Doughnut-like Shape Research Articles

Interparticle interaction-dependent jamming in colloids: insights into glass transition and morphology modulation during rapid evaporation-induced assembly.

Understanding the role of interparticle interactions in jamming phenomena is essential for gaining insights into the intriguing glass transition behavior observed in atomic and molecular systems. In this study, we investigate the jamming behavior of colloids with tunable interparticle interactions during evaporation-induced assembly (EIA). By manipulating the interaction among charged colloids using cationic polyethyleneimine (PEI) through electro-sorption and subsequent free polymer induced repulsion, we observe distinct jamming behavior in silica colloids during EIA, depending on the interparticle interactions. Silica colloids with strong repulsive interactions exhibit a repulsive colloidal glass state with a volume fraction of silica colloids in supraparticle ϕ ∼ 0.70. On the other hand, PEI-mediated attractive interactions among silica colloids lead to an attractive colloidal glass phase with a significantly lower ϕ ∼ 0.43. Free polymer induced repulsion of colloids at higher PEI concentration once again results in a repulsive glassy state with ϕ ∼ 0.61. Furthermore, we revealed that interparticle interactions not only influence the jamming behavior but also play a significant role in shaping the morphology of self-assembled structures during EIA, and the assembled structure undergoes a morphological reentrant transition from a doughnut-like shape to a spherical form and again back to a doughnut-like configuration. Jamming-dependent evolution of micropores and dynamics of the confined PEI have been probed using positron annihilation lifetime spectroscopy (PALS) and broadband dielectric spectroscopy (BDS). PALS reveals distinct variations in the micropores of the supraparticles with different PEI loadings, confirming the impact of jamming on the evolution of the micropores within the supraparticles. BDS measurements uncover non-monotonic dynamics of PEI molecules confined in the evolved pore network. It is revealed that the reentrant jamming behavior of colloids, modulated by PEI, holds profound significance for the long-term stability of supraparticles.

Controlled Morphology of Silica Particle by Spray Drying Method

The controlled morphology of mesoporous silica particle with colloidal silica as precursor solution was investigated using spray drying method. The colloidal silica solution was made from sodium silicate (waterglass) using sol-gel method. The operating condition of spray dring such as precursor solution volumetric rate and hot air flowrate was varied to study the effect of the silica particle’s morphology. Two-fluid nozzle was used as atomizer with volumetric rate ranged from 1.6 mL/min to 5 mL/min, and hot air heated from tubular furnace with flowrate ranged from 210 L/min to 414 L/min, both resulting doughnut-like shape with more doughnut fraction with increased volumetric rate. With the increase of volumetric rate from 1.6 mL/min to 5 mL/min, the surface area and total pore volume are tend to decrease (168.234 to 131.001 m2/g and 0.1652 to 0.1251 cc/g respectively). Meanwhile, for increasing hot air flowrate from 210 L/min to 414 L/min, the surface area are tend to increase (135.353 to 168.234 m2/g) but total pore volume tend to decrease (0.1921 to 0.1652 cc/g).

Waveform Diversity-Based Generation of Convergent Beam Carrying Orbital Angular Momentum

The orbital angular momentum (OAM) in radio frequency is expected to provide a new dimension to the OAM mode and benefit the degree of freedom of the electromagnetic wave. However, a central energy hollow exists in the OAM-carrying beam, and its radius varies with the OAM mode values, which is the main bottleneck in the radio frequency OAM applications. This article proposes a solution to eliminate the central hollow, by fundamentally changing the transmitted signal of the uniform circular array (UCA). To generate the unidirectional beam pattern, defined as the beaming OAM (BOAM), the orthogonal waveforms are radiated by UCA with an equidifferent initial phase. The BOAM wave can be received by one single antenna, and the separate OAM mode demodulation is then achieved based on the waveform diversity. This article studies the theoretical model of the BOAM field distribution and shows that the waveform diversity among distributed units can not only alter the doughnut-like shape into the closed beam, but also maintain the intact vortex characteristic. On this basis, the extended OAM mode multiplexing system is designed with one single UCA. A 16-element UCA is shown to be capable of generating 15 OAM modes simultaneously, with all modes superposing on the same direction. Furthermore, it is verified by the simulation that the vortex phase of each single mode can be precisely extracted from the OAM-mode-multiplexing signal.

