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Abstract According to previous studies, three representative avian adenoviral strains utilize coxsackievirus–adenovirus receptor (CAR) as a receptor and seem to exhibit diverse binding affinities and modes. Thus, further revealing the exact molecular mechanism underlying the interaction between different FAdVs and the attachment receptor CAR is necessary. In this study, we successfully solved the crystal structure of the FAdV-4 fiber1 knob at 1.6 Å resolution. The interaction between the fibre knob and different domains of CAR was verified by confocal microscopy, coimmunoprecipitation and surface plasmon resonance (SPR) analysis. The fibre knobs of the three representative fowl adenoviruses specifically recognized CAR domain 1 (D1), but the recognition of CAR domain 2 (D2) by chicken embryo lethal orphan (CELO) strains was weak. These results provide insights into the differences in adenovirus‒host cell interactions and have important implications for the exploration of viral invasion mechanisms.

In the title compound, [Cu(C9H6N3O2)2(C2H7N)2], the Cu2+ cation is situated on an inversion center and is coordinated by the N atoms of two dimethylamine ligands and the carboxylate O atoms of two 4-(1,2,4-triazol-1-yl)benzoate anions, leading to a slightly distorted square-planar N2O2 coordination environment. In the crystal, intermolecular N—H...N hydrogen bonds between the amine function and the central N atom of the triazole ring lead to the formation of ribbons parallel to [1\overline{1}1]. Weak intermolecular C—H...O hydrogen-bonding interactions are also observed that consolidate the crystal packing.

Two cytochrome P450 enzymes, CYP97A3 and CYP97C1, catalyze hydroxylations of the β- and ε-rings of α-carotene to produce lutein. Chirality is introduced at the C-3 atom of both rings, and the reactions are both pro-3R-stereospecific. We determined the crystal structures of CYP97A3 in substrate-free and complex forms with a nonnatural substrate and the structure of CYP97C1 in a detergent-bound form. The structures of CYP97A3 in different states show the substrate channel and the structure of CYP97C1 bound with octylthioglucoside confirms the binding site for the carotenoid substrate. Biochemical assays confirm that the ferredoxin-NADP+ reductase (FNR)-ferredoxin pair is used as the redox partner. Details of the pro-3R stereospecificity are revealed in the retinal-bound CYP97A3 structure. Further analysis indicates that the CYP97B clan bears similarity to the β-ring-specific CYP97A clan. Overall, our research describes the molecular basis for the last steps of lutein biosynthesis. [ABSTRACT FROM AUTHOR]

The reduction of protochlorophyllide (Pchlide) to chlorophyllide (Chlide) is the penultimate step of chlorophyll biosynthesis. In oxygenic photosynthetic bacteria, algae, and plants, this reaction can be catalyzed by the light-dependent Pchlide oxidoreductase (LPOR), a member of the short-chain dehydrogenase superfamily sharing a conserved Rossmann fold for NAD(P)H binding and the catalytic activity. Whereas modeling and simulation approaches have been used to study the catalytic mechanism of this light-driven reaction, key details of the LPOR structure remain unclear. We determined the crystal structures of LPOR from two cyanobacteria, Synechocystis sp. PCC 6803 and Thermosynechococcus elongatus. Structural analysis defines the LPOR core fold, outlines the LPOR-NADPH interaction network, identifies the residues forming the substrate cavity and the proton-relay path, and reveals the role of the LPOR-specific loop. These findings provide a basis for understanding the structurefunction relationships of the light-driven Pchlide reduction. [ABSTRACT FROM AUTHOR]

Two metal-organic coordination polymers constructed from tris(p-carboxylphenyl)phosphine oxide (TPOH3), namely, [Zn2(TPOH)(2,2'-bipy)(H2O) H2O DMF]n (1) and [Zn2(TPOH)2(1,4-bix)2 . 5H2O]n (2) (2,2'-bipy = 2,2'-bipydine, 1,4-bix = 1,4-bis(imidazol-1-ylmethyl)benzene), were synthesized and identified by IR, elemental analysis and single-crystal X-ray diffraction analysis. Both of the 2,2'- bipy and 1,4-bix ligands tailor the complexes 1 and 2 into chain structures. The thermal behavior and solid state photoluminescence properties correlated with the corresponding structural features were investigated. [ABSTRACT FROM AUTHOR]

