scholarly journals Interaction of Th(IV), Pu(IV) and Fe(III) with ferritin protein: how similar?

2022 ◽  
Vol 29 (1) ◽  
Author(s):  
Cyril Zurita ◽  
Satoru Tsushima ◽  
Pier Lorenzo Solari ◽  
Aurélie Jeanson ◽  
Gaëlle Creff ◽  
...  
Keyword(s):  
Oxidation State ◽  
Experimental Conditions ◽  
Ionic Radii ◽  
High Tendency ◽  
Ferric Oxyhydroxide ◽  
Main Protein ◽  
Horse Spleen Ferritin ◽  
Fe Storage ◽  
Very High ◽  
Actinide Elements

Ferritin is the main protein of Fe storage in eukaryote and prokaryote cells. It is a large multifunctional, multi-subunit protein consisting of heavy H and light L subunits. In the field of nuclear toxicology, it has been suggested that some actinide elements, such as thorium and plutonium at oxidation state +IV, have a comparable `biochemistry' to iron at oxidation state +III owing to their very high tendency for hydrolysis and somewhat comparable ionic radii. Therefore, the possible mechanisms of interaction of such actinide elements with the Fe storage protein is a fundamental question of bio-actinidic chemistry. We recently described the complexation of Pu(IV) and Th(IV) with horse spleen ferritin (composed mainly of L subunits). In this article, we bring another viewpoint to this question by further combining modeling with our previous EXAFS data for Pu(IV) and Th(IV). As a result, the interaction between the L subunits and both actinides appears to be non-specific but driven only by the density of the presence of Asp and Glu residues on the protein shell. The formation of an oxyhydroxide Th or Pu core has not been observed under the experimental conditions here, nor the interaction of Th or Pu with the ferric oxyhydroxide core.

Anion packing density: a universal quantity for both dense and porous crystalline inorganic phases

2002 ◽  
Vol 58 (3) ◽  
pp. 457-462 ◽  
Author(s):  
F. Liebau ◽  
H. Küppers
Keyword(s):  
High Pressure ◽  
Packing Density ◽  
Three Dimensional ◽  
Ionic Radii ◽  
Generalized Framework ◽  
Molal Volumes ◽  
Definition Of ◽  
Anion Packing ◽  
Very High ◽  
Framework Density

To compare densities of inorganic high-pressure phases their molal volumes or specific gravities are usually employed, whereas for zeolites and other microporous materials the so-called framework density, FD, is applied. The definition of FD, which refers only to phases with three-dimensional tetrahedron frameworks, is extended to a `generalized framework density' d f, which is independent of the dimensionality of the framework and the coordination number(s) of the framework cations. In this paper the anion packing density, d ap, is introduced as a new quantity which is not only applicable to any inorganic phase but, in contrast to FD and d f, also allows quantitative comparisons to be made for crystalline inorganic phases of any kind. The anion packing density can readily be calculated if the volume and content of the unit cell and the radii of the anions of a phase are known. From d ap values calculated for high-pressure silica polymorphs studied under very high pressure, it is concluded that Shannon–Prewitt effective ionic radii do not sufficiently take into account the compressibility of the anions.

scholarly journals Ferroxidase activity of ferritin: effects of pH, buffer and Fe(II) and Fe(III) concentrations on Fe(II) autoxidation and ferroxidation

1999 ◽  
Vol 338 (3) ◽  
pp. 615-618 ◽  
Author(s):  
Xiaoke YANG ◽  
N. Dennis CHASTEEN
Keyword(s):  
Ph Control ◽  
Alternative Mechanism ◽  
Experimental Conditions ◽  
Iron Storage ◽  
Ferroxidase Activity ◽  
Effects Of Ph ◽  
Ph Stat ◽  
Ph Buffer ◽  
Horse Spleen Ferritin

It is widely accepted that iron deposition in the iron storage protein ferritin in vitro involves Fe(II) oxidation, and that ferritin facilitates this oxidation at a ferroxidase site on the protein. However, these views have recently been questioned, with the protein ferroxidase activity instead being attributed to autoxidation from the buffer alone. Ligand exchange between another protein with ferroxidase activity and ferritin has been proposed as an alternative mechanism for iron incorporation into ferritin. In the present work, a pH stat apparatus is used to eliminate the influence of buffers on iron(II) oxidation. Here we show that the recent experiments questioning the ferroxidase activity of ferritin were flawed by inadequate pH control, that buffers actually retard rather than facilitate iron(II) oxidation, and that horse spleen ferritin has ferroxidase activity when measured under proper experimental conditions. Furthermore, high pH (7.0), a high Fe(II) concentration and the presence of Fe(III) all favour Fe(II) autoxidation in the presence or absence of ferritin.