Silicon-coated gold nanoparticles nanoscopy

This paper presents a method for modifying the point spread function (PSF) into a doughnut-like shape, through the utilization of the plasma dispersion effect (PDE) of silicon-coated gold nanoparticles. This modified PSF has spatial components smaller than the diffraction limit, and by scanning the sample with it, super-resolution can be achieved. The sample is illuminated using two laser beams. The first is the pump, with a wavelength in the visible region that creates a change in the refractive index of the silicon coating due to the PDE. This creates a change in the localized surface plasmon resonance wavelength. Since the pump beam has a Gaussian profile, the high intensity areas of the beam experience the highest refractive index change. When the second beam (i.e., the probe) illuminates the sample with a near-infrared wavelength, this change in the refractive index is transformed into a change in the PSF profile. The ordinary Gaussian shape is transformed into a doughnut shape, with higher spatial frequencies, which enables one to achieve super-resolution by scanning the specimen using this PSF. This is a step toward the creation of a nonfluorescent nanoscope.

New α- and γ-synuclein immunopathological lesions in human brain.

IntroductionSeveral neurodegenerative diseases are classified as proteopathies as they are associated with the aggregation of misfolded proteins. Synucleinopathies are a group of neurodegenerative disorders associated with abnormal deposition of synucleins. α-Synucleinopathies include Parkinson’s disease, dementia with Lewy bodies, and multiple system atrophy. Recently accumulation of another member of the synuclein family- γ−synuclein in neurodegenerative diseases compelled the introduction of the term γ−synucleinopathy. The formation of aggregates and deposits of γ−synuclein is facilitated after its oxidation at methionine 38 (Met38).ResultsSeveral types of intracytoplasmic inclusions containing post-translationally modified α- and γ−synucleins are detected. Oxidized Met38-γ-synuclein forms aberrant inclusions in amygdala and substantia nigra. Double staining revealed colocalization of oxidized-γ-synuclein with α-synuclein in the cytoplasm of neurons. Another type of synuclein positive inclusions in the amygdala of dementia with Lewy bodies patients has the appearance of Lewy bodies. These inclusions are immunoreactive when analyzed with antibodies to α-synuclein phosphorylated on serine 129, as well as with antibodies to oxidized-γ-synuclein. Some of these Lewy bodies have doughnut-like shape with round or elongated shape. The separate immunofluorescent images obtained with individual antibodies specific to oxidized-γ-synuclein and phospho-α-synuclein clearly shows the colocalization of these synuclein isoforms in substantia nigra inclusions. Phospho-α-synuclein is present almost exclusively at the periphery of these structures, whereas oxidized-γ-syn immunoreactivity is also located in the internal parts forming dot-like pattern of staining.We also identified several types of oxidized-γ-syn positive astrocytes with different morphology and examined their immunohistochemical phenotypes. Some of them are compact cells with short processes, others have longer processes. Oxidized-γ-synuclein positive astrocytes may also display mixed morphological and immunocytochemical phenotypes between protoplasmic and fibrous astrocytes.ConclusionsThese results reveal new γ−synuclein positive lesions in human brain. Oxidized-γ-synuclein is colocalized with phospho-α-synuclein in doughnut-like inclusions. Several types of astrocytes with different morphology are immunopositive for oxidized-γ-synuclein.

Fabrication of doughnut-shaped particles from spheroidal paramylon granules of Euglena gracilis using acetylation reaction.

An anhydrous type of paramylon, the micro-sized granular storage carbohydrate (β-1,3-glucan) of Euglena, was transformed from a spheroidal to a doughnut-like shape by acetylation. Fourier transform infrared spectroscopic measurements suggested that the doughnut formation is due to removal of accessible regions of paramylon particles by acetylation of glucans. A time-course observation of the paramylon granules during acetylation by using field emission scanning electron microscopy revealed that the doughnut-making process begins with the removal of an outer membrane of the granule and that the central region of the granules is preferentially removed with the survival of a thick rim part to give the doughnut-like particles.

