Effect of silver nanowires on the surface-enhanced Raman spectra (SERS) of the RNA bases

RNA bases have a great importance in the biological and genetics applications. The surface-enhanced Raman scattering (SERS) was used to study the orientation and adsorption structure of RNA bases adsorbed on the surface of silver nanowires (Ag NWs). The Ag NWs were prepared and its UV-vis spectra were recorded. The RNA bases oriented perpendicularly on the surface of Ag NWs, as the coverage area decreases. Consequently, the in-plane bands were enhanced according to the SERS selection rule. Many bands were red shifted due to the chemisorption of RNA bases on the Ag NWs surface. New bands corresponding to the base-surface bond were appeared in the SERS spectra.     

Preferential Lectin Binding of Cancer Cells upon Sialic Acid Treatment Under Nutrient Deprivation

The terminal monosaccharide of glycoconjugates on a eukaryotic cell surface is typically a sialic acid (Neu5Ac). Increased sialylation usually indicates progression and poor prognosis of most carcinomas. Here, we utilize two human mammary epithelial cell lines, HB4A (breast normal cells) and T47D (breast cancer cells), as a model system to demonstrate differential surface glycans when treated with sialic acid under nutrient deprivation. Under a starved condition, sialic acid treatment of both cells resulted in increased activities of α2→3/6 sialyltransferases as demonstrated by solid phase assay using lectin binding. However, a very strong Maackia amurensis agglutinin I (MAL-I) staining on the membrane of sialic acid-treated T47D cells was observed, indicating an increase of Neu5Acα2→3Gal on the cell surface. To our knowledge, this is a first report showing the utility of lectins, particularly MAL-I, as a means to discriminate between normal and cancer cells after sialic acid treatment under nutrient deprivation. This method is sensitive and allows selective detection of glycan sialylation on a cancer cell surface.     

Conversion efficiency of the high-temperature combustion technique for dissolved organic carbon and total dissolved nitrogen analysis

The measurements of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) in seawater are key in global change and coastal eutrophication studies. Nowadays, the high-temperature combustion (HTC) technique is a widely used method for DOC and TDN analysis. However, uncertainties exist about the operation of the catalyst in the conversion process of DOC and TDN in the HTC method. In this study, five different ‘catalyst’ materials were tested for their blanks, calibration slopes, and conversion efficiency of DOC and TDN using the Shimadzu TOC 5000A total organic carbon analyser coupled to a Sievers NCD 255 nitrogen chemiluminescence detector. The materials included four metallic catalysts (Shimadzu and Johnson 0.5% Pt–alumina, 13% Cu(II)O–alumina, 0.5% Pd–alumina) and quartz beads. The results indicated that DOC blank signals for the HTC approach using metallic catalysts with an alumina support are higher compared with quartz beads, as a result of the amphoteric nature of the alumina. However, the slopes of the standard calibration graphs were lowest for DOC and TDN determinations on the quartz beads. The DOC recoveries for the metallic catalysts were close to 100% for all compounds tested, with the exception of ammonium pyrrolidine dithiocarbamate. Using quartz beads, poor recoveries were obtained for a range of organic compounds, including the commonly used calibration compounds potassium hydrogen phthalate and glycine. The TDN recoveries for all compounds were typically >90%, with the exception of NaNO₂. Furthermore, analysis using the CuO–alumina and Pd–alumina catalysts and quartz beads showed low recoveries for NH₄Cl. This study showed that catalyst performance should be verified on a regular basis using model compounds and blank checks made during every run, and that the Shimadzu 0.5% Pt–alumina material was an efficient catalyst for DOC and TDN analyses using the coupled total organic carbon–nitrogen chemiluminescence detector (TOC-NCD) analyser.     

Synthesis of Some New Fused and Binary 1,3,4‐Thiadiazoles as Potential Antitumor and Antioxidant Agents

Annulations of 2‐amino‐1,3,4‐thiadiazole ( 1 ) with α,β‐unsaturated carbonyl compounds 2 , 5 , and 9 afforded thiadiazolo[3,2‐a]pyrimidin 3 , benzamide 7 , and bis‐pyrazole derivative 11 . Cyclization of benzamide 7 with POCl₃ gave binary imidazole derivative 8 . Moreover, alkylation of 1 with 2‐bromo‐1‐(2H‐chromen‐3‐yl) ethanone ( 9 ) followed by cyclization gave imidazo[2,1‐b]‐1,3,4‐thiadiazole derivative 15 . Multicomponent reaction of 1 with heterocyclic and/or aromatic aldehyde and thioglycolic acid afforded the corresponding thiazolidinones 17 and 19 . Finally, a one‐pot synthesis of 1 with isatin and thiosemicarbazide furnished the spirotriazole 20 . The newly synthesized compounds were evaluated as antitumor agents.     

