Search results for " radical"

Single-molecule magnetic behavior in a neutral terbium(III) complex of a picolinate-based nitronyl nitroxide free radical

2011

The terdentate anionic picolinate-based nitronyl nitroxide (picNN) free radical forms neutral and robust homoleptic complexes with rare earth-metal ions. The nonacoordinated Tb3+ complex Tb(picNN)3• 6H2O is a single-molecule magnet with an activation energy barrier Δ = 22.8 ± 0.5 K and preexponential factor τ0 = (5.5 ± 1.1) × 10-9 s. It shows magnetic hysteresis below 1 K. © 2011 American Chemical Society.

Effect of protonation and deprotonation on the gas phase reactivity of fluorinated 1,2,4-triazines

2008

Positive and negative electrospray mass spectrometry (MS), in-time and in-space MS n experiments, high-resolution and accurate mass measurements obtained with an Orbitrap, together with density functional theory calculations have been used to study the gas-phase ion chemistry of a series of fluorinated 1,2,4-triazines. As a result of low-energy collision-induced dissociations, occurring in an ion trap and in a triple quadrupole, their protonated and deprotonated molecules show interesting features depending on the nature and structure of the precursor ions. The occurrence of elimination/hydration reactions produced by positive ions in the ion trap is noteworthy. Decompositions of deprotonat…

Preparation of two sets of 5,6,7-trioxygenated dihydroflavonol derivatives as free radical scavengers and neuronal cell protectors to oxidative damag…

2009

An unusual class of 5,6,7-trioxygenated dihydroflavonols (3a-e and 4a-j) were designed and prepared. Their antioxidative properties were assessed by examining their capacities in several in vitro models, including superoxide anion and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, rat liver homogenate lipid peroxidation inhibition, PC12 cells protection from oxidative damage, and xanthine oxidase inhibition. These dihydroflavonols displayed positive quenching abilities towards O(2)(-) and DPPH free radicals, in which the majority exhibited superior antioxidant properties to Vitamin C. cis-Configurated compound (+/-)-3e demonstrated remarkable inhibition to LPO with an IC(50) value…

Photoreaction Between Benzoylthiophenes and N-BOC-Tryptophan Methyl Ester‡

2005

Drug-induced photoallergy requires as the first step formation of covalent drug-protein photoadducts. One of the key amino acids involved in this process is tryptophan (Trp). In this context, several diaryl ketones, including 2-benzoylthiophene (BT), [2-(5-benzoyl-5-thienyl)]-2-methylpropanoic methyl ester (TPA methyl ester) and 4-(2-thienylcarbonyl)phenyl]-2-methylpropanoic methyl ester (SUP methyl ester) have been irradiated in the presence of N-BOC-(L)-tryptophan methyl ester. Laser flash photolysis has allowed to detect three neutral radicals (ketyl, indolyl and skatolyl radicals) resulting from formal hydrogen-atom abstraction. This correlates well with the isolation of homodimers, as …

Theoretical Study of the Hydroxyl Radical Addition to Uracil and Photochemistry of the Formed U6OH• Adduct

2014

Hydroxyl radical ((•)OH) is produced in biological systems by external or endogenous agents. It can damage DNA/RNA by attacking pyrimidine nucleobases through the addition to the C5═C6 double bond. The adduct resulting from the attachment at the C5 position prevails in the experimental measurements, although the reasons for this preference remain unclear. The first aim of this work is therefore to shed light on the comprehension of this important process. Thus, the thermal (•)OH addition to the C5═C6 double bond of uracil has been studied theoretically by using DFT, MP2, and the multiconfigurational CASPT2//CASSCF methodologies. The in-vacuo results obtained with the latter protocol plus th…

Communication: Electronic UV-Vis transient spectra of the ·OH reaction products of uracil, thymine, cytosine, and 5,6-dihydrouracil by using the comp…

2013

Addition of ∙OH radicals to pyrimidine nucleobases is a common reaction in DNA/RNA damage by reactive oxygen species. Among several experimental techniques, transient absorption spectroscopy has been during the last decades used to characterize such compounds. Discrepancies have however appeared in the assignment of the adduct or adducts responsible for the reported transient absorption UV-Vis spectra. In order to get an accurate assignment of the transient spectra and a unified description of the absorption properties of the ∙OH reaction products of pyrimidines, a systematic complete active space self-consistent field second-order perturbation (CASPT2//CASSCF) theory study has been carried…

Investigating the possible impact of peritoneal tumor exposure amongst women with early stage cervical cancer treated with minimally invasive approac…

2021

Abstract Introduction Recent findings show a detrimental impact of the minimally invasive approach on patients with early stage cervical cancer (ECC). Reasons beyond these results are unclear. The aim of the present article is to investigate the possible role of peritoneal contamination during intracorporeal colpotomy. Methods patients with early stage cervical cancer were divided into 2 groups: no intraperitoneal exposure (N-IPE) intraperitoneal exposure (IPE) during minimally invasive surgery. Patients of the 2 groups were propensity-matched according to the major risk factors. Results 226 cases of the IPE group had a significant worst prognosis than the 142 cases of the N-IPE group (4.5-…

La mundialización simbólica

2001

l-Carnitine l-tartrate supplementation favorably affects biochemical markers of recovery from physical exertion in middle-aged men and women.

2009

The purpose of this study was to examine the effects of Carnipure tartrate (Lonza, Allendale, NJ) supplementation (total dose of 2 g/d of l-carnitine) on markers of performance and recovery from physical exertion in middle-aged men and women. Normally active and healthy men (n = 9, 45.4 +/- 5.3 years old) and women (n = 9, 51.9 +/- 5.0 years old) volunteered to participate in the investigation. Double-blind, placebo, balanced treatment presentation and crossover design were used with 3 weeks and 3 days of supplementation followed by a 1-week washout period before the other counterbalanced treatment was initiated. After 3 weeks of each supplementation protocol, each participant then performe…

Nitric oxide synthase inhibition and oxidative stress in cardiovascular diseases: Possible therapeutic targets?

2013

International audience; Nitric oxide (• NO) is synthetized enzymatically from L-arginine (L-Arg) by three NO synthase isoforms, iNOS, eNOS and nNOS. The synthesis of NO is selectively inhibited by guanidino-substituted analogs of L-Arg or methylarginines such as asymmetric dimethylarginine (ADMA), which results from protein degradation in cells. Many disease states, including cardiovascular diseases and diabetes, are associated with increased plasma levels of ADMA. The N-terminal catalytic domain of these NOS isoforms binds the heme prosthetic group as well as the redox cofactor, tetrahydrobiopterin (BH 4) associated with a regulatory protein, calmodulin (CaM). The enzymatic activity of NOS…