Search results for "Spectrometry"
showing 10 items of 3206 documents
Quantitative Vibrational Spectrometry in the 21st Century: A Scientometric Evaluation
2005
Abstract The state of the art of research on vibrational spectrometry–based quantitative methodologies was evaluated from the literature compiled in Analytical Abstracts from 1980. Medium and near infrared, Raman spectrometry, and photoacoustic methods of analysis were considered. The evolution of the number of published papers, the distribution of the literature as a function of the different application fields in which the vibrational methods were employed, and a study of the impact on this area of chemometric and automation studies clearly shows that, from the 1990s until now, the importance of vibrational spectrometry in application analysis has grown to reach maturity. This field provi…
Micelles of the chiral biocompatible surfactant (1R,2S)-dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide (DMEB): molecular dynamics …
2017
Rationale The study of self-assembly process of surfactant molecules in gas phase is of actually interest for several theoretical and technological reasons related to their possible exploitation as drug carriers, protein shields and cleaning agents in gas phase. Methods Stability and fragmentation patterns of singly and multiply charged (either positively or negatively) aggregates of the surfactant (1R,2S)-dodecyl(2-hydroxy-1-methyl-2-phenylethyl) dimethyl ammonium bromide (DMEB) in gas phase have been studied by ion mobility mass spectrometry and tandem mass spectrometry. Molecular dynamics (MD) simulations of positively and negatively singly and multiply charged DMEB aggregates have been …
Ammonium ion mediated resorcarene capsules: ESI-FTICRMS study on gas-phase structure and ammonium ion affinity of tetraethyl resorcarene and its per-…
2003
AbstractThe ammonium ion binding affinities of tetraethyl resorcarene (1) and its per-methylated derivative (2) were studied by electrospray ionization Fourier transform ion cyclotron resonance (ESI-FTICR) mass spectrometry. Ten different ammonium ions were tested as guests for the resorcarenes. A strong tendency for complex formation was observed with all ammonium ions of size and charge distribution suitable for noncovalent interactions with the cavities of the resorcarene hosts 1 and 2. Although differences in ammonium ion affinities were observed between 1 and 2 due to the dissimilar conformations, the overall tendency was that increase in the degree of substitution and the length of ca…
Enhanced organic mass fraction and decreased hygroscopicity of cloud condensation nuclei (CCN) during new particle formation events
2010
In a forested near-urban location in central Germany, the CCN efficiency of particles smaller than 100 nm decreases significantly during periods of new particle formation. This results in an increase of average activation diameters, ranging from 5 to 8% at supersaturations of 0.33% and 0.74%, respectively. At the same time, the organic mass fraction in the sub-100-nm size range increases from approximately 2/3 to 3/4. This provides evidence that secondary organic aerosol (SOA) components are involved in the growth of new particles to larger sizes, and that the reduced CCN efficiency of small particles is caused by the low hygroscopicity of the condensing material. The observed dependence of…
Carotenoids of two freshwater amphipod species (Gammarus pulex and G. roeseli) and their common acanthocephalan parasite Polymorphus minutus
2004
Carotenoid compositions of two freshwater Gammarus species (Crustacea: Amphipoda) and of their common acanthocephalan parasite Polymorphus minutus were characterized. The effect of carotenoid uptake by the parasite was addressed by comparing the carotenoid content of uninfected and infected female hosts. Using high-pressure liquid chromatography (HPLC), co-chromatography of reference pigments and electron ionization mass spectrometry of collected HPLC fractions (EI-MS), several xanthophylls and non-polar compounds were identified. Seven kinds of carotenoids, mainly xanthophylls, were identified in gammarids. Astaxanthin was predominant, amounting to 40 wt.% of total carotenoid in both uninf…
Field desorption mass spectrometric characterization of thiol conjugates related to the oxidative metabolism of the anticancer drug 4′-(9-acridinylam…
1983
Conjugation products with glutathione (GSH) and other endogenous thiol derivatives related to the oxidative metabolism of the anticancer drug, 4′-(9-acridinlyamino) methanesulfon-m-anisidide (m-AMSA) were synthesized and characterized by field desorption mass spectrometry. The primary microsomal oxidation product of m-AMSA, m-AQDI, was prepared by MnO2 oxidation of the parent drug and reacted with equimolar GSH, cysteine, N-acetylcysteine and N-acetylcysteine methyl ester to form m-AMSA-(5′)-thiol conjugates linkedat the aniline ring, as major products. Field desorption mass spectra of the conjugates provided abundant [MH]plus; ions, and characteristic fragment ions by cleavage at the thioe…
Identification of conjugation and cleavage products in the thiolytic metabolism of the anticancer drug 4'-(9-acridinylamino)methanesulfon-m-anisidide.
1981
Conjugation and cleavage products in the thiolytic metabolism of the anticancer drug 4′ -(9-acridinyl amino)methanesulfon-m-anisidide were identified primarily by high-pressure liquid chromatography in combination with field desorption mass spectrometry. The spontaneous metabolic pathway of the drug, as related to its susceptibility to nucleophilic attack by endogenous thiols at the 9-carbon atom of the acridine moiety, has been studied. Among the metabolite fraction of 4′-(9-acridinylamino)methanesulfon-m-anisidide excreted in rat bile after administration of a therapeutic dose, a conjugate was identified as the 9-acridinyl thioether of glutathione. This conjugation product and the corresp…
Amyloid Fibrils Formation of Concanavalin A at Basic pH
2011
Mechanisms of partial unfolding and aggregation of proteins are of extreme interest in view of the fact that several human pathologies are characterized by the formation and deposition of protein-insoluble material, mainly composed of amyloid fibrils. Here we report on an experimental study on the heat-induced aggregation mechanisms, at basic pH, of concanavalin A (ConA), used as a model system. Thioflavin T (ThT) fluorescence and multiangle light scattering allowed us to detect different intertwined steps in the formation of ConA aggregates. In particular, the ThT fluorescence increase, observed in the first phase of aggregation, reveals the formation of intermolecular β-sheet structure wh…
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…
Apparent content curves: description and analytical applications. Resolution of binary mixtures
1992
The apparent content curves and their analytical applications are described. Basing on these curves a mathematical method, which permits the identification of the interfering component present in a binary mixture as well as the determination of the contents of both constituents, is proposed. The existence of considerable interaction coefficients is not an impediment for its application. Besides, the analyte contents in the mixture can be obtained without the use of standard interference solutions. The proposed procedure is applied to the analysis of mixtures of dyes with overlapping absorption spectra.