron−Hole Pairs in Aqueous TiO2 Nanoparticles
Journal of Physical Chemistry B, 2004Co-Authors: Ilya A Shkrob, Myran C. SauerAbstract:It is shown that 532 and 1064 nm laser photoexcitation of trapped electrons generated by 355 nm photolysis of aqueous titania (TiO2) nanoparticles causes rapid photobleaching of their absorbance band in the visible and near-IR. This photobleaching occurs within the duration of the laser pulse (3 ns fwhm); it is caused by photoinduced electron detrapping followed by rapid recombination of the resulting free electron and a trapped hole. The quantum yield for the electron photobleaching is ca. 0.28 for 532 nm and ca. 0.024 for 1064 nm photoexcitation. Complete separation of the spectral contributions from trapped electron and hole is demonstrated using glycerol as a selective hole Scavenger. When glycerol is added to the solution, some light-absorbing holes are Scavenged promptly within the duration of the 355 nm photoexcitation pulse, some are Scavenged at a slower rate over the first 200 ns after the 355 nm pulse, and the rest are not Scavenged, even at high concentration of the Scavenger (>10 vol. %). A r...
-
hole scavenging and photo stimulated recombination of electron hole pairs in aqueous tio2 nanoparticles
Journal of Physical Chemistry B, 2004Co-Authors: Ilya A Shkrob, Myran C. SauerAbstract:It is shown that 532 and 1064 nm laser photoexcitation of trapped electrons generated by 355 nm photolysis of aqueous titania (TiO2) nanoparticles causes rapid photobleaching of their absorbance band in the visible and near-IR. This photobleaching occurs within the duration of the laser pulse (3 ns fwhm); it is caused by photoinduced electron detrapping followed by rapid recombination of the resulting free electron and a trapped hole. The quantum yield for the electron photobleaching is ca. 0.28 for 532 nm and ca. 0.024 for 1064 nm photoexcitation. Complete separation of the spectral contributions from trapped electron and hole is demonstrated using glycerol as a selective hole Scavenger. When glycerol is added to the solution, some light-absorbing holes are Scavenged promptly within the duration of the 355 nm photoexcitation pulse, some are Scavenged at a slower rate over the first 200 ns after the 355 nm pulse, and the rest are not Scavenged, even at high concentration of the Scavenger (>10 vol. %). A r...
-
hole scavenging and photo stimulated recombination of electron hole pairs in aqueous tio2 nanoparticles
arXiv: Chemical Physics, 2004Co-Authors: Ilya A Shkrob, Myran C. SauerAbstract:It is shown that 532 nm and 1064 nm laser photoexcitation of trapped electrons generated by 355 nm photolysis of aqueous titania (TiO2) nanoparticles causes rapid photobleaching of their absorbance band in the visible and near IR. This photobleaching occurs within the duration of the laser pulse (3 ns FWHM); it is caused by photoinduced electron detrapping followed by rapid recombination of the resulting free electron and a trapped hole. The quantum yield for the electron photobleaching is ca. 0.28 for 532 nm and ca. 0.024 for 1064 nm photoexcitation. Complete separation of the spectral contributions from trapped electron and hole is demonstrated using glycerol as a selective hole Scavenger. When glycerol is added to the solution, some light-absorbing holes are Scavenged promptly within the duration of the 355 nm photoexcitation pulse, some are Scavenged at a slower rate over the first 200 ns after the 355 nm pulse, and the rest are not Scavenged, even at high concentration of the Scavenger (> 10 vol %). A reaction with chemi- and physi- sorbed glycerol would account for the prompt and the slow hole decay, respectively. The implications of these results are discussed.
Jose Pedrazachaverri - One of the best experts on this subject based on the ideXlab platform.
