Compared with traditional structure-based approaches for the identification of species-specific ligands, the ab initio approach, based on large-scale protein sequences from different species, has been used to locate specific sites that may be important to the molecular selectivity of species. Statistically significant differences in the distribution of residues in different species and differences in the physicochemical properties of residue-specific sites may largely account for species selectivity. The nicotinic acetylcholine receptor (nAChR), an important neuro-receptor with significantly different ligand selectivity in different species, was used to test our method. Because of the lack of nAChR structural information, the mechanism of ligand discrimination is unclear which hinders attempts at novel molecular design. In this study, the specific site residues 186 and 189 in the principal subunits and residues 34, 55, 56, 57, 106 and 112 in complementary subunits of nAChR were identified by applying our method with stringent statistical cutoffs. These sites were predicted to contribute to ligand selectivity and this result coincides well with the known experimental data.
The crystal structure of the new title compound 3-（4-chlorophenyl）-8-cyano-2-（di-iso-propylamino）-5-methyl-7-（methylthio）-pyrido[4,3-d]pyrimidine-4（3H）-one（C22H24ClN5OS,Mr = 441.97）has been determined by single-crystal X-ray diffraction. The crystal is of orthorhombic,space group Pna21 with a = 7.6721（5）,b = 18.9370（11）,c = 15.6260（9）A,V = 2270.2（2）A^3,Z = 4,Dc = 1.293 g/cm^3,F（000）= 928,μ = 0.283 mm^-1,MoKa radiation（λ = 0.71073 A）,R = 0.0494 and wR = 0.1062 for 3278 observed reflections with I 〉 2σ（I）. X-ray diffraction analysis reveals that all ring atoms in the py-ridopyrimidinone moiety are almost coplanar. Intramolecular C（20）-H（20）···N（4）,C（19）-H（19A）···N（3）,C（18）-H（18C）···N（3）and C（16）-H（16B）···O（5）hydrogen bonds together with weak C···π interactions are found in the structure.
Started from salicylic acid（SA） and related commercialized plant activators,based on molecular threedimensional shape and pharmacophore similarity comparison（SHAFTS）,a new lead compound benzotriazole was predicted and a series of benzotriazole derivatives were designed and synthesized.The bioassay showed that benzotriazole had high activity against a broad spectrum of diseases including fungi and oomycetes in vivo,but no activity in vitro.And the introduction of proper groups at the1＇-position and 5＇-position was beneficial to the activity.So,they had the potential to be exploited as novel plant activators.
The 1,2,3-thiadiazole-carboxylate moiety was reported to be an important pharmacophore of plant activators.In this study,a series of novel plant activators based on thieno[2,3-d]-1,2,3-thiadiazole-6-carboxylate were designed and synthesized and their biological activity as plant activators was studied.The structures of the novel compounds were identifed by1H NMR,19F NMR and HRMS.The in vivo bioassay showed that these novel compounds had good effcacy against seven plant diseases.Especially,compounds 1a and 1c were more potent than the commercialized plant activator BTH.Almost no fungicidal activity was observed for the active compounds in the in vitro assay,which matched the requirements as plant activators.
A new crystal of 4-fluoro-N-（2-methyl-5-（（2-（p-tolyloxy）acetamido）methyl）pyrimi- din-4-yl）benzamide has been prepared at room temperature and characterized by 1H NMR, 13C- NMR, IR, MS, elemental analysis and X-ray single-crystal determination. The compound crystallizes in monoclinic, space group P21 /c with a = 17.226（5）, b = 13.934（4）, c = 17.262（5）, μ= 92.180（5）°, V = 4140（2） ？3, Dc = 1.311 g/cm3, Z = 8, F（000） = 1712 and ？？= 0.095 mm-1. The molecular packing in the crystal is the result of N-H…ydrogen bonds.
Silver nanoparticles （AgNPs） are one of the most widely used nanomaterials, but the mechanism of AgNP toxicity in terrestrial plants is still unclear. We compared the toxic effects of AgNPs and Ag＋ on Arabidopsis thaliana at the physiological, ultrastructural and molecular levels. AgNPs did not affect seed germination; however, they showed stronger inhibitory effect on root elongation than Ag＋ . The results of transmission electron microscopy and metal content analysis showed that AgNPs could be accumulated in leaves. These absorbed AgNPs disrupted the thylakoid membrane structure and decreased chlorophyll content, which can inhibit plant growth. By comparison, a small amount of Ag＋ was absorbed by seedlings, and it did not pronouncedly affect chloroplast structure and other metal ion absorption as AgNPs did. Compared with Ag＋ , AgNPs could alter the transcription of antioxidant and aquaporin genes, indicating that AgNPs changed the balance between the oxidant and antioxidant systems, and also affected the homeostasis of water and other small molecules within the plant body. All the data from physiological, ultrastructural and molecular levels suggest that AgNPs were more toxic than Ag＋ .
Haifeng QianXiaofeng PengXiao HanJie RenLiwei SunZhengwei Fu
