scholarly journals Thiourea Organocatalysts as Emerging Chiral Pollutants: En Route to Porphyrin-Based (Chir)Optical Sensing

Chemosensors ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 278
Author(s):  
Nele Konrad ◽  
Matvey Horetski ◽  
Mariliis Sihtmäe ◽  
Khai-Nghi Truong ◽  
Irina Osadchuk ◽  
...  
Keyword(s):  
Vibrio Fischeri ◽  
Safety Data ◽  
Soret Band ◽  
Environmental Safety ◽  
Cd Spectroscopy ◽  
X Ray Diffraction ◽  
Base Interaction ◽  
Significant Toxicity ◽  
Binding Event ◽  
Luminescence Inhibition

Environmental pollution with chiral organic compounds is an emerging problem requiring innovative sensing methods. Amino-functionalized thioureas, such as 2-(dimethylamino)cyclohexyl-(3,5-bis(trifluoromethyl)phenyl)thiourea (Takemoto’s catalyst), are widely used organocatalysts with virtually unknown environmental safety data. Ecotoxicity studies based on the Vibrio fischeri luminescence inhibition test reveal significant toxicity of Takemoto’s catalyst (EC50 = 7.9 mg/L) and its NH2-substituted analog (EC50 = 7.2–7.4 mg/L). The observed toxic effect was pronounced by the influence of the trifluoromethyl moiety. En route to the porphyrin-based chemosensing of Takemoto-type thioureas, their supramolecular binding to a series of zinc porphyrins was studied with UV-Vis and circular dichroism (CD) spectroscopy, computational analysis and single crystal X-ray diffraction. The association constant values generally increased with the increasing electron-withdrawing properties of the porphyrins and electron-donating ability of the thioureas, a result of the predominant Zn⋯N cation–dipole (Lewis acid–base) interaction. The binding event induced a CD signal in the Soret band region of the porphyrin hosts—a crucial property for chirality sensing of Takemoto-type thioureas.

Alkaloids of Rauvolfia salicifolia GRISEB species

1982 ◽  
Vol 47 (11) ◽  
pp. 2912-2921 ◽  
Author(s):  
Patricia Sierra ◽  
Ladislav Novotný ◽  
Zdeněk Samek ◽  
Miloš Buděšínský ◽  
Ladislav Dolejš ◽  
...  
Keyword(s):  
Absolute Configuration ◽  
Cd Spectroscopy ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Absolute

From the endemic Cuban species Rauvolfia salicifolia GRISEB nine alkaloids were isolated of which the following seven had been already described: (+)-ajmalidine (I), (-)-reserpiline (II), (-)-isoreserpiline (III), (-)-isocarapanaubine (IV), (-)-ajmalicine (V), (+)-vellosimine (VI), and (+)-yohimbine (VII). The structure of (-)-raucubaine (VIII) had been previously determined by X-ray diffraction and the structure of the alkaloid (-)-raucubainine (IX) was suggested on the basis of its conversion to (-)-raucubaine (VIII). The absolute configuration of (-)-raucubaine and (-)-raucubainine was elucidated by CD spectroscopy.

The relationship between composition and toxicity of tannery wastewater

2004 ◽  
Vol 49 (1) ◽  
pp. 39-46 ◽  
Author(s):  
M. Cotman ◽  
J. Zagorc-Končan ◽  
A. Žgajnar-Gotvajn
Keyword(s):  
Activated Carbon ◽  
Daphnia Magna ◽  
Vibrio Fischeri ◽  
Organic Pollution ◽  
Tannery Wastewater ◽  
Organic Load ◽  
Short Term ◽  
Air Stripping ◽  
Luminescence Inhibition ◽  
The Relationship

Key toxic components have been identified in pre-treated tannery wastewater with fractionation of samples through chemical and physical means (filtration, air stripping, adsorption on activated carbon, …). The goal of each fractionation step was to reduce the toxicity due to a specific group of chemicals and compare the results to the toxicity present in the unaltered sample. Toxicity short-term tests with the invertebrate Daphnia magna and the bacterial luminescence inhibition test with Vibrio fischeri were used in combination with chemical analyses. During the toxicity identification and evaluation fractionation, a portion of the sample was pressure filtered. Treated samples contained less organic pollution and metals and were less toxic especially to Daphnia magna. For the removal of ammonia the second portion of sample was air-stripped at different pH levels. We removed 84% of ammonia at pH 11; the toxicity to both organisms decreased but ammonia did not have a deciding effect on the toxicity of tannery wastewater when the organic load was still present. The most successful procedure for toxicity removal was adsorption on powdered activated carbon. We removed organic pollution detected as COD, organic nitrogen compounds and part of the metals. Zeolite treatment was a little less successful for removing ammonia than air-stripping.

scholarly journals Tetranuclear Cu(ii)-chiral complexes: synthesis, characterization and biological activity

