I18-Microfocus Spectroscopy
|
Open Access
Abstract: Purpose : The purpose of this study was to investigate the distribution of Ca, Fe and Zn using X-ray fluorescence in human RPE/Bruch’s membrane/choroid with and without early AMD.
Methods : We used a set of unfixed frozen human retinal pigment epithelium (RPE)/choroid samples from young (n=1, female aged 34) and aged donors with (n=4, males, aged 73-78) and without (n=3, one female, aged 75-77) early AMD from Manchester Eye Tissue Repository. Using X-ray fluorescence microscopy (I18 Diamond light source, UK) with a 2 um beam, we obtained high-resolution Ca, Zn, Fe, sulphur, potassium, chloride and phosphorus maps covering areas up to 100 x 600 um2 of 30 um thick sections placed on quartz holders and scanned at room temperature
Results : Calcification was observed in the 3 groups. In the 34-year old sample, sparse small Ca spherules (2x2 um2) at the RPE/Bruch’s membrane interface not colocalising with Zn or Fe. In aged samples, with and without AMD, calcified nodules within RPE cells, at RPE/Bruch’s membrane interface and within druse in AMD. Every calcified nodule colocalised with Zn. Quantification revealed two types (high Zn content, low Zn content). In aged donors without AMD, high-Zn calcified nodules with Ca concentration of 3083+1679 ppm (mean+SD) (maximum 12809+9311) and Zn 66+55 ppm (max 125+75). The average size was 27+15 um2. In aged samples with AMD, high-Zn calcified nodules with average Ca concentration of 4316+1723 ppm (max 13105+7563) and Zn 97+57 ppm (max 201+143). Size 26x10 um2. In the aged non-AMD group, the low zinc-calcification nodules contained an average Ca ppm of 915+259 (max 1475+380) and Zn 33+18 ppm (max 40+21). The average size 28x16 um2. In the AMD group, the low Zn calcified nodules average Ca ppm 1544+1450 (max 3526+5289) and average Zn ppm 47+23 (max 64+37). Average size 19x10 um2. Calcified plaques in Bruch’s membrane from aged donors with and without AMD. Some of these plaques colocalised with Zn and also Fe. Fe-loaded structures in the choriocapillaris underlying calcified nodules and plaques.
Conclusions : Calcific nodules contain zinc in older eyes with and without AMD. Calcified nodules with lower amounts of Ca contained lower amounts of Zn, so the accumulation of Ca may occur in parallel to Zn. It is possible that iron-loaded structures in the choriocapillaris are macrophages.
|
Jun 2020
|
|
I18-Microfocus Spectroscopy
|
Diamond Proposal Number(s):
[15802]
Open Access
Abstract: Bacteria acquire phosphate (Pi) by maintaining a periplasmic concentration below environmental levels. We recently described an extracellular Pi buffer which appears to counteract the gradient required for Pi diffusion. Here, we demonstrate that various treatments to outer membrane (OM) constituents do not affect the buffered Pi because bacteria accumulate Pi in the periplasm, from which it can be removed hypo-osmotically. The periplasmic Pi can be gradually imported into the cytoplasm by ATP-powered transport, however, the proton motive force (PMF) is not required to keep Pi in the periplasm. In contrast, the accumulation of Pi into the periplasm across the OM is PMF-dependent and can be enhanced by light energy. Because the conventional mechanism of Pi-specific transport cannot explain Pi accumulation in the periplasm we propose that periplasmic Pi anions pair with chemiosmotic cations of the PMF and millions of accumulated Pi pairs could influence the periplasmic osmolarity of marine bacteria.
|
May 2020
|
|
I18-Microfocus Spectroscopy
|
M.
Bourdenx
,
A.
Nioche
,
S.
Dovero
,
M.-l.
Arotcarena
,
S.
Camus
,
G.
Porras
,
M.-l.
Thiolat
,
N. P.
Rougier
,
A.
Prigent
,
P.
Aubert
,
S.
Bohic
,
C.
Sandt
,
F.
Laferrière
,
E.
Doudnikoff
,
N.
Kruse
,
B.
Mollenhauer
,
S.
