Fibrils are β-sheet-rich aggregates that are generally composed of several protofibrils and may adopt variable morphologies, such as twisted ribbons or flat-like sheets. This polymorphism is observed ...for many different amyloid associated proteins and polypeptides. In a previous study we proposed the existence of another level of amyloid polymorphism, namely, that associated with fibril supramolecular chirality. Two chiral polymorphs of insulin, which can be controllably grown by means of small pH variations, exhibit opposite signs of vibrational circular dichroism (VCD) spectra. Herein, using atomic force microscopy (AFM) and scanning electron microscopy (SEM), we demonstrate that indeed VCD supramolecular chirality is correlated not only by the apparent fibril handedness but also by the sense of supramolecular chirality from a deeper level of chiral organization at the protofilament level of fibril structure. Our microscopic examination indicates that normal VCD fibrils have a left-handed twist, whereas reversed VCD fibrils are flat-like aggregates with no obvious helical twist as imaged by atomic force microscopy or scanning electron microscopy. A scheme is proposed consistent with observed data that features a dynamic equilibrium controlled by pH at the protofilament level between left- and right-twist fibril structures with distinctly different aggregation pathways for left- and right-twisted protofilaments.
A low weight diode-pumped Nd:YAG laser (400 g, 1064 nm, 5 ns, 130 mJ per pulse) was developed for a compact laser-induced breakdown spectroscopy (LIBS) system to be installed on a robotized arm. ...Fiber optics delivery
vs.
conventional LIBS were compared for C, Si, Mn and Cr analysis in low-alloy steels. Fiber optics transformed the multimode laser beam to a flat-top beam with an improved fluence profile stability, resulting in shallow and more reproducible craters. A fast imaging study revealed that plasma generated by fiber optic pulses was plane-shaped, more uniform and dissipated two-fold faster compared with the plasma induced by direct laser beam focusing. Greater peak fluence for conventional LIBS provided plasma with 20-100 times more intensive emission due to the greater ablated mass, higher temperature and electron density. Improved reproducibility of shot-to-shot measurements was observed for plasma induced by fiber optic pulses, due to more stable ablation. The analytical capabilities of LIBS were compared for fiber optics
vs.
conventional LIBS in terms of calibration curve linearity, limits of detection and the root mean square error of the cross-validation procedure. Limits of detection for Si, Cr and Mn were always better for direct laser beam focusing; however, more importantly, the conventional LIBS system provided quantitative analysis for carbon in low-alloy steels (0.025-0.5% wt) with acceptable detection limits (55 ppm) while fiber optic pulses produced too-low intensity plasma.
A low weight diode-pumped Nd:YAG laser (400 g, 1064 nm, 5 ns, 130 mJ per pulse) was developed for a compact laser-induced breakdown spectroscopy (LIBS) system to be installed on a robotized arm.
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•Raman spectroscopy and machine learning is a universal tool for medical diagnosis.•Alzheimer’s disease is the most common form of dementia worldwide.•Raman spectroscopy is used for ...detecting Alzheimer’s disease in cerebrospinal fluid.•Statistical analysis improves the capability of the method for accurate diagnosis.•A novel method for detecting and diagnosing Alzheimer’s disease is proposed.
