Pathogenic Yersinia enterocolitica strains increase the outer membrane permeability in response to environmental stimuli by modulating lipopolysaccharide fluidity and lipid A structure

Pathogenic biotypes of Yersinia enterocolitica (serotypes O:3, O:8, O:9, and O:13), but not environmental biotypes (serotypes O:5, O:6, O:7,8, and O:7,8,13,19), increased their permeability to hydrophobic probes when they were grown at pH 5.5 or in EGTA-supplemented (Ca(2+)-restricted) media at 37 degrees C. A similar observation was also made when representative strains of serotypes O:8 and O:5 were tested after brief contact with human monocytes. The increase in permeability was independent of the virulence plasmid. The role of lipopolysaccharide (LPS) in this phenomenon was examined by using Y. enterocolitica serotype O:8. LPS aggregates of bacteria grown in acidic or EGTA-supplemented broth took up more N-phenylnaphthylamine than LPS aggregates of bacteria grown in standard broth and also showed a marked increase in acyl chain fluidity which correlated with permeability, as determined by measurements obtained in the presence of hydrophobic dyes. No significant changes in O-antigen polymerization were observed, but lipid A acylation changed depending on the growth conditions. In standard medium at 37 degrees C, there were hexa-, penta-, and tetraacyl lipid A forms, and the pentaacyl form was dominant. The amount of tetraacyl lipid A increased in EGTA-supplemented and acidic media, and hexaacyl lipid A almost disappeared under the latter conditions. Our results suggest that pathogenic Y. enterocolitica strains modulate lipid A acylation coordinately with expression of virulence proteins, thus reducing LPS packing and increasing outer membrane permeability. The changes in permeability, LPS acyl chain fluidity, and lipid A acylation in pathogenic Y. enterocolitica strains approximate the characteristics in Yersinia pseudotuberculosis and Yersinia pestis and suggest that there is a common outer membrane pattern associated with pathogenicity.

Adsorption of aqueous metal ions on oxygen and nitrogen functionalized nanoporous activated carbons

In this study, the adsorption characteristics of two series of oxygen and nitrogen functionalized activated carbons were investigated. These series were a low nitrogen content(similar to 1 wt % daf) carbon series derived from coconut shell and a high nitrogen content (similar to 8 wt % daf) carbon series derived from polyacrylonitrile. In both series, the oxygen contents were varied over the range similar to 2-22 wt % daf. The porous structures of the functionalized activated carbons were characterized using N-2 (77 K) and CO2 (273 K) adsorption. Only minor changes in the porous structure were observed in both series. This allowed the effect of changes in functional group concentrations on metal ion adsorption to be studied without major influences due to differences in porous structure characteristics. The surface group characteristics were examined by Fourier transform infrared (FTIR) spectroscopy, acid/base titrations, and measurement of the point of zero charge (pH(PZC)). The adsorption of aqueous metal ion species, M2+(aq), on acidic oxygen functional group sites mainly involves an ion exchange mechanism. The ratios of protons displaced to the amount of M2+(aq) metal species adsorbed have a linear relationship for the carbons with pH(PZC) <= 4.15. Hydrolysis of metal species in solution may affect the adsorption of metal ion species and displacement of protons. In the case of basic carbons, both protons and metal ions are adsorbed on the carbons. The complex nature of competitive adsorption between the proton and metal ion species and the amphoteric character of carbon surfaces are discussed in relation to the mechanism of adsorption.

Competitive adsorption of aqueous metal ions on an oxidized nanoporous activated carbon\

