SOMO–HOMO Conversion in Distonic Radical Anions: An Experimental Test in Solution by EPR Radical Equilibration Technique

Bond dissociation energies (BDEs) of O–H bond in the hydroxylamines deriving from neutral and deprotonated forms of 4-carboxy-TEMPO have been measured in solution (acetonitrile and dimethylsulfoxide) by using the EPR radical equilibration technique. The experimental results confirm that stabilizing interaction between a remote negative charge and stable radicals, occurring in gas phase, is completely lost in polar solvents as predicted by theoretical computations

Unraveling Unidirectional Threading of α‑Cyclodextrin in a [2]Rotaxane through Spin Labeling Approach

We present here the results of a CW-ESR investigation of a double spin labeled α-cyclodextrin-based [2]­rotaxane that is characterized by the presence of nitroxide labels both at the wheel and at the dumbbell. This was accomplished by synthesizing a spin labeled α-CD (the wheel) that was mechanically blocked on a thread containing a nitroxide unit by a Cu­(I) catalyzed azide–alkyne cycloaddition (CuAAC). Both ESI-MS analysis and NMR spectroscopy were used to provide evidence of the threading processes. Because of the unsymmetrical structure of both the wheel and the axle, two different geometrical isomers could be predicted on the basis of the orientation of the CD along the thread. By combining molecular dynamic calculations and information extracted from the CW-ESR spectra, we were able to determine the geometrical nature of the isomer that was isolated as the only species. The ESR spectra showed <i>J</i>-coupling between the two mechanically connected nitroxide units and were analyzed by a model assuming three main molecular states. The intramolecular noncovalent nature of spin exchange was confirmed by reversibly switching the magnetic interaction on–off by changing the pH of the solution in the presence of a competing macrocyclic host

Chiral <i>N</i>‑Hydroxybenzamides as Potential Catalysts for Aerobic Asymmetric Oxidations

Chiral <i>N</i>-hydroxy­benzamides (<b>1H</b>–<b>3H</b>) have been synthesized as precursors of chiral short-lived <i>N</i>-oxyl radicals <b>1</b>^<b>•</b>–<b>3</b>^<b>•</b>. The latter species have been generated by oxidation of <b>1H</b>–<b>3H</b> with Pb­(OAc)₄ or hydrogen abstraction from <b>1H</b>–<b>3H</b> by the <i>tert</i>-butoxyl radical and characterized by UV–vis spectro­photometry and EPR spectroscopy. Through a kinetic study of the hydrogen atom transfer processes promoted by <b>1</b>^<b>•</b>–<b>3</b>^<b>•</b> from three chiral benzylic substrates (1-phenyl­ethylamine, 1-phenyl­ethanol, and α-vinyl­benzyl alcohol), a moderate chiral discrimination has been found, with selectivity factors 0.5 ≤ <i>k</i>_H(<i>S</i>)/<i>k</i>_H(<i>R</i>) ≤ 2

Self-Organization of Mixtures of Fluorocarbon and Hydrocarbon Amphiphilic Thiolates on the Surface of Gold Nanoparticles

Self-assembled monolayers composed of a mixture of thiolate molecules, featuring hydrocarbon or perfluorocarbon chains (<i><b>H</b></i><b>-</b> and <i><b>F</b></i><b>-</b>chains) terminating with a short poly(oxoethylene) (PEG) moiety, are the most extreme example of surfactant immiscibility on gold nanoparticles reported so far. The phase segregation between <i><b>H</b></i>-chains and <i><b>F</b></i>-chains and the consequent, peculiar folding of PEG chains are responsible for the increased affinity of a selected radical probe for the fluorinated region, which increases as the size of the fluorinated domains decrease, independently of the shape of such domains. This feature has been revealed by ESR measurements and an <i>in silico</i> innovative multiscale molecular simulations approach in explicit water. Our results reveal an underlying mechanism of a transmission of the organization of the monolayer from the inner region close to the gold surface toward the external hydrophilic PEG region. Moreover, this study definitively proves that a mixed monolayer is a complex system with properties markedly different from those characterizing the parent homoligand monolayers

Impact of positive end expiratory pressure on cerebral hemodynamic in paediatric patients with post-traumatic brain swelling treated by surgical decompression

<div><p>Introduction</p><p>The objective of our present study is to evaluate the impact of different PEEP levels on cerebral hemodynamic, gas exchanges and respiratory system mechanics in paediatric patients with post-traumatic brain swelling treated with decompressive craniectomy (DC).</p><p>Materials and methods</p><p>A prospective physiologic study was carried out on 14 paediatric patients presenting with severe traumatic brain swelling treated with DC. Transcranial Doppler ultrasonography was performed on the middle cerebral artery bilaterally after DC. After assessment at ZEEP, intracranial pressure (ICP), cerebral perfusion pressure (CPP), mean arterial pressure (MAP), central venous pressure (CVP) and gas exchanges were recorded at PEEP 4 and PEEP 8.</p><p>Results</p><p>From ZEEP to PEEP 8, the compliance of respiratory system indexed to the weight of the patient significantly increased (P = 0.02) without ICP modifications. No significant variation of the MAP, CPP, Vmed, the total resistance of respiratory system and ohmic resistance of the respiratory system indexed to the weight of the patients was observed. CVP significantly increased between ZEEP and PEEP 8 (P = 0.005), and between PEEP 4 and PEEP 8 (P = 0.05).</p><p>Conclusions</p><p>PEEP values up to 8 cmH20 seem to be safe in paediatric patients with a severe post-traumatic brain swelling treated with DC.</p></div

Table1_Effects of unburned tobacco smoke on inflammatory and oxidative mediators in the rat prefrontal cortex.DOCX

Although the Food and Drug Administration has authorized the marketing of “heat-not-burn” (HnB) electronic cigarettes as a modified risk tobacco product (MRTP), toxicological effects of HnB smoke exposure on the brain are still unexplored. Here, paramagnetic resonance of the prefrontal cortex (PFC) of HnB-exposed rats shows a dramatic increase in reactive radical species (RRS) yield coupled with an inflammatory response mediated by NF-κB-target genes including TNF-α, IL-1β, and IL-6 and the downregulation of peroxisome proliferator-activated receptor (PPAR) alpha and gamma expression. The PFC shows higher levels of 8-hydroxyguanosine, a marker of DNA oxidative damage, along with the activation of antioxidant machinery and DNA repair systems, including xeroderma pigmentosum group C (XPC) protein complex and 8-oxoguanine DNA glycosylase 1. HnB also induces the expression of drug-metabolizing enzymes such as CYP1A1, CYP2A6, CYP2B6, and CYP2E, particularly involved in the biotransformation of nicotine and several carcinogenic agents such as aldehydes and polycyclic aromatic hydrocarbons here recorded in the HnB stick smoke. Taken together, these effects, from disruption of redox homeostasis, inflammation, PPAR manipulation along with enhanced bioactivation of neurotoxicants, and upregulation of cMYC protooncogene to impairment of primary cellular defense mechanisms, suggest a possible increased risk of brain cancer. Although the HnB device reduces the emission of tobacco toxicants, our findings indicate that its consumption may carry a risk of potential adverse health effects, especially in non-smokers so far. Further studies are needed to fully understand the long-term effects of these devices.</p