scholarly journals Dissociation, unfolding and refolding trials of pig kidney 3,4-dihydroxyphenylalanine (dopa) decarboxylase

1993 ◽  
Vol 295 (2) ◽  
pp. 493-500 ◽  
Author(s):  
P Dominici ◽  
P S Moore ◽  
C Borri Voltattorni
Keyword(s):  
Conformational Changes ◽  
Dopa Decarboxylase ◽  
Experimental Conditions ◽  
High Tendency ◽  
Denatured Protein ◽  
Pig Kidney ◽  
Plausible Model ◽  
Spectroscopic Characteristics ◽  
Equilibrium Transition ◽  
Almost All

The effect of guanidinium chloride (GuCl) on enzyme activity, hydrodynamic volume, circular dichroism, and fluorescence of 3,4-dihydroxyphenylalanine (Dopa) decarboxylase from pig kidney (pkDDC) was studied under equilibrium conditions. Unfolding proceeds in at least three stages. The first transition, occurring between 0 and 1 M GuCl, gives rise to a dimeric inactive species which has lost pyridoxal 5′-phosphate (PLP), and has a high tendency to aggregate, but retains almost all of the native spectroscopic characteristics. The second equilibrium transition, between 1 and 2.2 M GuCl, involves dimer dissociation, with some loss of tertiary and secondary structure. Additionally, gross conformational changes at or near the PLP microenvironment were detected by fluorescence of NaBH4-reduced enzyme. The third step, presumably representing complete unfolding of pkDDC, appears to be complete at 4.5 M GuCl, as indicated by the lack of further substantial changes in any of the signals being studied. Attempts at refolding resulted in the findings that: (1) partial reactivation is observed only starting from enzyme denatured at concentrations below 1.5 M GuCl, and (2) starting from completely denatured protein, the refolding process is apparently reversible down to concentrations of approx. 2 M GuCl. Taken together, this would seem to indicate that the monomer-dimer transition is impaired under the experimental conditions tested. A plausible model is presented for the unfolding/refolding of pkDDC.

scholarly journals Twofold advantage of gas bubbling for the advanced solvothermal preparation of efficient YAG:Ce nanophosphors

2020 ◽  
Vol 8 (27) ◽  
pp. 9382-9390 ◽  
Author(s):  
Alexandra Cantarano ◽  
Denis Testemale ◽  
Sonia de Sousa Nobre ◽  
Audrey Potdevin ◽  
Rémy Bruyère ◽  
...  
Keyword(s):  
Oxidation State ◽  
Gas Bubbles ◽  
Gas Bubbling ◽  
Solvothermal Preparation ◽  
Very High

Gas bubbles modify the nucleation, crystallinity and Ce oxidation state of YAG nanocrystals: towards very high photoluminescence yields.

Genotypic variation in proanthocyanidin status in the Leucaena genus

2002 ◽  
Vol 138 (2) ◽  
pp. 209-220 ◽  
Author(s):  
S. A. DALZELL ◽  
H. M. SHELTON
Keyword(s):  
Regression Analysis ◽  
Interspecific Hybrids ◽  
Dry Matter ◽  
Genotypic Variation ◽  
Genetic Regulation ◽  
Plant Defence ◽  
Interspecific Variation ◽  
Experimental Conditions ◽  
Commercial Cultivars ◽  
Very High