-
effect of heating on peroxynitrite scavenging capacity of garlic
Food and Chemical Toxicology, 2007Co-Authors: Jose Pedrazachaverri, Omar Noel Medinacampos, Sabina SegovianomurilloAbstract:Abstract The ability to Scavenge peroxynitrite (ONOO − ) was studied in the following aqueous garlic extracts: (a) unheated extract of garlic powder (GP), (b) heated extract of garlic powder (HGP), (c) unheated extract of raw garlic (RG), (d) heated extract of raw garlic (HRG), (e) extract of boiled garlic cloves (BG), (f) extract of microwave-treated garlic cloves (MG), and (g) extract of pickled garlic (PG). All the extracts Scavenged ONOO − in a concentration-dependent way. IC 50 (mg/mL) values for each extract were 0.30 ± 0.02 and 0.35 ± 0.04 for GP and HGP, respectively; and 0.84 ± 0.08, 0.59 ± 0.04, 0.76 ± 0.09, 1.71 ± 0.19, and 1.45 ± 0.07 for RG, HRG, BG, MG, and PG, respectively. The ONOO − scavenging capacity (IC 50 values) was not decreased in HGP (vs. GP, p > 0.05) and in HRG and BG ( p > 0.05 vs. RG). In contrast, the ONOO − scavenging capacity decreased in MG and PG (vs. RG, p 50 values for the reference compounds nordihydroguiaretic acid and penicillamine were 1.1 and 4.5 μg/mL. The heating before or after garlic cutting was unable to eliminate the capacity of the extracts to Scavenge ONOO − ; this capacity was significantly decreased in PG and MG.
-
nordihydroguaiaretic acid is a potent in vitro Scavenger of peroxynitrite singlet oxygen hydroxyl radical superoxide anion and hypochlorous acid and prevents in vivo ozone induced tyrosine nitration in lungs
Free Radical Research, 2006Co-Authors: Esau Florianosanchez, Cleva Villanueva, Omar N Medinacampos, Diana Rocha, Dolores Javier Sanchezgonzalez, Noemi Cardenasrodriguez, Jose PedrazachaverriAbstract:The antioxidant nordihydroguaiaretic acid (NDGA) has recently become well known as a putative anticancer drug. In this paper, it was evaluated the in vitro peroxynitrite (ONOO− ), singlet oxygen (1O2), hydroxyl radical (OH√), hydrogen peroxide (H2O2), superoxide anion and hypochlorous acid (HOCl) scavenging capacity of NDGA. It was found that NDGA Scavenges: (a) ONOO− (IC50 = 4 ± 0.94 μM) as efficiently as uric acid; (b) 1O2 (IC50 = 151 ± 20 μM) more efficiently than dimethyl thiourea, lipoic acid, N-acetyl-cysteine and glutathione; (c) OH√ (IC50 = 0.15 ± 0.02 μM) more efficiently than dimethyl thiourea, uric acid, trolox, dimethyl sulfoxide and mannitol, (d) (IC50 = 15 ± 1 μM) more efficiently than N-acetyl-cysteine, glutathione, tempol and deferoxamine and (e) HOCl (IC50 = 622 ± 42 μM) as efficiently as lipoic acid and N-acetyl-cysteine. NDGA was unable to Scavenge H2O2. In an in vivo study in rats, NDGA was able to prevent ozone-induced tyrosine nitration in lungs. It is concluded that NDGA is a potent...
Ilya A Shkrob - One of the best experts on this subject based on the ideXlab platform.
-
Hole Scavenging and Photo-Stimulated Recombination of Electron−Hole Pairs in Aqueous TiO2 Nanoparticles
Journal of Physical Chemistry B, 2004Co-Authors: Ilya A Shkrob, Myran C. SauerAbstract:It is shown that 532 and 1064 nm laser photoexcitation of trapped electrons generated by 355 nm photolysis of aqueous titania (TiO2) nanoparticles causes rapid photobleaching of their absorbance band in the visible and near-IR. This photobleaching occurs within the duration of the laser pulse (3 ns fwhm); it is caused by photoinduced electron detrapping followed by rapid recombination of the resulting free electron and a trapped hole. The quantum yield for the electron photobleaching is ca. 0.28 for 532 nm and ca. 0.024 for 1064 nm photoexcitation. Complete separation of the spectral contributions from trapped electron and hole is demonstrated using glycerol as a selective hole Scavenger. When glycerol is added to the solution, some light-absorbing holes are Scavenged promptly within the duration of the 355 nm photoexcitation pulse, some are Scavenged at a slower rate over the first 200 ns after the 355 nm pulse, and the rest are not Scavenged, even at high concentration of the Scavenger (>10 vol. %). A r...