Novello
,
M.
Morari
,
T.
Leste-lasserre
,
I. Trigo
Damas
,
M.
Goillandeau
,
C.
Perier
,
C.
Estrada
,
N.
Garcia-carrillo
,
A.
Recasens
,
N. N.
Vaikath
,
O. M. A.
El-agnaf
,
M. T.
Herrero
,
P.
Derkinderen
,
M.
Vila
,
J. A.
Obeso
,
B.
Dehay
,
E.
Bezard
Diamond Proposal Number(s):
[13009]
Open Access
Abstract: Dopaminergic neuronal cell death, associated with intracellular α-synuclein (α-syn)–rich protein aggregates [termed “Lewy bodies” (LBs)], is a well-established characteristic of Parkinson’s disease (PD). Much evidence, accumulated from multiple experimental models, has suggested that α-syn plays a role in PD pathogenesis, not only as a trigger of pathology but also as a mediator of disease progression through pathological spreading. Here, we have used a machine learning–based approach to identify unique signatures of neurodegeneration in monkeys induced by distinct α-syn pathogenic structures derived from patients with PD. Unexpectedly, our results show that, in nonhuman primates, a small amount of singular α-syn aggregates is as toxic as larger amyloid fibrils present in the LBs, thus reinforcing the need for preclinical research in this species. Furthermore, our results provide evidence supporting the true multifactorial nature of PD, as multiple causes can induce a similar outcome regarding dopaminergic neurodegeneration.
|
May 2020
|
|
I18-Microfocus Spectroscopy
|
Diamond Proposal Number(s):
[9914, 18747]
Abstract: Magmatic systems are dominated by five volatiles, namely H2O, CO2, F, Cl, and S (the igneous quintet). Multiple studies have measured partitioning of four out of these five volatiles (H2O, CO2, F, and Cl) between nominally volatile-free minerals and melts, whereas the partitioning of sulfur is poorly known. To better constrain the behavior of sulfur in igneous systems we measured the partitioning of sulfur between clinopyroxene and silicate melts over a range of pressure, temperature, and melt composition from 0.8 to 1.2 GPa, 1000 to 1240 °C, and 49 to 66 wt% SiO2 (13 measurements). Additionally, we determined the crystal-melt partitioning of sulfur for plagioclase (6 measurements), orthopyroxene (2 measurements), amphibole (2 measurements), and olivine (1 measurement) in some of these same run products. Experiments were performed at high and low oxygen fugacities, where sulfur in the melt is expected to be dominantly present as an S6+ or an S2– species, respectively. When the partition coefficient is calculated as the total sulfur in the crystal divided by the total sulfur in the melt, the partition coefficient varies from 0.017 to 0.075 for clinopyroxene, from 0.036 to 0.229 for plagioclase, and is a maximum of 0.001 for olivine and of 0.003 for orthopyroxene. The variation in the total sulfur partition coefficient positively correlates with cation-oxygen bond lengths in the crystals; the measured partition coefficients increase in the order: olivine < orthopyroxene < clinopyroxene ≤ amphibole and plagioclase. At high oxygen fugacities in hydrous experiments, the clinopyroxene/melt partition coefficients for total sulfur are only approximately one-third of those measured in low oxygen fugacity, anhydrous experiments. However when the partition coefficient is calculated as total sulfur in the crystal divided by S2– in the melt, the clinopyroxene/melt partition coefficients for experiments with melts between ~51 and 66 wt% SiO2 can be described by a single mean value of 0.063 ± 0.010 (1σ standard deviation about the mean). These two observations support the hypothesis that sulfur, as S2–, replaces oxygen in the crystal structure. The results of hydrous experiments at low oxygen fugacity and anhydrous experiments at high oxygen fugacity suggest that oxygen fugacity has a greater effect on sulfur partitioning than water. Although the total sulfur clinopyroxene-melt partition coefficients are affected by the Mg/(Mg+Fe) ratio of the crystal, partition coefficients calculated using S2– in the melt display no clear dependence upon the Mg# of the clinopyroxene. Both the bulk and the S 2– partition coefficients appear unaffected by IVAl in the clinopyroxene structure. No effect of anorthite content nor of iron concentration in the crystal was seen in the data for plagioclase-melt partitioning. The data obtained for orthopyroxene and olivine were too few to establish any trends. The partition coefficients of total sulfur and S 2– between the crystals studied and silicate melts are typically lower than those of fluorine, higher than those of carbon, and similar to those of chlorine and hydrogen. These sulfur partition coefficients can be combined with analyses of volatiles in nominally volatile-free minerals and previously published partition coefficients of H2O, C, F, and Cl to constrain the concentration of the igneous quintet, the five major volatiles in magmatic systems.
