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S,N-GOQDs with stable electroluminescence, photoluminescence, and photocatalytic properties have been developed. They can be used as emitters for LED devices and as photocatalysts for hydrogen evolution in photo-electro-chemical energy conversion.

We report the isolation and stereochemical determination of the predominant native cholesteryl 6

Human bleomycin hydrolase (hBH) catalyzes deamidation of the anticancer drug bleomycins (BLM). This enzyme is involved in BLM detoxification and drug resistance. Herein, we report the putative BLM-binding site and catalytic mechanism of hBH. The crystal structures and biochemical studies suggest that hBH cleaves its C-terminal residue without significant preference for the type of amino acid, and therefore can accordingly accommodate the β-aminoalanine amide moiety of BLM for deamidation. Interestingly, hBH is capable of switching from a cysteine protease to a serine protease that is unable to cleave the secondary amide of hBH C-terminus but reacts with the primary amide of BLMs.

Capreomycin (CMN) and viomycin (VIO) are nonribosomal peptide antituberculosis antibiotics, the structures of which contain four nonproteinogenic amino acids, including l-2,3-diaminopropionic acid (l-Dap), β-ureidodehydroalanine, l-capreomycidine, and β-lysine. Previous bioinformatics analysis suggested that CmnB/VioB and CmnK/VioK participate in the formation of l-Dap; however, the real substrates of these enzymes are yet to be confirmed. We herein show that starting from O-phospho-l-Ser (OPS) and l-Glu precursors, CmnB catalyzes the condensation reaction to generate a metabolite intermediate N-(1-amino-1-carboxyl-2-ethyl)glutamic acid (ACEGA), which undergoes NAD+-dependent oxidative hydrolysis by CmnK to generate l-Dap. Furthermore, the binding site of ACEGA and the catalytic mechanism of CmnK were elucidated with the assistance of three crystal structures, including those of apo-CmnK, the NAD+-CmnK complex, and CmnK in an alternative conformation. The CmnK-ACEGA docking model revealed that the glutamate α-hydrogen points toward the nicotinamide moiety. It provides evidence that the reaction is dependent on hydride transfer to form an imine intermediate, which is subsequently hydrolyzed by a water molecule to produce l-Dap. These findings modify the original proposed pathway and provide insights into l-Dap formation in the biosynthesis of other related natural products.

The main protease (M

We report here that pregnenolonyl-α-glucoside (2), a steryl glycoside synthesized directly from pregnenolone and glucose via a consecutive multienzyme-catalyzed process, exhibits marked dose-dependent cytotoxic activity against HT29, AGS, and ES-2 cells with IC50 values of 23.5 to 50.9 μM. An in vitro CYP17A1 binding pattern assay and protein-ligand docking model support that 2, like abiraterone, binds in the active site heme iron pocket of CYP17A1.

Three unsymmetrical diiodobichalcogenophenes SSeI2, STeI2, and SeTeI2 and a diiodoterchalcogenophene SSeTeI2 were prepared. Grignard metathesis of SSeI2, STeI2, SeTeI2, and SSeTeI2 occurred regioselectively at the lighter chalcogenophene site because of its relatively lower electron density and less steric bulk. Nickel-catalyzed Kumada catalyst-transfer polycondensation of these Mg species provided a new class of side-chain regioregular and main-chain AB-type alternating poly(bichalcogenophene)s—PSSe, PSTe, and PSeTe—through a chain-growth mechanism. The ring-walking of the Ni catalyst from the lighter to the heavier chalcogenophene facilitated subsequent oxidative addition, thereby suppressing the possibility of chain-transfer or chain-termination. More significantly, the Ni catalyst could walk over the distance of three rings (ca. 1 nm)—from a thiophene unit via a selenophene unit to a tellurophene unit—to form PSSeTe, the first ABC-type regioregular and periodic poly(terchalcogenophene) comprising three different types of 3-hexylchalcogenophenes., Three unsymmetrical diiodobichalcogenophenes SSeI2, STeI2, and SeTeI2 and a diiodoterchalcogenophene SSeTeI2 were prepared to synthesize a new class of polychalcogenophenes with precisely controlled sequences by catalyst-transfer polycondensation.