-
hole scavenging and photo stimulated recombination of electron hole pairs in aqueous tio2 nanoparticles
Journal of Physical Chemistry B, 2004Co-Authors: Ilya A Shkrob, Myran C. SauerAbstract:It is shown that 532 and 1064 nm laser photoexcitation of trapped electrons generated by 355 nm photolysis of aqueous titania (TiO2) nanoparticles causes rapid photobleaching of their absorbance band in the visible and near-IR. This photobleaching occurs within the duration of the laser pulse (3 ns fwhm); it is caused by photoinduced electron detrapping followed by rapid recombination of the resulting free electron and a trapped hole. The quantum yield for the electron photobleaching is ca. 0.28 for 532 nm and ca. 0.024 for 1064 nm photoexcitation. Complete separation of the spectral contributions from trapped electron and hole is demonstrated using glycerol as a selective hole Scavenger. When glycerol is added to the solution, some light-absorbing holes are Scavenged promptly within the duration of the 355 nm photoexcitation pulse, some are Scavenged at a slower rate over the first 200 ns after the 355 nm pulse, and the rest are not Scavenged, even at high concentration of the Scavenger (>10 vol. %). A r...
-
hole scavenging and photo stimulated recombination of electron hole pairs in aqueous tio2 nanoparticles
arXiv: Chemical Physics, 2004Co-Authors: Ilya A Shkrob, Myran C. SauerAbstract:It is shown that 532 nm and 1064 nm laser photoexcitation of trapped electrons generated by 355 nm photolysis of aqueous titania (TiO2) nanoparticles causes rapid photobleaching of their absorbance band in the visible and near IR. This photobleaching occurs within the duration of the laser pulse (3 ns FWHM); it is caused by photoinduced electron detrapping followed by rapid recombination of the resulting free electron and a trapped hole. The quantum yield for the electron photobleaching is ca. 0.28 for 532 nm and ca. 0.024 for 1064 nm photoexcitation. Complete separation of the spectral contributions from trapped electron and hole is demonstrated using glycerol as a selective hole Scavenger. When glycerol is added to the solution, some light-absorbing holes are Scavenged promptly within the duration of the 355 nm photoexcitation pulse, some are Scavenged at a slower rate over the first 200 ns after the 355 nm pulse, and the rest are not Scavenged, even at high concentration of the Scavenger (> 10 vol %). A reaction with chemi- and physi- sorbed glycerol would account for the prompt and the slow hole decay, respectively. The implications of these results are discussed.
Tory M Hagen - One of the best experts on this subject based on the ideXlab platform.
-
is α lipoic acid a Scavenger of reactive oxygen species in vivo evidence for its initiation of stress signaling pathways that promote endogenous antioxidant capacity
Iubmb Life, 2008Co-Authors: Kate Petersen Shay, Regis F Moreau, Eric J Smith, Tory M HagenAbstract:The chemical reduction and oxidation (redox) properties of α-lipoic acid (LA) suggest that it may have potent antioxidant potential. A significant number of studies now show that LA and its reduced form, dihydrolipoic acid (DHLA), directly Scavenge reactive oxygen species (ROS) and reactive nitrogen species (RNS) species and protect cells against a host of insults where oxidative stress is part of the underlying etiology. However, owing to its limited and transient accumulation in tissues following oral intake, the efficacy of nonprotein-bound LA to function as a physiological antioxidant has been questioned. Herein, we review the evidence that the micronutrient functions of LA may be more as an effector of important cellular stress response pathways that ultimately influence endogenous cellular antioxidant levels and reduce proinflammatory mechanisms. This would promote a sustained improvement in cellular resistance to pathologies where oxidative stress is involved, which would not be forthcoming if LA solely acted as a transient ROS Scavenger. © 2008 IUBMB IUBMB Life, 60(6): 362–367, 2008
Hae Young Chung - One of the best experts on this subject based on the ideXlab platform.
-
Zingerone as an antioxidant against peroxynitrite
Journal of Agricultural and Food Chemistry, 2005Co-Authors: Sang-guk Shin, Hae Young Chung, Jiyoung Kim, Ji-cheon JeongAbstract:Peroxynitrite (ONOO-), formed from the reaction of superoxide (•O2-) and nitric oxide (•NO), induces cellular and tissue injury, resulting in several human diseases such as stroke, Alzheimer's disease, and atherosclerosis. Due to the lack of endogenous enzymes responsible for ONOO- scavenging activity, finding a specific ONOO- Scavenger is of considerable importance. In this study we examined the scavenging effects of zingerone from ginger against ONOO-, intracellular RS (reactive species), and ONOO-. The data show that zingerone can efficiently Scavenge native ONOO- as well as ONOO- derived from the peroxynitrite donor 3-morpholinosydnonimine hydrochloride (SIN-1). Zingerone inhibited the formation of ONOO--mediated tyrosine nitration through electron donation, nitration of bovine serum albumin (BSA) by ONOO-, and intracellular RS and ONOO-. The present study suggests that zingerone has an efficient ONOO- scavenging ability, which may be a potent ONOO- Scavenger for the protection of the cellular defense...
