Ultrasound-induced membrane lipid peroxidation and cell damage of Escherichia coli in the presence of non-woven TiO2 fabrics

A non-woven titanium dioxide (TiO₂) fabric was applied to disinfection by ultrasound (US) irradiation, and the disinfection efficiency and lipid peroxidation of Escherichia coli (E. coli) cell membrane were evaluated to investigate the killing process. The addition of non-woven TiO₂ fabric enhanced hydroxyl (OH) radical generation and disinfection efficiency. Judging from the disinfection experiments using glutathione or t-butanol as a radical scavenger, the OH radical played a major role in cell killing in sonodynamic disinfection with non-woven TiO₂ fabric. Moreover, to understand the detailed killing process, damage to cell membrane was also evaluated using a diphenyl-1-pyrenylphosphine (DPPP) fluorescent probe, which detects the membrane’s lipid peroxidation. The addition of non-woven TiO₂ fabric aggravated this peroxidation. This aggravation was caused by the OH radical according to an assay using a radical scavenger. From these results, it was concluded that non-woven TiO₂ fabric as a sonocatalyst promoted peroxidation of the polyunsaturated phospholipid component of the lipid membrane initially and induced a major disorder in the E. coli cell membrane under US irradiation.     

Nickel(II), copper(II), palladium(II) and platinum(II) complexes of bidentate SN ligands derived from S-alkyldithiocarbazates and the X-ray crystal structures of the [Ni(tasbz)2] and [Cu(tasbz)2] · CHCl3 complexes

New complexes of general empirical formula, [M(NS)₂] · nCHCl₃ (M = Ni^II, Cu^II, Pd^II or Pt^II; NS = anionic form of the thiophene-2-aldehyde Schiff bases of S-methyl- and S-benzyldithiocarbazate; n = 0, 1) have been synthesized and characterized by physico-chemical techniques. Magnetic and spectroscopic evidence support a square-planar structure for these complexes. The crystal structures of the [Ni(tasbz)₂] and [Cu(tasbz)₂] · CHCl₃ complexes (tasbz = anionic form of the thiophene-2-aldehyde Schiff base of S-benzyldithiocarbazate) have been determined by X-ray diffraction. Both complexes have a trans-planar structure in which the two Schiff base ligands are coordinated to the metal(II) ion as uninegatively charged bidentate ligands via the thiolate sulfur and the azomethine nitrogen atoms. This revised version was published online in June 2006 with corrections to the Cover Date.     

Os(VIII)-catalysed oxidation of sulfides by sodium salt of N-chlorobenzenesulfonamide

Catalytic activity of Os(VIII) in the oxidation of some twenty organic sulfides with sodium salt of N-chlorobenzenesulfonamide (CAB) has been investigated in alkaline (pH8.7) t-butanol–water (1:1 v/v) medium. Significant retarding influence of [OH⁻] on the reactivity is exhibited. The catalysed reaction is strongly accelerated in the presence of Hg(II). Imperfections are observed in the linear Hammett relationship in the case of –NO₂ substituents.     

Retention mechanism of L-glutamide-derived noncrystalline stationary phases in reversed-phase high-performance liquid chromatography and application for separation of nucleic acid constituents

Double alkylated L-glutamide-derived noncrystalline stationary phases Sil-DSG and Sil-DBG have been prepared by coupling N',N'-dioctadecyl-N-[4-carboxybutanoyl]-L-glutamide (DSG) and N',N',-dibutyl-N-[4-carboxybutanoyl]-L-glutamide (DBG) with aminopropylated silica (Sil-APS). TEM observations of DSG and DBG showed that lipid DSG can aggregate in organic solvents (methanol, chloroform, toluene, etc.) and self-assembled nano fibers are observed while such fibrous aggregations are not observed for DBG. The resulting chromatographic data have been provided information about its selective interaction with guest molecules (PAHs) in RP-HPLC. We have observed that the carbonyl groups in Sil-DSG exist in ordered state by forming a condensing thin layer over silica surface while DBG cannot form such an ordered state due to its lower order of short alkyl chain. The ordered carbonyl groups present in Sil-DSG promotes multiple carbonyl pi-benzene pi interactions with guest PAHs isomers which enhance the selectivity for these compounds. The contribution of pi-pi interactions was also supported by the substantial effects on the selectivity of benzene and nitrobenzenes. The effect of pi-electron containing solvent on the retention behavior of the PAHs was also studied. The selectivity for nucleic acid constituents, i.e. nucleosides and its bases were also evaluated by Sil-DSG and the selectivity for these compounds on Sil-DSG was compared with the selectivity of conventional polymeric ODS phase. It has been found that Sil-DSG provided higher selectivity for nucleic acid constituents than polymeric ODS and that HPLC packing materials can be efficiently employed for routine analysis of these compounds. The effect of methanol content on the separation behavior of nucleosides was also studied.     