The proanthocyanidin (PA) status of 116 accessions from the Leucaena genus representing 21 species, 6 subspecies, 3 varieties and 4 interspecific hybrids was evaluated under uniform environmental and experimental conditions at Redland Bay, Queensland, Australia in October 1997. The PA content of lyophilized youngest fully expanded leaves was measured spectrophotometrically by the butanol/HCl assay referenced to L. leucocephala ssp. glabrata standard PA and expressed as L. leucocephala ssp. glabrata PA equivalents (LLPAE). Considerable interspecific variation in PA concentration existed within the genus, ranging from 0–339 g LLPAE/kg dry matter (DM). Taxa including L. confertiflora, L. cuspidata, L. esculenta and L. greggii contained very high (>180 g LLPAE/kg DM) PA concentrations. Similarly, many agronomically superior accessions from L. diversifolia, L. pallida and L. trichandra contained extremely high (up to 250 g LLPAE/kg DM) PA concentrations, although these taxa exhibited wide intraspecific variation in PA content offering the potential to select accessions with lower (120–160 g LLPAE/kg DM) PA content. Commercial cultivars of L. leucocephala ssp. glabrata, known to produce forage of superior quality, contained low amounts of PA (33–39 g LLPAE/kg DM). Artificial interspecific hybrids had PA contents intermediate to those of both parents. Lesser-known taxa, including L. collinsii, L. lanceolata, L. lempirana, L. macrophylla, L. magnifica, L. multicapitula, L. salvadorensis and L. trichodes, contained undetectable to low (0–36 g LLPAE/kg DM) quantities of PA and have potential as parents to breed interspecific hybrids of low PA status and superior forage quality. Extractable PA was the dominant PA component, accounting for 91% of total PA within the genus. Regression analysis of accession ranks from different experiments compared to these results indicated that genetic regulation of Leucaena spp. PA content was consistent (P<0·01) under different edapho-climatic environments. The distribution of PA within the Leucaena genus did not concur with the predictions of various evolutionary and phylogenetic plant defence theories.

scholarly journals Review on different welding techniques of Titanium and its alloys

2020 ◽  
pp. 286-294
Author(s):  
Malis Krishna Prasad Reddy ◽  
Ramawath Prashanth Naik ◽  
Madhukar Samatham ◽  
Chelluboina Harish Kumar
Keyword(s):  
Creep Property ◽  
Notch Toughness ◽  
Aerospace Engineering ◽  
Dissimilar Metals ◽  
Nuclear Engineering ◽  
High Tendency ◽  
Atmospheric Air ◽  
Welding Defects ◽  
Good Biocompatibility ◽  
Very High

Titanium and its alloys are the most commonly and most widely used due to its significant properties like good biocompatibility , good tensile strength , low density , and good creep property up to 300 degrees centigrade .It is used in the major engineering fields like civil engineering , nuclear engineering , aerospace engineering etc., but the welding of titanium in industries has become a major challenging objective to the fabricators because, a lot of titanium alloys are found in the form of sheets , problem arises mainly while fabricating the space crafts , marine bodies , jet engine’s where the ends are need to be joined through welding with a similar or dissimilar metals and titanium possess to have a very high tendency to oxidize at higher temperatures .As Titanium becomes highly reactive to chemicals in its environment. In regular air, welding contaminates titanium with carbides, nitrides, and oxides that make the weld and HAZ (heat-affected zone) brittle, resulting in lower fatigue resistance and notch toughness. so, In order to get a perfect weld it is very important to avoid the molten metal to the exposure of atmospheric air , which will lead to porosity and results into a poor welding conditions or welding defects. This paper reviews the different methods of welding titanium and its alloys.

scholarly journals CONVERSION OF STYRENE INTO BENZALDEHYDE AND STYRENE EPOXIDE OVER MgCoAl-LDH CATALYSTS

2017 ◽  
Vol 55 (4) ◽  
pp. 403 ◽  
Author(s):  
Nguyen Tien Thao ◽  
Dang Van Long ◽  
Dinh Minh Hoan
Keyword(s):  
Active Sites ◽  
Styrene Oxide ◽  
Metal Salts ◽  
Experimental Conditions ◽  
Cobalt Ions ◽  
Styrene Epoxide ◽  
Co Precipitation ◽  
Double Hydroxide ◽  
Very High ◽  
Styrene Conversion

Co-containing hydroxides have been successfully synthesized by the co-precipitation of starting-metal salts. The obtained materials were characterized by some physical means including XRD, EDS, BET… It is found that Co2+ ions are present in the layered double hydroxide (LDH) sheets. The presence of cobalt ions in LDH plays as active sites for the oxidation of styrene with air. The catalysts exhibited a very high activity in the conversion of styrene into two main products (benzaldehyde and styrene oxide). The highest styrene conversion is about 90-95% and the total selectivity to benzaldehyde and styrene oxide is in the range of 80-85% under reported experimental conditions.