Functional characterization of AIBp, a novel Aurora-A binding protein in centrosome structure and spindle formation

Aurora-A is involved in chromosome alignment, centrosome maturation, mitotic spindle assembly and regards to an oncogene. Aurora-A is also known to bind to several other proteins affecting its up-regulation or down-regulation and localization. However, how these different binding signals work together to regulate Aurora-A is not properly known. To explore more Aurora-A interacting proteins, the low-copy yeast two-hybrid screening using Aurora-A as bait protein was performed. One novel gene, AIBp, was demonstrated to associate with Aurora-A by the yeast two-hybrid method and in vitro GST pull-down assay. Molecular characterization showed that AIBp possessed a binding site at the C-terminal with Aurora-A (kinase domain). Interestingly, AIBp also interacts with hNinein at the N-terminal, which overlaps with a previously reported hNinein and GSK3beta binding site. Using a kinase assay, AIBp interacts with the Aurora-A kinase domain functions as a positive regulator, whereas AIBp binding to hNinein appears to block the phosphorylation of hNinein by both Aurora-A and GSK3beta. siRNA-mediated elimination of AIBp from HeLa cells, results in a doughnut-like shape, asymmetrical spindle pole and multiple spindle pole formation. We also demonstrated that both AIBp and Aurora-A are co-overexpressed in various brain tumors. These studies demonstrate that AIBp may not only be required for the dynamic movement of Aurora-A at the centrosomes and spindle apparatus during the cell cycle, but may also be important during brain tumorigenesis.

Effect of protein solution components in the adsorption of Herbaspirillum seropedicae GlnB protein on mica

The adsorption of proteins and its buffer solution on mica surfaces was investigated by atomic force microscopy (AFM). Different salt concentration of the Herbaspirillum seropedicae GlnB protein (GlnB-Hs) solution deposited on mica was investigated. This protein is a globular, soluble homotrimer (36 kDa), member of PII-like proteins family involved in signal transducing in prokaryote. Supramolecular structures were formed when this protein was deposited onto bare mica surface. The topographic AFM images of the GlnB-Hs films showed that at high salt concentration the supramolecular structures are spherical-like, instead of the typical doughnut-like shape for low salt concentration. AFM images of NaCl and Tris from the buffer solution showed structures with the same pattern as those observed for high salt protein solution, misleading the image interpretation. XPS experiments showed that GlnB protein film covers the mica surface without chemical reaction.

Kinetic Folding and Assembly Mechanisms Differ for Two Homologous Heptamers

Here we investigate the time-resolved folding and assembly mechanism of the heptameric co-chaperonin protein 10 (cpn10) in vitro. The structure of cpn10 is conserved throughout nature: seven β-barrel subunits are non-covalently assembled through β-strand pairings in an overall doughnut-like shape. Kinetic folding/assembly experiments of chemically denatured cpn10 from Homo sapiens ( hmcpn10) and Aquifex aeolicus ( Aacpn10) were monitored by far-UV circular dichroism and fluorescence. We find the processes to be complex, involving several kinetic steps, and to differ between the mesophilic and hyper-thermophilic proteins. The hmcpn10 molecules partition into two parallel pathways, one involving polypeptide folding before protein–protein assembly and another in which inter-protein interactions take place prior to folding. In contrast, the Aacpn10 molecules follow a single sequential path that includes initial monomer misfolding, relaxation to productive intermediates and, subsequently, final folding and heptamer assembly. An A. aeolicus variant lacking the unique C-terminal extension of Aacpn10 displays the same kinetic mechanism as Aacpn10, signifying that the tail is not responsible for the rapid misfolding step. This study demonstrates that molecular details can overrule similarity of native-state topology in defining apparent protein-biophysical properties.

