34 research outputs found
A Combined NMR and UV–Vis Approach to Evaluate Radical Scavenging Activity of Rosmarinic Acid and Other Polyphenols
No full textOxidative stress results from an imbalance between reactive oxygen species (ROS) production and the body’s ability to neutralize them. ROS are reactive molecules generated during cellular metabolism and play a crucial role in normal physiological processes. However, excessive ROS production can lead to oxidative damage, contributing to various diseases and aging. This study is focused on rosmarinic acid (RA), a hydroxycinnamic acid (HCA) derivative well known for its antioxidant activity. In addition, RA has also demonstrated prooxidant behavior under specific conditions involving high concentrations of transition metal ions such as iron and copper, high pH, and the presence of oxygen. In this study, we aim to clarify the underlying mechanisms and factors governing the antioxidant and prooxidant activities of RA, and to compare them with other HCA derivatives. UV–Vis, NMR, and EPR techniques were used to explore copper(II)’s binding ability of RA, caffeic acid, and p-coumaric acid. At the same time, UV–Vis and NMR methods were exploited to evaluate the polyphenols’ free radical scavenging abilities towards ROS generated by the ascorbic acid–copper(II) system. All the data indicate that RA is the most effective polyphenol both in copper binding abilities and ROS protection
Alle origini del baratto: l'Odin in Sardegna 1974-1975
No full textAbstract – IT La complessa vicenda del “baratto”, ideata e attuata da Eugenio Barba e l’Odin Teatret a partire dal 1973-74, è una delle più affascinanti imprese appartenenti alla storia del Nuovo Teatro del Novecento. Il saggio ricostruisce il più oggettivamente possibile la permanenza dell’Odin Teatret in Sardegna, tra il 1974 e il 1975, durante la quale le tante comunità sarde risposero spontaneamente alla proposta dell’Odin, "barattando" il proprio patrimonio di canti, balli e pratiche tradizionali. Nato nella città di Cagliari, l’autore ha potuto spesso cogliere nelle testimonianze di intellettuali e artisti isolani l’eco di quella avventura; una traccia viva, quando non proprio un modello mitico, per più di una generazione di operatori culturali tuttora attivi in Sardegna. Da qui il desiderio di ricucire il filo della memoria, nell’idea di restituire quanto più possibile anche una sottile zona del rimosso, osservando con attenzione le date di questa vicenda e alcune testimonianze ad esse correlate. In particolare, secondo l’autore, la così tanto celebrata fase avvenuta a Carpignano Salentino da maggio a ottobre del 1974, a cui si attribuisce convenzionalmente, da un punto di vista storico, la nascita del baratto, in realtà ha teso a oscurare un precedente assai rilevante, legato all’incursione in terra sarda di Barba e compagni, tra Campidano e Barbagia, avvenuta nel mese di gennaio dello stesso anno. Abstract – EN The complex history of the 'baratto', which was conceived and performed by Eugenio Barba and the Odin Teatret from 1973-74, is one of the most challenging and fascinating projects in the history of XX century theatre. The purpose of the present essay is to retrace, as objectively as possible, Odin's permanence in Sardinia between 1974 and 1975, a period during which many local communities gave a positive feedback to Barba's project by 'bartering' traditional songs, dance and rituals. Born in Cagliari (Sardinia's main city) the author has caught the echo of that experience through the voices of intellectuals and local artists; an experience that has become a definitive benchmark, a legendary event for more than a generation of cultural operators still active in the island. Stitching up the thread of memory, the author restores, as far as possible, a bygone history through a meticulous reconstruction of dates and statements. Particularly, the essay affirms that the celebrated period of Carpignano Salentino (May-October 1974), to which the birth of the 'baratto' is generally attributed, has overshadowed this very significant first Sardinian journey in Campidano and Barbagia at the very beginning of 1974
Identification of an iron-sulfur cluster that modulates the enzymatic activity in NarE, a Neisseria meningitidis ADP-ribosyltransferase.
