Structure, Vibrational Spectra and Related Physical Properties of Various Glasses in the PbO-Bi2O3-GeO2 System

1986 ◽  
Vol 88 ◽  
Author(s):  
J. E. Canale ◽  
R. A. Condrate ◽  
K. Nassau ◽  
B. C. Cornilsen
Keyword(s):  
Molar Volume ◽  
Bismuth Oxide ◽  
Transformation Temperature ◽  
Lead Oxide ◽  
Structural Changes ◽  
Physical Property ◽  
Volume Data ◽  
Dsc Measurements ◽  
Glass Transformation ◽  
High Concentrations

ABSTRACTVibrational spectroscopy and various physical property measurements (density, molar volume and glass transformation temperature) were used to investigate the structural changes that occurred with changes in composition for glasses prepared by standard melting and quenching techniques in the PbO-Bi2O3-GeO2 system. Regions of constant glass transformation temperature (Tg) were noted for these glasses at high GeO2 compositions, as determined from DSC measurements. These results clearly indicated the presence of amorphous phase separation. A model was proposed that could qualitatively interpret both the infrared and Raman spectra, and the molar volume data. At low lead oxide and bismuth oxide concentrations, lead acted primarily as a network modifier while bismuth acted as a mixed network former and modifier. At high concentrations, both lead and bismuth acted as network formers in linking discrete GeO4-units and possibly forming a lead oxide/bismuth oxide portion of the network. The observed results were also interpreted on the basis of Ge-O bonds involving bridged and non-bridged oxygen atoms, and on the basis of a possible change in coordination for germanium from four to six with metal oxide additions.

Native Ubiquitin Structural Changes Resulting from Complexation with β-methylamino-L-alanine (BMAA)

2020 ◽  
Author(s):  
Katie Mae Wilson ◽  
Aurora Burkus-Matesevac ◽  
Samuel Maddox ◽  
Christopher Chouinard
Keyword(s):  
Structural Changes ◽  
Noncovalent Complex ◽  
Unfolded Protein ◽  
Protein Size ◽  
High Concentrations ◽  
The Unfolded Protein Response ◽  
Critical Binding ◽  
Protein Response ◽  
The Brain ◽  
Lateral Sclerosis

β-methylamino-L-alanine (BMAA) has been linked to the development of neurodegenerative (ND) symptoms following chronic environmental exposure through water and dietary sources. The brains of those affected by this condition, often referred to as amyotrophic lateral sclerosis-parkinsonism-dementia complex (ALS-PDC), have exhibited the presence of plaques and neurofibrillary tangles (NFTs) from protein aggregation. Although numerous studies have sought to better understand the correlation between BMAA exposure and onset of ND symptoms, no definitive link has been identified. One prevailing hypothesis is that BMAA acts a small molecule ligand, complexing with critical proteins in the brain and reducing their function. The objective of this research was to investigate the effects of BMAA exposure on the native structure of ubiquitin. We hypothesized that formation of a Ubiquitin+BMAA noncovalent complex would alter the protein’s structure and folding and ultimately affect the ubiquitinproteasome system (UPS) and the unfolded protein response (UPR). Ion mobility-mass spectrometry revealed that at sufficiently high concentrations BMAA did in fact form a noncovalent complex with ubiquitin, however similar complexes were identified for a range of additional amino acids. Collision induced unfolding (CIU) was used to interrogate the unfolding dynamics of native ubiquitin and these Ubq-amino acid complexes and it was determined that complexation with BMAA led to a significant alteration in native protein size and conformation, and this complex required considerably more energy to unfold. This indicates that the complex remains more stable under native conditions and this may indicate that BMAA has attached to a critical binding location.

Native Ubiquitin Structural Changes Resulting from Complexation with β-methylamino-L-alanine (BMAA)

2020 ◽  
Author(s):  
Katie Mae Wilson ◽  
Aurora Burkus-Matesevac ◽  
Samuel Maddox ◽  
Christopher Chouinard
Keyword(s):  
Structural Changes ◽  
Noncovalent Complex ◽  
Unfolded Protein ◽  
Protein Size ◽  
High Concentrations ◽  
The Unfolded Protein Response ◽  
Critical Binding ◽  
Protein Response ◽  
The Brain ◽  
Lateral Sclerosis

