Shangzhong Liu

Functional analysis of a point mutation in the ryanodine receptor of Plutella xylostella (L.) associated with resistance to chlorantraniliprole.

BACKGROUND The diamondback moth, Plutella xylostella (L.) has developed extremely high resistance to chlorantraniliprole and other diamide insecticides in the field. A glycine to glutamic acid substitution (G4946E) in the P. xylostella ryanodine receptor (PxRyR) has been found in two resistant populations collected in Thailand and Philippines and was considered associated with the diamide insecticides resistance but no experimental evidence was provided. The present study aimed to clarify the function of the reported mutation in chlorantraniliprole resistance in P. xylostella. RESULTS We identified the same mutation (G4946E) in PxRyR from four field collected chlorantraniliprole resistant populations of Plutella xylostella in China. Most importantly, we found that the frequency of the G4946E mutation is significantly correlated to the chlorantraniliprole resistance ratios in P. xylostella (R(2)  = 0.82, P = 0.0003). Ligand binding assays showed that the binding affinities of the PxRyR to the chlorantraniliprole in three field resistant populations were 2.41-, 2.54- and 2.60-times lower than that in the susceptible one. CONCLUSION For the first time we experimentally proved that the G4946E mutation in PxRyR confers resistance to chlorantraniliprole in Plutella xylostella. These findings pave the way for the complete understanding of the mechanisms of diamide insecticides resistance in insects.

Impact of Halogen Substituents on Interactions between 2-Phenyl-2,3-dihydroqulinazolin-4(1H)-one Derivatives and Human Serum Albumin

A novel type of 2-(un)substituted phenyl-2,3-dihydroquinazolin-4(1H)-one (DQL) derivatives were designed and synthesized to study the impact of halogen substituents on interactions between DQL and human serum albumin (HSA) by comparison methodology. The interactions between DQL and HSA were studied by fluorescence spectroscopy. The intrinsic fluorescence of human serum albumin was quenched by DQL through a static quenching mechanism. Site marker competitive experiments showed that DQL bound to HSA in site II (subdomain IIIA). The binding constants, the numbers of binding sites and the thermodynamic parameters were measured too. The results indicated that the interactions were spontaneous, mainly through hydrophobic forces, and the substitution by halogen atoms in the benzene ring could increase the interactions between DQL and HSA. Furthermore, the binding affinity was enhanced gradually with the increasing of halogen atomic number.

Comparative Studies of Interactions between Fluorodihydroquinazolin Derivatives and Human Serum Albumin with Fluorescence Spectroscopy

In the present study, 3-(fluorobenzylideneamino)-6-chloro-1-(3,3-dimethylbutanoyl)-phenyl-2,3-dihydroquinazolin-4(1H)-one (FDQL) derivatives have been designed and synthesized to study the interaction between fluorine substituted dihydroquinazoline derivatives with human serum albumin (HSA) using fluorescence, circular dichroism and Fourier transform infrared spectroscopy. The results indicated that the FDQL could bind to HSA, induce conformation and the secondary structure changes of HSA, and quench the intrinsic fluorescence of HSA through a static quenching mechanism. The thermodynamic parameters, ΔH, ΔS, and ΔG, calculated at different temperatures, revealed that the binding was through spontaneous and hydrophobic forces and thus played major roles in the association. Based on the number of binding sites, it was considered that one molecule of FDQL could bind to a single site of HSA. Site marker competition experiments indicated that the reactive site of HSA to FDQL mainly located in site II (subdomain IIIA). The substitution by fluorine in the benzene ring could increase the interactions between FDQL and HSA to some extent in the proper temperature range through hydrophobic effect, and the substitution at meta-position enhanced the affinity greater than that at para- and ortho-positions.

