scholarly journals Spatial distribution of starch, proteins and lipids in maize endosperm probed by scanning transmission X-ray microscopy

2019 ◽  
Author(s):  
Camille Rivard ◽  
Benedicte Bakan ◽  
Claire Boulogne ◽  
Khalil Elmorjani ◽  
Sufal Swaraj ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Maize Endosperm ◽  
Maize Breeding ◽  
X Ray ◽  
Nexafs Spectroscopy ◽  
Scanning Transmission ◽  
High Resolution Images ◽  
Ultrathin Sections ◽  
Main Components ◽  
X Ray Absorption

The main storage components of the maize endosperm are starch, proteins and lipids. Starch and proteins are heterogeneously deposited, leading to the formation of vitreous and floury regions at the periphery and at the centre of the endosperm. The vitreous/floury mass ratio is a key physical parameter of maize end-uses for the food, feed and non-food sectors, as well as for the resistance of seeds to environmental aggressions. To improve maize breeding for vitreousness, one of the main issues is to finely delineate the molecular and physicochemical mechanisms associated with the formation of endosperm texture. In this context, we use scanning transmission X-ray microscopy at the C K-edge on maize endosperm resin-embedded ultrathin sections. The combination of local near edge X-ray absorption fine structure (NEXAFS) spectroscopy and high-resolution images enable us to achieve a quantitative fine description of the spatial distribution of the main components within the endosperm.

scholarly journals Spatially Resolved Characterization of Biogenic Manganese Oxide Production within a Bacterial Biofilm

2005 ◽  
Vol 71 (3) ◽  
pp. 1300-1310 ◽  
Author(s):  
Brandy Toner ◽  
Sirine Fakra ◽  
Mario Villalobos ◽  
Tony Warwick ◽  
Garrison Sposito
Keyword(s):  
Careful Consideration ◽  
Bacterial Biofilm ◽  
Bacterial Cells ◽  
X Ray ◽  
Spatially Resolved ◽  
Nexafs Spectroscopy ◽  
Promising Tool ◽  
Scanning Transmission ◽  
X Ray Absorption

ABSTRACT Pseudomonas putida strain MnB1, a biofilm-forming bacterial culture, was used as a model for the study of bacterial Mn oxidation in freshwater and soil environments. The oxidation of aqueous Mn+2 [Mn+2 (aq)] by P. putida was characterized by spatially and temporally resolving the oxidation state of Mn in the presence of a bacterial biofilm, using scanning transmission X-ray microscopy (STXM) combined with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy at the Mn L2,3 absorption edges. Subsamples were collected from growth flasks containing 0.1 and 1 mM total Mn at 16, 24, 36, and 48 h after inoculation. Immediately after collection, the unprocessed hydrated subsamples were imaged at a 40-nm resolution. Manganese NEXAFS spectra were extracted from X-ray energy sequences of STXM images (stacks) and fit with linear combinations of well-characterized reference spectra to obtain quantitative relative abundances of Mn(II), Mn(III), and Mn(IV). Careful consideration was given to uncertainty in the normalization of the reference spectra, choice of reference compounds, and chemical changes due to radiation damage. The STXM results confirm that Mn+2 (aq) was removed from solution by P. putida and was concentrated as Mn(III) and Mn(IV) immediately adjacent to the bacterial cells. The Mn precipitates were completely enveloped by bacterial biofilm material. The distribution of Mn oxidation states was spatially heterogeneous within and between the clusters of bacterial cells. Scanning transmission X-ray microscopy is a promising tool for advancing the study of hydrated interfaces between minerals and bacteria, particularly in cases where the structure of bacterial biofilms needs to be maintained.

Multi-elemental scanning transmission X-ray microscopy–near edge X-ray absorption fine structure spectroscopy assessment of organo–mineral associations in soils from reduced environments

2015 ◽  
Vol 12 (1) ◽  
pp. 64 ◽  
Author(s):  
Chunmei Chen ◽  
Donald L. Sparks
Keyword(s):  
Fine Structure ◽  
X Ray ◽  
Fe Oxides ◽  
Absorption Fine ◽  
Nexafs Spectroscopy ◽  
Mineral Associations ◽  
Fundamental Process ◽  
Scanning Transmission ◽  
Mineral Components ◽  
X Ray Absorption