Competitive adsorption is the usual situation in real applications, and it is of critical importance in determining the overall performance of an adsorbent. In this study, the competitive adsorption characteristics of all the combinations of binary mixtures of aqueous metal ion species Ca2+(aq), Cd2+(aq), Pb2+(aq), and Hg2+(aq) on a functionalized activated carbon were investigated. The porous structure of the functionalized active carbon was characterized using N-2 (77 K) and CO2 (273 K) adsorption. The surface group characteristics were examined by temperature-programmed desorption, Fourier transform infrared spectroscopy, Raman spectroscopy, acid/base titrations, and measurement of the point of zero charge (pH(PZC)). The adsorption of aqueous metal ion species M2+(aq), on acidic oxygen functional group sites mainly involves an ion exchange mechanism. The ratios of protons displaced to the amount of M2+(aq) metal species adsorbed have a linear relationship for both single-ion and binary mixtures of these species. Hydrolysis of metal species in solution may affect the adsorption, and this is the case for adsorption of Hg2+(aq) and Pb2+(aq). Competitive adsorption decreases the amounts of individual metal ions adsorbed, but the maximum amounts adsorbed still follow the order Hg2+(aq) > Pb2+(aq) > Cd2+(aq) > Ca2+(aq) obtained for single metal ion adsorption. The adsorption isotherms for single metal ion species were used to develop a model for competitive adsorption in binary mixtures, involving exchange of ions in solution with surface proton sites and adsorbed metal ions, with the species having different accessibilities to the porous structure. The model was validated against the experimental data.

Influence of solution chemistry on Cr(VI) reduction and complexation onto date-pits/tea-waste biomaterials

Tea waste (TW) and Date pits (DP) were investigated for their potential to remove toxic Cr(VI) ions from aqueous solution. Investigations showed that the majority of the bound Cr(VI) ions were reduced to Cr(III) after biosorption at acidic conditions. The electrons for the reduction of Cr(VI) may have been donated from the TW and DP biomasses. The experimental data obtained for Cr(VI)-TW and Cr(VI)-DP at different solution temperatures indicate a multilayer type biosorption, which explains why the Sips isotherm accurately represents the experimental data obtained in this study. The Sips maximum biosorption capacities of Cr(VI) onto TW and DP were 5.768 and 3.199 mmol/g at 333 K, respectively, which is comparatively superior to most other low-cost biomaterials. Fourier transform infrared spectroscopic analysis of the metal loaded biosorbents confirmed the participation of -COOH, -NH and O-CH groups in the reduction and complexation of chromium. Thermodynamic parameters demonstrated that the biosorption of Cr(VI) onto TW and DP biomass was endothermic, spontaneous and feasible at 303-333 K. The results evidently indicated that tea waste and date pits would be suitable biosorbents for Cr(VI) in wastewater under specific conditions.

Hydrobiogeochemical Interactions along “Flow Tubes” Controls: Watershed Scale Contaminant Flow and Transformation at the Oak Ridge IFRC

Geochemical,spectrographic, microbiological and hydrogeologic studies at the ORIFRC site indicate that groundwater transport in structured media may behave as a system of parallel flow tubes. These tubes are preferred flowpaths that enable contaminant transport parallel to bedding planes (strike) over distances of 1000s of meters. A significant flux of groundwater is focused within an interval defined by the interface between the competent bedrock and overlying highly-weathered saprolite, commonly referred to as the"transition zone." Characteristics of this transition zone are dense fractures and the relative absence of weathering products (e.g. clays)results in a significantly higher permeability compared to both the overlying clay-saprolite and underlying bedrock. Several stratabound low seismic velocity zones located below the transition zone were identified during geophysics studies and were also determined to be fractured high permeability preferred contaminant transport pathways during subsequent drilling activities. XANES analysis of precipitates collected from these deeper flow zones indicate 95% or more of the U deposited is U(VI). Linear combination fitting of the EXAFS data shows that precipitates are ~51±5% U(VI)-carbonate-like phase (e.g., liebigite) and ~49±5% U(VI) associated with an iron oxide phase; inclusion of a third component in the fit suggests that up to 15% of the U(VI) may be associated with a phosphate phase or OH- phase (e.g.,schoepite). Although precipitates with similar U(VI)-carbonate and/or phosphate associations were identified in the transition zone pathways,there were also U(VI) complexes adsorbed to mineral surfaces that would tend to be more readily mobilized. Groundwater in the different flow tubes has been determined to consist of different water quality types that vary with the solid phase encountered (e.g., clays, carbonates, clastics) as contaminants migrate along the flow paths. This lateral and vertical variability in geochemistry, particularly pH, has a significant impact on microbiological community composition and activity. Ribosomal RNA gene analyses coupled with physiological and genomic analyses suggest that bacteria from the genus Rhodanobacter(a diverse population of denitrifiers that are moderately acid tolerant) have a high relative abundance in the acidic source zone at the ORIFRC site.Watershed-scale analysis across different flow paths/tubes revealed strong negative correlation between pH and the absolute and relative abundance of Rhodanobacter. Recent studies also confirmed that the ORIFRC site hosts a diverse fungal community, with significant differences observed between acidic (pH <5) and circumneutral (>5) wells. The lack of nitrous oxide reduction capability in fungi, and the detection of denitrification potential in slurry microcosms suggest that fungi may have aheretofore under appreciated role in biogeochemical transformations, with implications forsite remediation and greenhouse gas emissions. Further research is needed to determine if these organisms can influence U(VI) mobility either directly through immobilization or indirectly through the depletion of nitrate.In conclusion, additional studies are required to quantify the processes (e.g., solid phase reactions, recharge, diffusion, microbial interactions) that are occurring along the groundwater flow tubes identified at the ORIFRC so predictive models can be parameterized and used to assess long-term contaminant fate and transport and remedial options.