Current Alzheimer’s disease (AD) diagnostics is based on clinical assessments, imaging and neuropsychological tests that are efficient only at advanced stages of the disease. Early diagnosis of AD will provide decisive opportunities for preventive treatment and development of disease-modifying drugs. Cerebrospinal fluid (CSF) is in direct contact with the human brain, where the deadly pathological process of the disease occurs. As such, the CSF biochemical composition reflects specific changes associated with the disease and is therefore the most promising body fluid for AD diagnostic test development. Here, we describe a new method to diagnose AD based on CSF via near infrared (NIR) Raman spectroscopy in combination with machine learning analysis. Raman spectroscopy is capable of probing the entire biochemical composition of a biological fluid at once. It has great potential to detect small changes specific to AD, even at the earliest stages of pathogenesis. NIR Raman spectra were measured of CSF samples acquired from 21 patients diagnosed with AD and 16 healthy control (HC) subjects. Artificial neural networks (ANN) and support vector machine discriminant analysis (SVM-DA) statistical methods were used for differentiation purposes, with the most successful results allowing for the differentiation of AD and HC subjects with 84% sensitivity and specificity. Our classification models show high discriminative power, suggesting the method has a great potential for AD diagnostics. The reported Raman spectroscopic examination of CSF can complement current clinical tests, making early AD detection fast, accurate, and inexpensive. While this study shows promise using a small sample set, further method validation on a larger scale is required to indicate the true strength of the approach.
Femtosecond laser-induced breakdown spectroscopy Labutin, Timur A; Lednev, Vasily N; Ilyin, Alexey A ...
Journal of analytical atomic spectrometry,
01/2016, Letnik:
31, Številka:
1
Journal Article
Recenzirano
The presented review summarizes nearly two decades of studies on femtosecond laser-induced breakdown spectrometry (fs-LIBS). When an ultra-short (<1 ps) laser pulse is used for ablation, the physics ...of laser-induced plasma changes dramatically in comparison with ablation by pico or nanosecond pulses. A femtosecond laser pulse interacts only with the electron subsystem, while nanosecond pulses continuously interact with different thermodynamic states of material, starting from solid through liquid into plasma. The properties of ultra-short laser radiation, the timescale of fs-laser ablation and the radiative properties of fs plasma are briefly described. We consider the advantages of fs-LIBS, namely, low ablation thresholds, high-spatial resolution, and rapid analysis of samples, which require minimal invasion and allow high-efficiency transportation of laser radiation in filamentation mode for remote analysis. Moreover, we discussed possible limitations of the technique and different approaches to overcome such constraints while retaining the unique possibilities of fs-LIBS.
The presented review summarizes nearly two decades of studies on femtosecond laser-induced breakdown spectrometry (fs-LIBS).
The unique enhanced sensitivity of vibrational circular dichroism (VCD) to the formation and development of amyloid fibrils in solution is extended to four additional fibril-forming proteins or ...peptides where it is shown that the sign of the fibril VCD pattern correlates with the sense of supramolecular filament chirality and, without exception, to the dominant fibril morphology as observed in AFM or SEM images. Previously for insulin, it has been demonstrated that the sign of the VCD band pattern from filament chirality can be controlled by adjusting the pH of the incubating solution, above pH 2 for “normal” left-hand-helical filaments and below pH 2 for “reversed” right-hand-helical filaments. From AFM or SEM images, left-helical filaments form multifilament braids of left-twisted fibrils while the right-helical filaments form parallel filament rows of fibrils with a flat tape-like morphology, the two major classes of fibril morphology that from deep UV resonance Raman scattering exhibit the same cross-β-core secondary structure. Here we investigate whether fibril supramolecular chirality is the underlying cause of the major morphology differences in all amyloid fibrils by showing that the morphology (twisted versus flat) of fibrils of lysozyme, apo-α-lactalbumin, HET-s (218–289) prion, and a short polypeptide fragment of transthyretin, TTR (105–115), directly correlates to their supramolecular chirality as revealed by VCD. The result is strong evidence that the chiral supramolecular organization of filaments is the principal underlying cause of the morphological heterogeneity of amyloid fibrils. Because fibril morphology is linked to cell toxicity, the chirality of amyloid aggregates should be explored in the widely used in vitro models of amyloid-associated diseases.
