Mechanical Deformation Mechanisms and Properties of Prion Fibrils Probed by Atomistic Simulations

Abstract Prion fibrils, which are a hallmark for neurodegenerative diseases, have recently been found to exhibit the structural diversity that governs disease pathology. Despite our recent finding concerning the role of the disease-specific structure of prion fibrils in determining their elastic properties, the mechanical deformation mechanisms and fracture properties of prion fibrils depending on their structures have not been fully characterized. In this work, we have studied the tensile deformation mechanisms of prion and non-prion amyloid fibrils by using steered molecular dynamics simulations. Our simulation results show that the elastic modulus of prion fibril, which is formed based on left-handed β-helical structure, is larger than that of non-prion fibril constructed based on right-handed β-helix. However, the mechanical toughness of prion fibril is found to be less than that of non-prion fibril, which indicates that infectious prion fibril is more fragile than non-infectious (non-prion) fibril. Our study sheds light on the role of the helical structure of amyloid fibrils, which is related to prion infectivity, in determining their mechanical deformation mechanisms and properties

Novel Templating Route Using Pt Infiltrated Block Copolymer Microparticles for Catalytic Pt Functionalized Macroporous WO3 Nanofibers and Its Application in Breath Pattern Recognition

We propose a new route for transferring catalysts onto macroporous metal oxide nanofibers (NFs) using metallic nanoparticles (NPs) infiltrated block copolymer microparticles as sacrificial templates. Pt decorated polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) copolymer microparticles (Pt-BCP MPs), produced from oil-in-water emulsions, were uniformly dispersed within electrospun PVP/W precursor composite NFs. The macropore-loaded WO3 NFs (macroporous Pt-WO3 NFs), which are additionally functionalized by Pt NPs (10 nm), were achieved by decomposition of polymeric components and oxidization of W precursor after high-temperature calcination. In particular, macropores with the similar size distribution (50300 nm) with BCP MPs were also formed on interior and exterior of WO3 NFs. Chemical sensing performance of macroporous Pt-WO3 NFs was investigated for pattern recognition of simulated breath gas components at highly humid ambient (95% RH). The result revealed that superior hydrogen sulfide sensitivity (R-air/R-gas = 834.2 +/- 20.1 at S ppm) and noticeable selectivity were achieved. In addition, H2S pattern recognition against other chemical components (acetone, toluene, and methyl mercaptan) was clearly identified without any overlapping of each pattern. This work demonstrates the potential application of BCP-templated maroporous Pt-WO3 NFs in exhaled breath analysis for noninvasive monitoring of physical conditions

Donor-Acceptor Random versus Alternating Copolymers for Efficient Polymer Solar Cells: Importance of Optimal Composition in Random Copolymers

The backbone composition of conjugated copolymers is of great importance in determining the conjugated structure and intermolecular assembly and in manipulating their optical, electrochemical, and electronic properties. However, limited attention has been directed at controlling the backbone composition of donor acceptor (D-A) type low bandgap polymers. Herein, we developed a series of D-A random copolymers (P(BDTT-r-DPP)) composed of different compositions of electron-rich (D) thienyl-substituted benzo[1,2-b:4,5-b']dithiophene (BDTT) and electron-deficient (A) pyrrolo[3,4-c]pyrrole-1,4-dione (DPP). The optical and electrical properties of D-A random copolymers could be controlled by tuning the ratios of BDTT to DPP (4:1, 2:1, 1:1, 1:2, and 1:4) in the polymer backbone; an increase in BDTT resulted in increased absorption in the range of 400-600 nm and a lower-lying highest occupied molecular orbital energy level, while a higher proportion of DPP induced stronger absorption in the range of 700-900 nm. The P(BDTT-r-DPP) copolymer with a D:A ratio of 2:1 produced the highest power conversion efficiency (PCE) of 5.63% in the polymer solar cells (PSCs), which outperformed the D-A alternating copolymer, P(BDTT-alt-DPP) (1:1)-based PSCs (PCE = 5.03%), because of the improved light absorption and open-circuit voltage. Thus, we highlight the importance of developing random copolymers with controlled D:A compositions for optimizing their optoelectronic properties and performances of PSCs. Also, we compared the polymer packing structure and the electrical properties between the P(BDTT-r-DPP) and P(BDTT-alt-DPP) copolymers and developed a quantitative understanding of the effect of the D:A monomer sequence on the structural, electrical, and photovoltaic properties of the D-A copolymers

Sequence-dependent aggregation-prone conformations of islet amyloid polypeptide

Amyloid proteins, which aggregate to form highly ordered structures, play a crucial role in various disease pathologies. Despite many previous studies on amyloid fibrils, which are an end product of protein aggregation, the structural characteristics of amyloid proteins in the early stage of aggregation and their related aggregation mechanism still remain elusive. The role of the amino acid sequence in the aggregation-prone structures of amyloid proteins at such a stage is not understood. Here, we have studied the sequence-dependent structural characteristics of islet amyloid polypeptide based on atomistic simulations and spectroscopic experiments. We show that the amino acid sequence determines non-bonded interactions that play a leading role in the formation of aggregation-prone conformations. Specifically, a single point mutation critically changes the population of aggregation-prone conformations, resulting in a change of the aggregation mechanism. Our simulation results were supported by experimental results suggesting that mutation affects the kinetics of aggregation and the structural characteristics of amyloid aggregates. Our study provides an insight into the role of sequence-dependent aggregation-prone conformations in the underlying mechanisms of amyloid aggregation

