Overproduction of mycotoxin biosynthetic enzymes triggers Fusarium toxisome-shaped structure formation via endoplasmic reticulum remodeling.

Mycotoxin deoxynivalenol (DON) produced by the Fusarium graminearum complex is highly toxic to animal and human health. During DON synthesis, the endoplasmic reticulum (ER) of F. graminearum is intensively reorganized, from thin reticular structure to thickened spherical and crescent structure, which was referred to as "DON toxisome". However, the underlying mechanism of how the ER is reorganized into toxisome remains unknown. In this study, we discovered that overproduction of ER-localized DON biosynthetic enzyme Tri4 or Tri1, or intrinsic ER-resident membrane proteins FgHmr1 and FgCnx was sufficient to induce toxisome-shaped structure (TSS) formation under non-toxin-inducing conditions. Moreover, heterologous overexpression of Tri1 and Tri4 proteins in non-DON-producing fungi F. oxysporum f. sp. lycopersici and F. fujikuroi also led to TSS formation. In addition, we found that the high osmolarity glycerol (HOG), but not the unfolded protein response (UPR) signaling pathway was involved in the assembly of ER into TSS. By using toxisome as a biomarker, we screened and identified a novel chemical which exhibited high inhibitory activity against toxisome formation and DON biosynthesis, and inhibited Fusarium growth species-specifically. Taken together, this study demonstrated that the essence of ER remodeling into toxisome structure is a response to the overproduction of ER-localized DON biosynthetic enzymes, providing a novel pathway for management of mycotoxin contamination.

Promising bifunctional chelators for copper 64-PET imaging: practical (64)Cu radiolabeling and high in vitro and in vivo complex stability.

Positron emission tomography (PET) using copper-64 is a sensitive and non-invasive imaging technique for diagnosis and staging of cancer. A bifunctional chelator that can present rapid radiolabeling kinetics and high complex stability with (64)Cu is a critical component for targeted PET imaging. Bifunctional chelates 3p-C-NE3TA, 3p-C-NOTA, and 3p-C-DE4TA were evaluated for complexation kinetics and stability with (64)Cu in vitro and in vivo. Hexadentate 3p-C-NOTA and heptadentate 3p-C-NE3TA possess a smaller TACN-based macrocyclic backbone, while nonadentate 3p-C-DE4TA is constructed on a larger CYCLEN-based ring. The frequently explored chelates of (64)Cu, octadentate C-DOTA and hexadentate C-NOTA were also comparatively evaluated. Radiolabeling kinetics of bifunctional chelators with (64)Cu was assessed under mild conditions. All bifunctional chelates instantly bound to (64)Cu in excellent radiolabeling efficiency at room temperature. C-DOTA was less efficient in binding (64)Cu than all other chelates. All (64)Cu-radiolabeled bifunctional chelates remained stable in human serum without any loss of (64)Cu for 2 days. When challenged by an excess amount of EDTA, (64)Cu complexes of C-NOTA, 3p-C-NE3TA and 3p-C-NOTA were shown to be more stable than (64)Cu-C-DOTA and (64)Cu-3p-C-DE4TA. (64)Cu complexes of the new chelates 3p-C-NE3TA and 3p-C-NOTA displayed comparable in vitro and in vivo complex stability to (64)Cu-C-NOTA. In vivo biodistribution result indicates that the (64)Cu-radiolabeled complexes of 3p-C-NOTA and 3p-C-NE3TA possess excellent in vivo complex stability, while (64)Cu-3p-C-DE4TA was dissociated as evidenced by high renal and liver retention in mice. The results of in vitro and in vivo studies suggest that the bifunctional chelates 3p-C-NE3TA and 3p-C-NOTA offer excellent chelation chemistry with (64)Cu for potential PET imaging applications.

Synthetic and theoretical investigation on the one-pot halogenation of ß-amino alcohols and nucleophilic ring opening of aziridinium ions.