A preliminary survey of micro-organisms in the gut and pellets of a tropical millipede Doratogonus uncinatus Attems (Diplopoda, Spirostreptida, Spirostreptidae).

Millipede gut microbiology and decomposition of faecal pellets over a period of eight weeks were studied in the laboratory. Bacterial numbers, carbon and nitrogen content, pH and weight loss were monitored. Heterotrophic bacteria were the most abundant and reached a peak in the first two weeks of decomposition. The amount of carbon was constant while ammonium nitrogen decreased from 1.51 % to 0.03 % after eight weeksThe pH of the pellets was slightly acidic and did not change much during the course of decomposition. A succession of micro-organisms was observed on decomposing pellets. Zygomycetes were replaced by Ascomycetes after 20 days of decomposition. Decomposition was significantly affected by temperature. The rate of decomposition was highest at 35[degree]C .

LIQUID MARBLES GRANULATED USING SUPER-HYDROPHOBIC METAL POWDERS

Superhydrophobic (SH) particles based on a copper substrate were prepared by a silver deposition technique of different particle sizes from 10µm to 425µm. Such SH particles were found to be pH-responsive and liquid marbles formed using the SH copper substrate destabilised under certain pH conditions. The exposure to high concentrations of acidic or basic gases caused immediate collapse of the liquid marble. However, low concentrations of acidic and basic gases could diffuse across the shell of liquid marbles without adversely affecting the structure. Liquid marbles formed with large SH particles (425
µm) did not fully form a mono-layer around the liquid droplet. This phenomenon, whereby SH particles slide down the surface of the water droplet until an equilibrium position is reached, was studied using a mathematical approach, which related the angle to the vertical axis of the SH particles at t
he equilibrium F, to the shape of liquid marble and the contact angle, ?.

Quantification of N-(glucitol)ethanolamine and N-(carboxymethyl)serine:two products of nonenzymatic modification of aminophospholipids formed in vivo

Chemical, nonenzymatic modification of protein and lipids by reducing sugars, such as glucose, is thought to contribute to age-related deterioration in tissue protein and cellular membranes and to the pathogenesis of diabetic complications. This report describes the synthesis and quantification of N-(glucitol)ethanolamine (GE) and N-(carboxymethyl)serine (CMS), two products of nonenzymatic modification of aminophospholipids. GE is the product of reduction and hydrolysis of glycated phosphatidylethanolamine (PE), while CMS is formed through reaction of phosphatidylserine (PS) with products of oxidation of either carbohydrate (glycoxidation) or lipids (lipoxidation). Gas chromatography/mass spectrometry procedures for quantification of the N,O-acetyl methyl ester derivatives of the modified head groups were developed. GE and CMS were quantified in samples of PE and PS, respectively, following incubation with glucose in vitro; CMS formation was dependent on the presence of oxygen during the incubation. Both GE and CMS were detected and quantified in lipid extracts of human red blood cell membranes. The content of GE, but not CMS, was increased in the lipids from diabetic compared to nondiabetic subjects. Measurement of these modified lipids should prove useful for assessing the role of carbonyl-amine reactions of aminophospholipids in aging and age-related diseases.