RSC Advances ◽  
2019 ◽  
Vol 9 (42) ◽  
pp. 24087-24091 ◽  
Author(s):  
Krisana Peewasan ◽  
Marcel P. Merkel ◽  
Kristof Zarschler ◽  
Holger Stephan ◽  
Christopher E. Anson ◽  
...  
Keyword(s):  
Biological Activity ◽  
Schiff Base ◽  
Single Crystal ◽  
Cd Spectroscopy ◽  
Schiff Base Complexes ◽  
X Ray Diffraction ◽  
Chiral Complexes ◽  
Enantiomerically Pure ◽  
X Ray

A pair of tetranuclear chiral Cu(ii)-Schiff-base complexes were synthesized using enantiomerically pure (S)-H2L and (R)-H2L ligands. These were characterised using single-crystal X-ray diffraction and CD spectroscopy and their biological activity tested.

scholarly journals Determination of the absolute stereostructure of a cyclic azobenzene from the crystal structure of the precursor containing a heavy element

2016 ◽  
Vol 12 ◽  
pp. 2211-2215 ◽  
Author(s):  
Reji Thomas ◽  
Nobuyuki Tamaoki
Keyword(s):  
Cd Spectroscopy ◽  
Chiral Molecules ◽  
X Ray Diffraction ◽  
X Ray ◽  
Heavy Atoms ◽  
Unambiguous Determination ◽  
The Common ◽  
The Absolute ◽  
Reverse Method

Single crystal X-ray diffraction has been used as one of the common methods for the unambiguous determination of the absolute stereostructure of chiral molecules. However, this method is limited to molecules containing heavy atoms or to molecules with the possibility of functionalization with heavy elements or chiral internal references. Herein, we report the determination of the absolute stereostructure of the enantiomers of molecule (E)-2, which lacks the possibility of functionalization, using a reverse method, i.e., defunctionalization of its precursor of known stereostructure with bromine substitution (S-(−)-(E)-1). A reductive debromination of S-(−)-(E)-1 results in formation of one of the enantiomers of (E)-2. Using a combination of HPLC and CD spectroscopy we could safely assign the stereostructure of one of the enantiomers of (E)-2, the reduced product R-(−)-(E)-1.

scholarly journals PHYSICAL STUDIES OF ISOLATED EUCARYOTIC NUCLEI

1972 ◽  
Vol 53 (3) ◽  
pp. 715-736 ◽  
Author(s):  
Donald E. Olins ◽  
Ada L. Olins
Keyword(s):  
Ethidium Bromide ◽  
Binding Capacity ◽  
Chromatin Condensation ◽  
Blue Shift ◽  
Cd Spectroscopy ◽  
Close Packing ◽  
Cd Spectra ◽  
X Ray Diffraction ◽  
X Ray ◽  
Solvent Environment

The degree of chromatin condensation in isolated rat liver nuclei and chicken erythrocyte nuclei was studied by phase-contrast microscopy as a function of solvent pH, K+ and Mg++ concentrations Data were represented as "phase" maps, and standard solvent conditions selected that reproducibly yield granular, slightly granular, and homogeneous nuclei Nuclei in these various states were examined by ultraviolet absorption and circular dichroism (CD) spectroscopy, low-angle X-ray diffraction, electron microscopy, and binding capacity for ethidium bromide Homogeneous nuclei exhibited absorption and CD spectra resembling those of isolated nucleohistone. Suspensions of granular nuclei showed marked turbidity and absorption flattening, and a characteristic blue-shift of a crossover wavelength in the CD spectra. In all solvent conditions studied, except pH < 2 3, low-angle X-ray reflections characteristic of the native, presumably superhelical, nucleohistone were observed from pellets of intact nuclei. Threads (100–200 A diameter) were present in the condensed and dispersed phases of nuclei fixed under the standard solvent conditions, and examined in the electron microscope after thin sectioning and staining Nuclei at neutral pH, with different degrees of chromatin condensation, exhibited similar binding capacities for ethidium bromide. These data suggest a model that views chromatin condensation as a close packing of superhelical nucleohistone threads but still permits condensed chromatin to respond rapidly to alterations in solvent environment.

