| 1. |
- Cai, Yixiao, et al.
(author)
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Changes in secondary structure of alpha-synuclein during oligomerization induced by reactive aldehydes
- 2015
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In: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 464:1, s. 336-341
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Journal article (peer-reviewed)abstract
- The oxidative stress-related reactive aldehydes 4-hydroxy-2-nonenal (HNE) and 4-oxo-2-nonenal (ONE) have been shown to promote formation of alpha-synuclein oligomers in vitro. However, the changes in secondary structure of alpha-synuclein and the kinetics of the oligomerization process are not known and were the focus of this study. Size exclusion chromatography showed that after 1 h of incubation, HNE induced the formation of an oligomeric alpha-synuclein peak with a molecular weight of about similar to 2000 kDa, which coincided with a decreasing similar to 50 kDa monomeric peak. With prolonged incubation (up to 24 h) the oligomeric peak became the dominating molecular species. In contrast, in the presence of ONE, a similar to 2000 oligomeric peak was exclusively observed after 15 min of incubation and this peak remained constant with prolonged incubation. Western blot analysis of HNE-induced alpha-synuclein oligomers showed the presence of monomers (15 kDa), SDS-resistant low molecular (30-160 kDa) and high molecular weight oligomers (>= 260 kDa), indicating that the oligomers consisted of both covalent and non-covalent protein. In contrast, ONE-induced alpha-synuclein oligomers only migrated as covalent cross-linked high molecular-weight material (>= 300 kDa). Both circular dichroism (CD) and Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy showed that the formation of HNE- and ONE-induced oligomers coincided with a spectral change from random coil to beta-sheet. However, ONE-induced alpha-synuclein oligomers exhibited a slightly higher degree of beta-sheet. Taken together, our results indicate that both HNE and ONE induce a change from random coil to beta-sheet structure that coincides with the formation of alpha-synuclein oligomers; albeit through different kinetic pathways depending on the degree of cross-linking. (C) 2015 Elsevier Inc. All rights reserved.
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| 2. |
- Ahlinder, Linnea, et al.
(author)
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Graphene oxide nanoparticle attachment and its toxicity on living lung epithelial cells
- 2015
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In: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 5:73, s. 59447-59457
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Journal article (peer-reviewed)abstract
- Since its discovery, graphene and its oxidized form, graphene oxide (GO), have attracted interest in a wide range of technical applications. Concerns about their potential toxicity calls for scrutinized studies, but hitherto conflicting results have been reported which partly may be due to variations of synthesis and exposure procedures. Here we report on the attachment and toxicity of contamination-free graphene oxide nanoparticles (GONP) in living lung epithelial cells. The synthesis of chemically pure GONP was made by an improvement of the Hummer's method based on graphene exfoliated from graphite using high-intensity ultrasonication, resulting in two dimensional sheets with a lateral dimension in the range 200 nm to 3 mu m and thickness of 0.9 nm. Confocal Raman spectroscopy combined with multivariate analysis was used to study the interaction of GONP and living cells. It is shown that overlapping Raman bands due to GONPs and biomolecules in the cells can clearly be separated with this approach. Orthogonal partial least squares discriminant analysis was used to compare spectral data collected from cells exposed to GONP with spectral data collected from non-exposed control cells, and spectral data from cells exposed to a surfactant known to induce apoptosis. Our analyses show that GONP readily attach to the cells, forming sheets which cover a large fraction of the cell surfaces, and induce small chemical changes. In particular, chemical modifications of proteins and lipids in lung epithelial cells are inferred. GONPs do not, however, decrease cell viability. In contrast, enhanced cell proliferation is observed. Our results shed new light on the interactions of GO, and in contrast to some previous reports, suggest that GO is not toxic. The hyperspectral Raman spectroscopy analysis employed here should be applicable for other fields in nanomedicine as a label-free non-perturbing analytical method.
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| 3. |
- Arvizu, Miguel A, et al.
(author)
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Electrochromic WO3 thin films attain unprecedented durability by potentiostatic pretreatment
- 2019
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In: Journal of Materials Chemistry A. - : ROYAL SOC CHEMISTRY. - 2050-7488 .- 2050-7496. ; 7:6, s. 2908-2918
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Journal article (peer-reviewed)abstract
- Electrochromic windows and glass facades are able to impart energy efficiency jointly with indoor comfort and convenience. Long-term durability is essential for practical implementation of this technology and has recently attracted broad interest. Here we show that a simple potentiostatic pretreatment of sputterdeposited thin films of amorphous WO3-the most widely studied electrochromic material-can yield unprecedented durability for charge exchange and optical modulation under harsh electrochemical cycling in a Li-ion-conducting electrolyte and effectively evades harmful trapping of Li. The pretreatment consisted of applying a voltage of 6.0 V vs. Li/Li+ for several hours to a film backed by a transparent conducting In2O3: Sn layer. Associated compositional and structural modifications were probed by several techniques, and improved durability was associated with elemental intermixing at the WO3/ITO and ITO/glass boundaries as well as with carbonaceous solid-electrolyte interfacial layers on the WO3 films. Our work provides important new insights into long-term durability of ion-exchange-based devices.