No full textIn prokaryotes, mono-ADP-ribose transfer enzymes represent a family of exotoxins that display activity in a variety of bacterial pathogens responsible for causing disease in plants and animals, including those affecting mankind, such as diphtheria, cholera, and whooping cough. We report here that NarE, a putative ADP-ribosylating toxin previously identified from Neisseria meningitidis, which shares structural homologies with Escherichia coli heat labile enterotoxin and toxin from Vibrio cholerae, possesses an iron-sulfur center. The recombinant protein was expressed in E. coli, and when purified at high concentration, NarE is a distinctive golden brown in color. Evidence from UV-visible spectrophotometry and EPR spectroscopy revealed characteristics consistent of an iron-binding protein. The presence of iron was determined by colorimetric method and by an atomic absorption spectrophotometer. To identify the amino acids involved in binding iron, a combination of site-directed mutagenesis and UV-visible and enzymatic assays were performed. All four cysteine residues were individually replaced by serine. Substitution of Cys(67) and Cys(128) into serine caused a drastic reduction in the E(420)/E(280) ratio, suggesting that these two residues are essential for the formation of a stable coordination. This modification led to a consistent loss in ADP-ribosyltransferase activity, while decrease in NAD-glycohydrolase activity was less dramatic in these mutants, indicating that the correct assembly of the iron-binding site is essential for transferase but not hydrolase activity. This is the first observation suggesting that a member of the ADP-ribosyltransferase family contains an Fe-S cluster implicated in catalysis. This observation may unravel novel functions exerted by this class of enzyme
Antioxidant activity of galloyl quinic derivatives isolated from P-lentiscus leaves
No full textThe antioxidant properties of galloyl quinic derivatives isolated from Pistacia lentiscus L. leaves have been investigated by means of Electron Paramagnetic Resonance spectroscopy (EPR) and UV-Vis spectrophotometry. Antioxidant properties have been also estimated using the biologically relevant LDL test. The scavenger activities of gallic acid, 5-O-galloyl, 3,5-O-digalloyl, 3,4,5-O-trigalloyl quinic acid derivatives, have been estimated against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, superoxide (O-2(-)) radical, and hydroxyl (OH) radical. On the whole, the scavenger activity raised as the number of galloyl groups on the quinic acid skeleton increased. The half-inhibition concentrations (IC50) of di- and tri-galloyl derivatives did not exceed 30 muM for all the tested free radicals. All the tested metabolites strongly reduced the oxidation of low-density lipoproteins (LDL), following a trend similar to that observed for the scavenger ability against OH radical
Le ragioni per dire no al "baratto amministrativo"
No full textL'articolo motiva le ragioni per le quali il ricorso al baratto amministrativo non deve essere confuso con le esperienze di amministrazione condivisa, dove le amministrazioni costruiscono alleanze con i cittadini per la risoluzione di problemi di interessi generali. Inoltre, l'autore mette in rilievo tutta una serie di problemi che mettono in discussione anche la legittimità di tali scelte.The article explains the rationales preventing the confusion between the experiences of "administrative barter" policies and the so called "sharing administration", where local authorities and citizens pool together in order to resolve problems of general public interest. In addiction, the author points out a range of problems coming from the "administrative barter" policies in terms of legitimac
Microdosimetry and Dose-Averaged LET Calculations of Protons in Liquid Water: A Novel Geant4-DNA Application
No full textThe spatial distribution of energy deposition events is an essential aspect in the determination of the radiobiological effects of ionizing radiation at the cellular level. Microdosimetry provides a theoretical framework for the description of these events, and has been used in several studies to address problems such as the characterization of Linear Energy Transfer (LET) and Relative Biological Effectiveness (RBE) of ion beams for proton therapy applications. Microdosimetry quantities and their distributions can be obtained by means of Monte Carlo simulations. In this work, we present a track structure Monte Carlo (MC) application, based on Geant4-DNA, for the computation of microdosimetric distributions of protons in liquid water. This application provides two sampling methods uniform and weighted, for the scoring of the quantities of interest in spherical sites, with diameters ranging from 1 to 10 mu m. As an element of novelty, the work shows the approach followed to calculate, without resorting to dedicated simulations, the distribution of energy imparted to the site per electronic collision of the proton, which can be used to obtain the macroscopic dose-averaged LET as proposed by Kellerer. Furthermore, in this work the concept of effective mean chord length is proposed to take into account delta-ray influx and escape in the calculation of macroscopic dose-averaged LET for proton track segments and retrieve the agreement predicted by Kellerer's formula. Finally, the results obtained demonstrate that our MC application is reliable and computational-efficient to perform calculations of microdosimetric distributions and dose-averaged LET of proton track segments in liquid water