Controlling symmetry of spin-orbit entangled pseudospin state through uniaxial strain

In layer-structured Sr2IrO4, strong crystal electric field and spin-orbit coupling result in an intriguing spin-orbit entangled J(eff) = 1/2 state, resembling the spin S = 1/2 state of high-temperature superconducting cuprates. Our study unravels the intricate relationship between the lattice and the pseudospin interactions using uniaxial strain. Applied along the [1 1 0] direction, a compressive strain does not induce any effect. In contrast, the strain along [1 0 0] triggers a dramatic detwinning of the magnetic domains bringing the system to a single domain at around 0.04% strain. The strain driven detwinning rate is temperature independent showing that it does not exhibit a spontaneous orthorhombic lattice distortion driven by the pseudo-Jahn-Teller effect.11Nscopu

Orbit Determination of KOMPSAT-1 and Cryosat-2 Satellites Using Optical Wide-field Patrol Network (OWL-Net) Data with Batch Least Squares Filter

The optical wide-field patrol network (OWL-Net) is a Korean optical surveillance system that tracks and monitors domestic\ud satellites. In this study, a batch least squares algorithm was developed for optical measurements and verified by Monte\ud Carlo simulation and covariance analysis. Potential error sources of OWL-Net, such as noise, bias, and clock errors, were\ud analyzed. There is a linear relation between the estimation accuracy and the noise level, and the accuracy significantly\ud depends on the declination bias. In addition, the time-tagging error significantly degrades the observation accuracy, while\ud the time-synchronization offset corresponds to the orbital motion. The Cartesian state vector and measurement bias were\ud determined using the OWL-Net tracking data of the KOMPSAT-1 and Cryosat-2 satellites. The comparison with known\ud orbital information based on two-line elements (TLE) and the consolidated prediction format (CPF) shows that the orbit\ud determination accuracy is similar to that of TLE. Furthermore, the precision and accuracy of OWL-Net observation data\ud were determined to be tens of arcsec and sub-degree level, respectively

Orbit Determination of KOMPSAT-1 and Cryosat-2 Satellites Using Optical Wide-field Patrol Network (OWL-Net) Data with Batch Least Squares Filter

The optical wide-field patrol network (OWL-Net) is a Korean optical surveillance system that tracks and monitors domestic\ud satellites. In this study, a batch least squares algorithm was developed for optical measurements and verified by Monte\ud Carlo simulation and covariance analysis. Potential error sources of OWL-Net, such as noise, bias, and clock errors, were\ud analyzed. There is a linear relation between the estimation accuracy and the noise level, and the accuracy significantly\ud depends on the declination bias. In addition, the time-tagging error significantly degrades the observation accuracy, while\ud the time-synchronization offset corresponds to the orbital motion. The Cartesian state vector and measurement bias were\ud determined using the OWL-Net tracking data of the KOMPSAT-1 and Cryosat-2 satellites. The comparison with known\ud orbital information based on two-line elements (TLE) and the consolidated prediction format (CPF) shows that the orbit\ud determination accuracy is similar to that of TLE. Furthermore, the precision and accuracy of OWL-Net observation data\ud were determined to be tens of arcsec and sub-degree level, respectively

Novel Templating Route Using Pt Infiltrated Block Copolymer Microparticles for Catalytic Pt Functionalized Macroporous WO₃ Nanofibers and Its Application in Breath Pattern Recognition

We propose a new route for transferring catalysts onto macroporous metal oxide nanofibers (NFs) using metallic nanoparticles (NPs) infiltrated block copolymer microparticles as sacrificial templates. Pt decorated polystyrene-<i>b</i>-poly­(4-vinylpyridine) (PS-<i>b</i>-P4VP) copolymer microparticles (Pt-BCP MPs), produced from oil-in-water emulsions, were uniformly dispersed within electrospun PVP/W precursor composite NFs. The macropore-loaded WO₃ NFs (macroporous Pt-WO₃ NFs), which are additionally functionalized by Pt NPs (10 nm), were achieved by decomposition of polymeric components and oxidization of W precursor after high-temperature calcination. In particular, macropores with the similar size distribution (50–300 nm) with BCP MPs were also formed on interior and exterior of WO₃ NFs. Chemical sensing performance of macroporous Pt-WO₃ NFs was investigated for pattern recognition of simulated breath gas components at highly humid ambient (95% RH). The result revealed that superior hydrogen sulfide sensitivity (<i>R</i>_air/<i>R</i>_gas = 834.2 ± 20.1 at 5 ppm) and noticeable selectivity were achieved. In addition, H₂S pattern recognition against other chemical components (acetone, toluene, and methyl mercaptan) was clearly identified without any overlapping of each pattern. This work demonstrates the potential application of BCP-templated maroporous Pt-WO₃ NFs in exhaled breath analysis for noninvasive monitoring of physical conditions