Background:Medical residents must sustain acute sleep deprivation, which can lead to nonfatal and fatal consequences in hospitals due to cognitive decline. Anodal transcranial direct current stimulation (a-tDCS) is a safe noninvasive neuromodulation technique that can induce depolarization of neurons. Previous studies in pilots have shown benefits against fatigue increasing wakefulness and cognitive performance. However, the effects of a-tDCS on cognition in acute sleep deprived healthcare workers remains unknown.Purpose:To evaluate cognitive changes in sleep deprived medical residents after one session of a-tDCS.Methods:Open clinical test-re-test study including 13 medical residents with acute sleep deprivation. Subjects received 1 session of bifrontal a-tDCS (2mAx20min), anodal over the left dorsolateral prefrontal region. Pre-and-post treatment subjects were tested with Beck anxiety inventory, Beck depression and HVLT tests, Rey´s and Taylor´s figures, Trail Making A/B, Stroop, Aleatory Digit retention test (WAIS), Digits and symbols and MoCA tests. Post-intervention was added the Executive functions and Frontal Lobes Neuropsychological Battery (BANFE2) test and changing the Taylor figure for Reyfigure.Results:Twelve medical residents were analyzed; 8 men and 4 women, 29.5 (+/-2.2) years mean age. All had a mean of 21.6 (+/-1.3) hours of sleep deprivation. There were no serious adverse events. We found statistically significant difference in Rey´s/Taylor´s figures (p=0.002), Trail Making Test (p=0.005), WAIS IV symbols (p=0.003), Word Stroop (p=0.021). BANFE-2 showed that the main affected area was the orbito-medial prefrontal region.Conclusion:a-tDCS appears safe and improves working memory, attention, response time and distractors elimination in acute sleep deprived medical residents.

The synthesis and spectroscopic properties of the three isomers of nitrocaffeic acid are described. The three pK(a) s of each isomer were measured by UV-visible spectroscopy. The comparison of the UV-visible spectra of nitrocaffeic acids and those obtained from the reaction of caffeic acid with reactive nitrogen species led to the conclusion that the nitration of caffeic acid with acidic nitrite does not significantly occur and confirmed the absence of nitration when caffeic acid reacts with peroxynitrite. Attempts to obtain free radical species from nitrocaffeic acids by classical methods showed a different reactivity to that of nitroaromatics and catechols. Nitrocaffeic acids do not autoxidize under aqueous basic conditions and are insensitive to t-BuOK or O-2(-.) (two reactants known for their capabilities to oxidize catechols and reduce nitroaromatics). Nitroaromatic anion radicals may be obtained using sodium borohydride as reductant and are particularly stable under an uncontrolled atmosphere. Copyright (C) 2000 John Wiley & Sons, Ltd.

4-Mercaptoimidazoles derived from the naturally occurring family of antioxidants, the ovothiols, were assayed for their antioxidant properties. These compounds are powerful HOCl scavengers, more potent than the aliphatic thiol N-acetylcysteine. They react slowly with hydrogen peroxide with second order rate constants of 0.13-0.89 M(-1)s(-1). Scavenging of hydroxyl radical occurs at a diffusion-controlled rate (k=2.0-5.0 x 10(10)M(-1)s(-1)) for the most active compounds, which are also able to inhibit copper-induced LDL peroxidation. The combination of radical scavenging and copper chelating properties may explain the inhibitory effects on LDL peroxidation. Two molecules of mercaptoimidazole can chelate a copper ion and form a square planar complex detected by EPR. Compounds bearing an electron-withdrawing group on position 2 of the imidazole ring are the most potent antioxidant molecules in this series.

Human ceruloplasmin (Cp) has been purified from cryoprecipitate-poor plasma as a by-product of the C1-inhibitor production chain. Highly purified Cp was obtained by subsequent ion-exchange chromatography on sulfate-Fractogel EMD and TMAE-Fractogel EMD. Treatments for viral safety included application of the solvent-detergent method and two nanofiltration steps using 35- and 15-nm pore size filters at the end of the process. Overall antigen yield was 95 (+/-5) %. Purified human ceruloplasmin was studied by electron spin resonance (ESR) to characterize its different types of copper complexes and to check its antioxidant properties. We distinguished three types of complexes: one type-2 Cu(II) with g// = 2.25 and A// = 180 G and two type-I Cu(II) exhibiting different narrow hyperfine splitting (A// = 72 G and A// = 90 G) with close g// (2.20 and 2.21). Purified Cp has a specific activity of 24.5+/-0.2 mU/mg of proteins. This process provides a method for Cp purification that could be easily integrated into modern plasma fractionation.