β-methylamino-L-alanine (BMAA) has been linked to the development of neurodegenerative (ND) symptoms following chronic environmental exposure through water and dietary sources. The brains of those affected by this condition, often referred to as amyotrophic lateral sclerosis-parkinsonism-dementia complex (ALS-PDC), have exhibited the presence of plaques and neurofibrillary tangles (NFTs) from protein aggregation. Although numerous studies have sought to better understand the correlation between BMAA exposure and onset of ND symptoms, no definitive link has been identified. One prevailing hypothesis is that BMAA acts a small molecule ligand, complexing with critical proteins in the brain and reducing their function. The objective of this research was to investigate the effects of BMAA exposure on the native structure of ubiquitin. We hypothesized that formation of a Ubiquitin+BMAA noncovalent complex would alter the protein’s structure and folding and ultimately affect the ubiquitinproteasome system (UPS) and the unfolded protein response (UPR). Ion mobility-mass spectrometry revealed that at sufficiently high concentrations BMAA did in fact form a noncovalent complex with ubiquitin, however similar complexes were identified for a range of additional amino acids. Collision induced unfolding (CIU) was used to interrogate the unfolding dynamics of native ubiquitin and these Ubq-amino acid complexes and it was determined that complexation with BMAA led to a significant alteration in native protein size and conformation, and this complex required considerably more energy to unfold. This indicates that the complex remains more stable under native conditions and this may indicate that BMAA has attached to a critical binding location.

scholarly journals Thermal properties of Na2O–P2O5–Fe2O3 polyphosphate glasses

2020 ◽  
Vol 142 (1) ◽  
pp. 203-209 ◽  
Author(s):  
Paweł Goj ◽  
Małgorzata Ciecińska ◽  
Magdalena Szumera ◽  
Paweł Stoch
Keyword(s):  
Thermal Properties ◽  
Phosphate Glass ◽  
Transformation Temperature ◽  
Glass Network ◽  
Iron Phosphate ◽  
Phosphate Glasses ◽  
Continuous Change ◽  
Glass Transformation ◽  
Immobilization Techniques ◽  
Iron Phosphate Glasses

Abstract Iron phosphate glasses are materials that can have many applications like durable matrixes in waste immobilization techniques, biomaterials, optoelectronic devices, etc. Their possible usage is related to their glass network and thermal properties. The influence of Na2O content on thermal properties and crystallization ability of iron phosphate glass of base composition 30 Fe2O3–70 P2O5 mol% were studied. Increasing the content of Na2O causes a decrease in transformation temperature and increase in ΔCp. Characteristic temperatures, thermal stability and crystallizing phases were determined. Increasing content of sodium causes depolarization of iron phosphate glass network which causes a continuous change in ΔCp and glass transformation temperature. Discontinuous change in some glass properties suggests structure rebuilding about 30 mol% of Na2O.

scholarly journals Distribution and stability of antisense phosphorothioate oligonucleotides in rodent brain following direct intraparenchymal controlled-rate infusion

1997 ◽  
Vol 3 (5) ◽  
pp. E6 ◽  
Author(s):  
William C. Broaddus ◽  
Sujit S. Prabhu ◽  
George T. Gillies ◽  
Jeffrey Neal ◽  
William S. Conrad ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Structural Changes ◽  
Tissue Concentration ◽  
Volume Of Distribution ◽  
Brain Parenchyma ◽  
Average Concentration ◽  
High Flow ◽  
Fischer 344 ◽  
High Concentrations ◽  
The Brain