Aziridinium ions are useful reactive intermediates for the synthesis of enantiomerically enriched building blocks. However, N,N-dialkyl aziridinium ions are relatively underutilized in the synthesis of optically active molecules as compared to other three-membered ring cogeners, aziridines and epoxides. The characterization of both optically active aziridinium ions and secondary ß-halo amines as the precursor molecules of aziridinium ions has been scarcely reported and is often unclear. In this paper, we report for the first time the preparation and experimental and theoretical characterization of optically active aziridinium ions and secondary ß-halo amines. Optically active secondary N,N-substituted ß-halo amines were efficiently synthesized from N,N-substituted alaninol via formation and ring opening at the more hindered carbon of aziridinium ions by halides. Optically active ß-halo amines and aziridinium ions were characterized by NMR and computational analyses. The structure of an optically active ß-chloro amine was confirmed via X-ray crystallographic analysis. The aziridinium ions derived from N,N-dibenzyl alaniol remained stable only for several hours, which was long enough for analyses of NMR and optical activity. The stereospecific ring opening of aziridinium ions by halides was computationally studied using DFT and highly-accurate DLPNO-CCSD(T) methods. The highly regioselective and stereoselective ring opening of aziridinium ions was applied for efficient one-pot conversion of ß-alaninols to enantiomerically enriched ß-amino alcohols, ß-amino nitriles, and vicinal diamine derivatives.

Novel (64)Cu-radiolabeled bile acid conjugates for targeted PET imaging.

A promising bifunctional chelate (N-NE3TA) was conjugated to bile acids, cholic acid (CA), deoxycholic acid (DCA), and chenodeoxycholic acid (CDCA) as tumor targeting vectors. Bile acid conjugates of N-NE3TA (CA-N-NE3TA, DCA-N-NE3TA, and CDCA-N-NE3TA) were comparatively evaluated for complexation with (64)Cu, an imaging probe for positron emission tomography (PET). N-NE3TA-bile acid conjugates were evaluated for radiolabeling kinetics with (64)Cu, and the corresponding (64)Cu-radiolabeled conjugates were screened for complex stability in human serum and EDTA solution. The NE3TA-bile acid conjugates instantly bound to (64)Cu with excellent radiolabeling efficiency at room temperature. All NE3TA-bile acid conjugates radiolabeled with (64)Cu remained inert in human serum for 2days without releasing a considerable amount of the radioactivity. The (64)Cu-radiolabeled complexes were further challenged by EDTA in a 100-fold molar excess. Bile acid-N-NE3TA conjugates radiolabeled with (64)Cu were quite stable with a minimal transfer of (64)Cu to EDTA at 4h time point. The in vitro data indicate that the bile acid-N-NE3TA conjugates deserve further biological evaluation for (64)Cu-based targeted PET imaging applications.

Synthesis and comparative biological evaluation of bifunctional ligands for radiotherapy applications of (90)Y and (177)Lu.

Zevalin® is an antibody-drug conjugate radiolabeled with a cytotoxic radioisotope ((90)Y) that was approved for radioimmunotherapy (RIT) of B-cell non-Hodgkin's lymphoma. A bifunctional ligand that displays favorable complexation kinetics and in vivo stability is required for effective RIT. New bifunctional ligands 3p-C-DE4TA and 3p-C-NE3TA for potential use in RIT were efficiently prepared by the synthetic route based on regiospecific ring opening of aziridinium ions with prealkylated triaza- or tetraaza-backboned macrocycles. The new bifunctional ligands 3p-C-DE4TA and 3p-C-NE3TA along with the known bimodal ligands 3p-C-NETA and 3p-C-DEPA were comparatively evaluated for potential use in targeted radiotherapy using ß-emitting radionuclides (90)Y and (177)Lu. The bifunctional ligands were evaluated for radiolabeling kinetics with (90)Y and (177)Lu, and the corresponding (90)Y or (177)Lu-radiolabeled complexes were studied for in vitro stability in human serum and in vivo biodistribution in mice. The results of the comparative complexation kinetic and stability studies indicate that size of macrocyclic cavity, ligand denticity, and bimodality of donor groups have a substantial impact on complexation of the bifunctional ligands with the radiolanthanides. The new promising bifunctional chelates in the DE4TA and NE3TA series were rapid in binding (90)Y and (177)Lu, and the corresponding (90)Y- and (177)Lu-radiolabeled complexes remained inert in human serum or in mice. The in vitro and in vivo data show that 3p-C-DE4TA and 3p-C-NE3TA are promising bifunctional ligands for targeted radiotherapy applications of (90)Y and (177)Lu.

Transition-metal-catalyzed C-H bond functionalizations: feasible access to a diversity-oriented ß-carboline library.