A useful new classification of dysmorphic urinary erythrocytes

Among dysmorphic urinary erythrocytes (D cells), G1 cells or doughnut-shaped erythrocytes with one or more blebs are considered to be reliable markers for glomerular diseases. However, although there are many D cells with cytoplasmic color loss and without blebs in the urinary sediment, the significance of these cells is not clear. In this study, we devised a classification system for D cells and examined the relation between these cell types and urinalysis data. We classified D cells into three types (D1, D2, and D3 cells): D1 cells showed a ring-like shape and severe loss of cytoplasmic color with protrusions or blebs; D2 cells showed a doughnut-like shape and moderate cytoplasmic color loss with protrusions or blebs; and D3 cells showed a doughnut-like shape and mild cytoplasmic color loss without protrusions or blebs. We calculated the numbers of D cells of each type in 45 patients with glomerular diseases and in 303 general outpatients. This was done by bright-field microscopy modified for the analysis of urinary sediment, and we also examined the significance of these cell types. In the 45 patients with glomerular diseases, the numbers of D1, D2, and D3 cells correlated with urine levels of proteinuria and hematuria and numbers of cellular and fatty casts. Numbers of D1 and D2 cells correlated with urine concentrations of albumin and N-acetyl-beta-D-glucosaminidase, and the proportions of D1 and D2 cells in D cells increased with the activity of glomerular diseases classified by urinalysis data. Only the number of D1 cells correlated with the urine concentration of potassium, which may increase in hemolysis. In the 303 outpatients, the sensitivity of D3 cells and D1 and/or D2 cells (G1 cells) was 73% and 46%, respectively, for the detection of glomerular diseases and the specificity was 93% and 99%, respectively. These data indicate that the D3 cell is a sensitive marker for glomerular diseases, and that D1 and/or D2 cells are markers for severe glomerular diseases.

Mode shaping at a given distance outside a resonator with diffractive optical elements

We designed an intra-cavity mode shaping system to get a desired intensity profile at a given distance from the exit window of a laser resonator. The diffractive optical element (DOE) in the resonator forms a real-valued output mode and another DOE adds the required phase shifts to the output mode. The simulations show the formation of a flat-top and doughnut-like shape at the given distance outside the resonator.

Urine cytology in renal glomerular disease and value of G1 cell in the diagnosis of glomerular bleeding

The objectives of the present study were to evaluate the cytology of urine sediments in patients with glomerular diseases, as well as the value of G1 dysmorphic erythrocytes (G1DE) or G1 cells in the detection of renal glomerular hematuria. Freshly voided urine samples from 174 patients with glomerular diseases were processed according to the method used for semiquantitative cytologic urinalysis. G1DEs (distorted erythrocytes with doughnut-like shape, target configuration with or without membranous protrusions or blebs), non-G1DEs (distorted erythrocytes without the above-mentioned morphologic changes), normal erythrocytes (NEs), and renal tubular cells (RTCs) were evaluated. Erythrocytic casts (ECs) were counted and graded as abundant (>1 per high-power field) or rare (1 per 5 high-power fields). G1DE/total erythrocyte ratios were calculated by counting 200 erythrocytes including G1DEs, non-G1DEs, and NEs. Only abundant NEs were found in 13 cases; abundant G1DEs, non-G1DEs, NEs, and no ECs in 95 cases; abundant NEs, non-G1DEs, and ECs and no G1DEs in 31 cases; and abundant NEs, G1DEs and non-G1DEs, and rare ECs in 35 cases. In 130 cases in which G1DEs were present, the G1DE/total erythrocyte ratios varied from 10% to 100%. This parameter was greater or equal to 80%, 50%, 20%, and 10% in 58 (44.6%), 29 (22.3%), 28 (21.5%), and 15 (11.5%) patients, respectively. In all cases, the number of RTCs was within normal limits or slightly increased, and a variable number of non-G1DEs were present in 161 cases. Thus, abundant ECs and/or G1DEs with a G1DE/total erythrocyte ratio of 10-100% proved to be specific urinary markers for renal glomerular diseases.

2-Cys peroxiredoxin PfTrx-Px1 is involved in the antioxidant defence of Plasmodium falciparum.

