87 research outputs found
Broad-Range Spectral Analysis for Chiral Metal Coordination Compounds: (Chiro)optical Superspectrum of Cobalt(II) Complexes
No full textChiroptical broad-range spectral analysis extending from UV to mid-IR was employed to study a family of Co(II) N-(1-(aryl)ethyl)salicylaldiminato Schiff base complexes with pseudotetrahedral geometry associated with chirality-at-metal of the Δ/∇ type. While common chiral organic compounds have well-separated absorption and circular dichroism spectra (CD) in the UV/vis and IR regions, chiral Co(II) complexes feature an almost unique continuum of absorption and CD bands, which cover in sequence the UV, visible, near-IR (NIR), and IR regions of the electromagnetic spectrum. They can be collected in a single (chiro)optical superspectrum ranging from the UV (230 nm, 5.4 eV) to the mid-IR (1000 cm-1, 0.12 eV), which offers a fingerprint of the structure and stereochemistry of the metal complexes. Each region of the superspectrum contributes to one piece of information: the NIR-CD region, in combination with TDDFT calculations, allows a reliable assignment of the metal-centered chirality; the UV-CD region facilitates the analysis of the Δ/∇ diastereomeric equilibrium in solution; and the IR-VCD region contains a combination of low-lying metal-centered electronic states (LLES) and ligand-centered vibrations and displays characteristically enhanced and monosignate VCD bands. Circular dichroism in the NIR and IR regions is crucial to reveal the presence of d-d transitions of the Co(II) core which, due to the electric-dipole forbidden character, would be otherwise overlooked in the corresponding absorption spectra
Synthesis, X-ray, and Spectroscopic Study of Dissymmetric Tetrahedral Zinc(II) Complexes from Chiral Schiff Base Naphthaldiminate Ligands with Apparent Exception to the ECD Exciton Chirality
No full textBidentate enantiopure Schiff base ligands, (R or S)-N-1-(Ar)ethyl-2-oxo-1-naphthaldiminate (R- or S-N^O), diastereoselectively provide λ- or δ-chiral-at-metal four-coordinated Zn(R- or S-N^O)2 Ar = C6H5; Zn-1R or Zn-1S and p-C6H4OMe; Zn-2R or Zn-2S. Two R- or S-N^O-chelate ligands coordinate to the zinc(II) in a tetrahedral mode and induce λ- or δ-configuration at the zinc metal center. In the solid state, the R- or S-ligand diastereoselectively gives λ- or δ-Zn configuration, respectively, and forms enantiopure crystals. Single crystal structure determinations show two symmetry-independent molecules (A and B) in each asymmetric unit to give Z′ = 2 structures. Electronic circular dichroism (ECD) spectra show the expected mirror image relationship resulting from diastereomeric excess toward the λ-Zn for R-ligands and δ-Zn for S-ligands in solution. ECD spectra are well reproduced by TDDFT calculations, while the application of the exciton chirality method, in the common point-dipole approximation, predicts the wrong sign for the long-wavelength couplet. A dynamic diastereomeric equilibrium (λ vs δ) prevails for both R- and S-ligand-metal complexes in solution, respectively, evidenced by 1H NMR spectroscopy. Variable temperature 1H NMR spectra show a temperature-dependent shift of the diastereomeric equilibrium and confirm δ-Zn configuration (for S-ligand) to be the most stable one and favored at low temperature. DSC analyses provide quantitative diastereomeric excess in the solid state for Zn-2R and Zn-2S, which is comparable to the results of solution studies
SPECTROPHOTOMETRIC DETERMI ATION OF CYPERMETHRI INSECTICIDE IN EGGPLANT, OKRA AND TOMATO COLLECTED FROM DHAKA CITY
No full textSher-e-Bangla Agricultural University Research System (SAURES
A new perspective of environmental stress in heterogeneously contaminated landscapesbeyond the individual effect
No full texthe use of chemical products for human health, agricultural, and industrial activities is steadily increasing worldwide. These chemicals and their metabolites can be released either- directly or indirectly- into aquatic environments, leading to negative impacts on aquatic biota. To detect the effects of contaminants on organisms and to support ecosystem protection, Environmental Risk Assessment (ERA) has traditionally relied on forced exposure approaches, in which organisms are continuously exposed to contaminants. While useful, this method overlooks the connectivity among habitats and the spatial heterogeneity of contamination. In natural systems, habitats are not uniformly contaminated and are often interconnected, allowing many organisms to migrate between them in search of more favorable conditions. Therefore, it is essential to broaden the framework through which toxicity is assessed. A recently developed, non-forced exposure approach- reflecting natural environmental connectivity- offers an ecologically relevant means of evaluating the consequences of pollution in chemically heterogeneous aquatic ecosystems. This method integrates novel ecological concepts into ERA, including avoidance/repellence and preference behaviors (from a habitat selection perspective), the meta-ecosystem framework (considering habitat heterogeneity and connectivity), colonization (focusing on ecosystem recovery and attractiveness), and habitat fragmentation (recognizing that chemical barriers can isolate populations spatially).