Diversification of the ß-carboline skeleton has been demonstrated to assemble a ß-carboline library starting from the tetrahydro-ß-carboline framework. This strategy affords feasible access to heteroaryl-, aryl-, alkenyl-, or alkynyl-substituted ß-carbolines at the C1, C3, or C8 position through three categorically different types of transition-metal-catalyzed CC bond-forming reactions, in the presence of multiple potentially reactive positions. These site-selective functionalizations include; 1) the Cu-catalyzed C1/C3-selective decarboxylative C sp 3C sp 2 and C sp 3Csp coupling of hexahydro-ß-carboline-3-carboxylic acid with a CH bond of a heteroarene or terminal alkyne; 2) the chelation-assisted Pd-catalyzed C1/C8-selective CH arylation of hexahydro-ß-carboline with aryl boron reagents; and 3) the chelation-assisted Pd-catalyzed C1/C3-selective oxidative CH/CH cross-coupling of ß-carboline-N-oxide with arenes, heteroarenes, or alkenes. The saturated structural feature of the hexahydro-ß-carboline framework can increase reactivity and control site selectivity. The robustness of these approaches has been demonstrated through the synthesis of hyrtioerectine analogues and perlolyrine. We believe that these strategies could provide inspiration for late-stage diversifications of bioactive core scaffolds.

Palladium-catalyzed tandem N-H/C-H arylation: regioselective synthesis of N-heterocycle-fused phenanthridines as versatile blue-emitting luminophores.

A general and highly regioselective synthetic protocol for structurally diverse N-heteroaryl-fused phenanthridines has been developed. Varieties of fluorescence molecules comprising imidazole-fused, benzoimidazole-fused, indole-fused and pyrrole-fused phenanthridines were obtained by this modular approach, some of which exhibit excellent blue-emitting performance, high quantum yields, long fluorescence lifetimes, interesting electrochemical properties, and thermal stabilities.

Rhodium or ruthenium-catalyzed oxidative C-H/C-H cross-coupling: direct access to extended π-conjugated systems.

Doubling up: a chemo- and regioselective oxidative cross-coupling between various N-heteroarene-containing arenes and heteroarenes has been carried out by rhodium- or ruthenium-catalyzed twofold C-H activation, to deliver an array of highly functionalized π-conjugated systems.

Design, Synthesis, and Pesticidal Activities of Pyrimidin-4-amine Derivatives Bearing a 5-(Trifluoromethyl)-1,2,4-oxadiazole Moiety.

It is important to discover new pesticides with new modes of action because of the increasing evolution of pesticide resistance. In this study, a series of novel pyrimidin-4-amine derivatives containing a 5-(trifluoromethyl)-1,2,4-oxadiazole moiety were designed and synthesized. Their structures were confirmed by 1H NMR, 13C NMR, and HRMS. Bioassays indicated that the 29 compounds synthesized possessed excellent insecticidal activity against Mythimna separata, Aphis medicagini, and Tetranychus cinnabarinus and fungicidal activity against Pseudoperonospora cubensis. Among these pyrimidin-4-amine compounds, 5-chloro-N-(2-fluoro-4-(5-(trifluoromethyl)-1,2,4-oxadiazol-3-yl)benzyl)-6-(1-fluoroethyl)pyrimidin-4-amine (U7) and 5-bromo-N-(2-fluoro-4-(5-(trifluoromethyl)-1,2,4-oxadiazol-3-yl)benzyl)-6-(1-fluoroethyl) pyrimidin-4-amine(U8) had broad-spectrum insecticidal and fungicidal activity. The LC50 values were 3.57 ± 0.42, 4.22 ± 0.47, and 3.14 ± 0.73 mg/L for U7, U8, and flufenerim against M. separata, respectively. The EC50 values were 24.94 ± 2.13, 30.79 ± 2.21, and 3.18 ± 0.21 mg/L for U7, U8, and azoxystrobin against P. cubensis, respectively. The AChE enzymatic activity testing revealed that the enzyme activities of compounds U7, U8, and flufenerim are 0.215, 0.184, and 0.184 U/mg prot, respectively. The molecular docking results of compounds U7, U8, and flufenerim with the AChE model demonstrated the opposite docking mode between compound U7 or U8 and positive control flufenerim in the active site of AChE. The structure-activity relationships are also discussed. This work provided excellent pesticide for further optimization. Density functional theory analysis can potentially be used to design more active compounds.

