Oxidation of free, peptide and protein tryptophan residues mediated by AAPH-derived free radicals: role of alkoxyl and peroxyl radicals

RSC Advances ◽  
2016 ◽  
Vol 6 (63) ◽  
pp. 57948-57955 ◽  
Author(s):  
E. Fuentes-Lemus ◽  
E. Dorta ◽  
E. Escobar ◽  
A. Aspée ◽  
E. Pino ◽  
...  
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Peroxyl Radicals ◽  
Free Peptide ◽  
Low Concentrations ◽  
Tryptophan Residues ◽  
High Concentrations

When AAPH is employed as a free radical source, at low concentrations of free, peptide and protein Trp residues, the oxidation is mostly induced by alkoxyl radicals. However, at high concentrations, both peroxyl and alkoxyl radicals are involved.

Loss of muonium in nonhomogeneous processes studied by level-crossing resonance

1990 ◽  
Vol 68 (9) ◽  
pp. 957-961
Author(s):  
Krishnan Venkateswaran ◽  
Mary V. Barnabas ◽  
Zhennan Wu ◽  
David C. Walker
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Resonance Spectroscopy ◽  
Level Crossing ◽  
Low Concentrations ◽  
High Concentrations ◽  
Radical Yield

Level-crossing resonance spectroscopy has been used to determine the yield of muonium atoms formed in water and in hexane through production of muonated free radicals. In the presence of high concentrations of solutes, which yield radicals, all muons injected into the solutions are found either in diamagnetic molecules or free radicals. However, at low concentrations, the free-radical yield was smaller and a "missing fraction" appeared. Inverse yield against inverse concentration plots were not linear, indicating that reactions leading to loss occurred with nonhomogeneously distributed species from the muon's expanding track.

Comparison of the free radical scavenger activities of quercetin and rutin — An experimental and theoretical study

2004 ◽  
Vol 82 (12) ◽  
pp. 1668-1673 ◽  
Author(s):  
Carolina Aliaga ◽  
Eduardo A Lissi
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Radical Scavenging ◽  
Peroxyl Radicals ◽  
Reactivity Index ◽  
Radical Scavenger ◽  
Hydroxyl Groups ◽  
Local Reactivity ◽  
Reactivity Indexes

Natural radical scavengers have recently received considerable interest owing to the role of free radicals in causing oxidative stress in living organisms. Flavonoids constitute one of the most important families of molecules with antioxidant activities, a characteristic associated with the presence in their structure of hydroxyl groups bound to aromatic rings. Quercetin is a potent antioxidant whose high reactivity could be associated with the presence of the OH group in the C ring. To address the role of this group in quercetin's free radical scavenging capacity, we have carried out experimental determinations and theoretical calculations regarding the reactivity of quercetin and rutin. The reactivity of both compounds towards free radicals was assessed employing the radical anion 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) and peroxyl radicals. These measurements indicate that quercetin is more reactive and has more reactive centers than rutin, suggesting that the extra OH group located in the C ring could directly contribute to reactivity of quercetin. This conclusion is in agreement with the evaluation of local reactivity indexes, such as the Fukui function.Key words: quercetin, rutin, antioxidant activity, ABTS•–, peroxyl radicals, Fukui function, local reactivity index.

Study of antioxidant potential in leaves, stems, nuts of Juglans regia L.

2012 ◽  
Vol 1 (10) ◽  
pp. 79 ◽  
Author(s):  
G. Raja* ◽  
Ivvala Anand Shaker ◽  
Inampudi Sailaja ◽  
R. Swaminathan ◽  
S. Saleem Basha ◽  
...  
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Antioxidant Activities ◽  
Radical Scavenging Activity ◽  
Juglans Regia ◽  
Radical Scavenging ◽  
Antioxidant Compounds ◽  
Free Radical Damage ◽  
Radical Damage