Oligomerization of protein into specific quaternary structures plays important biological functions, including regulation of gene expression, enzymes activity, and cell–cell interactions. Here, we report the determination of two crystal structures of the Grimontia hollisae (formally described as Vibrio hollisae) thermostable direct hemolysin (Gh–TDH), a pore-forming toxin. The toxin crystalized in the same space group of P21212, but with two different crystal packing patterns, each revealing three consistent tetrameric oligomerization forms called Oligomer–I, –II, and –III. A central pore with comparable depth of ~50 Å but differing in shape and size was observed in all determined toxin tetrameric oligomers. A common motif of a toxin dimer was found in all determined structures, suggesting a plausible minimum functional unit within the tetrameric structure in cell membrane binding and possible hemolytic activity. Our results show that bacterial toxins may form a single or highly symmetric oligomerization state when exerting their biological functions. The dynamic nature of multiple symmetric oligomers formed upon release of the toxin may open a niche for bacteria survival in harsh living environments.

Herein, we report the total synthesis of landomycins Q and R as well as the aglycone core, namely anhydrolandomycinone and a related core analogue. The synthesis features an acetate-assisted arylation method for construction of the hindered B-ring in the core component and a one-pot aromatization–deiodination–denbenzylation procedure to streamline the global functional and protecting group manuipulation. Subsequent cytotoxicity and antibacterial studies revealed that the landomycin R is a potential antibacterial agent against methicillin-resistant Staphylococcus aureus.

An enantioselective synthesis of iso-, isothio-, and isoselenohydantoin and diketopiperazine-fused tetrahydroisoquinolines from l-Dopa was reported. The route consists of an Pictet-Spengler reaction of ( S)-2-amino-3-(3,4-dimethoxyphenyl)propanoates with various aldehydes to afford diastereomeric tetrahydroisoquinolines. Next step, the tetrahydroisoquinolines were further reacted with iso-, isothio-, or isoselenocyanates to construct hydantoin. Similarly, the diketopiperazine moiety was constructed by subjecting tetrahydroisoquinolines to a condensation reaction with chloroacetyl chloride followed by nucleophilic addition with various primary amines.

Fern spores were traditionally classified into chlorophyllous (green) and nonchlorophyllous (nongreen) types based on the color visible to the naked eye. Recently, a third type, "cryptochlorophyllous spores", is recognized, and these spores are nongreen under white light but contain chlorophylls. Epifluorescence microscopy was previously used to detect chlorophylls in cryptochlorophyllous spores. In addition to epifluorescence microscopy, current study performed some other approaches, including spore-squash epifluorescence, absorption spectra, laser-induced fluorescence emission spectra, thin layer chromatography (TLC), and ultra-high performance liquid chromatography with ultraviolet and mass spectrometric detection (UHPLC-UV-MS) in order to detect chlorophylls of spores of seven ferns (Sphaeropteris lepifera, Ceratopteris thalictroides, Leptochilus wrightii, Leptochilus pothifolius, Lepidomicrosorum buergerianum, Osmunda banksiifolia, and Platycerium grande). Destructive methods, such as TLC and UHPLC-UV-MS, successfully detected chlorophylls inside the spores when their signals of red fluorescence under epifluorescence microscope were masked by spore wall. Although UHPLC-UV-MS analysis was the most sensitive and reliable for determining the chlorophylls of spores, spore-squash epifluorescence is not only reliable but also cost- and time-effective one among our study methods. In addition, we first confirmed that Lepidomicrosorium buergerianum, Leptochilus pothifolius, Leptochilus wrightii, and Platycerium grande, produce cryptochlorophyllous spores.

