The formation of adducts by reaction of active metabolites of two heterocyclic aromatic amines (NHOH-PhIP and NHOH-IQ) at nucleophilic sites of deoxynucleosides has been studied by LC-MS n analyses of the obtained reaction mixtures. Sequential MS 3 experiments were carried out on an ion trap mass spectrometer to gain extensive structural information on each adduct detected in the first MS step. Attribution of ions was supported by accurate mass measurements performed on an Orbitrap mass analyzer. Particular attention was given to ions diagnostic of the linking between the heterocyclic aromatic amine (HAA) and the deoxynucleoside. By this way, the structures of five adducts have been characterized in this study, among which two are new compounds: dG-N7-IQ and dA-N 6 -IQ. No depurinating adduct was found in the reactions investigated therein. As expected, the C8 and N 2 p p atoms of dG were found as the most reactive sites of deoxynucleosides, resulting in the formation of two different adducts with IQ and one adduct with PhIP. An unusual non-depurinating dG-N7-IQ adduct has been characterized and a mechanism is proposed for its formation on the basis of the reactivity of arylamines. A dA-N 6 -IQ adduct has been identified for the first time in this work, showing that HAAs can generate DNA adducts with bases other than dG. (J Am Soc

Objective Pickering emulsions are increasingly used in the pharmaceutical and cosmetic fields, especially for topical applications, since these systems require solid particles as emulsifiers instead of surfactants which are known to cause skin irritation. The solid inorganic nanoparticles (TiO2 and ZnO) used as UV filters in sunscreen formulations may also stabilize emulsion droplets, so that the utility of surfactants may be questioned. Surfactant‐free sunscreen emulsions solely stabilized by such nanoparticles (NPs) have been studied. Methods The ability of these NPs to stabilize o/w emulsions containing a ‘model’ oil phase, the C12‐C15 alkylbenzoate, has been assessed. ZnO and hydrophilic silica‐coated TiO2 NPs widely used in sunscreen products were used together with their mixtures. The emulsification efficiency, the control of droplet size and the stability of o/w Pickering emulsions solely stabilized by NPs were investigated. A ZnO/TiO2 NPs mixture characterized by a theoretical SPF of 45 was finally used as unique emulsifiers to develop a surfactant‐free sunscreen emulsion. Results Stable Pickering emulsions containing 10 up to 60 wt% of C12‐C15 alkyl benzoate were formulated with 2 wt% ZnO in the aqueous phase. The droplet size was controlled by the solid NPs content with respect to oil and the emulsification process. Hydrophilic TiO2 NPs did not allow the stabilization of emulsions. The substitution of TiO2 for ZnO up to 60–70 wt% in a 20/80 o/w emulsion was successfully performed. Finally, a ZnO/TiO2 NP mixture was tested as unique emulsifier system for the formulation of a sunscreen cream. Despite a lower viscosity, the obtained Pickering emulsion was stable and exhibited a photoprotective effect similar to the corresponding surfactant‐based sunscreen cream with an in vitro SPF of about 45. Conclusion Surfactant‐free Pickering emulsions can be stabilized by the UV‐filter nanoparticles for the manufacture of sunscreen products.

Heterocyclic aromatic amines (HAAs) generated during the cooking of meats are known to be genotoxic substances able to form covalent bonds with DNA bases after metabolic activation. This work aimed at the investigation of the influence of the local environment of nucleobases along the nucleotidic sequence on its modification induced by two different HAAs, namely 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), in order to identify possible sequences more susceptible to modification. A systematic study of the neighbouring base effect on the adduction was emphasized. Thus, PhIP and IQ adducts have been synthesized with various T-rich model single-strand oligonucleotides displaying different flanking bases (A, G, C or T) at the 3' or the 5' side of the targeted guanine, which allowed a comparison of the flanking base effects on adduction. Modified oligonucleotides were then analyzed by high-performance liquid chromatography (HPLC) coupled to electrospray ionization mass spectrometry. The localization of the modifications induced by PhIP or IQ along the oligonucleotide sequence was achieved by tandem mass spectrometry, and modification yields of the various model sequences were compared. Results indicate a favouring sequence context effect on the G-C8-IQ adduct formation with the sequence 5'GGG3'. Although higher than IQ, modification yields observed with PhIP showed a less obvious effect of the neighbouring base on the G-C8-PhIP adduct formation, with a preferential sequence 5'GGA/G/T3'.

Dinoterb (6-t-butyl-2,4-dinitrophenol), 1, Dinoseb (6-secbutyl-2,4-dinitrophenol), 2, TBP (2-t-butylphenol), 3, and DNP (2,4-dinitrophenol), 4, have been analyzed by electrospray ionization in the negative mode (ESI-N) - tandem mass spectrometry. Nominal laboratory collision energy was varied from zero to 60 eV during the experiments. Apparent fragmentation energies were estimated from a parametric fitting of the collision efficiency curves. In parallel, fragmentation mechanisms of the deprotonated molecules [M-H](-) were explored using quantum chemistry modeling at the B3LYP/6-31 + G(d,p) level. A major fragmentation of the [M-H](-) ions of Dinoterb and Dinoseb is elimination of an alcohol molecule. This reaction is shown to involve one oxygen atom originating from a nitro group rather than the phenoxide moiety. Eliminations of NO, C(4) and CH(2) = C(CH(3))(2), i.e. reactions involving significant rearrangements, constitute the major part of the other fragmentation pathways observed from [3-H](-) and [4-H](-) ions.