The xanthine oxidase (XO) family comprises molybdenum-dependent enzymes that usually form homodimers (or dimers of heterodimers/trimers) organized in three domains that harbor two [2Fe-2S] clusters, one FAD, and a Mo cofactor. In this work, we crystallized an unusual member of the family, the periplasmic aldehyde oxidoreductase PaoABC from Escherichia coli. This is the first example of an E. coli protein containing a molybdopterin-cytosine-dinucleotide cofactor and is the only heterotrimer of the XO family so far structurally characterized. The crystal structure revealed the presence of an unexpected [4Fe-4S] cluster, anchored to an additional 40 residues subdomain. According to phylogenetic analysis, proteins containing this cluster are widely spread in many bacteria phyla, putatively through repeated gene transfer events. The active site of PaoABC is highly exposed to the surface with no aromatic residues and an arginine (PaoC-R440) making a direct interaction with PaoC-E692, which acts as a base catalyst. In order to understand the importance of R440, kinetic assays were carried out, and the crystal structure of the PaoC-R440H variant was also determined.

Oxidized and sulfonated-activated carbons (AC) were tested in the catalytic conversion of glycerol by acetalization reactions. The solids were treated with concentrated nitric acid and/or fuming sulfuric acid (AC, AC-N, AC-S, and AC-NS). The presence of sulfur and an increase in the acidity of the solids demonstrate the suitability of the oxidation as well as the sulfonation process, especially in the sample treated with concentrated nitric acid and fuming sulfuric acid (AC-NS). The best catalyst for the reaction of glycerol acetalization with phenylacetaldehyde was AC-NS, with a phenylacetaldehyde conversion of 95 {%} after 90 min at 383 K and selectivity of 88 and 12 {%}, respectively, to dioxolane and dioxane. These products can be used as hyacinth fragrance flavoring compounds. Furthermore, a contribution of homogeneous catalysis in these systems was not identified. Thus, we identified a possibility of glycerol conversion, a biodiesel by-product, into value-added products by suitable catalysts produced from activated carbons.

During the course of evolution, the cellulosome, one of Nature's most intricate multi-enzyme complexes, has been continuously fine-tuned to efficiently deconstruct recalcitrant carbohydrates. To facilitate the uptake of released sugars, anaerobic bacteria use highly ordered protein-protein interactions to recruit these nanomachines to the cell surface. Dockerin modules located within a non-catalytic macromolecular scaffold, whose primary role is to assemble cellulosomal enzymatic subunits, bind cohesin modules of cell envelope proteins, thereby anchoring the cellulosome onto the bacterial cell. Here we have elucidated the unique molecular mechanisms used by anaerobic bacteria for cellulosome cellular attachment. The structure and biochemical analysis of five cohesin-dockerin complexes revealed that cell surface dockerins contain two cohesin-binding interfaces, which can present different or identical specificities. In contrast to the current static model, we propose that dockerins utilize multivalent modes of cohesin recognition to recruit cellulosomes to the cell surface, a mechanism that maximises substrate access while facilitating complex assembly.

The limitations of platinum complexes in cancer treatment have motivated the extensive investigation into other metal complexes such as ruthenium. We herein present the synthesis and characterization of a new family of ruthenium compounds 1a–5a with the general formula [Ru(bipy)2L][CF3SO3]2 (bipy = 2,2′-bipyridine; L = bidentate ligand: N,N; N,P; P,P; P,As) which have been characterized by elemental analysis, ES-MS, 1H and 31P–{1H} NMR, FTIR and conductivity measurements. The molecular structures of four Ru(II) complexes were determined by single crystal X-ray diffraction. All compounds displayed moderate cytotoxic activity in vitro against human A2780 ovarian, MCF7 breast and HCT116 colorectal tumor cells. Compound 5a was the most cytotoxic compound against A2780 and MCF7 tumor cells with an IC50 of 4.75 ± 2.82 μM and 20.02 ± 1.46 μM, respectively. The compounds showed no cytotoxic effect on normal human primary fibroblasts but rather considerable selectivity for A2780, MCF7 and HCT116 tumor cells. All compounds induce apoptosis and autophagy in A2780 ovarian carcinoma cells and some nuclear DNA fragmentation. All compounds interact with CT-DNA with intrinsic binding constants in the order 1a > 4a > 2a > 3a > 5a. The observed hyperchromic effect may be due to the electrostatic interaction between positively charged cations and the negatively charged phosphate backbone at the periphery of the double helix-CT-DNA. Interestingly, compound 1a shows a concentration dependent DNA double strand cleavage. In addition in vivo toxicity has been evaluated on zebrafish embryos unveiling the differential toxicity between the compounds, with LC50 ranging from 8.67 mg L−1 for compound 1a to 170.30 mg L−1 for compound 2a.