We report on the preparation of a new type of immunotoxin by conjugation of an epidermal growth factor receptor (EGFR)-binding peptide and an R46E mutation of thermostable direct hemolysin from Grimontia hollisae, (Gh-TDH(R) (46E) /EB). The hybrid immunotoxin was purified to homogeneity and showed a single band with slight slower mobility than that of Gh-TDH(R) (46E) . Cytotoxicity assay of Gh-TDH(R) (46E) /EB on EGFR highly, moderately, low, and non-expressed cells, A431, MDA-MB-231, HeLa, and HEK293 cells, respectively, showed apparent cytotoxicity on A431 and MDA-MB-231 cells but not on HeLa or HEK293 cells. In contrast, no cytotoxicity was observed for these cells treated with either Gh-TDH(R) (46E) or EB alone, indicating enhanced cytotoxic efficacy of Gh-TDH(R) (46E) by the EGFR binding moiety. Further antitumor activity assay of Gh-TDH(R) (46E) /EB in a xenograft model of athymic nude mice showed obvious shrinkage of tumor size and degeneration, necrosis, and lesions of tumor tissues compared to the normal tissues. Therefore, the combination of Gh-TDH(R) (46E) with target affinity agents opens new possibilities for pharmacological treatment of cancers and potentiates the anticancer drug's effect.

In this study, surface-func- tionalized, branched polyethylenimine (BPEI)-modified YVO4:Bi 3 + ,Eu 3 + nano- crystals (NCs) were successfully syn- thesized by a simple, rapid, solvent-free hydrothermal method. The BPEI- coated YVO4:Bi 3 + ,Eu 3 + NCs with high crystallinity show broad-band excita- tion in the l = 250 to 400 nm near-ultra- violet (NUV) region and exhibit a sharp-line emission band centered at l = 619 nm under excitation at l = 350 nm. The surface amino groups con- tributed by the capping agent, BPEI, not only improve the dispersibility and water/buffer stability of the BPEI- coated YVO4:Bi 3 + ,Eu 3 + NCs, but also provide a capability for specifically tar- geted biomolecule conjugation. Folic acid (FA) and epidermal growth factor (EGF) were further attached to the BPEI-coated YVO4:Bi 3 + ,Eu 3 + NCs and exhibited effective positioning of fluorescent NCs toward the targeted folate receptor overexpressed in HeLa cells or EGFR overexpressed in A431 cells with low cytotoxicity. These re- sults demonstrate that the ligand-func- tionalized, BPEI-coated YVO4:Bi 3 + , Eu 3 + NCs show great potential as a new-generation biological lumines- cent bioprobe for bioimaging applica- tions. Moreover, the unique lumines- cence properties of BPEI-coated YVO4:Bi 3 + ,Eu 3 + NCs show potential to combine with a UVA photosensitiz- ing drug to produce both detective and therapeutic effects for human skin cancer therapy.

Vibrio hollisae, a halophilic species recently reclassified as Grimontia hollisae, is a causative agent of gastroenteritis and septicaemia. One important pathogenic Vibrio factor, thermostable direct haemolysin (TDH), has been purified and crystallized in two crystal forms using the vapour-diffusion method. The crystals belonged to an orthorhombic space group, with unit-cell parameters a = 104.8, b = 112.4, c = 61.3 Å and a = 122.9, b = 123.3, c = 89.8 Å. The crystals contained either four or eight molecules per asymmetric unit, with predicted solvent contents of 49.4 and 46.3% and Matthews coefficients (V(M)) of 2.4 and 2.3 Å(3) Da(-1), respectively. These crystals were suitable for structure determination, which would yield structural details related to the cytotoxicity and oligomeric structure of this pore-forming toxin.

Recombinant thermostable direct hemolysin from Grimontia hollisae (Gh-rTDH) exhibits paradoxical Arrhenius effect, where the hemolytic activity is inactivated by heating at 60 oC but is reactivated by additional heating above 80 oC. This study investigated individual or collective mutational effect of Tyr53, Thr59, and Ser63 positions of Gh-rTDH on hemolytic activity, Arrhenius effect, and biophysical properties. In contrast to the Gh-rTDH wild-type (Gh-rTDHWT) protein, a 2-fold decrease of hemolytic activity and alteration of Arrhenius effect could be detected from the Gh-rTDHY53H/T59I and Gh-rTDHT59I/S63T double-mutants and the Gh-rTDHY53H/T59I/S63T triple-mutant. Differential scanning calorimetry results showed that the Arrhenius effect-loss and -retaining mutants consistently exhibited higher and lower endothermic transition temperatures, respectively, than that of the Gh-rTDHWT. Circular dichroism measurements of Gh-rTDHWT and Gh-rTDHmut showed a conspicuous change from a β-sheet to α-helix structure around the endothermic transition temperature. Consistent with the observation is the conformational change of the proteins from native globular form into fibrillar form, as determined by Congo red experiments and transmission electron microscopy.