Application of Fenton oxidation to reduce the toxicity of mixed parabens

2016 ◽  
Vol 74 (8) ◽  
pp. 1867-1875 ◽  
Author(s):  
Rui C. Martins ◽  
Marta Gmurek ◽  
André F. Rossi ◽  
Vanessa Corceiro ◽  
Raquel Costa ◽  
...  
Keyword(s):  
Neuronal Activity ◽  
Vibrio Fischeri ◽  
Brain Slices ◽  
Oxygen Demand ◽  
Point Of View ◽  
Water Matrix ◽  
Luminescence Inhibition ◽  
Toxicity Analysis ◽  
Single Compound ◽  
The Impact

The aims of the present work were to assess the application of a chemical process to degrade a mixture of parabens and determine the influence of a natural river water matrix on toxicity. Model effluents containing either a single compound, namely methylparaben, ethylparaben, propylparaben, butylparaben, benzylparaben or p-hydroxybenzoic acid, or to mimic realistic conditions a mixture of the six compounds was used. Fenton process was applied to reduce the organic charge and toxic properties of the model effluents. The efficiency of the decontamination has been investigated using a chemical as well as a toxicological approach. The potential reduction of the effluents' toxicity after Fenton treatment was evaluated by assessing (i) Vibrio fischeri luminescence inhibition, (ii) lethal effects amongst freshwater Asian clams (Corbicula fluminea), and (iii) the impact on mammalian neuronal activity using brain slices. From the environmental point of view such a broad toxicity analysis has been performed for the first time. The results indicate that Fenton reaction is an effective method for the reduction of chemical oxygen demand of a mixture of parabens and their toxicity to V. fischeri and C. fluminea. However, no important differences were found between raw and treated samples in regard to mammalian neuronal activity.

scholarly journals Application of geochemical and ecotoxicity indices for assessment of heavy metals content in soils / Zastosowanie wskaźników geochemicznych i ekotokysycznych w ocenie zawartości metali ciężkich w glebach

2015 ◽  
Vol 41 (2) ◽  
pp. 54-63 ◽  
Author(s):  
Agnieszka Baran ◽  
Jerzy Wieczorek
Keyword(s):  
Heavy Metals ◽  
Soil Pollution ◽  
Vibrio Fischeri ◽  
Pollution Index ◽  
Geochemical Background ◽  
Human Pressure ◽  
Southern Poland ◽  
Metal Contents ◽  
Luminescence Inhibition ◽  
High Level

Abstract The research aimed to use chemical, geochemical, and ecotoxicity indices to assess the heavy metals content in soils with different degrees of exposure to human pressure. The research was conducted in southern Poland, in the Malopolska (Little Poland) province. All metal contents exceeded geochemical background levels. The highest values of the Igeo index were found for cadmium and were 10.05 (grasslands), 9.31 (forest), and 5.54 (arable lands), indicating extreme soil pollution (class 6) with this metal. Mean integrated pollution index (IPI) values, depending on the kind of use, amounted to 3.4 for arable lands, 4.9 for forests, and 6.6 for grasslands. These values are indicative of a high level of soil pollution in arable lands and an extremely high level of soil pollution in grasslands and forests. Depending on the type of soil use, Vibrio fischeri luminescence inhibition was from -33 to 59% (arable lands), from -48 to 78% (grasslands), and from 0 to 88% (forest). Significantly the highest toxicity was found in soils collected from forest grounds.

scholarly journals Trioxatriangulenium (TOTA+) as a Robust Carbon-based Lewis Acid in Frustrated Lewis Pair Chemistry

2020 ◽  
Author(s):  
Aslam Shaikh ◽  
Jose M Veleta ◽  
Jules Moutet ◽  
thomas Gianetti
Keyword(s):  
Lewis Acid ◽  
Disulfide Bonds ◽  
Variable Temperature ◽  
X Ray Diffraction ◽  
Frustrated Lewis Pairs ◽  
Acid Base ◽  
Base Interaction ◽  
Paramagnetic Resonance ◽  
Heterolytic Cleavage ◽  
Encounter Complex

We report the reactivity between the Lewis acidic trioxotriangulenium ion (TOTA<sup>+</sup>) and a series of Lewis bases such as phosphines and <i>N</i>-heterocyclic carbene (NHC). The nature of the Lewis acid-base interaction was analyzed via variable temperature (VT) NMR spectroscopy, single-crystal X-ray diffraction, UV-visible spectroscopy, and DFT calculations. While small and strongly nucleophilic phosphines, such as PMe<sub>3</sub>, led to the formation of a stable Lewis acid-base adduct, frustrated Lewis pairs (FLPs) were observed for sterically hindered bases such as P(<i><sup>t</sup></i>Bu)<sub>3</sub>. The TOTA<sup>+</sup>-P(<i><sup>t</sup></i>Bu)<sub>3</sub> FLP was characterized as an encounter complex, and was found to promote the heterolytic cleavage of disulfide bonds, formaldehyde fixation, dehydrogenation of 1,4-cyclohexadiene, heterolytic cleavage of C–Br bond, and interception of Staudinger reaction intermediate. Moreover, TOTA<sup>+</sup> and NHC was found to first undergo single-electron transfer (SET) to form [TOTA]<sup>•</sup>[NHC]<sup> •+</sup>, which was confirmed via electron paramagnetic resonance (EPR) spectroscopy, and subsequently form a [TOTA-NHC]<sup>+</sup> adduct or a mixture of products depending the reaction condition used.

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