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MalE is a maltose/maltodextrin‐binding protein (MBP) that plays a critical role in most bacterial maltose/maltodextrin‐transport systems. Previously reported wild‐type MBPs are monomers comprising an N‐terminal domain (NTD) and a C‐terminal domain (CTD), and maltose‐like molecules are recognized between the NTD and CTD and transported to the cell system. Because MBP does not undergo artificial dimerization, it is widely used as a tag for protein expression and purification. Here, the crystal structure of a domain‐swapped dimeric MalE from Salmonella enterica (named SeMalE) in complex with maltopentaose is reported for the first time, and its structure is distinct from typical monomeric MalE family members. In the domain‐swapped dimer, SeMalE comprises two subdomains: the NTD and CTD. The NTD and CTD of one molecule of SeMalE interact with the CTD and NTD of the partner molecule, respectively. The domain‐swapped dimeric conformation was stabilized by interactions between the NTDs, CTDs and linkers from two SeMalE molecules. Additionally, a maltopentaose molecule was found to be located at the interface between the NTD and CTD of different SeMalE molecules. These results provide new insights that will improve the understanding of maltodextrin‐binding MalE proteins. [ABSTRACT FROM AUTHOR]

Pyridoxal 5′-phosphate (PLP) is the active form of vitamin B6, but it is highly reactive and poisonous in its free form. YggS is a PLP-binding protein found in bacteria and humans that mediates PLP homeostasis by delivering PLP to target enzymes or by performing a protective function. Several biochemical and structural studies of YggS have been reported, but the mechanism by which YggS recognizes PLP has not been fully elucidated. Here, we report a functional and structural analysis of YggS from Fusobacterium nucleatum (FnYggS). The PLP molecule could bind to native FnYggS, but no PLP binding was observed for selenomethionine (SeMet)-derivatized FnYggS. The crystal structure of FnYggS showed a type III TIM barrel fold, exhibiting structural homology with several other PLP-dependent enzymes. Although FnYggS exhibited low (<35%) amino acid sequence similarity with previously studied YggS proteins, its overall structure and PLP-binding site were highly conserved. In the PLP-binding site of FnYggS, the sulfate ion was coordinated by the conserved residues Ser201, Gly218, and Thr219, which were positioned to provide the binding moiety for the phosphate group of PLP. The mutagenesis study showed that the conserved Ser201 residue in FnYggS was the key residue for PLP binding. These results will expand the knowledge of the molecular properties and function of the YggS family. [ABSTRACT FROM AUTHOR]

Two novel Co (II) MOFs based on 5-(4-(imidazolyl-1-yl)phenyl) isophthalic acid (H 2 L), namely [Co(L)(tib)(H 2 O) 2 ] n (CP 1) and [Co(L)(bip) 0.5 ] n (CP 2) (tib ​= ​1,3,5-tirs (1-imidazolyl) benzene, bip ​= ​3,5-bis(1-imidazolyl) pyridine ether) have been synthesized under solvothermal conditions and characterized by powder X-ray diffraction, single crystal X-ray diffraction. The photodegradation studies demonstrate that CPs 1 – 2 show high-efficiency degradation of MV (Methyl violet), and the mechanism studies demonstrate that the main active species are ⋅OH radicals. Meanwhile, electrochemistry studies demonstrate that CPs 1 – 2 can catalyze water oxidation under alkaline conditions, and CPs 1 – 2 only need the overpotential of 348 ​mV–760 mV to deliver the current density of 1 ​mA ​cm−2. Two novel Co (II) MOFs (CP 1 and CP 2) have been synthesized by H 2 L, tib, and bip. The photodegradation studies demonstrate that CPs 1-2 show high-efficiency degradation of MV. Simultaneously, electrochemistry studies show that CPs 1-2 could catalyze water oxidation with relatively low overpotential. [Display omitted] • Two novel Co-based MOFs were synthesized by solvothermal method. • Exhibit efficient photocatalytic degradation abilities towards MV/MB in aqueous solution. • Only need the overpotential of 348 ​mV–760 mV to deliver the current density of 1 ​mA ​cm−2. [ABSTRACT FROM AUTHOR]

In this work, five novel Cd/Zn-based MOFs with different topological framework, namely {[Cd(bimb)(Hbipa)]·H 2 O} n (1), {[Cd 3 (dimb) 3 (bipa) 2 (H 2 O) 2 ·2H 2 O} n (2) , [Cd(bimd)(Hbipa)(H 2 O)] n (3) , {[Zn(bipd)(Hbipa)]·H 2 O} n (4) and [Zn(bimb)(Hbipa)] n (5) had been synthesized and characterized. Worth noting, Complex 1 and 2 had effective separation behaviors towards MO and MBE dyes respectively, which could reach the adsorption equilibrium within a quite short time even if there existed another kind of dye in the system. Meanwhile, Complex 3 – 5 showed great performance in CR adsorption. Additionally, Complex 3 – 5 also showed excellent photocatalytic degradation capabilities toward MB and MV dyes under UV irradiation. According to the study, these five metal-organic frameworks can be used as a kind of functional materials in the adsorption and photocatalytic degradation of organic dyes in wastewater. [Display omitted] • Produce novel Cd/Zn -based MOFs that possess novel 3D structure. • Selectively absorb specific aromatic dyes in a mixed aqueous system. • Exhibit efficient photocatalytic degradation abilities towards MB/MV in aqueous solution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Produce two novel Zn-based MOFs under solvothermal conditions. • Both of Zn-based MOFs possess analogous layered stacked structure. • Selectively absorb specific aromatic dyes in a mixed aqueous system. • Exhibit efficient photocatalytic degradation abilities towards MB/MV in aqueous solution. Two novel Zn-MOFs constructed from 5-hydroxy-2-nitroisophthalic acid (H 2 DIPA) and 5-(4-carboxy-2-nitrophenoxy)-2-nitroisophthalic acid (H 3 BPPA), namely: {[Zn 2 (DIPA) 2 (bimp) 5 ]·DMF·2H 2 O} n (Zn-MOF 1), {[Zn 2 (HBPPA) 2 (bibp) 2 ]·2H 2 O} n (Zn-MOF 2) (bimp = 1,4-di(1H-imidazol-1-yl)butane, bibp = 4,4′-bis(imidazolyl) biphenyl), have been synthesized under solvothermal conditions and characterized by single crystal X-ray diffraction, elemental analysis, IR spectra, powder X-ray diffraction (PXRD) and thermogravimetric analysis (TG). The single-crystal X-ray diffraction analysis indicates that Zn-MOF 1 exhibits an uncommon 3-nodal framework with a (4·6·8)(4·63·82)(66) topology, whereas Zn-MOF 1 exhibits an uninodal 4-connected framework with a (44·62) topology. Moreover, both of the two Zn-MOFs exhibit exceptional dye adsorption capacities towards the organic dyes with high adsorption rates and excellent adsorption amounts. Particularly, Zn-MOF 1 can selectively adsorb the cationic dye malachite green (MG) whereas Zn-MOF 2 adsorb the anionic dye methyl orange (MO) when there exists another kind of dye in the system. The adsorption process can be illustrated by pseudo-second order kinetic and Langmuir isotherm, and the feasible adsorption mechanism could be the electrostatical interactions, hydrogen bonding between the MOFs and the dyes. Meanwhile, the two Zn-MOFs also show good photocatalytic degradation capabilities toward MB/MV dyes under UV irradiation, and the mechanism studies demonstrate that the main active species are ·OH radicals. Therefore, this functional MOF materials can be treated as a convenient and cost-efficient solution for the sewage handling and environmental protection. [ABSTRACT FROM AUTHOR]