Boronic acids (BAs) provide strong potential in orientation immobilization of antibody and the modification method is crucial for efficiency optimization. A highly effective method has been developed for rapid antibody immobilization on gold electrodes through the electrodeposition of a BA–containing linker in this study. Aniline-based BA forms a condense layer while antibody could automatically immobilize on the surface of the electrode. Compare to traditional self-assembled monolayer method, the electrodeposition process dramatically reduces the modification time from days to seconds. It also enhances the immobilized efficiency from 95 to 408 (ng/cm2) with a strong preference being exhibited for shorter aniline-based linkers.

Xylose reductase (XR), which requires NADPH as a co-substrate, catalyzes the reduction of D-xylose to xylitol, which is the first step in the metabolism of D-xylose. The detailed three-dimensional structure of XR will provide a better understanding of the biological significance of XR in the efficient production of xylitol from biomass. XR of molecular mass 36.6 kDa from Candida tropicalis was crystallized using the hanging-drop vapour-diffusion method. According to X-ray diffraction data from C. tropicalis XR crystals at 2.91 A resolution, the unit cell belongs to space group P3(1) or P3(2). Preliminary analysis indicated the presence of four XR molecules in the asymmetric unit, with 68.0% solvent content.

BackgroundG. hollisae thermostable direct hemolysin (Gh-TDH) is produced by most strains of G. hollisae. This toxin has been reported to be absorbed in the intestines in humans. Secondary liver injury might be caused by venous return of the toxin through the portal system. We aimed to firstly analyze the in vitro and in vivo hepatotoxicity of Gh-TDH.MethodsLiver cells (primary human non-cancer cell and FL83B mouse cells) were treated and mice (BALB/c) were fed with this toxin to investigate its hepatotoxicity. Morphological examination and cytotoxicity assays using liver cells were also performed. Fluorescein isothiocyanate-conjugated toxin was used to analyze the localization of this protein in liver cells. Mice were subjected to liver function measurements and liver biopsies following toxin treatment and wild-type bacterial infection. PET (positron emission tomography)/CT (computed tomography) images were taken to assess liver metabolism during acute injury and recovery.ResultsThe effect of hepatotoxicity was dose and time dependent. Cellular localization showed that the toxin was initially located around the cellular margins and subsequently entered the nucleus. Liver function measurements and liver biopsies of the mice following treatment with toxin or infection with wild-type Grimontia hollisae showed elevated levels of transaminases and damage to the periportal area, respectively. The PET/CT images revealed that the reconstruction of the liver continued for at least one week after exposure to a single dose of the toxin or bacterial infection.ConclusionsThe hepatotoxicity of Gh-TDH was firstly demonstrated. The damage was located in the periportal area of the liver, and the liver became functionally insufficient.

Recombinant thermostable direct hemolysin from Grimontia hollisae (Gh-rTDH) exhibits paradoxical Arrhenius effect, where the hemolytic activity is inactivated by heating at 60 °C but is reactivated by additional heating above 80 °C. This study investigated individual or collective mutational effect of Tyr53, Thr59, and Ser63 positions of Gh-rTDH on hemolytic activity, Arrhenius effect, and biophysical properties. In contrast to the Gh-rTDH wild-type (Gh-rTDH(WT)) protein, a 2-fold decrease of hemolytic activity and alteration of Arrhenius effect could be detected from the Gh-rTDH(Y53H/T59I) and Gh-rTDH(T59I/S63T) double-mutants and the Gh-rTDH(Y53H/T59I/S63T) triple-mutant. Differential scanning calorimetry results showed that the Arrhenius effect-loss and -retaining mutants consistently exhibited higher and lower endothermic transition temperatures, respectively, than that of the Gh-rTDH(WT). Circular dichroism measurements of Gh-rTDH(WT) and Gh-rTDH(mut) showed a conspicuous change from a β-sheet to α-helix structure around the endothermic transition temperature. Consistent with the observation is the conformational change of the proteins from native globular form into fibrillar form, as determined by Congo red experiments and transmission electron microscopy.