In the present PhD study, it has been hypothesized that contamination in aquatic environments may interfere with the organisms' habitat selection process and alter the natural response of organisms to a stressor. However, it is difficult to simulate chemically heterogeneous habitats, which are connected and that can be selected by organisms. Therefore, different scale multi-compartmented systems (HeMHAS- Heterogeneous Multi-Habitat Assay System) were built to provide organisms with the necessary conditions to test the effect of contamination considering the ecological interactions in a spatially broader and connected landscape. The primary objective was firstly to assess to what extent the contaminants are crucial in the decision of the organisms to stay in, or avoid, a habitat; secondly, to assess the individual (biochemical/physiological damage to organisms) and ecological (changes in the community structure) consequences due to an organism's decision to stay or not in a contaminated environment. Different chemical contaminants covered various modes of primary action like metals (copper), contaminants of emerging concern (CEC) (ibuprofen, irgarol, terbuthylazine) and antidepressants (fluoxetine) were used in this study. Regarding the test species, different model organisms of shrimps and fish were tested.
We found that the tested chemicals have deleterious effects on the aquatic ecosystem. These contaminants cause both behavioral and biochemical changes in aquatic organisms. Organisms (fish and shrimp) studied in this experiment were able to avoid contaminants gradients in different ways. The avoidance behavior of species might depend on a cost-benefit balance between the risk of predation and exposure to the contaminants as well as chemicals mode of action. The study suggested that the avoidance/colonization pattern of species could jeopardize population persistence and species' habitat selection thereby indicating that contaminants may strongly affect interspecies relations. By using a mesocosm approach, the study also showed how contamination effects can be assessed in the HeMHAS combining effects on the structure and functioning and ecological relationships of ecosystems. The study highlighted the potential use of the HeMHAS system as a valuable tool to investigate and gain insights into the behavioral responses of organisms to various contaminants. The implementation of this work will help to protect, conserve and restore aquatic ecosystems, to avoid their deterioration, to understand the effects of contamination from a landscape perspective and to preserve the ecosystems' resources and services
Emerg Infect Dis
No full textDromedary camels are bred domestically and imported into Bangladesh. In 2015, of 55 camels tested for Middle East respiratory syndrome coronavirus in Dhaka, 17 (31%) were seropositive, including 1 bred locally. None were PCR positive. The potential for infected camels in urban markets could have public health implications and warrants further investigation
Spatial avoidance, inhibition of recolonization and population isolation in zebrafish (Danio rerio) caused by copper exposure under a non-forced approach
No full textAquatic ecosystems receive run-off and discharges from different sources that lead to the accumulation of contaminants such as copper. Besides producing lethal and sub-lethal effects, copper has shown to be aversive to zebrafish (Danio rerio) by triggering avoidance response. The primary aim of the present study was to evaluate how a copper gradient could affect the spatial distribution of D. rerio by triggering avoidance, preventing recolonization and isolating populations. Secondly, to what extent the food availability in a previously avoided environment could make it a less aversive environment was assessed. A non-forced, multi-compartmented exposure system with a copper gradient (0–300 μg·L), through which fish could move, was used for the avoidance and recolonization assays. To test the effect of copper on population isolation, two uncontaminated connected zones were separated by a chemical barrier with a copper concentration of 90 μg·L (a