Effect of size and shape controlled biogenic synthesis of gold nanoparticles and their mode of interactions against food borne bacterial pathogens

In this study, size and shape controlled biogenic synthesis of gold nanoparticles and their antibacterial activity against food borne bacterial pathogens were investigated. Synthesis of gold nanoparticles was carried out using two medicinally important plants Cucurbita pepo and Malva crispa and the size and shape of the nanoparticles were controlled by altering various parameters in the reaction medium. Results obtained from UV–Vis, FE-SEM, EDS and HR-TEM analyses supported the nanoparticles formation. FT-IR analysis confirmed the presence of biomolecules in the plant leaves extracts responsible for reducing and capping agents. Interestingly, the plant extract synthesized gold nanoparticles showed effective inhibition zone against Gram-positive and Gram-negative pathogens. The minimum inhibitory concentration (MIC) of synthesized gold nanoparticles at 400 μg/ml concentration showed effective inhibitory activity against Escherichia coli and Listeria monocytogenes. Conductivity of the medium continuously increased during the nanoparticles treatment with food borne bacterial pathogens resulting in indirect indication of the disruption of bacterial cell membranes. In addition, mode of interactions of gold nanoparticles against food borne bacterial pathogens was demonstrated using Bio-TEM analysis which is clear evident for the disruption of bacterial cell membranes.     

Parallel Breakup of Polymer Drops under Simple Shear

The deformation and breakup of a single polycarbonate drop in a polyethylene matrix is studied at high temperatures under simple shear flow using a transparent Couette device. We observed “parallel breakup” where the drop breaks after being stretched into a thin sheet parallel to the flow. The breakup occurs at a viscosity ratio greater than 3.5. Deborah number and a stress ratio incorporating elastic moduli can characterize the “parallel breakup”.

Deformation and breakup of a polycarbonate drop in a polyethylene matrix.     

Synthesis,spectroscopic studies,and antibacterial activities of 14-membered tetraazamacrocyclic complexes of divalent transition metal ions

A new series of macrocyclic complexes, [M(C₄₈H₃₂N₄)X₂], where M?=?Co(II),?Ni(II),?Cu(II), and Zn(II); X?=?Cl^?,?NO₃ ^?,?CH₃COO^?, have been synthesized by condensation of 1,8-diaminonaphthalene and benzil, in the presence of divalent metal salts in methanolic medium. The complexes have been characterized by elemental analyses, conductance measurements, magnetic measurements, and electronic, NMR, IR, and MS spectral studies. The low value of molar conductance indicates the presence of non-electrolytes. A distorted octahedral geometry is proposed for the complexes. The metal complexes were also tested for their in vitro antibacterial activities against some bacterial strains and compared with the standard antibiotic Ciprofloxacin. Some tested complexes show good antibacterial activities against some bacterial strains.     

Synthesis,spectroscopic characterization,and antibacterial assays in vitro of a new platinum(II) complex with methionine sulfoxide

A new platinum(II) complex with methionine sulfoxide was synthesized and characterized by chemical and spectroscopic techniques. Elemental analyses, mass spectrometric measurements (electrospray ionization quadrupole time-of-flight mass spectrometry), and thermal analyses of the solid compound fit the composition [(C₅H₁₀NO₃S)Pt(µ-Cl)₂Pt(C₅H₁₀NO₃S)]?·?2.5H₂O. Infrared spectroscopic data indicate coordination of the ligand to Pt(II) through the nitrogen of NH₂ and the sulfur of the S=O group. ¹H-¹⁵N nuclear magnetic resonance spectroscopic data confirm nitrogen coordination. Antibacterial activities were evaluated by antibiogram assays using the disc diffusion method. The platinum(II) complex showed antibacterial activity against Gram-negative Pseudomonas aeruginosa bacterial cells.     

Synthesis and antibacterial activity of cephradine metal complexes

Cephradine (Hcephra) interacts with transition metal ions to give [Fe(cephra)Cl₂] and [M(cephra)Cl] complexes (M?=?Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)) which were characterized by physicochemical and spectroscopic methods; a tetrahedral geometry is suggested for their structures where cephradine behaves as monoanionic tridentate ligand. The complexes have been screened for antibacterial activity against several bacteria, and the results showed that all metal complexes tested had lower antibiotic activity than the free ligand.     

Synthesis and antibacterial activity of some novel thieno[2,3-c]pyridazines using 3-amino-5-phenyl-2-ethoxycarbonylthieno[2,3-c]pyridazine as a starting material

3-Amino-5-phenyl-2-ethoxycarbonylthieno[2,3-c]pyridazine (6) was prepared by reaction of 4-cyano-6-phenylpyridazine-3(2H)-thione (4) with ethyl chloroacetate in the presence of sodium ethoxide. Hydrazinolysis of compound 6 yielded the corresponding carbohydrazide, (9) which on treatment with acetylacetone and ethyl acetoacetate produced the novel thieno[2,3-c]pyridazines (10 and 11). Treatment of compound 9 with nitrous acid yielded the corresponding carboazide (13), which upon boiling in toluene furnished imidazo[4′,5′:4,5]thieno[2,3-c]pyridazine (15). Pyrimidothienopyridazines (16–18) were achieved by cyclocondensation of compound 9 with some reagents, namely acetic anhydride, formic acid, and triethyl orthoformate. The newly synthesized compounds were confirmed by elemental analyses and spectral data. The antibacterial activities of the new compounds were also evaluated.     

New borrelidin derivatives from an endophytic Streptomyces sp.

Three new borrelidin-type macrolactones, designated as borrelidins J?L (4–6), together with borrelidin A (1), borrelidin E (2), and 12-desnitrile-12-carboxyl-borrelidin (3) were isolated from a plant endophytic Streptomyces sp. NA06554. Their structures were determined by extensive spectroscopic analysis including HRESIMS, 1D and 2D NMR data. The antibacterial activities for compounds 1–6 were examined. Borrelidins A (1) and L (6) showed potent and moderate antibacterial activity against Micrococcus luteus, respectively, whereas other derivatives (2–5) are almost inactive, which allows us to propose a plausible structure-activity relationship.     

Effect of sunlight on the preparation and properties of cellulose/silver nanoparticle composite films by in situ method using Ocimum sanctum leaf extract as a reducing agent

Cellulose/silver nanoparticle composite films with in situ-generated silver nanoparticles (AgNPs) were prepared using Ocimum sanctum leaf extract as a reducing agent in the absence and presence of sunlight and were characterized by SEM, FTIR, XRD, and antibacterial tests. Sunlight hastened up the preparation of these composite films. The average size of the in situ-generated AgNPs was reduced by the sunlight. The antibacterial activity and other properties of the composites were enhanced by the sunlight. The cellulose/AgNP composite films with improved properties by sunlight can be considered for medical purpose as antibacterial dressing materials.     

概念图在化学教学中应用的中外研究对比——基于CiteSpace的知识图谱可视化分析

以CiteSpace为工具,对2009-2018年10年间概念图在化学教学中应用的中外研究文献进行可视化的对比分析.研究表明:与国外研究相比,在应用范围上,国内缺少概念图在大学化学教学中应用的相关研究;在研究内容上,国内学者应加强概念图培养学生高阶思维能力及创造力的研究;从评估方式看,国内较少采用定性和定量相结合的评估...