7-Hydroxymethyl chlorophyll a reductase (HCAR) catalyzes the second half-reaction in chlorophyll b to chlorophyll a conversion. HCAR is required for the degradation of light-harvesting complexes and is necessary for efficient photosynthesis by balancing the chlorophyll a/b ratio. Reduction of the hydroxymethyl group uses redox cofactors [4Fe-4S] cluster and FAD to transfer electrons and is difficult because of the strong carbonoxygen bond. Here, we report the crystal structure of Arabidopsis HCAR at 2.7-Å resolution and reveal that two [4Fe-4S] clusters and one FAD within a very short distance form a consecutive electron pathway to the substrate pocket. In vitro kinetic analysis confirms the ferredoxin-dependent electron transport chain, thus supporting a proton-activated electron transfer mechanism. HCAR resembles a partial reconstruction of an archaeal F420-reducing [NiFe] hydrogenase, which suggests a common mode of efficient proton-coupled electron transfer through conserved cofactor arrangements. Furthermore, the trimeric form ofHCARprovides a biological clue of its interaction with light-harvesting complex II. [ABSTRACT FROM AUTHOR]

Hard X-ray Fabry-Perot resonators (FPRs) made from sapphire crystals were constructed and characterized. The FPRs consisted of two crystal plates, part of a monolithic crystal structure of Al2O3, acting as a pair of mirrors, for the backward reflection (0 0 0 30) of hard X-rays at 14.3147 keV. The dimensional accuracy during manufacturing and the defect density in the crystal in relation to the resonance efficiency of sapphire FPRs were analyzed from a theoretical standpoint based on X-ray cavity resonance and measurements using scanning electron microscopic and X-ray topographic techniques for crystal defects. Well defined resonance spectra of sapphire FPRs were successfully obtained, and were comparable with the theoretical predictions. [ABSTRACT FROM AUTHOR]

A new uranyl silicate, K2Ca4[(UO2)(Si2O7)2], with a 1D chain structure has been synthesized from a solution of mixed alkali- and alkaline-earth-metal cations under hydrothermal conditions at 550 °C and 1400 bar and characterized by single-crystal X-ray diffraction and photoluminescence spectroscopy. It crystallizes in the triclinic space group P1̅ (No. 2) with a = 6.6354(2) Å, b = 6.6791(2) Å, c = 9.6987(3) Å, α = 98.324(2)°, β = 93.624(2)°, γ = 112.310(2)°, and Z = 1. Its crystal structure consists of a 1D chain of uranyl disilicate formed of corner-sharing UO6 tetragonal bipyramids and Si2O7 double groups. The adjacent chains are separated by K+ and Ca2+ cations. It is the first example of uranyl silicate with a 1D chain structure. [ABSTRACT FROM AUTHOR]

