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Orcinol O-methyltransferase (OOMT) 1 and 2 catalyze the last two steps of the biosynthetic pathway leading to the phenolic methyl ether 3,5-dimethoxytoluene (DMT), the major scent compound of many rose (Rosa x hybrida) varieties. Modern roses are descended from both European and Chinese species, the latter being producers of phenolic methyl ethers but not the former. Here we investigated why phenolic methyl ether production occurs in some but not all rose varieties. In DMT-producing varieties, OOMTs were shown to be localized specifically in the petal, predominanty in the adaxial epidermal cells. In these cells, OOMTs become increasingly associated with membranes during petal development, suggesting that the scent biosynthesis pathway catalyzed by these enzymes may be directly linked to the cells' secretory machinery. OOMT gene sequences were detected in two non-DMT-producing rose species of European origin, but no mRNA transcripts were detected, and these varieties lacked both OOMT protein and enzyme activity. These data indicate that up-regulation of OOMT gene expression may have been a critical step in the evolution of scent production in roses.

Cold atmospheric pressure plasmas (CAPPs) are known to have bactericidal effects but the mechanism of their interaction with microorganisms remains poorly understood. In this study the bacteria Escherichia coli were used as a model and were exposed to CAPPs. Different gas compositions, helium with or without adjunctions of nitrogen or oxygen, were used. Our results indicated that CAPP induced bacterial death at decontamination levels depend on the duration, post-treatment storage and the gas mixture composition used for the treatment. The plasma containing O2 in the feeding gas was the most aggressive and showed faster bactericidal effects. Structural modifications of treated bacteria were observed, especially significant was membrane leakage and morphological changes. Oxidative stress caused by plasma treatment led to significant damage of E. coli. Biochemical analyses of bacterial macromolecules indicated massive intracellular protein oxidation. However, reactive oxygen and nitrogen species (RONS) are not the only actors involved in E. coli’s death, electrical field and charged particles could play a significant role especially for He-O2 CAPP.

Engineering of glycosidases with efficient transglycosidases activity is an alternative to glycosyltransferases or glycosynthases for the synthesis of oligosaccharides and glycoconjugates. However, the engineering of transglycosidases by directed evolution methodologies is hampered by the lack of efficient screening systems for sugar-transfer activity. We report here the development of digital imaging-based high-throughput screening methodology for the directed evolution of glycosidases into transgalactosidases. Using this methodology, we detected transglycosidase mutants in intact Escherichia coli cells by digital imaging monitoring of the activation of non- or low-hydrolytic mutants by an acceptor substrate. We screened several libraries of mutants of beta-glycosidase from Thermus thermophilus using this methodology and found variants with up to a 70-fold overall increase in the transglycosidase/hydrolysis activity ratio. Using natural disaccharide acceptors, these transglycosidase mutants were able to synthesise trisaccharides, as a mixture of two regioisomers, with up to 76% yield.

Peptide ligand-induced dimerization of the extracellular region of the epidermal growth factor receptor (sEGFR) is central to the signal transduction of many cellular processes. A small molecule microarray screen has been developed to search for non-peptide compounds able to bind to sEGFR. We describe the discovery of nitro-benzoxadiazole (NBD) compounds that enhance tyrosine phosphorylation of EGFR and thereby trigger downstream signaling pathways and other receptor tyrosine kinases in cancer cells. The protein phosphorylation profile in cells exposed to NBD compounds is to some extent reminiscent of the profile induced by the cognate ligand. Experimental studies indicate that the small compounds bind to the dimerization domain of sEGFR, and generate stable dimers providing allosteric activation of the receptor. Moreover, receptor phosphorylation is associated with inhibition of PTP-1B phosphatase. Our data offer a promising paradigm for investigating new aspects of signal transduction mediated by EGFR in cancer cells exposed to electrophilic NBD compounds.

This work studies the reactivity of poly (N-vinylcaprolactam-co-vinyl acetate-co-vinylbenzyl Rose Bengal) microgels (VBRB@MG) as heterogeneous photosensitizers in a continuous-flow process for sustainable singlet oxygen sensitized photooxygenation of a bio-based molecule.Experiments were carried out in a LED-driven spiral-shaped microreactor in which slurry Taylor flows were generated, allowing accurate control of irradiation, light absorption and gas-liquid flow conditions. The benchmark photooxygenation of -terpinene was implemented in ethanol to provide a green solvent using air as a safe supply of oxygen. Swollen RB-grafted colloids formed an efficient substrate for converting -terpinene into ascaridole, providing up to high conversion with high selectivity under continuous-flow conditions, and within short residence times of a few minutes. The supported RB exhibited a reactivity similar to that of the free RB.The reactivity of the supported photosensitizer was maintained for several cycles with a reproducible level after 8 months of storage. Under experimental conditions favouring photobleaching of RB, the photobleaching level of RB was lower with the VBRB@MG colloids than with free RB, suggesting that grafting RB molecules onto the colloid can prevent their photodegradation. KEYWORDSFlow photochemistry. Singlet oxygen. Photoactive polymer colloids. Green conditions. Rose Bengal. Alpha-terpinene.

In a context of volatile organic compound photodecomposition, we have addressed TiO2-based macroscoscpic fiber generation. We have extruded hybrid sols of amorphous titania nanoparticles, latex nanoparticles, and nonionic surfactant (Tergitol) as structure-directing agents into a poly(vinyl alcohol) (PVA) solution bearing salts acting as a flocculating medium. The resulting nanocomposite TiO2/latex/PVA macroscopic fibers were thermally treated in air to open porosity by organic removal while generating the photocatalytically active anatase phase of TiO2 along with residual brookite. Considering the synthetic paths, we have varied both the diameter of the latex particles as well as their concentration within the starting sol. These parameters allow tuning both the voids created through the applied thermal treatment and the fiber final diameters. For gas-phase photocatalysis, we have shown that the fiber diameters, mesoscopic roughness, and macroscopic topological defects represent indeed important morphological parameters acting cooperatively toward both acetone degradation and its mineralization processes. Particularly, triggering the fiber morphological characteristics, we have increased their efficiency toward acetone degradation of around 550% when compared with previous work.