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Reaction Efficiency (reaction + efficiency)
Selected AbstractsVancomycin covalently bonded to titanium alloy prevents bacterial colonizationJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 7 2007Valentin Antoci Jr. Abstract Periprosthetic infection is a devastating consequence of implant insertion and can arise from hematogenous sources or surgical contamination. Microbes can preferentially colonize the implant surface and, by forming a biofilm, escape immune surveillance. We hypothesized that if an antibiotic can be tethered to a titanium alloy (Ti) surface, it will inhibit bacterial colonization, prevent biofilm formation, and avert late-stage infection. To test this hypothesis, a Ti rod was covalently derivatized with vancomycin. Reaction efficiencies were evaluated by colorimetric and spectrophotometric measurements. The vancomycin-modified surface was stable in aqueous solutions over extended time periods and maintained antibiotic coverage, even after press-fit insertion into a cadaverous rat femora. When evaluated using fluorescently labeled bacteria, or by direct colony counts, the surface-bound antibiotic prevented bacterial colonization in vitro after: (1) exposure to high levels of S. aureus; (2) extended incubation in physiological buffers; and (3) repeated bacterial challenges. Importantly, whereas the vancomycin-derivitized pins prevented bacterial colonization, S. aureus adhered to control pins, even in the presence of concentrations of vancomycin that exceeded the strain MIC. These results demonstrate that we have effectively engineered a stable, bactericidal Ti surface. This new surface holds great promise in terms of mitigating or preventing periprosthetic infection. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:858,866, 2007 [source] Gas-phase ion chemistry in the ternary silane,propyne,phosphine systemJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2004Lorenza Operti Abstract The gas-phase ion chemistry of propyne,phosphine and silane,propyne,phosphine mixtures was studied by ion trap mass spectrometry. For the binary mixture, the effect of different partial pressures of the reagents on the yield of C and P-containing ions was evaluated. Reaction sequences and rate constants were determined and reaction efficiencies were calculated from comparison of experimental and collisional rate constants. In the ternary silane,propyne,phosphine systems, the reaction pathways leading to formation of SimCnPpHq+ ions were determined and the rate constants of the most important steps were measured. For some ion species, selected by double isolation procedures (MS/MS), the low ion abundances prevented determination of the reaction rate constants. Si, C and P-containing ions are mainly produced in reactions of SimPpHq+ ions with propyne, while the reactivity of the SimCnHq+ ions towards PH3 and of the CnPpHq+ ions towards SiH4 is very low. The formation of hydrogenated SiCP ions is interesting for their possible role as precursors of amorphous silicon carbides doped with phosphorus, obtained in a single step, by deposition from properly activated silane,propyne,phosphine mixtures. Copyright © 2004 John Wiley & Sons, Ltd. [source] Gas-phase ion chemistry in the ternary SiH4,C3H6,PH3 systemJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2002Stefania Calderan Abstract Propene,phosphine and the silane,propene,phosphine gaseous mixtures were studied by ion trap mass spectrometry. For the binary mixture the variation of ion abundances under different partial pressures and the mechanisms of ion,molecule reactions are reported. Moreover, the rate constants of the main processes were measured and compared with the collisional rate constants to determine the reaction efficiencies. In the ternary silane,propene,phosphine mixture the mechanisms of formation of ion clusters were elucidated, but the complexity of the system and the low abundances of the ions usually isolated by successive steps prevented the determination of rate constants. The hydrogenated ternary ions are mainly formed by reactions of ions with propene, whereas a minor contribution comes from reactions of ions with phosphine. The ions show very low reactivity with silane. The formation processes of these species are discussed in relation to their possible role as precursors of amorphous silicon carbides doped with phosphorus obtained by deposition from properly activated silane,propene,phosphine mixtures. Copyright © 2001 John Wiley & Sons, Ltd. [source] Antimicrobial finishing of regular and modified nylon-6 fabricsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008S. E. Shalaby Abstract A simple, efficient, and practically applicable functional approach for improvement antimicrobial properties of nylon-6 fabrics and increase the washing durability of biofunctions was developed. This finishing approach is based on grafting of the fabrics with methacrylic acid (MAA) to create additional carboxylic groups in nylon-6 macromolecules, followed by subsequent reaction with dimethylalklbenzyl ammonium chloride (DMABAC) solution under alkaline conditions. The carboxylic groups react with cationic agent through ionic interaction, which led to the immobilization of QAS on nylon-6 fabrics. This immobilization was proofed through determination of nitrogen content, applying scanning electron microscopy (SEM), and FTIR microscopy. The effect of treatment conditions on salt uptake (SUT) on nylon-6 fabrics and reaction efficiency (RE) was investigated. The antimicrobial assessment of regular and grafted with PMAA nylon-6 fabrics treated with DMABAC revealed that both types of fabrics are characterized before washing, by quite strong biocide effect on Bacillus mycoides, Escherichia coli and Candida albicans. The role of grafting nylon-6 fabrics before treatment with salt on durability of antimicrobial functions seems to be more significant as the samples were repeatedly washed. Even after Laundring 10 times the grafted samples could still provide 80%, 100%, and 87.5% microbial reduction against B. mycoides, E. coli and C. albicans, respectively, in contrast with 42.6%, 65.6%, and 42.5% in case of regular nylon-6 fabrics. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008. [source] Gas-phase basicities for ions from bradykinin and its des-arginine analoguesJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 8 2001Nigel P. Ewing Abstract Apparent gas-phase basicities (GBapps) for [M + H]+ of bradykinin, des-Arg1 -bradykinin and des-Arg9 -bradykinin have been assigned by deprotonation reactions of [M + 2H]2+ in a Fourier transform ion cyclotron resonance mass spectrometer. With a GBapp of 225.8 ± 4.2 kcal mol,1, bradykinin [M + H]+ is the most basic of the ions studied. Ions from des-Arg1 -bradykinin and des-Arg9 -bradykinin have GBapp values of 222.8 ± 4.3 kcal mol,1 and 214.9 ± 2.3 kcal mol,1, respectively. One purpose of this work was to determine a suitable reaction efficiency ,break point' for assigning GBapp values to peptide ions using the bracketing method. An efficiency value of 0.1 (i.e. approximately 10% of all collisions resulting in a deprotonation reaction) was used to assign GBapps. Support for this criterion is provided by the fact that our GBapp values for des-Arg1 -bradykinin and des-Arg9 -bradykinin are identical, within experimental error, to literature values obtained using a modified kinetic method. However, the GBapps for bradykinin ions from the two studies differ by 10.3 kcal mol,1. The reason for this is not clear, but may involve conformation differences produced by experimental conditions. The results may be influenced by salt-bridge conformers and/or by conformational changes caused by the use of a proton-bound heterodimer in the kinetic method. Factors affecting the basicities of these peptide ions are also discussed, and molecular modeling is used to provide information on protonation sites and conformations. The presence of two highly basic arginine residues on bradykinin results in its high GBapp, while the basicity of des-Arg1 -bradykinin ions is increased by the presence of two proline residues at the N-terminus. The proline residue in the second position folds the peptide chain in a manner that increases intramolecular hydrogen bonding to the protonated N-terminal amino group of the proline at the first position. Copyright © 2001 John Wiley & Sons, Ltd. [source] Evaluation of a p30 Gene-Based Real-Time Reverse Transcriptase Polymerase Chain Reaction Assay for Detection of Feline CalicivirusesJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 1 2004Brian A. Scansen This report describes a feline calicivirus (FCV) p30 gene-based real-time SYBR Green I reverse transcriptase polymerase chain reaction (RT-PCR) assay that is capable of detecting low virus concentrations and a broad range of FCV isolates. The assay consisted of a 1-step RT-PCR reaction with primers delineating a 126-base-pair (bp) region of the FCV p30 gene. Sensitivity of the RT-PCR assay was determined to be equivalent to a FCV titer of 1.2 × 101 to 1.2 × 102 TCID50/mL. The assay was linear over a wide range of template concentrations and had a reaction efficiency of 95%. Specific FCV amplification products were detected from 51 wild-type FCV isolates, whereas specific products were not detected from a canine calicivirus, a rabbit calicivirus, and a bovine calicivirus. The primers used in this study amplified a large number of North American FCV isolates and further confirm the diagnostic utility of p30 gene-based real-time RT-PCR for detection of FCV. [source] Preparation of strach-graft-polyacrylamide copolymers by reactive extrusion,POLYMER ENGINEERING & SCIENCE, Issue 10 2003J. L. Willett Graft copolymers of starch and polyacrylamide (PAAm) were prepared by reactive extrusion using a co-rotating twin-screw extruder and ammonium presulfate initiator. Feed rates were 109 g/min to 325 g/min (all components) at a moisture content of 50%, with screw speeds in the range 100 rpm to 300 rpm. Starch/acrylamide weight ratios ranged from 5:1 to 1.3:1. Conversions of acrylamide to PAAm were generally 80% or greater with residence times of 400 seconds or less. Conversion increased with feed rate, suggesting that reaction efficiency was proportional to the degree of fill in the extruder. Grafting efficiencies were in the range of 50% to 80%. PAAm molecular weight increased with increasing acrylamide content, consistent with free radical polymerization kinetics. Extrusion temperature had no significant impact on acrylamide conversion. Graft frequency, as measured by the number of anhydroglucose units per graft, was essentially constant over the starch: acrylamide ratio and temperature range studied. These results show that reactive extrusion offers the potential for rapid production of starch graft copolymers with unsaturated monomers. [source] Effect of Modified Enzymatic Catalysis on the Extraction of Diosgenin from Dioscorea zingiberensis C.,H.CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 11 2007Wright Abstract Multi-enzymatic catalysis combined with acid hydrolysis is studied in order to enhance the efficiency of the enzymatic catalysis and reduce the mass transfer resistance from starch and cellulose in the extraction of diosgenin from Dioscorea zingiberensis C.,H. Wright. The cellulase is modified by polyethylene to increase its optimal reaction temperature and pH value. The modified cellulase shows better thermostability and resistance to alkali. The modified cellulase, , -amylase and , -glycosidase are used to construct the multi-enzyme and multi-enzyme catalysis is used as a pretreatment process. Compared to primary industrial techniques including acid hydrolysis, spontaneous fermentation and enzymatic catalysis, conventional techniques are optimized by using multi-enzymatic catalysis together with acid hydrolysis because of the higher reaction efficiency and lower levels of manipulation required. The purity of the product is more than 96,% with this technique, and the melting point is 205,207,°C. The diosgenin yield rate and the extraction rate reached are 2.43,% and 98,%, respectively. IR and 1H NMR spectroscopy were used to confirm the structure of the product. [source] | |||||||||||||