Benchmarking Human Performance in Semi-Automated Image Segmentation

2020 ◽  
Vol 32 (3) ◽  
pp. 233-245
Author(s):  
Mark Eramian ◽  
Christopher Power ◽  
Stephen Rau ◽  
Pulkit Khandelwal
Keyword(s):  
Image Segmentation ◽  
Human Performance ◽  
State Of The Art ◽  
Automated Segmentation ◽  
Experimental Conditions ◽  
Algorithm Performance ◽  
Sharp Focus ◽  
Segmentation Algorithms ◽  
The Impact ◽  
Very High

Abstract Semi-automated segmentation algorithms hold promise for improving extraction and identification of objects in images such as tumors in medical images of human tissue, counting plants or flowers for crop yield prediction or other tasks where object numbers and appearance vary from image to image. By blending markup from human annotators to algorithmic classifiers, the accuracy and reproducability of image segmentation can be raised to very high levels. At least, that is the promise of this approach, but the reality is less than clear. In this paper, we review the state-of-the-art in semi-automated image segmentation performance assessment and demonstrate it to be lacking the level of experimental rigour needed to ensure that claims about algorithm accuracy and reproducability can be considered valid. We follow this review with two experiments that vary the type of markup that annotators make on images, either points or strokes, in tightly controlled experimental conditions in order to investigate the effect that this one particular source of variation has on the accuracy of these types of systems. In both experiments, we found that accuracy substantially increases when participants use a stroke-based interaction. In light of these results, the validity of claims about algorithm performance are brought into sharp focus, and we reflect on the need for a far more control on variables for benchmarking the impact of annotators and their context on these types of systems.

scholarly journals The State of Trace Elements (In, Cu, Ag) in Sphalerite Studied by X-Ray Absorption Spectroscopy of Synthetic Minerals

Minerals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 640 ◽  
Author(s):  
Nikolay D. Trofimov ◽  
Alexander L. Trigub ◽  
Boris R. Tagirov ◽  
Olga N. Filimonova ◽  
Polina V. Evstigneeva ◽  
...  
Keyword(s):  
Solid Solution ◽  
Oxidation State ◽  
Absorption Spectroscopy ◽  
Atomic Structure ◽  
Salt Flux ◽  
Ionic Radii ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption ◽  
Exafs Spectra

The oxidation state and local atomic environment of admixtures of In, Cu, and Ag in synthetic sphalerite crystals were determined by X-ray absorption spectroscopy (XAS). The sphalerite crystals doped with In, Cu, Ag, In–Cu, and In–Ag were synthesized utilizing gas transport, salt flux, and dry synthesis techniques. Oxidation states of dopants were determined using X-ray absorption near edge structure (XANES) technique. The local atomic structure was studied by X-ray absorption fine structure spectroscopy (EXAFS). The spectra were recorded at Zn, In, Ag, and Cu K-edges. In all studied samples, In was in the 3+ oxidation state and replaced Zn in the structure of sphalerite, which occurs with the expansion of the nearest coordination shells due to the large In ionic radius. In the presence of In, the oxidation state of Cu and Ag is 1+, and both metals can form an isomorphous solid solution where they substitute for Zn according to the coupled substitution scheme 2Zn2+ ↔ Me+ + In3+. Moreover, Ag K-edges EXAFS spectra fitting, combined with the results obtained for In- and Au-bearing sphalerite shows that the Me-S distances in the first coordination shell in the solid solution state are correlated with the ionic radii and increase in the order of Cu < Ag < Au. The distortion of the atomic structure increases in the same order. The distant (second and third) coordination shells of Cu and Ag in sphalerite are split into two subshells, and the splitting is more pronounced for Ag. Analysis of the EXAFS spectra, coupled with the results of DFT (Density Function Theory) simulations, showed that the In–In and Me+–In3+ clustering is absent when the metals are present in the sphalerite solid solution. Therefore, all studied admixtures (In, Cu, Ag), as well as Au, are randomly distributed in the matrix of sphalerite, where the concentration of the elements in the “invisible” form can reach a few tens wt.%.

Very high field magnetization and AC susceptibility of native horse spleen ferritin

2007 ◽  
Vol 308 (1) ◽  
pp. 97-100 ◽  
Author(s):  
R.P. Guertin ◽  
N. Harrison ◽  
Z.X. Zhou ◽  
S. McCall ◽  
F. Drymiotis
Keyword(s):  
High Field ◽  
Ac Susceptibility ◽  
Field Magnetization ◽  
High Field Magnetization ◽  
Horse Spleen Ferritin ◽  
Very High
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