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| 4. |
- Boyadjiev, Stefan I., et al.
(author)
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Study of the electrochromic properties of MAPLE and PLD deposited WO3 thin films
- 2017
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Conference paper (peer-reviewed)abstract
- Tungsten trioxide (WO3) thin films were grown by matrix assisted pulsed laser evaporation (MAPLE) and pulsed laser deposition (PLD), and their properties were investigated for electrochromic applications. The structure, morphology and optical properties of these MAPLE and PLD grown from monoclinic WO3 nano-sized particles WO3 thin films were also studied. A KrF* excimer (λ=248 nm, ζFWHM=25 ns) laser source was used in all experiments. The films were studied by atomic force microscopy (AFM), grazing incidence X-ray diffraction (GIXRD) and Fourier transform infrared spectroscopy (FTIR). Cyclic voltammetry measurements were also performed in glove box with Ar atmosphere towards Li electrode, and the coloring and bleaching states were investigated. The morpho-structural investigations disclosed the synthesis of single-phase monoclinic WO3 films consisting of crystalline nano-grains embedded in an amorphous matrix. All thin films showed good electrochromic properties - strong coloration and fast and full bleaching. The effect was observed for many cycles, the strong coloration and full bleaching being preserved. These results are promising for future application of MAPLE and PLD deposited WO3 thin films in the development of electrochromic devices.
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| 5. |
- Cindemir, Umut, 1986-, et al.
(author)
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Characterization of nanocrystalline-nanoporous nickel oxide thin films prepared by reactive advanced gas deposition
- 2019
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In: Materials Chemistry and Physics. - : ELSEVIER SCIENCE SA. - 0254-0584 .- 1879-3312. ; 227, s. 98-104
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Journal article (peer-reviewed)abstract
- Nanocrystalline-nanoporous Ni oxide is of much interest for gas sensors and other applications. Reactive advanced gas deposition (AGD) stands out as a particularly promising technique for making thin films of this material owing to the techniques ability to separate between the growth of individual nanoparticles and their subsequent deposition to create a consolidated material on a substrate. Here we report on the characterization of Ni oxide films, made by reactive AGD, by several methods. X-ray diffractometry showed that the films had a face centered cubic NiO structure, and scanning electron microscopy indicated a compact nanoparticulate composition. X-ray photoelectron spectroscopy showed the presence of Ni3+ and demonstrated that these states became less prominent upon heat treatment in air. Extended x-ray absorption fine structure analysis elucidated the local atomic structure; in particular, data on interatomic distances and effects of annealing on local disorder showed that the Ni oxide nanoparticles crystallize upon annealing while maintaining their nanoparticle morphology, which is a crucial feature for reproducible fabrication of Ni oxide thin films for gas sensors. Importantly, several techniques demonstrated that grain growth remained modest for annealing temperatures as high as 400 degrees C for 1700-nm-thick films. The present article is a sequel to an earlier one [U. Cindemir et al., Sensors and Actuators B 242 (2017) 132-139] in which we reported on fluctuation-enhanced and conductometric gas sensing with Ni oxide films prepared by AGD.
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| 6. |
- Geremariam Welearegay, Tesfalem, et al.
(author)
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Diagnosis of Human Echinococcosis via Exhaled Breath Analysis : A Promise for Rapid Diagnosis of Infectious Diseases Caused by Helminths
- 2019
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In: Journal of Infectious Diseases. - : Oxford University Press (OUP). - 0022-1899 .- 1537-6613. ; 219:1, s. 101-109
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Journal article (peer-reviewed)abstract
- Background: Human echinococcosis is a neglected infectious disease affecting more than 1 million people globally. Its diagnosis is expensive and difficult because of lack of adequate resources in low-resource locations, where most cases occur.Methods: A group of volunteers diagnosed with the 2 main types of echinococcosis and corresponding control groups were recruited from hospitals in Tunisia (32 patients with cystic echinococcosis and 43 controls) and Poland (16 patients with alveolar echinococcosis and 8 controls). Breath samples were collected from all patients and analyzed by gas chromatography coupled to mass spectrometry, and a specifically developed electronic nose system.Results: The chemical analysis revealed statistically different concentrations of 2 compounds in the breath of patients with cystic echinococcosis compared to controls, and statistically different concentrations of 7 compounds in the breath of patients with alveolar echinococcosis compared to controls. The discrimination accuracy achieved by the electronic nose system was 100% for cystic echinococcosis and 92.9% for alveolar echinococcosis, while the discrimination accuracy between these 2 patient groups was 92.1%.Conclusion: Here we advocate a noninvasive, fast, easy-to-operate and nonexpensive diagnostic tool for the diagnosis of human echinococcosis disease through exhaled breath analysis, suitable for early diagnosis and population screening.