Environmental context Organo–mineral associations represent a fundamental process for stabilising organic carbon in soils. In this study, we employed scanning transmission X-ray microscopy–near edge X-ray absorption fine structure (STXM-NEXAFS) spectroscopy at C, Al and Si K-edges as well as Ca and Fe L-edges to conduct submicrometre-level investigations of the associations of C with mineral components in soils from reduced environments. This study provides the first insights into organo–mineral associations in reduced environments and shows progress towards examining, at the submicrometre level, compositional chemistry and associative interactions between organic matter and soil mineral components. Abstract Organo–mineral associations represent a fundamental process for stabilising organic carbon (OC) in soils. However, direct investigation of organo–mineral associations has been hampered by a lack of methods that can simultaneously characterise organic matter (OM) and soil minerals, and most investigations have focussed only on well drained soils. In this study, we employed scanning transmission X-ray microscopy–near edge X-ray absorption fine structure (STXM-NEXAFS) spectroscopy at C, Al and Si K-edges as well as Ca and Fe L-edges to conduct submicrometre-level investigations of the associations of C with mineral components in soils from reduced environments. Soils were collected from a forest footslope that is periodically poorly drained as well as a waterlogged wetland. OM was coated on mineral particles as thin films. Part of the mineral surface did not show detectable OM coverage with OC loadings of ≥1.3mg C m–2 determined for the clay fractions from these soils. C was not preferentially associated with Fe oxides in the footslope soil. A generally good C–Ca association was found in the anoxic wetland soil, which is free of Fe oxides. It was demonstrated for the first time that OM composition varied spatially at the submicrometre scale in the reduced soils free of Fe oxides. The composition of OM in the organo–mineral interface in the anoxic environments was highly complex and composed of aromatic, phenolic, aliphatic, carboxyl, carboxylamide and O-alkyl C functional groups. There was no consistent pattern for the association of certain types of organics with specific mineral components in both soils. The anoxic conditions resulted in the reduction of Fe in the aluminosilicates. This study provides the first insights into organo–mineral associations in reduced environments.

Microspectroscopic Analysis of the X-Ray-induced Photoreduction in Fe- and Mn-containing SMMs

2010 ◽  
Vol 65 (3) ◽  
pp. 390-398 ◽  
Author(s):  
Norman Schmidt ◽  
Andreas Scheurer ◽  
Stefan Sperner ◽  
Rainer H. Fink
Keyword(s):  
Metal Ions ◽  
Single Molecule ◽  
Theoretical Studies ◽  
X Ray ◽  
Nexafs Spectroscopy ◽  
Valence States ◽  
Fe And Mn ◽  
Scanning Transmission ◽  
X Ray Absorption ◽  
Dose Dependent

Scanning transmission X-ray microspectroscopy (STXM) and L-edge near-edge X-ray absorption fine structure (NEXAFS) spectroscopy have been applied to study the valence states of metal ions in various Fe- and Mn-containing single-molecule magnet materials, in particular the ligand-stabilized metal complexes NaFe6 (so-called “ferric wheel”), Fe4 (so-called “ferric star”) and Mn7 (so-called “manganese wheel”).We compare dose-dependent L-edge absorption spectra with the results of theoretical studies of the involved metal ions to conclude on the change in oxidation state upon increasing the X-ray dose. It is found that even low-intensity irradiation induces the reduction of the weakly interacting metal ions, and that the soft X-ray-induced photoreduction is less pronounced in microcrystalline films.

Magnesium and sulfur in mast cell and basophil granules of lower vertebrates in relation with histamine

1992 ◽  
Vol 50 (2) ◽  
pp. 1596-1597
Author(s):  
Kenichi Takaya
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Mast Cell ◽  
Mast Cells ◽  
Tree Frog ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Fresh Frozen ◽  
Ultrathin Sections

Mast cell and basophil granules of the vertebrate contain heparin or related sulfated proteoglycans. Histamine is also present in mammalian mast cells and basophils. However, no histamine is detected in mast cell granules of the amphibian or fish, while it is shown in those of reptiles and birds A quantitative x-ray microanalysis of mast cell granules of fresh frozen dried ultrathin sections of the tongue of Wistar rats and tree frogs disclosed high concentrations of sulfur in rat mast cell granules and those of sulfur and magnesium in the tree frog granules. Their concentrations in tree frog mast cell granules were closely correlated (r=0.94).Fresh frozen dried ultrathin sections and fresh air-dried prints of the tree frog tongue and spleen and young red-eared turtle (ca. 6 g) spleen and heart blood were examined by a quantitative energy-dispersive x-ray microanalysis (X-650, Kevex-7000) for the element constituents of the granules of mast cells and basophils. The specimens were observed by transmission electron microscopy (TEM) (80-200 kV) and followed by scanning transmission electron microscopy (STEM) under an analytical electron microscope (X-650) at an acceleration voltage of 40 kV and a specimen current of 0.2 nA. A spot analysis was performed in a STEM mode for 100 s at a specimen current of 2 nA on the mast cell and basophil granules and other areas of the cells. Histamine was examined by the o-phthalaldehyde method.

