Hybrid CdSe/ZnS Quantum Dot-Gold Nanoparticle Composites Assembled by Click Chemistry: Toward Affordable and Efficient Redox Photocatalysts Working with Visible Light.

A new modular, easy-to-synthesize photocatalyst was prepared by assembling colloidal CdSe/ZnS quantum dots (QD) and gold nanoparticles (AuNP) via their ligands thanks to copper-catalyzed azide to alkyne cycloaddition (CuAAC) click chemistry. The resulting composite (QD-AuNP) photocatalyst was tested with a benchmark photoredox system previously reported by our group, for which QD alone acted as a photocatalyst but with a modest quantum yield (QY = 0.06%) and turnover number (TON = 350 in 3 h) due to poor charge separation.

Nuclear and Urinary Measurements Show the Efficacy of Sun-Protection Factor 50+ Sunscreen against DNA Photoproducts upon Real-Life Recreational Exposure.

Sunscreens have been shown to protect against UVR-induced DNA damage in human skin under laboratory conditions. We presently extended these observations to real-life conditions in volunteers after their ordinary exposure habits during summer holidays. Volunteers were randomly assigned to a control group and an educated group supplied with a SPF ≥50 sunscreen and receiving instructions for use.

A noncanonical response to replication stress protects genome stability through ROS production, in an adaptive manner.

Cells are inevitably challenged by low-level/endogenous stresses that do not arrest DNA replication. Here, in human primary cells, we discovered and characterized a noncanonical cellular response that is specific to nonblocking replication stress. Although this response generates reactive oxygen species (ROS), it induces a program that prevents the accumulation of premutagenic 8-oxoguanine in an adaptive way.

Fine Tuning of Quantum Dots Photocatalysts for the Synthesis of Tropane Alkaloid Skeletons.

Several types of Quantum Dots (QDs) (CdS, CdSe and InP, as well as core-shell QDs such as type I InP-ZnS, quasi type-II CdSe-CdS and inverted type-I CdS-CdSe) were considered for generating α-aminoalkyl free radicals. The feasibility of the oxidation of the N-aryl amines and the generation of the desired radical was evidenced experimentally by quenching of the photoluminescence of the QDs and by testing a vinylation reaction using an alkenylsulfone radical trap. The QDs were tested in a radical [3+3]-annulation reaction giving access to tropane skeletons and that requires the completion of two consecutive catalytic cycles.

Natural variability and modulation by environmental stressors of global genomic cytosine methylation levels in a freshwater crustacean, Gammarus fossarum.

To improve the assessment of aquatic organism responses to environmental stressors, there is an interest in studying epigenetic marks in addition to other validated biomarkers. Indeed, the epigenetic marks may be influenced by the surrounding environment. Non-model invertebrates such as gammarids are sentinel organisms representative of the diversity of natural stream communities.

6-Formylindolo[3,2-b]carbazole (FICZ) is a Very Minor Photoproduct of Tryptophan at Biologically Relevant Doses of UVB and Simulated Sunlight.

Exposure to solar UV is at the origin of numerous photodegradation pathways in biomolecules. Tryptophan is readily modified by UVB radiation into ring-opened and oxidized photoproducts. One of them, 6-formylindolo[3,2-b]carbazole (FICZ), has been extensively studied in the recent years because it very efficiently binds to AhR, a major factor in numerous biologic processes, such as metabolism of xenobiotics.

Nonredox thiolation in tRNA occurring via sulfur activation by a [4Fe-4S] cluster.

Sulfur is present in several nucleosides within tRNAs. In particular, thiolation of the universally conserved methyl-uridine at position 54 stabilizes tRNAs from thermophilic bacteria and hyperthermophilic archaea and is required for growth at high temperature. The simple nonredox substitution of the C2-uridine carbonyl oxygen by sulfur is catalyzed by tRNA thiouridine synthetases called TtuA.

Impact of topical application of sulfur mustard on mice skin and distant organs DNA repair enzyme signature.

Sulfur mustard (SM) is a chemical warfare agent that, upon topical application, damages skin and reaches internal organs through diffusion in blood. Two major toxic consequences of SM exposure are inflammation, associated with oxidative stress, and the formation of alkylated DNA bases. In the present study, we investigated the impact of exposure to SM on DNA repair, using two different functional DNA repair assays which provide information on several Base Excision Repair (BER) and Excision/Synthesis Repair (ESR) activities.

A comprehensive approach to determining BER capacities and their change with aging in Drosophila melanogaster mitochondria by oligonucleotide microarray.

DNA repair mechanisms are key components for the maintenance of the essential mitochondrial genome. Among them, base excision repair (BER) processes, dedicated in part to oxidative DNA damage, are individually well known in mitochondria. However, no large view of these systems in differential physiological conditions is available yet.

Functional DNA repair signature of cancer cell lines exposed to a set of cytotoxic anticancer drugs using a multiplexed enzymatic repair assay on biochip.

The development of resistances to conventional anticancer drugs compromises the efficacy of cancer treatments. In the case of DNA-targeting chemotherapeutic agents, cancer cells may display tolerance to the drug-induced DNA lesions and/or enhanced DNA repair. However, the role of DNA damage response (DDR) and DNA repair in this chemoresistance has yet to be defined.

An oligonucleotide microarray for the monitoring of repair enzyme activity toward different DNA base damage.

Characterization of DNA-N-glycosylase activities in cell extract is a challenging problem and could represent a major concern for medical applications. Synthetic oligonucleotides which contain base lesions located on specific sites constitute suitable substrates for their study. An in vitro miniaturized assay was developed that allows the measurement of cleavage activities of DNA repair enzymes on a set of oligonucleotides (ODNs) that contained different lesions.

Predominance of the 1,N2-propano 2'-deoxyguanosine adduct among 4-hydroxy-2-nonenal-induced DNA lesions.

4-Hydroxy-2-nonenal (HNE), one of the main aldehydic compounds released during lipid peroxidation, has been proposed to react with DNA bases in cells. Several classes of DNA lesions involving addition of either HNE or its 2,3-epoxide (epox-HNE) have been identified. In the present work, HPLC associated with tandem mass spectrometry was used to determine the pattern of HNE-induced DNA lesions.

Singlet oxygen-mediated damage to cellular DNA determined by the comet assay associated with DNA repair enzymes.

The damage profile produced by the reaction of singlet molecular oxygen with cellular DNA was determined using the comet assay associated with DNA repair enzymes. Singlet oxygen was produced intracellularly by thermal decomposition of a water-soluble endoperoxide of a naphthalene derivative which is able to penetrate through the membrane into mammalian cells. We found that the DNA modifications produced by singlet oxygen were almost exclusively oxidised purines recognised by the formamidopyrimidine DNA N-glycosylase.