Antimicrobial Activities of a Series of Diphenyl (4′-(Aryldiazenyl)Biphenyl-4-Ylamino)(Pyridin-3-YL)Methylphosphonates

Abstract

A series of diphenyl (4′-(aryldiazenyl)biphenyl-4-ylamino)(pyridin-3-yl)methyl- phosphonates 2–7 was synthesized in high yields and their antimicrobial activities were investigated. Some compounds showed high antimicrobial activities against Escherichia coli as a gram-negative bacterium, Bacillus subtilis and Staphylococcus aureus as gram-positive bacteria, and Candida albicans and Schccaromycies cerevisiae as fungi and at low concentrations (10–1000 μg/mL). Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Excimer laser photofragmentation of metallic nanoparticles

Copper nanoparticles (Cu NPs) were prepared by different chemical methods possessing different sizes. While, silver nanoparticles (Ag NPs) were prepared by borohydride reduction method. The influences the changes in sizes of Ag NPs and Cu NPs were demonstrated by the absorption spectra. When Ag NPs and Cu NPs irradiated with 193 and 308 nm excimer laser, respectively; the maximum absorption decreased as the number of pulses increased up to 10 thousands pulse; due to the size reduction. The TEM photography gives good criteria about the size reduction process. Moreover, the mechanism of photofragmentation was described.     

Watt-level single-frequency tunable Nd:YLF/periodically poled KTiOPO(4) red laser

Intracavity second-harmonic generation of a diode-pumped Nd:YLiF(4) ring laser oscillating on the sigma-polarized (4)F(3/2) - (4)I(13/2) transition (lambda(omega) ~ 1314 nm) with a temperature-tuned periodically poled KTiOPO(4) (ppKTP) crystal is reported, yielding up to 0.92 W tunable (lambda(2omega) = 656-658 nm) single-frequency output. Evidence of self-mode-locking via cascading nonlinearities is observed when the ppKTP is strongly phase mismatched.     

Characteristics of flow field and water concentration in a horizontal deadleg

Deadlegs are defined as the inactive portion of the pipe where the flow is stagnant. Corrosion in deadlegs occurs as a result of water separation due to the very low flow velocity. The present work provides an investigation of the effect of deadleg geometry and average flow velocity on flow field and oil/water separation in deadlegs. The investigation is based on the solution of the mass and momentum conservation equations of an oil/water mixture together with the volume fraction equation for the secondary phase. A fluid flow model based on the time-averaged governing equations of 3-D turbulent flow has been developed. An algebraic slip mixture model is utilized for the calculation of the two immiscible fluids (water and crude oil). The model solves the continuity and momentum equations for the mixture, and the volume fraction equation for the secondary phase utilizing an algebraic expression for the relative velocity. Flow visualization experiments were conducted in order to validate the numerical procedure. Good agreement was obtained between the calculated and measured flow patterns. Results are obtained for different lengths of the deadleg. The considered fluid mixture contains 90% oil and 10% water (by volume). The inlet flow velocity ranges from 0.2 to 10 m/s and the deadleg length to diameter ratio (L/D) ranges from 1 to 10. The results showed that the size of the stagnant fluid region increases with the increase of L/D and decreases with the increase of inlet velocity. The results also indicated that the water volumetric concentration increases with the increase of L/D and influenced by the deadleg geometry.     

Turbulent natural convection in vertical parallel-plate channels

The problem of buoyancy driven turbulent flow in parallel-plate channels is investigated. The investigation is limited to vertical channels of uniform cross-section with different modes of heating. The details of the flow and thermal fields are obtained from the solution of the conservation equations of mass, momentum, and energy in addition to equations of the low Reynolds number turbulence model. The study covers Rayleigh number ranging from 10⁵ to 10⁷ and focuses on the effect of channel geometry on the characteristic of the flow and thermal fields as well as the local and average Nusselt number variation. A Nusselt number correlation has been developed in terms of a modified Rayleigh number and channel aspect ratio for the cases of symmetrically heated isothermal and isoflux conditions.     

2,3-Seco-2,3-dioxo-lyngbyatoxin A from a Red Sea strain of the marine cyanobacterium Moorea producens

Chemical investigation of the organic extract of a Red Sea strain of the cyanobacterium Moorea producens has afforded 2,3-seco-2,3-dioxo-lyngbyatoxin A (1). Five known compounds including lyngbyatoxin A (2), majusculamides A and B (3 and 4), aplysiatoxin (5) and debromoaplysiatoxin (6) were also isolated. Their structures were elucidated by using HR-FAB-MS, 1D and 2D NMR analyses. The compounds were evaluated for antiproliferative activity against HeLa cancer cells. Lyngbyatoxin A (2) showed potent activity, with an IC₅₀ of 9.2 nM, while 5 and 6 displayed modest activity with IC₅₀ values of 13.3 and 3.03 μM, respectively. In contrast, compounds 1, 3 and 4 were inactive, with IC₅₀ values greater than 50 μM. The lack of cytotoxicity for 2,3-seco-2,3-dioxo-lyngbyatoxin A (1) demonstrates that the indole moiety in lyngbyatoxin (2) is essential for its cytotoxicity, and suggests that detoxification of 2 may be carried out by biological oxidation of the indole moiety to yield 1.