Natural antioxidants can protect the human body from free radicals and retard the progress of many chronic diseases as well as lipid oxidative rancidity in foods. The role of antioxidants has protected effect against free radical damage that may cause many diseases including cancer. Primary sources of naturally occurring antioxidants are known as whole grains, fruits, and vegetables. Several studies suggest that regular consumption of nuts, mostly walnuts, may have beneficial effects against oxidative stress mediated diseases such as cardiovascular disease and cancer. The role of antioxidants has attracted much interest with respect to their protective effect against free radical damage that may cause many diseases including cancer. Juglans regia L. (walnut) contains antioxidant compounds, which are thought to contribute to their biological properties. Polyphenols, flavonoids and flavonols concentrations and antioxidant activity of Leaves, Stems and Nuts extract of Juglans regia L. as evaluated using DPPH, ABTS, Nitric acid, hydroxyl and superoxide radical scavenging activity, lipid peroxidation and total oxidation activity were determined. The antioxidant activities of Leaves, Stems and Nuts extract of Juglans regia L. were concentration dependent in different experimental models and it was observed that free radicals were scavenged by the test compounds in all the models.

scholarly journals Environmentally persistent free radicals are ubiquitous in wildfire charcoals and remain stable for years

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Gabriel Sigmund ◽  
Cristina Santín ◽  
Marc Pignitter ◽  
Nathalie Tepe ◽  
Stefan H. Doerr ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Free Radicals ◽  
Reactive Oxygen ◽  
Resonance Spectroscopy ◽  
Oxygen Species ◽  
Pyrogenic Carbon ◽  
Spin Resonance ◽  
Long Time ◽  
High Concentrations

AbstractGlobally landscape fires produce about 256 Tg of pyrogenic carbon or charcoal each year. The role of charcoal as a source of environmentally persistent free radicals, which are precursors of potentially harmful reactive oxygen species, is poorly constrained. Here, we analyse 60 charcoal samples collected from 10 wildfires, that include crown as well as surface fires in forest, shrubland and grassland spanning different boreal, temperate, subtropical and tropical climate. Using electron spin resonance spectroscopy, we measure high concentrations of environmentally persistent free radicals in charcoal samples, much higher than those found in soils. Concentrations increased with degree of carbonization and woody fuels favoured higher concentrations. Moreover, environmentally persistent free radicals remained stable for an unexpectedly long time of at least 5 years. We suggest that wildfire charcoal is an important global source of environmentally persistent free radicals, and therefore potentially of harmful reactive oxygen species.

scholarly journals Colchicine-binding protein of the liver. Its characterization and relation to microtubules.

1975 ◽  
Vol 66 (3) ◽  
pp. 609-620 ◽  
Author(s):  
C Patzelt ◽  
A Singh ◽  
Y L Marchand ◽  
L Orci ◽  
B Jeanrenaud
Keyword(s):  
High Speed ◽  
Specific Binding ◽  
Electrophoretic Analysis ◽  
Binding Activity ◽  
Low Concentrations ◽  
Electrophoretic Behavior ◽  
High Affinity Binding Site ◽  
High Concentrations

Colchicine-binding activity of mouse liver high-speed supernate has been investigated. It has been found to be time and temperature dependent. Two binding activities with different affinities for colchicine seem to be present in this high-speed supernate, of which only the high-affinity binding site (half maximal binding at 5 x 10(-6) M colchicine) can be attributed to microtubular protein by comparison with purified tubulin. Vinblastine interacted with this binding activity by precipitating it when used at high concentrations (2 x 10(-3) M), and by stabilizing it at low concentrations (10(-5) M). Lumicolchicine was found not to compete with colchicine. The colchicine-binding activity was purified from liver and compared with that of microtubular protein from brain. The specific binding activity of the resulting preparation, its electrophoretic behavior, and the electron microscope appearance of the paracrystals obtained upon its precipitation with vinblastine permitted its identification as microtubular protein (tubulin). Electrophoretic analysis of the proteins from liver supernate that were precipitated by vinblastine indicated that this drug was not specific for liver tubulin. Preincubation of liver supernate with 5 mM EGTA resulted in a time-dependent decrease of colchicine-binding activity, which was partly reversed by the addition of Ca++. However, an in vitro formation of microtubules upon lowering the Ca++ concentration could not be detected. Finally, a method was developed enabling that portion of microtubular protein which was present as free tubulin to be measured and to be compared with the total amount of this protein in the tissue. This procedure permitted demonstration of the fact that, under normal conditions, only about 40% of the tubulin of the liver was assemled as microtubules. It is suggested that, in the liver, rapid polymerization and depolymerization of microtubules occur and may be an important facet of the functional role of the microtubular system.