Peroxiredoxins (Trx-Px) are ubiquitous antioxidant enzymes that catalyse the thioredoxin-dependent reduction of hydroperoxides. The number of characteristic active site (VCP/T) motifs defines these proteins as 1-Cys and 2-Cys Trx-Px. Steady-state kinetic parameters of Plasmodium falciparum 2-Cys Trx-Px (PfTrx-Px1) were determined using stopped flow rapid kinetics. The bi-substrate reaction displays ping-pong kinetics and the K(m) values for H2O2 and thioredoxin were determined to be 0.78+/-0.14 microM and 18.94+/-3.01 microM, respectively. The Vmax(app) and kcat(app) for H2O2 were found to be 4+/-0.6 U mg(-1) and 1.67+/-0.25 s(-1), respectively and those for thioredoxin are 23.0+/-0.2 U mg(-1) and 9.65+/-0.1 s(-1), emphasising the specificity of the enzyme for the substrate H2O2. After subjection to exogenous and endogenous oxidative stress, P. falciparum blood stage forms showed a marked elevation of PfTrx-Px1 mRNA and protein levels consistent with the hypothesis that it is an important component of the parasite's antioxidant machinery. Gel filtration, cross-linking and electron microscopy (EM) revealed that the protein forms decamers consisting of pentamers of homodimers that have a doughnut-like shape consistent with the structures of related proteins. No dimeric forms of the protein were detectable after gel filtration suggesting that PfTrx-Px1 predominantly exists as an oligomer.

At the Core of Splicing

MOLECULAR BIOLOGY In eukaryotes, the family of Sm proteins is known to participate in RNA processing events, such as splicing of pre-messenger RNAs. It is thought that seven distinct members of the family assemble into a doughnutlike shape and that this provides the binding surface for the uridine-

Lytic transglycosylases.

Although cleaving the same glycosidic bond between MurNAc and GlcNAc in murein, lytic transglycosylases differ from lysozymes by catalyzing an intramolecular transglycosylation of the glycosyl-bond onto the C6 hydroxyl group of the muramic acid residue yielding 1.6-anhydromuramic acid-carrying products. The three dimensional structure of the soluble lytic transglycosylase Slt70 of E. coli revealed a doughnut-like shape that would allow the protein to encircle the polysaccharide strands of the murein. Despite the absence of significant sequence homology, the catalytic center shows structural similarity to lysozymes, although the catalytic aspartate is missing. All lytic transglycosylases which have been characterized up until now turned out to be processive exo-glycosylases.

Deformation Process of a Water Droplet Impinging on a Solid Surface

This paper is concerned with numerical simulations of the deformation behavior of a liquid droplet impinging on a flat solid surface, as well as the flow field inside the droplet. In the present situation, the case where a droplet impinges on the surface at room temperature with a speed in the order of a few [m/s], is treated. These simulations were performed using the MAC-type solution method to solve a finite-differencing approximation of the Navier-Stokes equations governing an axisymmetric and incompressible fluid flow. For the first case where the liquid is water, the liquid film formed by the droplet impinging on the solid surface flows radially along it and expands in a fairly thin discoid-like shape. Thereafter, the liquid flow shows a tendency to stagnate at the periphery of the circular film, with the result that water is concentrated there is a doughnut-like shape. Subsequently, the water begins to flow backwards toward the center where it accumulates in the central region. For the second case where a n-heptane droplet impinges the surface, the film continues to spread monotonically up to a maximum diameter and there is no recoiling process to cause a backwards flow towards the central region. In this study the whole deformation process was investigated from numerical as well as experimental points of view. We find that the results obtained by the present mathematical model give fairly good agreement with the experimental observations. The effects of the viscous stresses and the surface tension on the deformation process of the droplets are estimated and discussed from a practical standpoint.