Carboxymethylethanolamine, a biomarker of phospholipid modification during the maillard reaction in vivo

Nepsilon-(Carboxymethyl)lysine (CML) is a stable chemical modification of proteins formed from both carbohydrates and lipids during autoxidation reactions. We hypothesized that carboxymethyl lipids such as (carboxymethyl)phosphatidylethanolamine (carboxymethyl-PE) would also be formed in these reactions, and we therefore developed a gas chromatography-mass spectrometry assay for quantification of carboxymethylethanolamine (CME) following hydrolysis of phospholipids. In vitro, CME was formed during glycation of dioleoyl-PE under air and from linoleoylpalmitoyl-PE, but not from dioleoyl-PE, in the absence of glucose. In vivo, CME was detected in lipid extracts of red blood cell membranes, approximately 0.14 mmol of CME/mol of ethanolamine, from control and diabetic subjects, (n = 22, p > 0.5). Levels of CML in erythrocyte membrane proteins were approximately 0.2 mmol/mol of lysine for both control and diabetic subjects (p > 0.5). For this group of diabetic subjects there was no indication of increased oxidative modification of either lipid or protein components of red cell membranes. CME was also detected in fasting urine at 2-3 nmol/mg of creatinine in control and diabetic subjects (p = 0.085). CME inhibited detection of advanced glycation end product (AGE)-modified protein in a competitive enzyme-linked immunosorbent assay using an anti-AGE antibody previously shown to recognize CML, suggesting that carboxymethyl-PE may be a component of AGE lipids detected in AGE low density lipoprotein. Measurement of levels of CME in blood, tissues, and urine should be useful for assessing oxidative damage to membrane lipids during aging and in disease.

Development of novel oral formulations prepared via hot melt extrusion for targeted delivery of photosensitizer to the colon

Colon-residing bacteria, such as vancomycin-resistant Enterococcus faecalis and Bacteroides fragilis, can cause a range of serious clinical infections. Photodynamic antimicrobial chemotherapy (PACT) may be a novel treatment option for these multidrug resistant organisms. The aim of this study was to formulate a Eudragit®-based drug delivery system, via hot melt extrusion (HME), for targeting colonic release of photosensitizer. The susceptibility of E. faecalis and B. fragilis to PACT mediated by methylene blue (MB), meso-tetra(N-methyl-4-pyridyl)porphine tetra-tosylate (TMP), or 5-aminolevulinic acid hexyl-ester (h-ALA) was determined, with tetrachlorodecaoxide (TCDO), an oxygen-releasing compound, added in some studies. Results show that, for MB, an average of 30% of the total drug load was released over a 6-h period. For TMP and h-ALA, these values were 50% and 16% respectively. No drug was released in the acidic media. Levels of E. faecalis and B. fragilis were reduced by up to 4.67 and 7.73 logs, respectively, on PACT exposure under anaerobic conditions, with increased kill associated with TCDO. With these formulations, photosensitizer release could potentially be targeted to the colon, and colon-residing pathogens killed by PACT. TCDO could be used in vivo to generate oxygen, which could significantly impact on the success of PACT in the clinic.

Nile blue-based nano-sized pH sensors for simultaneous far-red and near-infrared live bioimaging

Diblock copolymer vesicles are tagged with pH-responsive Nile Blue-based labels and used as a new type of pH-responsive colorimetric/fluorescent biosensor for far-red and near-infrared imaging of live cells. The diblock copolymer vesicles described herein are based on poly(2-(methacryloyloxy)ethyl phosphorylcholine-block-2-(diisopropylamino)ethyl methacrylate) [PMPC-PDPA]: the biomimetic PMPC block is known to facilitate rapid cell uptake for a wide range of cell lines, while the PDPA block constitutes the pH-responsive component that enables facile vesicle self-assembly in aqueous solution. These biocompatible vesicles can be utilized to detect interstitial hypoxic/acidic regions in a tumor model via a pH-dependent colorimetric shift. In addition, they are also useful for selective intracellular staining of lysosomes and early endosomes via subtle changes in fluorescence emission. Such nanoparticles combine efficient cellular uptake with a pH-responsive Nile Blue dye label to produce a highly versatile dual capability probe. This is in marked contrast to small molecule dyes, which are usually poorly uptaken by cells, frequently exhibit cytotoxicity, and are characterized by intracellular distributions invariably dictated by their hydrophilic/hydrophobic balance.