Chemical and orientational imaging of polymeric samples

1994 ◽  
Vol 52 ◽  
pp. 68-69
Author(s):  
H. Ade ◽  
B. Hsiao ◽  
G. Mitchell ◽  
E. Rightor ◽  
A. P. Smith ◽  
...  
Keyword(s):  
Ethylene Terephthalate ◽  
National Laboratory ◽  
Brookhaven National Laboratory ◽  
Carbonyl Groups ◽  
Aromatic Rings ◽  
Edge Structure ◽  
X Ray ◽  
Scanning Transmission ◽  
Polymeric Samples ◽  
X Ray Absorption

We have used the Scanning Transmission X-ray Microscope at beamline X1A (X1-STXM) at Brookhaven National Laboratory (BNL) to acquire high resolution, chemical and orientation sensitive images of polymeric samples as well as point spectra from 0.1 μm areas. This sensitivity is achieved by exploiting the X-ray Absorption Near Edge Structure (XANES) of the carbon K edge. One of the most illustrative example of the chemical sensitivity achievable is provided by images of a polycarbonate/pol(ethylene terephthalate) (70/30 PC/PET) blend. Contrast reversal at high overall contrast is observed between images acquired at 285.36 and 285.69 eV (Fig. 1). Contrast in these images is achieved by exploring subtle differences between resonances associated with the π bonds (sp hybridization) of the aromatic groups of each polymer. PET has a split peak associated with these aromatic groups, due to the proximity of its carbonyl groups to its aromatic rings, whereas PC has only a single peak.

scholarly journals Artifacts from manganese reduction in rock samples prepared by focused ion beam (FIB) slicing for X-ray microspectroscopy

2019 ◽  
Vol 8 (1) ◽  
pp. 97-111
Author(s):  
Dorothea S. Macholdt ◽  
Jan-David Förster ◽  
Maren Müller ◽  
Bettina Weber ◽  
Michael Kappl ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Oxidation States ◽  
X Ray ◽  
Scientific Debate ◽  
Rock Samples ◽  
Valence States ◽  
Scanning Transmission ◽  
Visualization Techniques

Abstract. The spatial distribution of transition metal valence states is of broad interest in the microanalysis of geological and environmental samples. An example is rock varnish, a natural manganese (Mn)-rich rock coating, whose genesis mechanism remains a subject of scientific debate. We conducted scanning transmission X-ray microscopy with near-edge X-ray absorption fine-structure spectroscopy (STXM-NEXAFS) measurements of the abundance and spatial distribution of different Mn oxidation states within the nano- to micrometer thick varnish crusts. Such microanalytical measurements of thin and hard rock crusts require sample preparation with minimal contamination risk. Focused ion beam (FIB) slicing was used to obtain ∼100–1000 nm thin wedge-shaped slices of the samples for STXM, using standard parameters. However, while this preparation is suitable for investigating element distributions and structures in rock samples, we observed artifactual modifications of the Mn oxidation states at the surfaces of the FIB slices. Our results suggest that the preparation causes a reduction of Mn4+ to Mn2+. We draw attention to this issue, since FIB slicing, scanning electron microscopy (SEM) imaging, and other preparation and visualization techniques operating in the kilo-electron-volt range are well-established in geosciences, but researchers are often unaware of the potential for the reduction of Mn and possibly other elements in the samples.

scholarly journals Diverse Chemical Mixing States of Aerosol Particles in the Southeastern United States

2018 ◽  
Author(s):  
Amy L. Bondy ◽  
Daniel Bonanno ◽  
Ryan C. Moffet ◽  
Bingbing Wang ◽  
Alexander Laskin ◽  
...  
Keyword(s):  
Chemical Species ◽  
Accumulation Mode ◽  
X Ray ◽  
Internal Mixing ◽  
Scanning Transmission ◽  
Sea Spray Aerosol ◽  
Cloud Activation ◽  
Mixing States ◽  
X Ray Absorption ◽  
Individual Particles