scholarly journals Antibacterial Peptides Resistance in Staphylococcus aureus: Various Mechanisms and the Association with Pathogenicity

Genes ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1527
Author(s):  
Miki Kawada-Matsuo ◽  
Mi Nguyen-Tra Le ◽  
Hitoshi Komatsuzawa
Keyword(s):  
Staphylococcus Aureus ◽  
Antimicrobial Peptides ◽  
Antibacterial Peptides ◽  
Low Concentrations ◽  
Component Systems ◽  
Two Component Systems ◽  
Resistant Strains ◽  
Resistant Mutants ◽  
High Concentrations

Staphylococcus aureus is a bacterium that mainly colonizes the nasal cavity and skin. To colonize the host, it is necessary for S. aureus to resist many antibacterial factors derived from human and commensal bacteria. Among them are the bacteria-derived antimicrobial peptides (AMPs) called bacteriocins. It was reported that some two-component systems (TCSs), which are signal transduction systems specific to bacteria, are involved in the resistance to several bacteriocins in S. aureus. However, the TCS-mediated resistance is limited to relatively low concentrations of bacteriocins, while high concentrations of bacteriocins still exhibit antibacterial activity against S. aureus. To determine whether we could obtain highly bacteriocin-resistant mutants, we tried to isolate highly nisin A-resistant mutants by exposing the cells to sub-minimum inhibitory concentrations (MICs) of nisin A. Nisin A is one of the bacteriocins produced by Lactococcus lactis and is utilized as a food preservative worldwide. Finally, we obtained highly nisin A-resistant mutants with mutations in one TCS, BraRS, and in PmtR, which is involved in the expression of pmtABCD. Notably, some highly resistant strains also showed increased pathogenicity. Based on our findings, this review provides up-to-date information on the role of TCSs in the susceptibility to antibacterial peptides. Additionally, the mechanism for high antimicrobial peptides resistance and its association with pathogenicity in S. aureus is elucidated.

Role of cell replication in regulation of Na-coupled hexose transport in LLC-PK1 epithelial cells

1986 ◽  
Vol 250 (2) ◽  
pp. C314-C318 ◽  
Author(s):  
A. Moran ◽  
J. S. Handler ◽  
M. Hagan
Keyword(s):  
Epithelial Cells ◽  
Ionizing Radiation ◽  
Thymidine Incorporation ◽  
Regulatory Process ◽  
Hexose Transport ◽  
Cell Replication ◽  
Response Data ◽  
Low Concentrations ◽  
High Concentrations

The glucose concentration in growth medium has been shown to regulate the number of sodium-coupled glucose transporters in LLC-PK1 epithelial cells. Epithelia grown in high concentrations of glucose express fewer transporters than epithelia grown in low concentrations of glucose. In the present work, the effect of a dose of ionizing radiation sufficient to block the incorporation of thymidine was examined in order to gauge the importance of cell replication in the hexose transport regulatory process. The low rate of thymidine incorporation in the plateau phase was completely eliminated by ionizing radiation. Under conditions of irradiation that completely blocked thymidine incorporation, down-regulation, namely the loss of alpha-methylglucoside-concentrating capacity, brought about by switching the epithelium from low to high glucose-containing medium, is independent of the irradiation and therefore most likely is also independent of cell replication. In contrast, the up-regulatory phenomenon is strongly impaired by radiation. This impairment may be due to specific radiation impairment of gene expression necessary for the up-regulatory process. It is apparent from the dose-response data that up-regulation is not inhibited by irradiation in a simple manner and is not inhibited at the same radiation dose as cell replication.

