Inhibition of DNA polymerization and antifungal specificity of furanocoumarins present in traditional medicines

Antifungal activity is positively correlated to furanocoumarin content in extracts of the traditional phytomedicine northern prickly ash (Zanthoxylum americanum Mill. [Rutaceae]). The specificity of these furanocoumarins in inhibiting replication of DNA was investigated with reference to significant base composition differences between fungal and mammalian mitochondrial DNA. We developed a polymerase chain reaction-based assay to investigate whether (1) furanocoumarins inhibit DNA polymerization and (2) distinct furanocoumarins specifically inhibit DNA replication depending on base composition. Specific inhibition of DNA polymerization by 5-methoxypsoralen and psoralen through high-adenine and thymine (AT) (84.3%) and low-AT (51.9%) DNA, respectively, suggests that furanocoumarins inhibit replicative functions of genomes or of regions within the genome that differ in base composition. Greater overall inhibition of DNA polymerization by Z. americanum husk extracts than with single or mixed furanocoumarins suggests that inhibitory compounds in addition to the major furanocoumarins are present in Z. americanum.     

Specific detection of Lewis x-carbohydrates in biological samples using liquid chromatography/multiple-stage tandem mass spectrometry

The Lewis x structure [Lex, Galbeta1-4(Fucalpha1-3)GlcNAc] motif is one of the tumor antigens and plays an important role in oncogenesis, development, cellular differentiation and adhesion. The detection of Lex-carbohydrates and their structural analysis are necessary to clarify the role of Lex in several biological events. Mass spectrometry has been preferably used for the structural analysis of carbohydrates. Especially, collision-induced dissociation (CID) tandem mass spectrometry (MS/MS), which causes a glycosidic bond cleavage, is used for carbohydrate sequencing. However, Lex cannot be identified by MS/MS due to the existence of the positional isomers, such as Lewis a [Galbeta1-3(alpha1-4Fuc)GlcNAc]. In the present study, we demonstrate the specific detection of Lex-carbohydrates in a biological sample by using multiple-stage MS/MS (MSn). Using pyridylaminated oligosaccharides bearing Lex, we found that the Lex-motif yields a cross-ring fragment by the cleavage of a bond between C-3 and C-4 of GlcNAc in Gal(Fuc)GlcNAc. The Lex-specific cross-ring fragment ion at m/z 259 was effectively detected by sequential scans, consisting of a full MS1 scan, data-dependent CID MS2 scan, MS3 of [Gal(Fuc)GlcNAc+Na]+ at m/z 534, and MS4 of [GalGlcNAc+Na]+ at m/z 388. The sequential scan was applied to N-linked oligosaccharide profiling using a LC/ESI-MSn system equipped with a graphitized carbon column. We successfully detected the Lex-motif and elucidated the structures of several Lex and Lewis y [(Fucalpha1-2)Galbeta1-4(Fucalpha1-3)GlcNAc] oligosaccharides in the murine kidney used as a model tissue. Our method is expected to be a powerful tool for the specific detection of the Lex-motif, and structural elucidation of Lex-carbohydrates in biological samples.     

Binding studies of costunolide and dehydrocostuslactone with HSA by spectroscopy and atomic force microscopy

Human serum albumin (HSA), a major plasma protein and plasma-derived therapeutic, interacts with a wide variety of drugs and native plasma metabolites. In this study the interactions of costunolide (CE) and dehydrocostuslactone (DE) with HSA were investigated by molecule modeling, atomic force microscopy (AFM), and different optical techniques. In the mechanism discussion, it was proved that fluorescence quenching of HSA by both of the drugs is a result of the formation of drug-HSA complexes. Binding parameters for the reactions were determined according to the Stern-Volmer equation and static quenching. The results of thermodynamic parameters ΔG⁰, ΔH⁰, and ΔS⁰ at different temperatures indicated that hydrogen bonding interactions play a major role in the drug-HSA associations process. The binding properties were further studied by quantitative analysis of CD, FTIR, and Raman spectra. Furthermore, AFM results showed that the dimension of HSA molecules became more swollen after binding with the drugs.     

Novel nanoarchitecture of arginine-glycine-aspartate conjugated gold nanoparticles: a sensitive and selective platform for detecting arachidonic acid

Analytical and Bioanalytical Chemistry - A novel electrochemical approach for determination of arachidonic acid (ARA) was developed based on the linear arginine-glycine-aspartic-Au (RGD-Au)...     

Multifunctional Tubular Organic Cage‐Supported Ultrafine Palladium Nanoparticles for Sequential Catalysis

The imine condensation reaction of 5,5′‐(benzo[c][1,2,5]thiadiazole‐4,7‐diyl)diisophthalaldehyde with cyclohexanediamine resulted in a shape‐persistent multifunctional tubular organic cage (MTC1). It exhibits selective fluorescence sensing towards divalent Pd ions with a very low detection limit (38 ppb), suggesting effective complexation between these two species. Subsequent reduction of MTC1 and Pd(OAc)₂ with NaBH₄ afforded a cage‐supported catalyst with well‐dispersed ultrafine Pd nanoparticles (NPs) in a narrow size distribution (1.9±0.4 nm), denoted as Pd@MTC1‐1/5. Such ultrafine Pd NPs in Pd@MTC1‐1/5, in cooperation with photocatalytically active MTC1, enable efficient sequential reactions involving visible light‐induced aerobic hydroxylation of 4‐nitrophenylboronic acid to 4‐nitrophenol and the following hydride reduction with NaBH₄. This is the first example of a multifunctional organic cage capable of sensing, directing nanoparticle growth, and catalyzing sequential reactions.     

Iridium complex of porphycene: a new member of metalloporphycene

Iridium(Ⅲ) porphycene complex was synthesized and structurally characterized for the first time. The introduction of the posttransition iridium(Ⅲ) ion not only significantly enhances the absorption intensity at the end of visible region, but also displays efficient singlet oxygen quantum yield(76%), which is applicable for photodynamic therapy in living cells.     

Comparison of the base catalytic activity of MgO prepared by thermal decomposition of hydroxide,basic carbonate,and oxalate under atmospheric conditions

Research on Chemical Intermediates - To obtain highly active solid base catalyst of magnesium oxide (MgO) under atmospheric conditions, hydroxide (Mg(OH)2), basic carbonate...     

CFD simulation of particle suspension in a stirred tank

Particle suspension characteristics are predicted computationally in a stirred tank driven by a Smith turbine. In order to verify the hydrodynamic model and numerical method, the predicted power number and flow pattern are compared with designed values and simulated results from the literature, respectively. The effects of particle density, particle diameter, liquid viscosity and initial solid loading on particle suspension behavior are investigated by using the Eulerian–Eulerian two-fluid model and the standard k–? turbulence model. The results indicate that solid concentration distribution depends on the flow field in the stirred tank. Higher particle density or larger particle size results in less homogenous distribution of solid particles in the tank. Increasing initial solid loading has an adverse impact on the homogeneous suspension of solid particles in a low-viscosity liquid, whilst more uniform particle distribution is found in a high-viscosity liquid.