Abstract The W/SeCys-FdhAB formate dehydrogenase from Desulfovibrio vulgaris Hildenborough is a dimeric periplasmic enzyme that catalyzes the reversible oxidation of formate and reduction of CO2. It belongs to the group of metal-dependent FDHs, with a tungsten at the active site coordinated by two pyranopterin guanine dinucleotides, a selenocysteine, and one labile sulfur atom. FdhAB has a remarkably high activity and unusual tolerance to oxygen, making it an ideal model system to study biological CO2 reduction.

Glucans are polymers of D-glucose with differing linkages in linear or branched sequences. They are constituents of microbial and plant cell-walls and involved in important bio-recognition processes including immunomodulation, anti-cancer activities, pathogen virulence and plant cell-wall biodegradation. Translational possibilities for these activities in medicine and biotechnology are considerable. High-throughput micro-methods are needed to screen proteins for recognition of specific glucan sequences as a lead to structure-function studies and their exploitation. We describe construction of a glucome microarray, the first sequence-defined glycome-scale microarray, using a designer approach from targeted ligand-bearing glucans in conjunction with a novel high-sensitivity mass spectrometric sequencing method, as a screening tool to assign glucan recognition motifs. The glucome microarray comprises 153 oligosaccharide probes with high purity, representing major sequences in glucans. The negative-ion electrospray tandem mass spectrometry with collision-induced dissociation was used for complete linkage analysis of gluco-oligosaccharides in linear homo and hetero and branched sequences. The system is validated using antibodies and carbohydrate-binding modules known to target α- or β-glucans in different biological contexts, extending knowledge on their specificities, and applied to reveal new information on glucan recognition by two signalling molecules of the immune system against pathogens: Dectin-1 and DC-SIGN. The sequencing of the glucan oligosaccharides by the MS method and their interrogation on the microarrays provides detailed information on linkage, sequence and chain length requirements of glucan-recognizing proteins, and are a sensitive means of revealing unsuspected sequences in the polysaccharides.

The cooperative assembly of biopolymers and small molecules can yield functional materials with precisely tunable properties. Here, the fabrication, characterization, and use of multicomponent hybrid gels as selective gas sensors are reported. The gels are composed of liquid crystal droplets self-assembled in the presence of ionic liquids, which further coassemble with biopolymers to form stable matrices. Each individual component can be varied and acts cooperatively to tune gels' structure and function. The unique molecular environment in hybrid gels is explored for supramolecular recognition of volatile compounds. Gels with distinct compositions are used as optical and electrical gas sensors, yielding a combinatorial response conceptually mimicking olfactory biological systems, and tested to distinguish volatile organic compounds and to quantify ethanol in automotive fuel. The gel response is rapid, reversible, and reproducible. These robust, versatile, modular, pliant electro-optical soft materials possess new possibilities in sensing triggered by chemical and physical stimuli.

Metal-dependent formate dehydrogenases (Fdh) catalyze the reversible conversion of CO2 to formate, with unrivalled efficiency and selectivity. However, the key catalytic aspects of these enzymes remain unknown, preventing us from fully benefiting from their capabilities in terms of biotechnological applications. Here, we report a time-resolved characterization by X-ray crystallography of the Desulfovibrio vulgaris Hildenborough SeCys/W-Fdh during formate oxidation. The results allowed us to model five different intermediate structures and to chronologically map the changes occurring during enzyme reduction. Formate molecules were assigned for the first time to populate the catalytic pocket of a Fdh. Finally, the redox reversibility of DvFdhAB in crystals was confirmed by reduction and reoxidation structural studies.