Molecularly Imprinted Polymers for the isolation of bioactive naphthoquinones from plant extracts

Molecularly Imprinted Polymers (MIPs) targeting shikonin, a potent antioxidant and wound healing agent, have been prepared using methacrylic acid (MAA) and 2-diethylaminoethyl methacrylate (DEAEMA) as functional monomers. An investigation of solution association between shikonin and both acidic and basic functional monomers by UV-Vis titrations, suggested stronger affinity towards the basic functionality. Strong inhibition of the co-polymerisation reaction of such basic monomers was observed, but was overcome by reduction of the amount of template used during polymer synthesis. Polymer morphology was severely impacted by the template’s radical scavenging behaviour as demonstrated by solid state NMR spectroscopy measurements. HPLC evaluation of the final materials in polar conditions revealed limited imprinting effects and selectivity, with the MAA polymers exhibiting marginally better performance. During application of the polymers as MI-SPE sorbents in non-polar solvents it was found that the DEAEMA based polymer was more selective towards shikonin compared to the MAA counterpart, while shikonin recoveries of up to 72% were achieved from hexane solutions of a commercial sample of shikonin, hexane extract of Alkanna tinctoria roots and a commercial pharmaceutical ointment.

Dental erosion among 12-14 year old school children in Khartoum:A pilot study

Objectives: To investigate dental erosion among 12-14 year old Sudanese school children and evaluate the associated risk factors. Basic Research Design: Cross sectional survey in secondary schools in Khartoum city, Sudan. Method and Participants: A sample of 157 school children was obtained from both private and public schools. Erosion on the labial and palatal surfaces of maxillary incisors was measured by criterion based on the Smith and Knight Tooth Wear Index. Dietary intake and other related factors were assessed using a questionnaire. Results: The overall erosion prevalence in this group was 66.9%, of which 45.2% was mild and 21.7% was moderate erosion. A strong association was found between erosion and private schooling (higher socioeconomic groups), carbonated drinks, herbal hibiscus drink and traditional acidic food consumption. Conclusion: There was a high prevalence of dental erosion among Sudanese school children which was mild to moderate in severity and was strongly associated with acidic dietary intake © BASCD 2007.

Trimethoxymethane as an alternative fuel for a direct oxidation PBI polymer electrolyte fuel cell

The oxidation of trimethoxymethane (TMM) (trimethyl orthoformate) in a direct oxidation PBI fuel cell was examined by on-line mass spectroscopy and on-line FTIR spectroscopy. The results show that TMM was almost completely hydrolyzed in a direct oxidation fuel cell which employs an acid doped polymer electrolyte to form a mixture of methylformate, methanol and formic acid. It also found that TMM was hydrolyzed in the presence of water at 120°C even without acidic catalyst. The anode performance improves in the sequence of methanol, TMM, formic acid/methanol, and methylformate solutions. Since formic acid is electrochemically more active than methanol, these results suggest that formic acid is probably a key factor for the improvement of the anode performance by using TMM instead of methanol under these conditions. © 1998 Elsevier Science Ltd. All rights reserved.

Alkyloxycarbonyl group migration in furanosides

A migration of methyloxycarbonyl group from secondary to primary hydroxyl was observed in furanosides (ribosides and xylosides) under usual desilylation conditions using tetrabutylammonium fluoride. The migration was studied further on several alkyloxycarbonyl furanosides under either basic or acidic conditions. As follows from C labelling experiments and product distribution, the migration in xylosides, proceeds intramolecularly via six-membered cyclic carbonate, whereas in ribosides, the migration is intermolecular. Acidic conditions prevented the migration in ribosides whereas the migration in xylosides was circumvented under neutral conditions. © 2012 Elsevier Ltd. All rights reserved.