Abstract. Aerosols in the atmosphere are chemically complex with thousands or more chemical species distributed in different proportions across individual particles in an aerosol population. An internal mixing assumption, with species present in the same proportions across all aerosols, is used in many models and calculations of secondary organic aerosol (SOA) formation, cloud activation, and aerosol optical properties. However, many of these effects depend on the distribution of species within individual particles, and important information can be lost when internal mixtures are assumed. Herein, we show that during the Southern Oxidant and Aerosol Study (SOAS) in Centreville, Alabama, at a rural, forested location, that aerosols frequently are not purely internally mixed, even in the accumulation mode (0.2–1.0 µm). A range of aerosol sources and mixing states were obtained using computer controlled scanning electron microscopy with energy dispersive X-ray spectroscopy (CCSEM-EDX) and scanning transmission X-ray microscopy-near-edge X-ray absorption fine structure spectroscopy (STXM-NEXAFS). Particles that were dominated by SOA and inorganic salts were the majority of particles by number fraction from 0.2–5 microns with an average of 78 % SOA in the accumulation mode. However, during certain periods contributions by sea spray aerosol (SSA) and mineral dust were significant to accumulation (22 % SSA and 26 % dust) and coarse mode number concentrations (38 % SSA and 63 % dust). The fraction of particles containing key elements (Na, Mg, K, Ca, and Fe) were determined as a function of size for specific classes of particles. Within internally mixed SOA/sulfate particles

scholarly journals Demonstration of Transmission Mode Soft X-ray NEXAFS Using Third- and Fifth-Order Harmonics of FEL Radiation at SACLA BL1

2020 ◽  
Vol 10 (21) ◽  
pp. 7852
Author(s):  
Hiroshi Iwayama ◽  
Masanari Nagasaka ◽  
Ichiro Inoue ◽  
Shigeki Owada ◽  
Makina Yabashi ◽  
...  
Keyword(s):  
Fine Structure ◽  
Free Electron ◽  
Free Electron Laser ◽  
Transmission Mode ◽  
Pump Probe ◽  
X Ray ◽  
The Third ◽  
Nexafs Spectroscopy ◽  
Fifth Order ◽  
X Ray Absorption

We demonstrate the applicability of third- and fifth-order harmonics of free-electron laser (FEL) radiation for soft X-ray absorption spectroscopy in the transmission mode at SACLA BL1, which covers a photon energy range of 20 to 150 eV in the fundamental FEL radiation. By using the third- and fifth-order harmonics of the FEL radiation, we successfully recorded near-edge X-ray absorption fine structure (NEXAFS) spectra for Ar 2p core ionization and CO2 C 1s and O 1s core ionizations. Our results show that the utilization of third- and fifth-order harmonics can significantly extend the available photon energies for NEXAFS spectroscopy using an FEL and opens the door to femtosecond pump-probe NEXAFS using a soft X-ray FEL.

Near Edge X-Ray Absorption Fine Structure (NEXAFS) Microscopy: Chemical Analysis at Sub Visible Spatial Resolution

1997 ◽  
Vol 3 (S2) ◽  
pp. 851-852
Author(s):  
H. Ade
Keyword(s):  
Fine Structure ◽  
Compositional Analysis ◽  
High Sensitivity ◽  
Linear Dichroism ◽  
X Rays ◽  
X Ray ◽  
Absorption Fine ◽  
Nexafs Spectroscopy ◽  
Wide Range ◽  
X Ray Absorption

Infrared, Raman, and fluorescence/luminescence microspectroscopy/microscopy in many instances seek to provide high sensitivity compositional and functional information that goes beyond mere elemental composition. This goal is shared by NEXAFS microscopy, in which Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy is employed to provide chemical sensitivity and can be relatively easily adopted in a scanning transmission x-ray microscope (STXM). In addition to compositional information, NEXAFS microscopy can exploit the dependence of x-ray absorption resonances on the bond orientation relative to the linearly polarized x rays (linear dichroism microscopy). For compositional analysis, NEXAFS microscopy is analogous to Electron Energy Loss Spectroscopy (EELS) in an electron microscope. However, when utilizing near edge spectral features, NEXAFS microscopy requires a considerable lower dose than EELS microscopy which makes it very suitable to studying radiation sensitive materials such as polymers. NEXAFS has shown to have excellent sensitivity to a wide range of moieties in polymers, including sensitivity to substitution isomerism.

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