Reducing CO2 is a challenging chemical transformation that biology solves easily, with high efficiency and specificity. In particular, formate dehydrogenases are of great interest since they reduce CO2 to formate, a valuable chemical fuel and hydrogen storage compound. The metal-dependent formate dehydrogenases of prokaryotes can show high activity for CO2 reduction. Here, we report an expression system to produce recombinant W/Sec-FdhAB from Desulfovibrio vulgaris Hildenborough fully loaded with cofactors, its cata-lytic characterization and crystal structures in oxidised and reduced states. The enzyme has very high activi-ty for CO2 reduction and displays remarkable oxygen stability. The crystal structure of the formate-reduced enzyme shows Sec still coordinating the tungsten, supporting a mechanism of stable metal coordination during catalysis. Comparison of the oxidised and reduced structures shows significant changes close to the active site. The DvFdhAB is an excellent model for studying catalytic CO2 reduction and probing the mecha-nism of this conversion.Reducing CO2 is a challenging chemical transformation that biology solves easily, with high efficiency and specificity. In particular, formate dehydrogenases are of great interest since they reduce CO2 to formate, a valuable chemical fuel and hydrogen storage compound. The metal-dependent formate dehydrogenases of prokaryotes can show high activity for CO2 reduction. Here, we report an expression system to produce recombinant W/Sec-FdhAB from Desulfovibrio vulgaris Hildenborough fully loaded with cofactors, its cata-lytic characterization and crystal structures in oxidised and reduced states. The enzyme has very high activi-ty for CO2 reduction and displays remarkable oxygen stability. The crystal structure of the formate-reduced enzyme shows Sec still coordinating the tungsten, supporting a mechanism of stable metal coordination during catalysis. Comparison of the oxidised and reduced structures shows significant changes close to the active site. The DvFdhAB is an excellent model for studying catalytic CO2 reduction and probing the mecha-nism of this conversion.

The functional and biological significance of the selected CASP12 targets are described by the authors of the structures. The crystallographers discuss the most interesting structural features of the target proteins and assess whether these features were correctly reproduced in the predictions submitted to the CASP12 experiment. This article is protected by copyright. All rights reserved.

Abstract Aldehyde Oxidase (hAOX1) is a cytosolic enzyme involved in the metabolism of drugs and xenobiotic compounds. The enzyme belongs to the xanthine oxidase (XO) family of Mo containing enzyme and is a homo-dimer of two 150 kDa monomers. Nonsynonymous Single Nucleotide Polymorphisms (nsSNPs) of hAOX1 have been reported as affecting the ability of the enzyme to metabolize different substrates. Some of these nsSNPs have been biochemically and structurally characterized but the lack of a systematic and comprehensive study regarding all described and validated nsSNPs is urgent, due to the increasing importance of the enzyme in drug development, personalized medicine and therapy, as well as in pharmacogenetic studies. The objective of the present work was to collect all described nsSNPs of hAOX1 and utilize a series of bioinformatics tools to predict their effect on protein structure stability with putative implications on phenotypic functional consequences. Of 526 nsSNPs reported in NCBI-dbSNP, 119 are identified as deleterious whereas 92 are identified as nondeleterious variants. The stability analysis was performed for 119 deleterious variants and the results suggest that 104 nsSNPs may be responsible for destabilizing the protein structure, whereas five variants may increase the protein stability. Four nsSNPs do not have any impact on protein structure (neutral nsSNPs) of hAOX1. The prediction results of the remaining six nsSNPs are nonconclusive. The in silico results were compared with available experimental data. This methodology can also be used to identify and prioritize the stabilizing and destabilizing variants in other enzymes involved in drug metabolism.

A new and never yet reported hetero arylidene-9(10H)-anthrone structure (4) was unexpectedly isolated on reaction of 1,2-dimethyl-3-ethylimidazolium iodide (2) and 9-anthracenecarboxaldehyde (3) under basic conditions. Its structure was unequivocally attributed by X-ray crystallography. No cytotoxicity in human healthy fibroblasts and in two different cancer cell lines was observed indicating its applicability in biological systems. Compound 4 interacts with CT-DNA by intercalation between the adjacent base pairs of DNA with a high binding affinity (Kb = 2.0(± 0.20) x 105 M-1) which is 10x higher than that described for doxorubicin (Kb = 3.2 (±0.23) × 104 M-1). Furthermore, compound 4 quenches the fluorescence emission of GelRed-CT-DNA system with a quenching constant (KSV) of 3.3(±0.3) x 103 M-1 calculated by the Stern-Volmer equation.