concentration producing an avoidance of 50% - AC). Zebrafish avoided copper and the 2 h-AC was 90.8 μg·L. The recolonization was in accordance with avoidance and the relationship AC/RC (RC: recolonization concentration) was around 2.5. When food was provided in the highest copper concentration, the recolonization pattern was altered, although the distribution of the fish was not statistically different from the scenario without food. The chemical barrier formed by copper (90 μg·L) impaired the migratory potential of the fish population by 41.3%; when food was provided in the last compartment, no statistically significant trend of fish moving towards that concentration was observed. Copper might act as an environmental disruptor by triggering spatial avoidance, preventing recolonization and isolating populations in zebrafish. The present study allows simultaneously including three ecological concepts to ecotoxicological studies that have received little attention: habitat selection, recolonization and habitat chemical fragmentation.C.V.M. Araújo is grateful to the Spanish Ministry of Science, Innovation and Universities for a Juan de la Cierva contract (IJCI-2014-19318). That Ministry partially funded this study (Explora Project #CGL2017-92160-EXP)
Behavioral and biochemical effects of fluoxetine on Poecilia reticulata: A relaxing state or an unapparent crisis?
No full textFluoxetine is an antidepressant used for the treatment of depression and anxiety disorders. We hypothesized that fluoxetine may positively influence the well-being of fish. We used Poecilia reticulata as a model organism and evaluated the behavioral, ecological and biochemical alterations following fluoxetine exposure at 0.05, 2.0, and 80 μg/L. For the behavioral analysis, we assessed swimming patterns, aggressiveness, social interactions and predatory behavior in a novel tank. Avoidance and colonization were evaluated as behavioral endpoints using the non-forced HeMHAS (Heterogeneous Multi-Habitat Assay System) as a novel approach to assess behavioral endpoints. The biochemical approach was based on the biotransformation enzyme activity (EROD and GST), anti-oxidative defense markers (GPx and GSH), oxidative damage indicators (LPO and DNA damage) and neurotoxicity (AChE activity). We found that the swimming patterns, aggressiveness and social behavior were reduced from 2 μg/L (p < 0.001) and the time spent by P. reticulata in the top and bottom areas differed significantly from 0.05 μg/L (p < 0.05). Additionally, organisms exposed to fluoxetine required more time (significantly from 2 μg/L; p < 0.001) to attack all the Daphnia sp. provided as prey. Further, in the colonization and avoidance tests, P. reticulata did not display colonization behavior (50–60 % time spent in the control compartment), and exhibited only weak avoidance responses, instead appearing to be either lethargic or in a relaxing state. The biochemical analysis showed that GST and LPO levels were elevated (p < 0.001), while both the GPx and GSH were reduced (p < 0.05).This study is part of the BeingHavior project (PID2022-137402OB- I00) funded by the Spanish Ministry of Science, Innovation and Universities (MCIN/AEI/10.13039/501100011033/FEDER, EU). The authors would like to acknowledge the Science and Technology Fellowship Trust (STFT), GoB for providing doctoral funding. The authors thank Jon Nesbit for his English revision of the text. The authors also express gratitude to Dr. Syed Muneeb, Duda, Andressa, Joel, Dr. Md Khurshid Alam Bhuiyan, Dr. María Úbeda, David Salvatierra, María Pilar Gonzalez for their support during the research. Camilo Dias Seabra Pereira thanks FAPESP (Process 2022/06151-0) and CNPq for Productivity Fellowship.Peer reviewe
Emerg Infect Dis
No full textDespite molecular and serologic evidence of Nipah virus in bats from various locations, attempts to isolate live virus have been largely unsuccessful. We report isolation and full-genome characterization of 10 Nipah virus isolates from Pteropus medius bats sampled in Bangladesh during 2013 and 2014.R01 TW005869/TW/FIC NIH HHS/United State
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