A One-Pot Approach to Pyridyl Isothiocyanates from Amines

A one-pot preparation of pyridyl isothiocyanates (ITCs) from their corresponding amines has been developed. This method involves aqueous iron(III) chloride-mediated desulfurization of a dithiocarbamate salt that is generated in situ by treatment of an amine with carbon disulfide in the present of DABCO or sodium hydride. The choice of base is of decisive importance for the formation of the dithiocarbamate salts. This one-pot process works well for a wide range of pyridyl ITCs. Utilizing this protocol, some highly electron-deficient pyridyl and aryl ITCs are obtained in moderate to good yields.

Fluorescent Probes for Insect Ryanodine Receptors: Candidate Anthranilic Diamides

Diamide insecticides with high efficacy against pests and good environmental safety are broadly applied in crop protection. They act at a poorly-defined site in the very complex ryanodine (Ry) receptor (RyR) potentially accessible to a fluorescent probe. Two N-propynyl analogs of the major anthranilic diamide insecticides chlorantraniliprole (Chlo) and cyantraniliprole (Cyan) were accordingly synthesized and converted into two fluorescent ligands by click reaction coupling with 3-azido-7-hydroxy-2H-chromen-2-one. The new diamide analogs and fluorescent ligands were shown to be nearly as potent as Chlo and Cyan in inhibition of [3H]Chlo binding and stimulation of [3H]Ry binding in house fly thoracic muscle RyR. Although the newly synthesized compounds had only moderate activity in insect larvicidal activity assays, their high in vitro potency in a validated insect RyR binding assay encourages further development of fluorescent probes for insect RyRs.

Synthesis of Chrysogeside B from Halotolerant Fungus Penicillium and Its Antimicrobial Activities Evaluation

Chrysogeside B, a natural cerebroside, was efficiently synthesized from commercial feedstocks. The bioassays showed that compounds 4, 5 and 6 exhibited enhanced biological activities compared Chrysogeside B. Further studies revealed that free hydroxyl groups and glycosidic bond have significant impact on the antimicrobial activities. The synthesis of Chrysogeside B and analogues designed to allow identification of the features of this glycolipid required for recognition by tested bacteria and Hela cells is described.

Affinity-based fluorescence polarization assay for screening molecules acting on insect ryanodine receptors

Insect ryanodine receptors constitute calcium ion channels, and are the target of novel diamide insecticides containing two types of phthalic and anthranilic diamides. Ryanodine receptors in Periplaneta americana leg muscle were extracted through homogenization and centrifugation. Based on the potential usefulness of a fluorescent probe identified in a previous study, a fluorescence polarization assay was developed with extracted Periplaneta ryanodine receptors, and this technique was used to test the affinity binding of two types of active diamide compounds. Results showed that anthranilic diamides could replace the binding of the fluorescent probe on the ryanodine receptor, but phthalic analogs, including flubendiamide, did not affect the binding of fluorescent probe. Therefore, the developed fluorescence polarization (FP) assay is an easier and more efficient technique to study the affinity binding of small molecules on fluorescent probe binding sites on ryanodine receptors than the [3H] labeled-based assay.

Synthesis and Herbicidal Activity ofN-(4-Chloro-2-fluoro-5- substituted phenyl)isoindole-1,3-dione Derivatives

为了发现新的农药先导化合物,以氯酰亚酞和苯氧羧酸酯结构为基础,通过活性亚结构拼接方法,设计合成了一系列新型的N-（2-氟-4氯-5-取代苯基）异吲哚-1,3-二酮衍生物6a~6f和7a~7k.目标化合物以2-氯-4-氟-5-硝基苯酚为原料,经4步反应制得,其结构经过1H NMR,13C NMR,HRMS确证.初步生物活性测试结果表明,大部分化合物在1500 g/ha剂量下,对双子叶杂草苘麻、反枝苋具有优异的芽前芽后除草活性.进一步活性筛选发现,化合物6d在750g/ha剂量下对苘麻、反枝苋具有100%抑制活性,化合物7a,7i在22.5 g/ha剂量下对苘麻的芽后抑制率大于80%,远高于对照药剂三氟羧草醚.