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| 7. |
- Geremariam Welearegay, Tesfalem, et al.
(author)
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Fabrication and characterisation of ligand-functionalised ultrapure monodispersed metal nanoparticle nanoassemblies employing advanced gas deposition technique
- 2018
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In: Nanotechnology. - : IOP PUBLISHING LTD. - 0957-4484 .- 1361-6528. ; 29:6
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Journal article (peer-reviewed)abstract
- Here, we report for the first time the fabrication of ligand-functionalised ultrapure monodispersed metal nanoparticles (Au, Cu, and Pt) from their pure metal precursors using the advanced gas deposition technique. The experimental conditions during nanoparticle formation were adjusted in order to obtain ultrafine isolated nanoparticles on different substrates. The morphology and surface analysis of the as-deposited metal nanoparticles were investigated using scanning electron microscopy, x-ray diffraction and Fourier transform infra-red spectroscopy, which demonstrated the formation of highly ordered pure crystalline nanoparticles with a relatively uniform size distribution of similar to 10 nm (Au), similar to 4 nm (Cu) and similar to 3 nm (Pt), respectively. A broad range of organic ligands containing thiol or amine functional groups were attached to the nanoparticles to form continuous networks of nanoparticle-ligand nanoassemblies, which were characterised by scanning electron microscopy and x-ray photoelectron spectroscopy. The electrical resistance of the functional nanoassemblies deposited in the gap spacing of two microfabricated parallel Au electrodes patterned on silicon substrates ranged between tens of k Omega and tens of M Omega, which is suitable for use in many applications including (bio)chemical sensors, surface-enhanced Raman spectroscopy and molecular electronic rectifiers.
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| 8. |
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| 9. |
- Haas, Julian, et al.
(author)
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Polycrystalline diamond thin-film waveguides for mid-infrared evanescent field sensors
- 2018
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In: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 3:6, s. 6190-6198
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Journal article (peer-reviewed)abstract
- Photonic design and optimization of thin-film polycrystalline diamond waveguides are shown, serving as advanced evanescent field transducers in the mid-infrared fingerprint regime (2000-909 cm(-1); 5-11 mu m). Design constraints inherent to optical/system considerations and the material were implemented in a finite element method (FEM)-based simulation method that allowed three-dimensional modeling of the overall structure. Thus, lateral mode confinement, attenuation in the direction of radiation propagation, and physical resilience were evaluated. In a final step, the designed structures were fabricated, and their utility in combination with a broadly tunable external cavity quantum cascade laser for chemical sensing of a liquid phase analyte was demonstrated.
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| 10. |
- Henych, Jiri, et al.
(author)
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Chemical warfare agent simulant DMMP reactive adsorption on TiO2/graphene oxide composites prepared via titanium peroxo-complex or urea precipitation
- 2018
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In: Journal of Hazardous Materials. - : Elsevier. - 0304-3894 .- 1873-3336. ; 359, s. 482-490
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Journal article (peer-reviewed)abstract
- Two water-based methods were used to produce TiO2/graphene oxide (GO) nanocomposites with 1 and 2 wt.% GO. Both procedures exclude the use of organometallic precursors, as well as the high-pressure and high-temperature treatments, which facilitate pure and energy efficient synthesis amenable for larger scale synthesis. Nanocomposites with narrow (< 10 nm) and long spindle-like (< 100 nm) TiO2 nanoparticles supported on GO flakes were obtained (TiO2/GO), and their properties for reactive destruction of the organophosphorus simile chemical warfare agent (CWA) dimethyl methylphosphonate (DMMP) were investigated by in situ DRIFTS spectroscopy. Both synthesis procedures yielded highly reactive nanocomposites with markedly different properties compared to similarly prepared pure TiO2 nanoparticles. GO also induced morphology and texture changes, which were observed to have a significant impact on the adsorption and reactivity of the nano composites, and which were strongly related to synthesis procedure. In particular, the reduction state of GO, as measured by Raman spectroscopy, was observed to play a major role for the reactivity of the TiO2/GO nano composites.
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