In this paper, we briefly described the ecological consequences of six space rocket accidents launched from the Baikonur Cosmodrome between 1999 and 2018 and focused on an assessment of efficiency of ...soil remediation following the accidental crash of launch vehicle Proton-M on July 2, 2013, which resulted in the severest environmental impact in the modern Russian space industry. On the day after the accident, the content of carcinogenic unsymmetrical dimethylhydrazine and nitrosodimethylamine, as well as nitrate in soils of the crash site exceeded their maximal permissible concentrations by 8900, 6100 and 85 times, respectively. Mitigation measures included soil detoxication by a solution of 10% H2O2 and 1% iron complexonate, soil excavation and ploughing. Two years later (in April 2015), both unsymmetrical dimethylhydrazine and nitrosodimethylamine concentrations were below 0.05 mg/kg and nitrate concentration did not exceed 3.9 g/kg. As compared to background sites, soils of the crash site had significantly (P-value<0.05) lower values of pH and the content of total organic carbon, basicity from soda and carbonates and higher total nitrogen and soluble salt contents. Soil microbial communities were the most vulnerable component of the disturbed arid ecosystems, as their suppressed condition was indicated by a low biochemical oxygen demand and a very low cellulase activity.
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•10% H2O2 and 1% iron complexonate reduces UDMH soil pollution effectively.•Soil pollution by rocket propellants was negligible 2 years after accidental falling.•Soil chemical proxies recovered to normal after accidental UDMH pollution in 4 years.•Soil microbial communities is the most vulnerable component of disturbed ecosystems.
Remediation of soils affected by the accidental crash of launch vehicle (detoxication by 10% H2O2 and 1% iron complexonate, soil excavation and ploughing) reduced concentration of rocket propellants during 2 years and recovered soil chemical proxies in 4 years.
A two-step process of protein detection at a single molecule level using SERS was developed as a proof-of-concept platform for medical diagnostics. First, a protein molecule was bound to a linker in ...the bulk solution and then this adduct was chemically reacted with the SERS substrate. Traut's Reagent (TR) was used to thiolate Bovine serum albumin (BSA) in solution followed by chemical cross linking to a gold surface through a sulfhydryl group. A Glycine-TR adduct was used as a control sample to identify the protein contribution to the SER spectra. Gold SERS substrates were manufactured by electrochemical deposition. Solutions at an ultralow concentration were used for attaching the TR adducts to the SERS substrate. Samples showed the typical behavior of a single molecule SERS including spectral fluctuations, blinking and Raman signal being generated from only selected points on the substrate. The fluctuating SER spectra were examined using Principle Component Analysis. This unsupervised statistics allowed for the selecting of spectral contribution from protein moiety indicating that the method was capable of detecting a single protein molecule. Thus we have demonstrated, that the developed two-step methodology has the potential as a new platform for medical diagnostics.
One of the most important problems of environmental sciences is to determine limits for the sustainable functioning of affected ecosystems. The effects of volatile hydrocarbons (such as gasoline and ...kerosene) on plants in natural ecosystems have been poorly studied to date. The present work outlines the data of a field experiment on the effects of kerosene on the plants of forest and bog communities in Central Russia. In this paper, we model the influence of kerosene spillage on plants growing in a coniferous broad-leaved (aspen–spruce) forest and a raised bog with a subshrub–sphagnum pine forest. We used TS-1 kerosene, which is the most commonly used fuel for commercial aviation in Russia. The applied pollutant (loads of 1 to 100 g/kg) had a significant impact on herbaceous plants, leading to the death of individuals even at minimal doses. The shrubs of the bog community as well as the mosses of both communities were more resistant to kerosene. The recovery processes of plant communities were clearly pronounced as early as 2 years after the application of the pollutant. The level of kerosene threshold exposure, which significantly affects the dominant plants of the herb–shrub layer, can be defined as 1–5 g/kg for the forest community and 5–10 g/kg for the bog community.
The controlled reversal of supramolecular helical chirality in protein fibrils is reported for the first time. Normal or reversed insulin fibrils were grown by precise adjustment of pH. AFM images ...show two polymorphs corresponding to opposite senses of helical twist of the supramolecular structure with the same cross-β-sheet core.
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