High-flow microinfusion is a novel technique for delivery of compounds directly into the brain parenchyma, bypassing the blood-brain barrier. The feasibility of this technique has been demonstrated with low-molecular-weight compounds, macromolecular dyes, and proteins. Delivery of antisense oligonucleotides into the brain parenchyma represents an additional potential application of this technique not previously described. In this report, the authors examined the distribution and disposition of phosphorothioate oligodeoxynucleotide (PS-ODN) infused for this reason. An 18-mer 35S-PS-ODN (molecular weight approximately 6000) was infused over 1 hour into the caudate putamen of Fischer 344 rats. At 1, 6, 12, 24, and 48 hours after beginning the infusion, the brains were extracted and analyzed using quantitative autoradiographic techniques. Cerebrospinal fluid (CSF) was also aspirated from the cisterna magna and analyzed for radioactivity and stability of the 35S-PS-ODN. At 1 hour, the infused ODN was uniformly distributed in brain tissue, with a maximum average concentration of 4806.5 ± 210.5 nCi/g. This represents a tissue concentration of 19.2 ± 0.84 μM. Extensive spread into surrounding parenchyma was observed over the ensuing 47 hours. The 35S-PS-ODN radioactivity peaked in the CSF at the end of the 1-hour infusion, containing 10% (50 ± 20 nCi) of the infused radioactivity. Activity then decayed exponentially over 11 hours, stabilizing at a lower CSF content of 0.2% (1 ± 0.1 nCi). The volume of distribution (Vd) was 105 ± 7.9 mm3 at 1 hour, representing a ratio of Vd/Vi (volume of infusion) of 5.2. The Vd increased to 443.4 ± 62.3 mm3 at the end of 48 hours, whereas the average minimum tissue concentration decreased from 15.2 to 3.2 μM. Undegraded 18-mer was seen throughout the 48-hour period using 20% polyacrylamide/7M urea gel electrophoresis. The animals tolerated the infusion without evidence of toxicity, and minimal structural changes in tissue were observed on histological examination. Thus, PS-ODN can be safely delivered in high concentrations to wide areas of the rat brain by using high-flow microinfusion, and the concentrations remain stable even after 48 hours in situ.

scholarly journals Influence of Erbium Doping on Dielectric Properties of Zinc Borotellurite Glass System

2016 ◽  
Vol 846 ◽  
pp. 161-171 ◽  
Author(s):  
Siti Shafinas Zulkefly ◽  
Halimah Mohamed Kamari ◽  
Muhammad Nor Azlan Abdul Azis ◽  
Wan Mohd Daud Wan Yusoff
Keyword(s):  
Dielectric Properties ◽  
Molar Volume ◽  
Structural Changes ◽  
Low Frequency ◽  
Interfacial Polarization ◽  
Xrd Analysis ◽  
Glass System ◽  
Response Measurement ◽  
Xrd Pattern ◽  
Higher Temperature

Glasses of the system {[ (TeO2)70 (B2O3)30]70 (ZnO)30}100-y (Er2O3)y containing different concentration of Er2O3 (ranging from 0 to 5 mol %) was prepared from melt-quenching technique. The structural changes were studied by XRD analysis and FTIR analysis. The XRD pattern shows the glasses are amorphous. The higher concentration of Er2O3, the more unit of TeO3 would transform to TeO4 and formation of B-O vibrational groups. The density and molar volume was obtained attribute to non-bridging oxygen (NBO) and are found the density and molar volume of the glass system are increasing. The densities range from 3630 kg/m3 to 3960 kg/m3. The dielectric constant ε’ and dielectric loss factor ε’’ which were characterized in the frequency range 10-2 – 106 Hz over temperature range 50°C – 200 °C, show a larger value at lower frequency and higher temperature (above 110°C ). The results of dielectric response measurement show that interfacial polarization at low frequency, and orientation polarization at intermediate and high frequency.Keywords: Dielectric properties; Activation Energy; Rare Earth; Polarization; Non-Bridging Oxygen;

Mechanical and thermal properties of the glassy semiconductor chlorinated Se0 997As0 003 used as an X-ray imaging material

1989 ◽  
Vol 67 (7) ◽  
pp. 686-693 ◽  
Author(s):  
S. O. Kasap ◽  
S. Yannacopoulos
Keyword(s):  
Thermal Properties ◽  
Structural Changes ◽  
Relaxation Times ◽  
Thermal Relaxation ◽  
Mechanical And Thermal Properties ◽  
Debye Relaxation ◽  
X Ray ◽  
Temperature Range ◽  
Glass Transformation ◽  
X Ray Imaging