Discovery of a species-specific novel antifungal compound against Fusarium graminearum through an integrated molecular modeling strategy.

BACKGROUND: The cyanoacrylate fungicide phenamacril targeting fungal myosin I has been widely used for controlling Fusarium head blight (FHB) of wheat caused by the pathogenic fungus Fusarium graminearum worldwide. Therefore, there is great interest in the discovery and development of novel FgMyo1 inhibitors through structure-based drug design for the treatment of FHB. RESULTS: In this study, the binding mechanism of phenamacril with FgMyo1 was predicted by an integrated molecular modeling strategy. The predicted key phenamacril-binding residues of FgMyo1 were further experimentally validated by point mutagenesis and phenamacril sensitivity assessment. Four novel key residues responsible for phenamacril binding were identified, highlighting the reliability of the theoretical predictions. The subsequent optimization of phenamacril derivatives led to the discovery of a novel compound (10) which shows better activity than phenamacril against conidial germination of F. graminearum, but not against other fungal species. Moreover, 10 also inhibits conidial germination of phenamacril-resistant strains effectively. Further experiments illustrated that application of 10 could dramatically inhibit deoxynivalenol biosynthesis. CONCLUSION: Overall, our results further optimize and develop the binding model of phenamacril-myosin I. Furthermore, 10 was found and has the potential to be developed as a species-specific fungicide for management of FHB. © 2020 Society of Chemical Industry.

Preferential formation of homochiral helical sandwich-shaped architectures through the metal-mediated assembly of tris(imidazoline) ligands with a set of d(3)-d(10) transition-metal ions.

A novel type of chiral tris-monodentate imidazolinyl ligands ((S,S,S)-4 and (R,R,R)-4) has been achieved in good yields. The ligands show a strong tendency to induce the generation of the discrete sandwich-shaped M(3)L(2) architectures with programmed helicity through the edge-directed complexation with a series of d(3)-d(10) transition-metal ions, while taking advantage of the steric hindrance of the bulky substituents of the imidazoline rings to avoid the formation of extended metal-organic frameworks (MOFs). In spite of different coordination geometries, monovalent metal ions (e.g. Ag(+)), divalent metal ions (e.g. Pd(2+), Cu(2+), Cd(2+), Zn(2+), Co(2+), Mn(2+), and Ni(2+)), and even trivalent metal ions (e.g. Fe(3+) and Cr(3+)) exhibit isostructural coordination. Installation of stereocenters fused onto the imidazoline rings results in favored handedness of the self-assemblies through the expression of molecular chirality into supramolecular helicity. In the crystal structures of [M(3){(S,S,S)-4}(2)], the self-assembly has to adopt the M form to relax the van der Waals repulsions of the phenyl and isopropyl groups. The replacement of (S,S,S)-4 with (R,R,R)-4 exclusively affords the opposite helicity (P). These results should provide important insights for the design of chiral helical capsule-like assemblies.

Design, Synthesis, and Biological Evaluation of Polyaminocarboxylate Ligand-Based Theranostic Conjugates for Antibody-Targeted Cancer Therapy and Near-Infrared Optical Imaging.

We report the design, synthesis, and evaluation of polyaminocarboxylate ligand-based antibody conjugates for potential application in targeted cancer therapy and near-infrared (NIR) fluorescence imaging. We synthesized a new polyaminocarboxylate chelate (CAB-NE3TA) as a potential anticancer agent. CAB-NE3TA displayed potent inhibitory activities against various cancer cell lines. We then designed a multifunctional theranostic platform (CAB-NE3TA-PAN-IR800) constructed on an epidermal growth factor receptor (EGFR)-targeted antibody (panitumumab, PAN) labeled with a NIR fluorescent dye. We also built the first atomistic model of the EGFR-PAN complex and loaded it with the cytotoxic CAB-NE3TA and the NIR dye. The therapeutic (CAB-NE3TA-PAN) and theranostic (CAB-NE3TA-PAN-IR800) conjugates were evaluated using an EGFR-positive A431 (human skin cancer) cell xenograft mouse model. Biodistribution studies using NIR fluorescence imaging demonstrated that the CAB-NE3TA-PAN labeled with the IR800 dye selectively targeted the A431 tumors in mice and resulted in prolonged retention in the tumor tissue and displayed excellent clearance in blood and normal organs. The therapeutic conjugate was capable of significantly inhibiting tumor growth, leading to nearly complete disappearance of tumors in the mice. The results of our pilot in vivo studies support further evaluation of the novel ligand-based therapeutic and theranostic conjugates for targeted iron chelation cancer therapy and imaging applications.