Differentiation of Hematuria Using a Uniquely Shaped Red Cell

Although variously shaped urinary red cells have been reported in glomerulonephritic hematuria, no specific shapes with concrete definition have been proposed. This made morphological differentiation of hematuria vague and caused different results among different observers. To solve these problems and improve the diagnostic rate, we employed a uniquely shaped red cell, which only appeared in glomerulonephritic hematuria, as a probe for diagnosis. We studied 182 hematuria cases from 90 glomerulonephritic patients and 95 hematuria cases from 68 urological disease patients. Fresh urine was collected and observed by differential interference microscopy. The red cell, referred to as G1, has a distinctive doughnut-like shape with blebs and was highly specific for glomerulonephritic hematuria. Occurrence of G1 cells increased at lower pH an higher osmolality of urine. A presence of 5% or more G1 cells could be an indicator of glomerulonephritic hematuria. Specificity and sensitivity of this criterion were 100 and 73%. However, when only acidic concentrated urine (pH < or = 6.4, osmolality > or = 400 mosm/kg H2O) was used, the specificity and sensitivity increased to 100 and 99.2%, respectively. Glomerulonephritic and urological hematuria were correctly diagnosed by counting the urinary red cells with doughnut-like shape in acidic and concentrated urine. This method seems to be superior to others in diagnostic rate, simplicity and clarity.

Fragmentation, dissipative expansion, and freeze-out in medium energy heavy-ion collisions

The collision dynamics of 96Mo + 96Mo at 55 A MeV is simulated by solving numerically the Boltzmann-Uehling-Uhlenbeck (BUU) transport equation for the one-body phase-space distribution-function of nucleons with and without Coulomb interaction. A scatter-plot of the one-body density distribution shows an initial compression, subsequent homogeneous expansion, a breaking into “fragments”, a very slow creeping expansion up to a freeze-out and in the case of included Coulomb-interaction a Coulomb-explosion. In the calculation which included Coulomb-interaction the overall shape of the ensemble of dense fragments is spherical. The fragments are created over the entire volume of the dense part of the source and not at the surface only. In the simulation without Coulomb interaction a doughnut-like shape may develop.

Image Analysis by Electron Microscopy of Two-Dimensional Crystals Developed on a Mercury Surface of Chaperonin from &lt;italic&gt;Thermus thermophilus&lt;/italic&gt;

Two-dimensional crystals of functional chaperonin molecules, which are protein complexes of cpn60 and cpn10, isolated from Thermus thermophilus were prepared on a mercury surface under oxygen atmosphere and were observed by electron microscope after transferring them to carbon coated specimen grids. The crystals showed the hexagonal lattice with unit cell dimensions of a = b = 12.4 nm and gamma = 120 degrees. The averaged image at a 3 nm resolution of the chaperonin has a doughnut-like shape which has seven peripheral masses and a central cavity. Preincubation of the chaperonin with MgATP changed the mobility in non-denaturating PAGE but did not cause distinguishable change of shape. The location of cpn10 in the chaperonin molecule is discussed.

Fiberoptic study on the effects of transluminal angioplasty in experimental occlusive arterial thrombosis

Percutaneous transluminal coronary angioplasty has been proposed as definitive therapy for coronary recanalization of occluded coronary arteries in patients with acute myocardial infarction (AMI). The effects of transluminal angioplasty (TA) on experimental occlusive canine arterial thrombi that closely simulated the clinical condition was examined by a fiberoptic method. Experimental arterial thrombosis was produced by endothelial denudation and induction of luminal stenosis. Eighteen dogs that showed total occlusion of the iliac artery with thrombi were evaluated. Seven dogs (group A) with 6-hour-old thrombi received 20,000 IU/kg intravenous urokinase (UK) but did not show recanalization. TA was performed with a Gruentzig or Simpson-Robert balloon catheter and its effect was evaluated by a vascular fibroscope. Eight dogs (group B) with 6-hour-old thrombi underwent primary TA. After TA, less than 50% luminal obstruction with residual thrombi was visualized in five dogs (71%) of group A and four dogs (50%) of group B. Residual thrombi showed a doughnut-like or globular type shape and consisted of dense fibrin networks and compact platelet aggregates. All dogs in group B received 20,000 IU/kg intravenous UK after TA, but most of them showed progression of thrombus size despite UK infusion. In conclusion, the results suggest (1) that TA is effective in recanalization of an occluded artery with aged thrombus that is resistant to thrombolytic therapy and (2) that vascular fiberscope is a useful method for evaluation of the effects of TA on occlusive arterial thrombus.