One-step synthesis of labeled sugar nucleotides for protein O-GlcNAc modification studies by chemical function analysis of an archaeal protein

Herein we present the chemical function analysis of a recombinant sugar nucleotidyltransferase from the hyperthermophile Pyrococcus furiosus and its use in the one-pot synthesis of chloroacetyl- and alkyne-tagged analogues of uridinediphospho-N-acetylglucosamine (UDP-GlcNAc). The gene was originally annotated as a glucose-1-phosphate deoxythymidylyltransferase; however, kinetic analysis of a panel of sugar-1-phosphates with the protein shows that it is better described as a bifunctional protein that synthesizes UDP-GlcNAc from glucosamine-1-phosphate and acetyl coenzyme A (CoA). A new mass-spectrometry-based assay for the rapid analysis of the acyltransferase activity demonstrates that the enzyme can also accept cheaper truncated N-acetylcysteamine thioester substrates in place of the natural acetyl CoA. The enzyme can tolerate alkyne or chloride substitutions in the acyl moiety, thereby allowing the facile synthesis of tagged sugar nucleotides for future use in protein O-GlcNAc modification studies.     

Evaluation of selectivity for l-glutamide-derived highly ordered assemblies in reversed-phase high-performance liquid chromatography

Two dioctadecyl l-glutamic acid derivatives with amide and ester type bondings have been synthesized and immobilized from 3-aminopropyltrimethoxysilane (APS) grafted silica (Sil-APS) to be used in reversed-phase high-performance liquid chromatography (RP-HPLC). Subsequent studies showed that dioctadecyl-l-glutamide derivative (GLN) can self-assemble into highly ordered structures by forming three-dimensional fibrillar aggregates as observed in scanning and transmission electron microscopes (SEM and TEM). Variable temperature ¹H NMR and FT-IR spectra of organogel revealed that the special aggregation morphology shown by GLN was stabilized by inter and or intra molecular hydrogen bonding among amide moieties. However, such ordered aggregated or self-assembled structures were not observed for the dioctadecyl-l-glutamate (GLU) derivative. The stationary phases Sil-GLN and Sil-GLU were characterized by DRIFT, elemental analysis, TGA, and ¹³C and ²⁹Si CP-MAS NMR spectroscopic measurements. The chromatographic selectivity for both stationary phases was evaluated from the retention studies of different size and shape polycyclic aromatic hydrocarbons (PAHs). The chromatographic experiment for PAHs and geometrical isomers in RP-HPLC showed that Sil-GLN demonstrated extremely enhanced selectivity than Sil-GLU. The higher selectivity attributed by Sil-GLN has been brought by multiple π-π interactions among the π-electrons of the grafted organic phase and π-electrons of the guest PAHs molecules. Thermodynamic studies for linear and nonlinear PAHs revealed that the retention behavior does not change over a temperature range from 10 to 60 °C for both stationary phases.     

Secondary ion yields produced by keV atomic and polyatomic ion impacts on a self-assembled monolayer surface

A suite of keV polyatomic or 'cluster' projectiles was used to bombard unoxidized and oxidized self-assembled monolayer surfaces. Negative secondary ion yields, collected at the limit of single ion impacts, were measured and compared for both molecular and fragment ions. In contrast to targets that are orders of magnitude thicker than the penetration range of the primary ions, secondary ion yields from polyatomic projectile impacts on self-assembled monolayers show little to no enhancement when compared with monatomic projectiles at the same velocity. This unusual trend is most likely due to the structural arrangement and bonding characteristics of the monolayer molecules with the Au(111). Copyright 1999 John Wiley & Sons, Ltd.     

Direct equilibration of soil water for delta(18)O analysis and its application to tracer studies

Current methods for stable oxygen isotopic (delta (18)O) analysis of soil water rely on separation of water from the soil matrix before analysis. These separation procedures are not only time consuming and require relatively large samples of soil, but also have been shown to introduce a large potential source of error. Current research at Queen's University Belfast is focused on using direct equilibration of CO(2) with the pore water to eliminate this extraction step using the automated Multiprep system and a Micromass Prism III isotope ratio mass spectrometer (IRMS). The findings of this research indicate the method is less time consuming, more reliable, and reproducible to within accepted limits (+/-0.1% per thousand delta (18)O). In this study the direct equilibration method is used to analyse delta (18)O tracer profiles in the unsaturated zone of field soils, concurrently with chloride tracer profiles, which can be used to assess infiltration rates and mechanisms through the unsaturated zone. Copyright 1999 John Wiley & Sons, Ltd.