|
May 2020
|
|
I18-Microfocus Spectroscopy
|
Open Access
Abstract: The first experimental results from a new transmissive diagnostic instrument for synchrotron X-ray beamlines are presented. The instrument utilizes a single-crystal chemical-vapour-deposition diamond plate as the detector material, with graphitic wires embedded within the bulk diamond acting as electrodes. The resulting instrument is an all-carbon transmissive X-ray imaging detector. Within the instrument's transmissive aperture there is no surface metallization that could absorb X-rays, and no surface structures that could be damaged by exposure to synchrotron X-ray beams. The graphitic electrodes are fabricated in situ within the bulk diamond using a laser-writing technique. Two separate arrays of parallel graphitic wires are fabricated, running parallel to the diamond surface and perpendicular to each other, at two different depths within the diamond. One array of wires has a modulated bias voltage applied; the perpendicular array is a series of readout electrodes. X-rays passing through the detector generate charge carriers within the bulk diamond through photoionization, and these charge carriers travel to the nearest readout electrode under the influence of the modulated electrical bias. Each of the crossing points between perpendicular wires acts as an individual pixel. The simultaneous read-out of all pixels is achieved using a lock-in technique. The parallel wires within each array are separated by 50 µm, determining the pixel pitch. Readout is obtained at 100 Hz, and the resolution of the X-ray beam position measurement is 600 nm for a 180 µm size beam.
|
May 2020
|
|
B18-Core EXAFS
I18-Microfocus Spectroscopy
|
Adam J.
Fuller
,
Peter
Leary
,
Neil D.
Gray
,
Helena S.
Davies
,
J. Frederick W.
Mosselmans
,
Filipa
Cox
,
Clare H.
Robinson
,
Jon K.
Pittman
,
Clare M.
Mccann
,
Michael
Muir
,
Margaret C.
Graham
,
Satoshi
Utsunomiya
,
William R.
Bower
,
Katherine
Morris
,
Samuel
Shaw
,
Pieter
Bots
,
Francis R.
Livens
,
Gareth T. W.
Law
Diamond Proposal Number(s):
[10163, 12767, 12477]
Open Access
Abstract: Understanding the long-term fate, stability, and bioavailability of uranium (U) in the environment is important for the management of nuclear legacy sites and radioactive wastes. Analysis of U behavior at natural analogue sites permits evaluation of U biogeochemistry under conditions more representative of long-term equilibrium. Here, we have used bulk geochemical and microbial community analysis of soils, coupled with X-ray absorption spectroscopy and μ-focus X-ray fluorescence mapping, to gain a mechanistic understanding of the fate of U transported into an organic-rich soil from a pitchblende vein at the UK Needle's Eye Natural Analogue site. U is highly enriched in the Needle's Eye soils (∼1600 mg kg−1). We show that this enrichment is largely controlled by U(VI) complexation with soil organic matter and not U(VI) bioreduction. Instead, organic-associated U(VI) seems to remain stable under microbially-mediated Fe(III)-reducing conditions. U(IV) (as non-crystalline U(IV)) was only observed at greater depths at the site (>25 cm); the soil here was comparatively mineral-rich, organic-poor, and sulfate-reducing/methanogenic. Furthermore, nanocrystalline UO2, an alternative product of U(VI) reduction in soils, was not observed at the site, and U did not appear to be associated with Fe-bearing minerals. Organic-rich soils appear to have the potential to impede U groundwater transport, irrespective of ambient redox conditions.
