Search results for "Radicals"

Dietary flavonols and flavan-3ols as modulators of superoxide radicals production: opposite dose-dependent effects

2012

Analysis of the spatial distribution of free radicals in ammonium tartrate by pulse EPR techniques

2009

Using pulse electron paramagnetic resonance (EPR) on a series of l(+)-ammonium tartrate (AT) dosimeters exposed to radiations with different linear energy transfer (LET), we assessed the ability of pulse EPR spectroscopy to discriminate the quality of various radiation beams such as (60)Co gamma-ray photons, protons and thermal neutrons at various doses by analyzing the local radical distributions produced by the different beams. We performed two types of pulse EPR investigations: two-pulse electron spin echo decay obtained by varying the microwave power, and a double electron-electron resonance (DEER) study. Both methods provide information about the dipolar interactions among the free rad…

Squaramide-based reagent for selective chromogenic sensing of Cu(II) through a zwitterion radical.

2010

A minimalist squaramide-based chemodosimeter for Cu(2+) is described. Upon selective chelation to 2, Cu(2+) induces the formation of a highly colored zwitterionic radical, which is kinetically stable for hours. The presence of a radical is confirmed by EPR and ESI-MS. It is then possible to use reagent 2 for visual and selective sensing of Cu(2+) at neutral pH.

Two in one against motor neuron degeneration: tackling oxidative stress and inflammation with a sulfasalazine derivative.

2012

Increased p53 mutation load in nontumorous human liver of Wilson disease and hemochromatosis: Oxyradical overload diseases

2000

Hemochromatosis and Wilson disease (WD), characterized by the excess hepatic deposition of iron and copper, respectively, produce oxidative stress and increase the risk of liver cancer. Because the frequency of p53 mutated alleles in nontumorous human tissue may be a biomarker of oxyradical damage and identify individuals at increased cancer risk, we have determined the frequency of p53 mutated alleles in nontumorous liver tissue from WD and hemochromatosis patients. When compared with the liver samples from normal controls, higher frequencies of G:C to T:A transversions at codon 249 ( P < 0.001) and C:G to A:T transversions and C:G to T:A transitions at codon 250 ( P < 0.001 and P &…

Of Thiols and Disulfides: Methods for Chemoselective Formation of Asymmetric Disulfides in Synthetic Peptides and Polymers.

2018

In protein or peptide chemistry, thiols are frequently chosen as a chemical entity for chemoselective modification reactions. Although it is a well-established methodology to address cysteines and homocysteines in aqueous media to form S-C bonds, possibilities for the chemoselective formation of asymmetric disulfides have been less approached. Focusing on bioreversibility in conjugation chemistry, the formation of disulfide bonds is highly desirable for the attachment of thiol-containing bioactive agents to proteins or in cross-linking reactions, because disulfide bonds can combine stability in blood with degradability inside cells. In this Concept article, recent approaches in the field of…

Free radical-mediated systemic immunity in plants.

2014

SPE IPM; Systemic acquired resistance (SAR) is a form of defense that protects plants against a broad-spectrum of secondary infections by related or unrelated pathogens. SAR related research has witnessed considerable progress in recent years and a number of chemical signals and proteins contributing to SAR have been identified. All of these diverse constituents share their requirement for the phytohormone salicylic acid, an essential downstream component of the SAR pathway. However, recent work demonstrating the essential parallel functioning of nitric oxide (NO)-derived and reactive oxygen species (ROS)-derived signaling together with SA provides important new insights in the overlapping …

Interaction of sodium, lithium, caesium, and potassium ions with ascorbyl radicals.

1987

Abstract The influence of the concentration of sodium, lithium , caesium, and potassium ions as well as of the ionic strength of the solutions used on the dismutation rate of ascorbyl radicals has been investigated. While the dismutation rate was not influenced by Li+, it decreased, however, with increasing concentrations of the other ions investigated. The largest effect was obtained with Na+. This change in dismutation rate indicates a stabilizing effect on ascorbyl radical by these ions.

Studies on pathways of ring opening of benzene in a Fenton system

1995

Ring-opened products of benzene metabolism have been postulated to play a role in hematotoxicity and leukemogenesis. The reaction of benzene in the Fenton system was reexamined to determine the presence of compounds which might serve as intermediates in the formation of trans, trans-muconaldehyde (MUC), a microsomal hematotoxic metabolite of benzene. Benzene dihydrodiol (DHD) was found in this system based on coelution with authentic standard, ultraviolet (UV) absorption characteristics, and molecular weight. Incubation of DHD in the Fenton system resulted in the formation of phenol (PH), catechol (CAT), and products which reacted with thiobarbituric acid to form chromogens absorbing at 495…

Inbreeding-related trade-offs in stress resistance in the ant Formica exsecta

2014

Inbred individuals and populations are predicted to suffer from inbreeding depression, especially in times of stress. Under natural conditions, organisms are exposed to more than one stressor at any one time, highlighting the importance of stress resistance traits. We studied how inbreeding- and immunity-related traits are correlated under different dietary conditions in the ant Formica exsecta . Its natural diet varies in the amount and nature of plant secondary compounds and the level of free radicals, all of which require detoxification to maintain organismal homeostasis. We found that inbreeding decreased general antibacterial activity under dietary stress, suggesting inbreeding-relate…