-
peroxynitrite scavenging activity of sinapic acid 3 5 dimethoxy 4 hydroxycinnamic acid isolated from brassica juncea
Journal of Agricultural and Food Chemistry, 2002Co-Authors: Jae Sue Choi, Hae Young ChungAbstract:: Peroxynitrite (ONOO(-)), formed from a reaction of superoxide and nitric oxide, is one of the most potent cytotoxic species that are known to oxidize cellular constituents including essential proteins, lipids, and DNA. In this study, the ability of sinapic acid (3,5-dimethoxy-4-hydroxycinnamic acid), isolated from Brassica juncea, to Scavenge ONOO(-) was investigated. The data obtained show that sinapic acid can efficiently Scavenge native ONOO(-) as well as ONOO(-) derived from the peroxynitrite donor 3-morpholinosydnonimine hydrochloride (SIN-1). Spectrophotometric analyses revealed that sinapic acid suppressed the formation of ONOO(-)-mediated tyrosine nitration through an electron donation mechanism. In further studies, sinapic acid also showed a significant ability of inhibiting nitration of bovine serum albumin and low-density lipoprotein (LDL) in a dose-dependent manner. Sinapic acid decreased the LDL peroxidation induced by SIN-1-derived ONOO(-). The present study suggests that sinapic acid has an efficient ONOO(-) scavenging ability, which may well be a potent ONOO(-) oxidant Scavenger for the protection of the cellular defense activity against the ONOO(-)-involved diseases.
-
Peroxynitrite scavenging activity of herb extracts
Phytotherapy Research, 2002Co-Authors: Hye Rhi Choi, Jae Sue Choi, Hae Young ChungAbstract:Peroxynitrite (ONOO−) is a cytotoxicant with strong oxidizing properties toward various cellular constituents, including sulphydryls, lipids, amino acids and nucleotides and can cause cell death, lipid peroxidation, carcinogenesis and aging. The aim of this study was to characterize ONOO− scavenging constituents from herbs. Twenty-eight herbs were screened for their ONOO− scavenging activities with the use of a fluorometric method. The potency of scavenging activity following the addition of authentic ONOO− was in the following order: witch hazel bark > rosemary > jasmine tea > sage > slippery elm > black walnut leaf > Queen Anne's lace > Linden flower. The extracts exhibited dose-dependent ONOO− scavenging activities. We found that witch hazel (Hamamelis virginiana L.) bark showed the strongest effect for scavenging ONOO− of the 28 herbs. Hamamelitannin, the major active component of witch hazel bark, was shown to have a strong ability to Scavenge ONOO−. It is suggested that hamamelitannin might be developed as an effective peroxynitrite Scavenger for the prevention of ONOO− involved diseases. Copyright © 2002 John Wiley & Sons, Ltd.
-
Peroxynitrite scavenging activity of herb extracts.
Phytotherapy research : PTR, 2002Co-Authors: Hye Rhi Choi, Jae Sue Choi, Yong Nam Han, Song Ja Bae, Hae Young ChungAbstract:Peroxynitrite (ONOO(-)) is a cytotoxicant with strong oxidizing properties toward various cellular constituents, including sulphydryls, lipids, amino acids and nucleotides and can cause cell death, lipid peroxidation, carcinogenesis and aging. The aim of this study was to characterize ONOO(-) scavenging constituents from herbs. Twenty-eight herbs were screened for their ONOO(-) scavenging activities with the use of a fluorometric method. The potency of scavenging activity following the addition of authentic ONOO(-) was in the following order: witch hazel bark > rosemary > jasmine tea > sage > slippery elm > black walnut leaf > Queen Anne's lace > Linden flower. The extracts exhibited dose-dependent ONOO(-) scavenging activities. We found that witch hazel (Hamamelis virginiana L.) bark showed the strongest effect for scavenging ONOO(-) of the 28 herbs. Hamamelitannin, the major active component of witch hazel bark, was shown to have a strong ability to Scavenge ONOO(-). It is suggested that hamamelitannin might be developed as an effective peroxynitrite Scavenger for the prevention of ONOO(-) involved diseases.