|
Apr 2020
|
|
I18-Microfocus Spectroscopy
|
Abstract: We report on the alteration history of the olivine-phyric, highly depleted (HD) shergottite, Northwest Africa (NWA) 10416, paying particular attention to the origin of the aqueous alteration seen affecting the meteorite’s olivine megacrysts. The rock’s interior displays 1 mm, zoned, altered olivine megacrysts set in a groundmass of clinopyroxene, unzoned olivine, and interstitial plagioclase and maskelynite. Synchrotron micro X-ray diffraction (µ-XRD) and transmission electron microscopy (TEM) show that plagioclase and maskelynite have been partially replaced by kaolinite. The relict olivine megacryst cores display a unique concentric colouration for Martian meteorites, having central amber-coloured zones surrounded by a brown mantle zone, with the rims remaining clear and unaltered. This colouration is a result of fluid alteration and partial replacement, with hydration. TEM analysis revealed the ∼200 nm scale banded and largely amorphous nature of the alteration, but with some (∼ 20%) relict crystalline olivine patches. Although the coloured olivine zones show cation and anion site vacancies compared to stoichiometric olivine, a relict igneous compositional trend is preserved in the megacrysts, from Mg-rich altered cores (Mg# = 76) to unaltered stoichiometric rims (Fo53). Synchrotron Fe-K X-ray absorption near-edge structure (XANES) analysis revealed that the coloured zones of the megacryst have different Fe oxidation values. High ferric contents are present in the brown mantle zones (Fe3+/ΣFe ≤ 0.92) and the amber zones (Fe3+/ΣFe ≤ 0.30), whereas the clear rims are ferrous. This suggests alteration occurred in an oxidising environment and that the sharp contrast in colour of the megacryst (brown to clear) is a record of a relict fluid reaction front.
In order to test the terrestrial or extraterrestrial origin of the alteration, olivine material from a shock-melt vein was analysed by TEM. The analysis revealed 0.952 nm curved d-spacing’s from clay alteration undisturbed by any shock effects, strongly suggesting a terrestrial origin. The d-spacing values most likely represent a collapsed saponite or vermiculite, showing that in some places olivine has been replaced by crystalline clay.
Oxygen isotope analysis of bulk (Δ17O = 0.309 ± 0.009 (2σ) ‰) and amber-coloured megacryst material (= 0.271 ± 0.002 (2σ) ‰), are also consistent with terrestrial alteration. We propose a model in which, during the meteorite’s time in Northwest Africa, low-temperature, likely acidic, groundwater exploited fractures. The fluid altered the olivine megacrysts in a way that was controlled by the pre-existing, igneous compositional zonation, with Mg-rich olivine being more susceptible to alteration in this fluid environment. The plagioclase and maskelynite were also altered to a high degree. After the alteration event it is likely that NWA 10416 had a significant residence time in Northwest Africa, accounting for terrestrial calcite and the dehydration of some clay phases.
|
Apr 2020
|
|
I18-Microfocus Spectroscopy
|
Open Access
Abstract: Iron is an essential element, and cornflake-style cereals are typically fortified with iron to a level up to 14 mg iron per 100 g. Even single cornflakes exhibit magnetic behaviour. We extracted iron microparticles from samples of two own-brand supermarket cornflakes using a strong permanent magnet. Synchrotron iron K-edge X-ray absorption near-edge spectroscopic data were consistent with identification as metallic iron, and X-ray diffraction studies provided unequivocal identification of the extracted iron as body-centred cubic (BCC) α-iron. Magnetometry measurements were also consistent with ca. 14 mg per 100 g BCC iron. These findings emphasise that attention must be paid to the speciation of trace elements, in relation to their bioavailability. To mimic conditions in the stomach, we suspended the iron extract in dilute HCl (pH 1.0–2.0) at 310 K (body temperature) and found by ICP-MS that over a period of 5 hours, up to 13% of the iron dissolved. This implies that despite its metallic form in the cornflakes, the iron is potentially bioavailable for oxidation and absorption into the body.