Silk fibroin is a biobased material with excellent biocompatibility and mechanical properties, but its use in bioelectronics is hampered by the difficult dissolution and low intrinsic conductivity. Some ionic liquids are known to dissolve fibroin but removed after fibroin processing. However, ionic liquids and fibroin can cooperatively give rise to functional materials, and there are untapped opportunities in this combination. The dissolution of fibroin, followed by gelation, in designer ionic liquids from the imidazolium chloride family with varied alkyl chain lengths (2–10 carbons) is shown here. The alkyl chain length of the anion has a large impact on fibroin secondary structure which adopts unconventional arrangements, yielding robust gels with distinct hierarchical organization. Furthermore, and due to their remarkable air-stability and ionic conductivity, fibroin ionogels are exploited as active electrical gas sensors in an electronic nose revealing the unravelled possibilities of fibroin in soft and flexible electronics.

Metal-dependent formate dehydrogenases are very promising targets for enzyme optimization and design of bio-inspired catalysts for CO2 reduction, towards novel strategies for climate change mitigation. For effective application of these enzymes, the catalytic mechanism must be fully understood, and the molecular determinants clarified. Despite numerous studies, several doubts persist, namely regarding the role played by the possible dissociation of the SeCys ligand from the Mo/W active site. Additionally, the O2 sensitivity of these enzymes must also be understood as it poses an important obstacle for biotechnological applications. Here we present a combined biochemical, spectroscopic, and structural characterization of Desulfovibrio vulgaris FdhAB (DvFdhAB) when exposed to oxygen in the presence of a substrate (formate or CO2). This study reveals that O2 inactivation is promoted by the presence of either substrate and involves forming a new species in the active site, captured in the crystal structures, where the SeCys ligand is displaced from tungsten coordination and replaced by a dioxygen or peroxide molecule. This new form was reproducibly obtained and supports the conclusion that, although W-DvFdhAB can catalyze the oxidation of formate in the presence of oxygen for some minutes, it gets irreversibly inactivated after prolonged O2 exposure in the presence of either substrate. These results reveal that oxidative inactivation does not require reduction of the metal, as widely assumed, as it can also occur in the oxidized state in the presence of CO2.Competing Interest StatementThe authors have declared no competing interest.AORAldehyde Oxido-reductaseDTTDithiothreitolDvDesulfovibrio vulgarisEPRElectron Paramagnetic ResonanceFdhFormate dehydrogenaseHPHigh PressureMGDMolybdopterin Guanine DinucleotidesNDNew dropROSReactive Oxygen SpeciesSODSuperoxide dismutaseTSAThermal Shift Assay

Interactions of glycan-specific epitopes to human lectin receptors represent novel immune checkpoints for investigating cancer and infection diseases. By employing a multidisciplinary approach that combines isothermal titration calorimetry, NMR spectroscopy, molecular dynamics simulations, and X-ray crystallography, we disclosed the molecular determinants that govern the recognition of the tumour and pathogenic glycobiomarker LacdiNAc (GalNAc?1-4GlcNAc, LDN), including their comparison with the ubiquitous LacNAc epitope (Gal?1-4GlcNAc, LN), by two human immune-related lectins, galectin-3 (hGal-3) and the macrophage galactose C-type lectin (hMGL). A different mechanism of binding and interactions is observed for the hGal-3/LDN and hMGL/LDN complexes, which explains the remarkable difference in the binding specificity of LDN and LN by these two lectins. The new structural clues reported herein are fundamental for the chemical design of mimetics targeting hGal-3/hMGL recognition process.