The radical-scavenging mechanism of fourteen 4-mercaptoimidazoles, derived from the natural family of ovothiols, was studied via a QSAR approach, cyclic voltammetry, ESR and NMR spectroscopy. A significant correlation was found between the DPPH scavenging abilities of test compounds and thermodynamic parameters like overall ease of disulphide formation. The production of a disulphide compound via thiyl radical formation is proposed. Upon DPPH scavenging, hydrogen abstraction from thiols yields transient short-lived thiyl radicals, which were characterised by ESR and rapidly dimerise to form a disulphide compound. Cyclic voltammetry showed that the best DPPH scavengers exhibit low oxidation potentials for their oxidation to disulphides.

4-Mercaptoimidazoles derived from the naturally occurring antioxidants, ovothiols, were tested for their glutathione peroxidase-like (GSH Px-like) activity and protection against peroxynitrite-induced damage. All the thiol compounds displayed similar significant GSH Px-like activities, which are however weaker than that of the reference compound, ebselen. The inhibitions of the peroxynitrite-dependent oxidation of Evans blue dye and dihydrorhodamine 123 showed that the thiol compounds substituted on position 5 of the imidazole ring were nearly as effective as ebselen while the C-2 substituted ones were less effective. Both assays corroborate the large superiority of mercaptoimidazoles over glutathione as inhibitors of peroxynitrite-dependent oxidation.

Treatment of electron-rich aromatic derivatives with cerium (IV) ammonium nitrate coated on silica (CAN/SiO2) affords nitro aromatic compounds. The scope and the limitation of this reaction are discussed.

α-keto primary alcohols or α-silyloxy ketones have been obtained with a high level of selectivity from enolic α-keto esters in two steps, with the reduction of the α-silyloxy α,β-unsaturated ester by LiAlH4 as the key step. The methodology developed in this work represents a “reversed” chemoselective reduction of the ester group instead of the keto of an enolic α-keto ester due to a one-pot sequential ester reduction-desilylation or silyl migration process.

A series of copper complexes of bis(hydroxysalicylidene)ethylenediamine (hydroxy-salens) have been synthesized. The hydroxy group in the ortho, meta, or para position on each salicylidene unit was added to reinforce the stability of the copper complex and to create a hydroquinone system cooperating with the copper redox system to facilitate the spontaneous formation of oxidizing Cu-III species. Cyclic voltammetry and ESR spectroscopy in combination with electrochemistry and spin trapping experiments have been used to characterize the structure and the redox state of the hydroxy-salen-copper complexes and to evidence the production of oxygen-based free radicals. A complete set of magnetic values were determined. In addition, we studied the capacity of complexes 3a,b,c to cleave DNA in the absence of activating agents. The meta isomer 3b does not generate oxygen radicals, and as a result it cannot cleave DNA. In sharp contrast, the para isomer 3c and to a lower extent the ortho isomer 3a exhibit nuclease activities in relation to their capacities to produce oxygen radicals. Electrochemistry provides unequivocal evidence for the formation of Cu-III species with compounds 3a and 3c, but not with 3b. The nuclease activity correlates well with the ability of the hydroxy-salens to form the oxidizing Cu-III species. The redox properties and therefore the DNA cleaving activities of the complexes depend crucially on the position of the OH groups which contribute significantly to stabilize the square planar copper complexes. The present work supports the hypothesis that a hydroquinone system can cooperate with a redox metal system to trigger DNA cleavage. The design of metallo(hydroxy-salens) provides an original route for the development of self-activated chemical nucleases.

Bis(hydroxy)salen.Fe complexes were designed as self-activated chemical nucleases. The presence of a hy-droxyl group on the two salicylidene moieties serve to form a hydroquinone system cooperating with the iron redox system to facilitate spontaneous formation of free radicals. We compared the DNA binding and cleaving properties of the ortho -, meta- and para -(bishydroxy) salen.Fe complexes with that of the corresponding chelate lacking the hydroxyl groups. DNA melting temperature studies indicated that the para complex exhibits the highest affinity for DNA. In addition, this para compound was considerably more potent at cleaving supercoiled plasmid DNA than the regio-isomeric ortho - and meta -hydroxy-salen.Fe complexes, even in the absence of a reducing agent, such as dithiothreitol used to activate the metal complex. The DNA cleaving activity of the para isomer is both time and concentration dependent and the complexed iron atom is absolutely essential for the sequence uniform cleavage of DNA. From a mechanistic point of view, electron spin resonance measurements suggest that DNA contributes positively to the activation of the semi-quinone system and the production of ligand radical species responsible for subsequent strand scission in the absence of a reducing agent. The para -hydroxy-salen.Fe complex has been used for detecting sequence-specific drug-DNA interactions. Specific binding of Hoechst 33258 to AT sequences and chromomycin to GC sequences were shown. The para -bis(hydroxy)salen.Fe derivative complements the tool box of footprinting reagents which can be utilised to produce efficient cleavage of DNA.