The Role of Free Radicals in Traumatic Brain Injury

2012 ◽  
Vol 15 (3) ◽  
pp. 253-263 ◽  
Author(s):  
Karen M. O’Connell ◽  
Marguerite T. Littleton-Kearney
Keyword(s):  
Traumatic Brain Injury ◽  
Free Radicals ◽  
Free Radical ◽  
Brain Injury ◽  
Current Knowledge ◽  
Cellular Level ◽  
Secondary Brain Injury ◽  
Secondary Injury ◽  
The Military

Traumatic brain injury (TBI) is a significant cause of death and disability in both the civilian and the military populations. The primary impact causes initial tissue damage, which initiates biochemical cascades, known as secondary injury, that expand the damage. Free radicals are implicated as major contributors to the secondary injury. Our review of recent rodent and human research reveals the prominent role of the free radicals superoxide anion, nitric oxide, and peroxynitrite in secondary brain injury. Much of our current knowledge is based on rodent studies, and the authors identified a gap in the translation of findings from rodent to human TBI. Rodent models are an effective method for elucidating specific mechanisms of free radical-induced injury at the cellular level in a well-controlled environment. However, human TBI does not occur in a vacuum, and variables controlled in the laboratory may affect the injury progression. Additionally, multiple experimental TBI models are accepted in rodent research, and no one model fully reproduces the heterogeneous injury seen in humans. Free radical levels are measured indirectly in human studies based on assumptions from the findings from rodent studies that use direct free radical measurements. Further study in humans should be directed toward large samples to validate the findings in rodent studies. Data obtained from these studies may lead to more targeted treatment to interrupt the secondary injury cascades.

H+ current response to CO2 and carbonic anhydrase inhibition in turtle bladder

1976 ◽  
Vol 231 (2) ◽  
pp. 565-572 ◽  
Author(s):  
JH Schwartz
Keyword(s):  
Carbonic Anhydrase ◽  
Maximum Rate ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Current Response ◽  
Low Concentrations ◽  
Ph Stat ◽  
High Concentrations ◽  
Co2 Addition

To evaluate the role of CO2 and carbonic anhydrase (CA) in H+ transport (JH) by turtle urinary bladder the effect of CO2 addition, with and without addition of CA inhibitiors, was examined on JH. Since in the presence of exogenous CO2 and HCO3- the pH stat-measured rate of mucosal (M) acidification underestimates JH by the rate of electroneutral HCO3- secretion, the reverse short-circuit current (RSCC) applied across ouabain-treated bladders was used to estimate JH. That the RSCC is a measure of JH was demonstrated by: 1) in the absence of added CO2 and HCO3- the rate of M acidification totally accounted for the RSCC, and 2) increases in RSCC with CO2 addition occurred without changes in Na+ and K+ fluxes or the coupled ration of HCO3- secretion for Cl-absorption. When serosal (S) percent CO2 was progressively progressively increased JH achieved a maximum rate of 64 +/- 3 muA (SE) with 4.5% CO2. At higher S percent CO2 JH did not change, suggesting that factors other than the rate of CO2 hydration were rate limiting. The maximum rate of JH was not decreased by low concentrations of CA inhibitors (acetazolamide, 5 X 10(-5) M), although the percent CO2 at which this maximum rate occurred increased to 8.5%. The increased percent CO2 requirement for the maximum rate of JH with low concentrations of CA inhibitors suggests that these agents alter JH by decreasing the rate of enzymatic CO2 hydration. At high concentrations (acetazolamide, 5 X 10(-4) M) these inhibitors decrease the maximum rate of JH in the presence of CO2, implying that these inhibitors at higher concentrations directly interfere with the H+ transport system.

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