Search results for "HALO"
showing 10 items of 2623 documents
Keyhole limpet haemocyanin: negative staining in the presence of trehalose
1995
Abstract Samples of unpurified and purified haemocyanin from the giant keyhole limpet Megathura crenulata have been studied by transmission electron microscopy (TEM) using mixtures of trehalose with the negative stains, uranyl acetate and ammonium molybdate. Trehalose is a known protein preservative during air and freeze drying, UV irradiation and high temperatures, and therefore offers the possibility of protecting proteins during the drying of negatively-stained specimens and their subsequent electron microscopical study. Evidence is presented that trehalose possesses satisfactory stability within the electron beam during conventional room temperature, negative-staining studies. The combi…
Design and synthesis of new trehalose-conjugated pentapeptides as inhibitors of Aβ(1-42) fibrillogenesis and toxicity
2009
Aggregation of the amyloid A? peptide and its accumulation into insoluble deposits (plaques) are believed to be the main cause of neuronal dysfunction associated with Alzheimer's disease (AD); small molecules that can interfere with the A? amyloid fibril formation are therefore of interest for a potential therapeutic strategy. Three new trehalose-conjugated peptides of the well known ?-sheet breaker peptide iA?5p,were synthesized. The disaccharide was covalently attached to different sites of the LPFFD peptide chain, i.e. at the N-terminus, C-terminus or at the Asp side chain. CD spectroscopy in different solvents was used to assess changes in the peptide conformation of these compounds. Th…
Negative staining across holes: application to fibril and tubular structures.
2007
The negative staining technique, when used with holey carbon support films, presents superior imaging conditions than is the case when samples are adsorbed to continuous carbon films. A demonstration of this negative staining approach is presented, using ammonium molybdate in combination with trehalose, applied to several fibrillar and tubular samples. Fibrils formed from the amyloid-beta peptide and the protease inhibitor pepstain A spread very well unsupported across holes and the different polymorphic fibril forms can be readily assessed. However, tubular forms of amyloid-beta have a tendency to be flattened, due to surface tension forces prior to and during specimen drying. Sub-fibril a…
Statistical methods for the comparison of measurements derived from orthodontic imaging
2000
Biometric comparison procedures for dental imaging methods with continuous outcome were reviewed, mainly concentrating on assessment and comparison of accuracy and precision according to the study design. Univariate graphical and numerical representations of corresponding deviations were summarized to derive a 'check list' of minimum information necessary to compare the measurement methods. The methods reviewed in this investigation are illustrated by the comparison of conventional (radiographic) cephalometry versus assessment using the DigiGraph in 50 female children. A paired t-test and the corresponding confidence interval approach were used to assess deviations in location of two imagin…
Diffusion technique for the generation of gaseous halogen standards
2009
Abstract Halogens are known to play an important role in the tropospheric ozone-depletion chemistry and are of special interest because of their influence on the atmospheric oxidation capacity. In this paper, we investigate the application of a capillary diffusion technique for the generation of gaseous halogen standards like Br 2 , IBr, ICl and I 2 . The influence of capillary dimension (i.e. length and inner diameter), ambient pressure and headspace volume of the diffusion vessel on the test gas output has been evaluated. The experimental output rates are determined from the mass loss of the analyte vessel on a regular schedule and compared with their respective theoretical predictions. W…
Evaluation of analytical performance of gas chromatography coupled with atmospheric pressure chemical ionization Fourier transform ion cyclotron reso…
2019
Abstract A new analytical method was established and validated for the analysis of eighteen halogenated flame retardants (HFRs)in food products. Gas chromatography (GC) coupled to Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) employing atmospheric pressure chemical ionization (APCI) was used for the identification and quantitation of contaminants. Intra-laboratory validation of the method was performed with respect to recovery, repeatability, linear calibration ranges, instrumental and method limits of quantitation (i-LOQ and m-LOQ), and trueness was verified where possible by analysis of reference materials (RMs). The validation results indicated recoveries of ana…
Multi-analyte method for the analysis of legacy and alternative brominated and chlorinated flame retardants in food products of animal origin using g…
2019
Abstract An analytical method was developed and validated for the analysis of 32 halogenated flame retardants (HFRs), including 13 polybrominated diphenyl ethers (PBDEs), 9 dechlorane-related compounds (DRCs) and 10 of the so-called alternative BFRs in food samples of animal origin. Gas chromatography (GC) coupled with magnetic sector high resolution mass spectrometry (HRMS) was used for the instrumental analysis. Intralaboratory validation of the developed method was performed in terms of recovery, repeatability, linear calibration ranges, instrumental and method limits of quantitation (i-LOQ and m-LOQ). Where possible, trueness was verified by the analysis of reference materials (RMs). Fo…
Detection of fluorine using laser-induced breakdown spectroscopy and Raman spectroscopy
2017
In general, the detection of F and other halogens is challenging through conventional techniques. In this paper, various approaches for the qualitative and quantitative analysis of F using the laser-induced breakdown spectroscopy (LIBS) technique were demonstrated. In LIBS, fluorine detection can be realized by means of atomic lines and molecular bands. For the purposes of our experiment, two sets of pellets with various contents of CaF2, CaCO3 and cellulose were analyzed using a lab-based LIBS system under a He atmosphere. The fluorine atomic line at 685.60 nm was correlated with CaF signals proving their close relationship. Consequently, the limits of detection were determined for both an…
Turning lipophilic phthalocyanines/TiO2 composites into efficient photocatalysts for the conversion of CO2 into formic acid under UV–vis light irradi…
2014
Metal-free, Cu(II)- or Zn(II) tetrakis [4-(2,4-bis-(1,1-dimethylpropyl)phenoxy)]phthalocyanines loaded over TiO2 (anatase) proved to be active in the photoreduction of CO2 to formic acid (HCO2H) in water under UV-vis light. CuPc/TiO2 is catalyst of choice, allowing to reach a maximum yield of HCO2H, unequalled by any other similar catalytic systems. Because of their low environmental impact, low potential cost, and efficient power conversion, these multipurpose materials show promise in the setup of sustainable methods for CO2 valorization. (C) 2014 Elsevier B.V. All rights reserved.
Hybrid TiO2 @ phthalocyanine catalysts in photooxidation of 4-nitrophenol: Effect of the matrix and sensitizer type
2020
Abstract Microcrystalline and nanocrystalline anatase (TiO2) based hybrid photocatalysts including selected phthalocyanine sensitizers were explored in photooxidation of 4-nitrophenol (4-NP) in water. Composites obtained with the homemade pure nano-anatase displayed a very poor catalytic performance compared to the other ones prepared from the commercial Tioxide-Huntsman (micro) and Evonik P25 (nano) products. In particular, the microcrystalline anatase impregnated with sandwich phthalocyanines of Gd or Yb showed excellent results both in photooxidation of 4-NP and hydroquinone, and proved the only ones which completely removed these two compounds from the system during the same reaction cy…