An intramolecular hydride delivery process largely contributes during the double reduction of α-keto esters into diols by NaBH4. In the case of enolic α-keto esters, the first step of the process, the reduction of the keto group, occured exclusively through an 1,2-hydride addition despite the predominance of the tautomeric enolic form. The clear-cut difference of reaction rate between enolic and non enolic substrate 4 for reaction carried out in methanol is interpreted in terms of competitive hydride consumption due to the extremely favorable reaction between this solvent and NaBH4.

Two anthraquinone derivatives of the anticancer drugs mitoxantrone and ametantrone were examined for their ability to bind to DNA and to modulate the formation of topoisomerase-DNA cleavable complexes in vitro. The guanidinium groups introduced at the termini of the two aminoethylamino side chains of mitoxantrone can reinforce the interaction with DNA as judged from thermal denaturation studies with calf thymus DNA and polynucleotides. Footprinting experiments indicate that the binding to DNA of compound SR107 lacking the 5,8-hydroxyl substituents is essentially nonspecific whereas its congener SR 103 interacts preferentially with GC-rich sequences, particularly those containing 5'-(A/T)CG sites. Compound SR103, which bears two hydroxyl groups on the anthraquinone chromophore, promotes the cleavage of DNA by topoisomerase II and is cytotoxic toward human KB carcinoma cells in vitro. In contrast, the analogue SR107, which lacks OH groups, has no effect on topoisomerase II and is not cytotoxic.

A series of metal complexes that combine the structure of phenanthroline and salen have been synthesized and characterized by electron paramagnetic resonance spectroscopy. The effects of the 2,9-bis(2-hydroxyphenyl)-1,10-phenanthroline compounds complexed with CuII, NiII, CoII or MnIII on the temperature-dependent helix-to-coil transition of DNA have been measured. The interaction with DNA is metal-dependent and the highest stabilization is observed with the Co complex. The DNA cleaving activities have been studied with plasmid DNA and/or with a 32P-labelled duplex oligonucleotide depending on the redox properties of the complexes. The Cu complex is inactive whereas the Co chelate efficiently cleaves DNA in the presence of a reducing agent. Cleavage of DNA by the Mn complex can occur either in the presence of a reducing agent via the production of oxygen radicals (which are detected by EPR spectroscopy) or in the presence of an oxidant such as KHSO5. In both cases, the cleavage of nucleic acids is very efficient whereas no cleavage is observed with the Ni complex. The complexes of bis(hydroxyphenyl)phenanthroline with Mn and Co complement the tool-box of reagents available for cleavage of DNA.

Fourteen 4-mercaptoimidazoles derived from the naturally occurring family of antioxidants, the ovothiols, have been synthesized by cyclization of thioamides with trimethylsilyl trifluoromethanesulfonate (triflate). These compounds have been assayed for their radical-scavenging activity.

Treatment of phenylacetones 1 with boron tribromide gives the 1,3-dimethyl-2-phenylnaphtalenes 2 in good yields by a tandem aldol condensation-intramolecular Friedel-Crafts cyclization. In the cases of methoxyphenylacetones, a demethylation occurs leading to 1,3-dimethyl-2-hydroxyphenylnaphtols. © 1997 Published by Elsevier Science Ltd.

The synthesis of a DNA-cutting agent that conjugates an ellipticine chromophore and a copper complex of bis(salicylidene)ethylenediamine, referred to as a salen, is reported. The presence of the salen Cu complex allows cleavage of DNA via oxygen-based radicals, and the ellipticine moiety serves as a DNA anchor. Spectroscopic measurements indicate that the intercalation geometry of the ellipticine chromophore is preserved with the hybrid. The cleavage is much more efficient with the conjugate than with the Schiff base copper complex alone.

In the presence of oxygen donnor compounds, a functionalized salen-nickel complex poorly cuts double-stranded DNA but induces strong cleavages at guanine residues in the single-stranded region of hairpin oligonucleotides.

α-hydroxyesters 5a-g or diols 6a-g have been obtained in high yields by reduction of aromatic α-ketoesters 4 once or twice respectively by using NaBH4 as the reducer under suitable conditions. The use of a solvent that does not interact with the reagent allowed the double reduction to occur with only a slight excess of borohydride in very mild conditions.

Linkage of a salen·Cu complex to a distamycin analogue leads to a hybrid molecule that binds selectively to AT-rich sequences in DNA. The cleavage of DNA in the presence of a reducing agent remains efficient but weakly selective.