Human metapneumovirus (hMPV) is an important cause of acute viral respiratory infection. As the only target of neutralizing antibodies, the hMPV fusion (F) protein has been a major focus for vaccine development and targeting by drugs and monoclonal antibodies (MAbs). While X-ray structures of trimeric prefusion and postfusion hMPV F proteins from genotype A, and monomeric prefusion hMPV F protein from genotype B have been determined, structural data for the postfusion conformation for genotype B is lacking. We determined the crystal structure of this protein and compared the structural differences of postfusion hMPV F between hMPV A and B genotypes. We also assessed the receptor binding properties of the hMPV F protein to heparin and heparan sulfate (HS). A library of HS oligomers was used to verify the HS binding activity of hMPV F, and several compounds showed binding to predominantly prefusion hMPV F, but had limited binding to postfusion hMPV F. Furthermore, MAbs to antigenic sites III and the 66-87 intratrimeric epitope block heparin binding. In addition, we evaluated the efficacy of postfusion hMPV B2 F protein as a vaccine candidate in BALB/c mice. Mice immunized with hMPV B2 postfusion F protein showed a balanced Th1/Th2 immune response and generated neutralizing antibodies against both subgroup A2 and B2 hMPV strains, which protected the mice from hMPV challenge. Antibody competition analysis revealed the antibodies generated by immunization target two known antigenic sites (III and IV) on the hMPV F protein. Overall, this study provides new characteristics of the hMPV F protein, which may be informative for vaccine and therapy development. IMPORTANCE Human metapneumovirus (hMPV) is an important cause of viral respiratory disease. In this paper, we report the X-ray crystal structure of the hMPV fusion (F) protein in the postfusion conformation from genotype B. We also assessed binding of the hMPV F protein to heparin and heparan sulfate, a previously reported receptor for the hMPV F protein. Furthermore, we determined the immunogenicity and protective efficacy of postfusion hMPV B2 F protein, which is the first study using a homogenous conformation of the protein. Antibodies generated in response to vaccination give a balanced Th1/Th2 response and target two previously discovered neutralizing epitopes. [ABSTRACT FROM AUTHOR]

First-principle calculations reveal that the configuration system of hexagonal boron nitride (h-BN) monolayer with triangular vacancy can induce obvious magnetism, contrary to that of the nonmagnetic pristine boron nitride monolayer. Interestingly, the h-BN with boron atom vacancy (VB-BN) displays metallic behavior with a total magnetic moment being 0.46μB per cell, while the h-BN with nitrogen atom vacancy (VN-BN) presents a half-metallic characteristic with a total magnetic moment being 1.0μB per cell. Remarkably, piezoelectric stress coefficient e11 of the VN-BN is about 1.5 times larger than that of pristine h-BN. Furthermore, piezoelectric strain coefficient d11 (12.42 pm/V) of the VN-BN is 20 times larger than that of pristine h-BN and also one order of magnitude larger than the value for the h-MoS2 monolayer, which is mainly due to the spin-down electronic state in the VN-BN system. Our study demonstrates that the nitrogen atom vacancies can be an efficient route to tailoring the magnetic and piezoelectric properties of h-BN monolayer, which have promising performances for potential applications in nano-electromechanical systems (NEMS) and nanoscale electronics devices. [ABSTRACT FROM AUTHOR]

Using Cu 2 O nanowires as sacrificial templates, SnO 2 nanotubes have been synthesized via wet chemical process. The morphology and the fine crystalline structure of the produced SnO 2 nanotubes have been characterized. None of any oxidizing agents or acid was added into the reaction system, which makes the mechanism much different from the known ones based on acidic or oxidative/redox etching of metal oxide templates. Accordingly one discusses the growth mechanism and attributes it to the hydrolysis of Sn 4+ , to form SnO 2 , and the coordination of CuCl with Cl − , to form soluble [CuClx] 1−x , eliminating Cu 2 O nanowires. [ABSTRACT FROM AUTHOR]

Members of glycosyltransferase family 75 (GT75) not only reversibly catalyze the autoglycosylation of a conserved arginine residue with specific NDP-sugars but also exhibit NDPpyranose mutase activity that reversibly converts specific NDP-pyranose to NDP-furanose. The latter activity provides valuable NDP-furanosyl donors for glycosyltransferases and requires a divalent cation as a cofactor instead of FAD used by UDP-D-galactopyranose mutase. However, details of the mechanism for NDP-pyranose mutase activity are not clear. Here we report the first crystal structures of GT75 family NDPpyranose mutases. The novel structures of GT75 member MtdL in complex with Mn2+ and GDP, GDP-D-glucopyranose, GDPL-fucopyranose, GDP-L-fucofuranose, respectively, combined with site-directed mutagenesis studies, reveal key residues involved in Mn2+ coordination, substrate binding, and catalytic reactions. We also provide a possible catalytic mechanism for this unique type of NDP-pyranose mutase. Taken together, our results highlight key elements of an enzyme family important for furanose biosynthesis. [ABSTRACT FROM AUTHOR]