Dose‐averaged LET calculation for proton track segments using microdosimetric Monte Carlo simulations
No full textPurpose There is an increasing interest in calculating linear energy transfer (LET) distributions for proton therapy treatments in order to assess the influence of this quantity in biological terms. Microdosimetric Monte Carlo (MC) simulations are useful tools to calculate dose-averaged LET, as this has been broadly proposed as the most adequate quantity to characterize these biological effects. However, a straightforward uniform sampling of the scoring site turns out to be computationally unaffordable. In contrast, some issues have been pointed out with the more efficient weighted sampling approach, frequently used in literature. Here, we address the issues associated with the latter method and propose adequate corrections to achieve reliable calculations of dose-averaged LET values from microdosimetry. Methods and materials Proton track structures have been simulated with Geant4-DNA considering two different approaches. One version employs a uniform sampling for placing the spherical site and is used as the reference. The other one uses a weighted sampling by considering the spatial distribution of transfer points. Some corrections are proposed for calculating a dose-averaged LET comparable to the reference case. An additional MC approach is proposed to obtain the weighted mean of the energy imparted per electronic collision of the proton within the site, the delta 2 function, related to the straggling distribution, as an intermediate step in the LET calculation. Results Energy imparted per event distributions are different when employing either sampling methods, due to the different geometrical randomness. We have found an agreement below (0.15 +/- 0.05) keV/mu m in the worst case for uniform and weighted methods in dose-averaged LET values when the weighted sampling results are corrected according to our proposal. Our analysis is restricted to spherical sites of 1 and 10 mu m diameter and monoenergetic beams in the range from 2 to 90 MeV. Conclusions This work shows a reliable and computational-efficient method to perform calculations of track segment dose-averaged LET using MC simulations for proton therapy beams, including the necessary considerations for obtaining the straggling distribution characteristics. The validity of this approach remains as long as the stopping power of the proton can be considered as constant along its track within the site
Basic mathematical skills with geometry
No full textIndeks *** *** Bibliografi hlm.xxvi, 851 hlm. :il. ;22 cm
Unravelling the Non-Native Low-Spin State of the Cytochrome c-Cardiolipin Complex: Evidence of the Formation of a His-Ligated Species Only
No full textThe interaction between cytochrome c (Cyt c) and cardiolipin (CL) plays a vital role in the early stages of apoptosis. The binding of CL to Cyt c induces a considerable increase in its peroxidase activity that has been attributed to the partial unfolding of the protein, dissociation of the Met80 axial ligand, and formation of non-native conformers. Although the interaction between Cyt c and CL has been extensively studied, there is still no consensus regarding the conformational rearrangements of Cyt c that follow the protein-lipid interaction. To rationalize the different results and gain better insight into the Cyt c-CL interaction, we have studied the formation of the CL complex of the horse heart wild-type protein and selected mutants in which residues considered to play a key role in the interaction with CL (His26, His33, Lys72, Lys73, and Lys79) have been mutated. The analysis was conducted at both room temperature and low temperatures via ultraviolet-visible absorption, resonance Raman, and electron paramagnetic resonance spectroscopies. The trigger and the sequence of CL-induced structural variations are discussed in terms of disruption of the His26-Pro44 hydrogen bond. We unequivocally identify the sixth ligand in the partially unfolded, non-native low-spin state that Cyt c can adopt following the protein-lipid interaction, as a His ligation, ruling out the previously proposed involvement of a Lys residue or an OH- ion