Streptococcus dysgalactiae subsp. dysgalactiae (SDSD) are considered exclusive animal pathogens; however, a putative zoonotic upper limb cellulitis, a prosthetic joint infection and an infective endocarditis were described in humans. To unravel if bovine SDSD isolates are able to infect human cells, the adherence and internalization to human primary keratinocytes of two bovine SDSD strains isolated from milk collected from udder were analyzed. Bacterial adhesion assays and confocal microscopy indicate a high adherence and internalization of SDSD isolates to human cells, suggesting for the first time the ability of bovine isolates to infect human cells. (C) 2015 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

Biological microfibers are remarkable materials with diverse structural and mechanical properties, such as high wear-resistance, elasticity, and biodegradability. However, with current techniques, there are few robust ways to sense the surface properties of the fibers, which crucially affect the organization of the fibers and their interactions with the surrounding material. In this paper, we show that surfaces of diverse biofibers, including spider silks and cellulosic fibers, can be easily sensed by depositing droplets of a nematic fluid onto the fibers. The droplets reveal the surface properties of the fibers via their optical images, notably showing also the fiber chirality. Further, the droplets are used to study the entanglement of biofibers, as a route toward novel biological and bioinspired materials.Probing the surface morphology of microthin fibers such as naturally occurring biofibers is essential for understanding their structural properties, biological function, and mechanical performance. The state-of-the-art methods for studying the surfaces of biofibers are atomic force microscopy imaging and scanning electron microscopy, which well characterize surface geometry of the fibers but provide little information on the local interaction potential of the fibers with the surrounding material. In contrast, complex nematic fluids respond very well to external fields and change their optical properties upon such stimuli. Here we demonstrate that liquid crystal droplets deposited on microthin biofibers—including spider silk and cellulosic fibers—reveal characteristics of the fibers’ surface, performing as simple but sensitive surface sensors. By combining experiments and numerical modeling, different types of fibers are identified through the fiber-to-nematic droplet interactions, including perpendicular and axial or helicoidal planar molecular alignment. Spider silks align nematic molecules parallel to fibers or perpendicular to them, whereas cellulose aligns the molecules unidirectionally or helicoidally along the fibers, indicating notably different surface interactions. The nematic droplets as sensors thus directly reveal chirality of cellulosic fibers. Different fiber entanglements can be identified by depositing droplets exactly at the fiber crossings. More generally, the presented method can be used as a simple but powerful approach for probing the surface properties of small-size bioobjects, opening a route to their precise characterization.

The limitations of platinum complexes in cancer treatment have motivated the extensive investigation into other metal complexes such as ruthenium. We herein present the synthesis and characterization of a new family of ruthenium compounds 1a-5a with the general formula [Ru(bipy)2L][CF3SO3]2 (bipy = 2,2[prime or minute]-bipyridine; L = bidentate ligand: N,N; N,P; P,P; P,As) which have been characterized by elemental analysis, ES-MS, 1H and 31P-{1H} NMR, FTIR and conductivity measurements. The molecular structures of four Ru(ii) complexes were determined by single crystal X-ray diffraction. All compounds displayed moderate cytotoxic activity in vitro against human A2780 ovarian, MCF7 breast and HCT116 colorectal tumor cells. Compound 5a was the most cytotoxic compound against A2780 and MCF7 tumor cells with an IC50 of 4.75 +/- 2.82 [small mu ]M and 20.02 +/- 1.46 [small mu ]M, respectively. The compounds showed no cytotoxic effect on normal human primary fibroblasts but rather considerable selectivity for A2780, MCF7 and HCT116 tumor cells. All compounds induce apoptosis and autophagy in A2780 ovarian carcinoma cells and some nuclear DNA fragmentation. All compounds interact with CT-DNA with intrinsic binding constants in the order 1a > 4a > 2a > 3a > 5a. The observed hyperchromic effect may be due to the electrostatic interaction between positively charged cations and the negatively charged phosphate backbone at the periphery of the double helix-CT-DNA. Interestingly, compound 1a shows a concentration dependent DNA double strand cleavage. In addition in vivo toxicity has been evaluated on zebrafish embryos unveiling the differential toxicity between the compounds, with LC50 ranging from 8.67 mg L-1 for compound 1a to 170.30 mg L-1 for compound 2a.