|
Mar 2020
|
|
I18-Microfocus Spectroscopy
|
Abstract: The hallmark of neurodegenerative disease in humans, including Alzheimer’s, Amyotrophic Lateral Sclerosis and Parkinson’s, lies in our inability to efficiently restore damaged neurons. Contrary to widespread belief, humans can regenerate neurons within the Peripheral Nervous System (PNS) and some areas of the Central Nervous System (CNS), however the underlying mechanisms which drive or repress complete functional and structural neuronal regeneration remain elusive. To develop our understanding of this natural phenomenon one should focus on species which are capable of efficient neuronal regeneration following neurotrauma. The earthworm species Eisenia fetida can regenerate their Cerebral Ganglion (CG) - loosely defined as the brain, within a few weeks following surgical removal. The characterization of fundamental aspects of neuronal regeneration in the earthworm promises to provide an insight as to why humans have largely lost that capability. Here we present a detailed micro-dissection protocol that has been developed to excise the CG and study the progression of its regeneration. The Ventral Nerve Cord (VNC) of the worm is a tissue which connects the CG to the rest of the nervous system via the Circumpharyngeal Connectives (CC). Exploration of molecular dynamics through changes in the transcriptome were determined in the VNC and CC at 1 week and 5-week post-decerebration using an RNAseq approach (90 million reads/condition, 100bp Paired End). RNAseq established that specific groups of genes are up- or downregulated in the regenerating VNC. More than 500 significantly enriched biological processes were identified throughout the regeneration process, including vascular development, neurogenesis and extracellular matrix organization, as well as more than 100 significantly enriched molecular functions, including calcium ion binding, metal ion binding and metalloendopeptidase activity. Differential expression of transcripts was confirmed via qPCR. Examples of transcripts which have been validated at 1w post-decerebration, include catalase (~34-fold), superoxide dismutase 1 (sod-1) (~12-fold) and transcription factor jun-B (junb) (~3-fold). On the other hand, examples of transcripts which have been validated at 5w post-decerebration, include Glial Fibrillary Acidic Protein (GFAP) (~101-fold), adam19 (~17-fold) and Bone Morphogenetic Protein 1 (BMP1) (~3-fold). Moreover, the large number of differentially expressed metalloproteins (ADAMs, BMPs, MMPs, metallothionein) identified in the transcriptome, led to the hypothesis that metal trafficking could play a role in the course of regeneration. This was confirmed using a synchrotron-based approach, namely X-Ray Fluorescence (XRF) spectroscopy, where Zinc (Zn) and Iron (Fe) show a differential distribution pattern across different stages (at 1 week to 10-weeks post-decerebration) of regeneration. Lastly, various histological techniques were implemented to characterize/describe neuronal structures during the regenerating process, including immunohistochemistry and Terminal deoxynucleotidyl transferase dUTP Nick End Labeling (TUNEL). Furthermore, numerous novel markers and biological processes have been identified which, to date, have not been linked to neuronal regeneration. In summary, the results suggest that the increase of axon growth promoting factors as well the decrease of growth inhibitory factors act in conjunction to ensure efficient neuronal regeneration in the earthworm.
|
Mar 2020
|
|
I18-Microfocus Spectroscopy
|
Diamond Proposal Number(s):
[17304]
Abstract: The ability to manipulate the composition of semiconductor alloys on-demand and at nanometer-scale resolutions is a powerful tool that could be exploited to tune key properties such as the electronic bandgap, mobility, and refractive index. However, existing methods to modify the composition involve altering the stoichiometry by temporal or spatial modulation of the process parameters during material growth, limiting the scalability and flexibility for device fabrication. Here, we report a laser processing method for localized tailoring of the composition in amorphous silicon-germanium (a-SiGe) nanoscale thin films on silicon substrates, post-deposition, by controlling phase segregation through the scan speed of the laser-induced molten zone. Laser-driven phase segregation at speeds adjustable from 0.1 to 100 mm s-1 allows access to previously unexplored solidification dynamics. The steady-state spatial distribution of the alloy constituents can be tuned directly by setting the constant laser scan speed to achieve indefinitely long Si1-xGex microstructures exhibiting the full range of compositions (0
|
Feb 2020
|
|