Suppression of Winfree turbulence under weak spatiotemporal perturbation.

Winfree turbulence is a chaotic wave pattern developing through negative-tension instability of scroll wave filaments in three-dimensional weak excitable media. Here, we investigate the response of Winfree turbulence to a spatiotemporal forcing in the form of a traveling-wave modulation of the medium excitability. It is shown that turbulent waves can be suppressed much more rapidly by this method, in comparison with the space-uniform modulation of the medium excitability. Since the occurrence of Winfree turbulence is currently regarded as one of the possible mechanisms underlying cardiac fibrillation, this method turns out to be suggestive of a possible low-amplitude defibrillation approach.

Transferrin conjugates of triazacyclononane-based bifunctional NE3TA chelates for PET imaging: Synthesis, Cu-64 radiolabeling, and in vitro and in vivo evaluation.

Three different polyaminocarboxylate-based bifunctional NE3TA (7-[2-[carboxymethyl)amino]ethyl]-1,4,7-triazacyclononane-1,4-diacetic acid) chelating agents were synthesized for potential use in copper 64-PET imaging applications. The bifunctional chelates were comparatively evaluated using transferrin (Tf) as a model targeting vector that binds to the transferrin receptor overexpressed in many different cancer cells. The transferrin conjugates of the NE3TA-based bifunctional chelates were evaluated for radiolabeling with (64)Cu. In vitro stability and cellular uptake of (64)Cu-radiolabeled conjugates were evaluated in human serum and prostate (PC-3) cancer cells, respectively. Among the three NE3TA-Tf conjugates tested, N-NE3TA-Tf was identified as the best conjugate for radiolabeling with (64)Cu. N-NE3TA-Tf rapidly bound to (64)Cu (>98% radiolabeling efficiency, 1min, RT), and (64)Cu-N-NE3TA-Tf remained stable in human serum for 2days and demonstrated high uptake in PC-3 cancer cells. (64)Cu-N-NE3TA-Tf was shown to have rapid blood clearance and increasing tumor uptake in PC-3 tumor bearing mice over a 24h period. This bifunctional chelate presents highly efficient chelation chemistry with (64)Cu under mild condition that can be applied for radiolabeling of various tumor-specific biomolecules with (64)Cu for potential use in PET imaging applications.

Application of aziridinium ring opening for preparation of optically active diamine and triamine analogues: Highly efficient synthesis and evaluation of DTPA-based MRI contrast enhancement agents.

Ring opening of aziridinium ions with nitrogen nucleophiles was applied to the highly efficient synthesis of optically active vicinal diamines and diethylene triamine pentaacetic acid (DTPA) analogues as potential magnetic resonance imaging (MRI) contrast enhancement agents. The synthetic method features a column-free isolation of the regiospecific and stereospecific nucleophilic substitution products of enantiomerically enriched aziridinium ions in excellent yield.

A sensitive colorimetric and fluorescent sensor based on imidazolium-functionalized squaraines for the detection of GTP and alkaline phosphatase in aqueous solution.

Imidazolium-functionalized squaraine ImSQ8 is synthesized as a sensitive colorimetric and fluorescent chemosensor for GTP in aqueous solution. The detection limit of GTP reaches 5.4 ppb. Its applications in the live-cell imaging and enzyme activity assay have also been demonstrated.

Radical cascade cyanomethylation of activated alkenes to construct cyano substituted oxindoles.

The cyanomethyl radical was easily generated from acetonitrile by using DTBP, which was applied to a cascade alkene addition and cyclization reaction to construct useful oxindole derivatives. This protocol features simple manipulation, cheap reagents and a broad substrate scope. In addition, nitro substituted oxindoles were also synthesized for the first time.

Dehydrogenative Heck coupling of biologically relevant N-heteroarenes with alkenes: discovery of fluorescent core frameworks.

A Pd/Cu-catalyzed dehydrogenative Heck coupling is established that allows direct alkenylation of various biologically relevant N-heteroarenes with alkenes. The resulting π-extended alkenylated N-heteroarenes exhibit interesting fluorescent properties and have proven to be potentially useful fluorescent probes for bioimaging.