Mechanical and thermal properties of a typical X-ray imaging material amorphous Se0.997As0.003, chlorinated in the ppm range were investigated using thermal microhardness analysis (TμHA) and differential scanning calorimetry (DSC). The experiments were carried out over a temperature range encompassing the glass transformation to study the nature of structural changes controlling the mechanical and thermal properties. It is shown that the mechanical property microhardness when examined on an Itoh–Shishokin plot of log Vickers hardness number (VHN) vs. temperature (T) exhibits a hardness transition temperature, Tg*, in the glass transformation region. The rates of relaxation of the mechanical and thermal properties in the glass transformation region were studied by investigating the heating rate dependence of the glass transition temperatures, Tg* and Tg, defined empirically on the log VHN vs. T behavior and the DSC glass transformation endotherm, respectively. By applying the present thermoanalytical methods, it has proved possible to identify a typical Vogel–Tammann–Fulcher type of behavior in the mechanical and thermal relaxation times that correlates remarkably well with the viscosity–temperature data of M. Cukierman and D. R. Uhlmann (J. Non-Cryst. Solids, 12, 199 (1973)) as well as the dielectric loss experiments of M. Abkowitz, D. F. Pochan, and J. M. Pochan (J. Appl. Phys. 51, 1539 (1980)). The latter had previously exposed a Williams–Landel–Ferry relation for the Debye relaxation times in a-Se and a-Se: 1% As. It is therefore concluded that the behavior of mechanical, thermal, and dielectric properties of a-Se0997As0003 in the glass transformation region is inversely proportional to the viscosity, which in turn can be adequately described over a temperature range above ~30 °C by a Vogel expression.

Delindeite titanosilicates and lourenswalsite, two new from the Magnet Cove region, Arkansas

1987 ◽  
Vol 51 (361) ◽  
pp. 417-425 ◽  
Author(s):  
Daniel E. Appleman ◽  
Howard T. Evans ◽  
Gordon L. Nord ◽  
Edward J. Dwornik ◽  
Charles Milton
Keyword(s):  
Electron Diffraction ◽  
Molar Volume ◽  
Hot Spring ◽  
Unit Cell ◽  
Volume Data ◽  
X Ray ◽  
Ion Probe ◽  
Layer Disorder ◽  
Miarolitic Cavities ◽  
Measured Density

AbstractDelindeite and lourenswalsite are two new barium titanosilicate minerals found as microscopic crystals in miarolitic cavities in nepheline syenite in the Diamond Jo quarry, Hot Spring County, Arkansas. Delindeite is found as aggregates of flake-like crystallites in compact spherules, light pinkish grey in colour, with a resinous, pearly lustre. The flakes are biaxial positive with average n ∼ 1.813; the measured density is 3.3 g/cm3. Electron diffraction revealed a monoclinic unit cell in space group C2/m or subgroup, with a = 21.617(13), b = 6.816(5), c = 5.383(3) Å, β = 94.03(5)° (refined from X-ray powder data). The strongest X-ray lines are (hkl, dobs, Irel): (200, 10.80, 100); (311, 3.54, 24); (6̄01, 3.083, 28); (601, 2.888, 31); (2̄21, 2.806, 20); (910, 2.262,18). The crystals are submicroscopically twinned on (100) and also produce additional continuous diffraction streaks parallel to a*, which double the b and c axes. The formula derived from electron and ion probe analyses (H2O by difference), as constrained by density and molar volume data, is approximately (Na,K)2.7(Ba,Ca)4(Ti,Fe,Al)6Si8O26(OH)14, with Na > K, Ba ≫ Ca, Ti ≫ Fe,Al; Z = 1. Lourenswalsite occurs as very thin hexagonal plates in rosettes, silver grey to light brownish grey in colour. The crystals are biaxial negative with very low 2V angle. Indices of refraction are nα = 1.815, nβ ≈ nγ = 1.840; the measured density is 3.17 g/cm = 1.840; the measured density is 3.17 g/cm3. X-ray and electron diffraction show a sharp pseudohexagonal lattice with a = 5.244 Å, but extremely diffuse diffraction streaks normal to the hk0 plane. In these streaks a period of 20.5 Å can be discerned. A hexagonal unit cell with a = 5.244(2) Å, c = 20.49(3) Å can be refined from the powder diffraction data but does not account for some lines, probably because of extreme layer disorder as shown by precession single-crystal patterns. The strong X-ray powder lines are (002, 10.22, 20); (-, 3.93, 20); (111, 2.608, 100); (300, 1.5145, 80); (220, 1.3111, 25). The formula given by microprobe analyses, constrained by density and molar volume data, is approximately (K,Ba)2(Ti,Mg,Ca,Fe)4(Si,Al,Fe)6O14(OH)12 with K > Ba, Ti ≫ (Mg,Ca,Fe), Si > Al > Fe; Z = 1. These minerals are formed under oxidizing weathering conditions, and iron is assumed to be in the Fe3+ state.

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