Destabilization Of Structure Research Articles

Thioether-Based Polymeric Micelles with Fine-Tuned Oxidation Sensitivities for Chemotherapeutic Drug Delivery.

Oxidation-sensitive drug delivery systems (DDSs) have attracted attention due to the potential to improve efficacy and safety of chemotherapeutics. These systems are designed to release the payload in response to oxidative stress conditions, which are associated with many types of cancer. Despite extensive research on the development of oxidation-sensitive DDS, the lack of selectivity toward cancer cells over healthy cells remains a challenge. Here, we report the design and characterization of polymeric micelles containing thioether groups with varying oxidation sensitivities within the micellar core, which become hydrophilic upon thioether oxidation, leading to destabilization of the micellar structure. We first used the thioether model compounds, 3-methylthiopropylamide (TPAM), thiomorpholine amide (TMAM), and 4-(methylthio)benzylamide (TPhAM) to investigate the effect of the chemical structures of the thioethers on the oxidation by hydrogen peroxide (H2O2). TPAM shows the fastest oxidation, followed by TMAM and TPhAM, showing that the oxidation reaction of thioethers can be modulated by changing the substituent groups bound to the sulfur atom. We next prepared micelles containing these different thioether groups within the core (TP, TM, and TPh micelles). The micelles containing the thioether groups with a higher oxidation sensitivity were destabilized by H2O2 at a lower concentration. Micelle destabilization was also tested in human liver cancer (HepG2) cells and human umbilical vein endothelial cells (HUVECs). The TP micelles having the highest oxidation sensitivity were destabilized in both HepG2 cells and HUVECs, while the TPh micelles, which showed the lowest reactivity toward H2O2, were stable in these cell lines. The TM micelles possessing a moderate oxidation sensitivity were destabilized in HepG2 cells but were stable in HUVECs. Furthermore, the micelles were loaded with doxorubicin (Dox) to evaluate their potential in drug delivery applications. Among the micelles, the TM micelles loaded with Dox showed the enhanced relative toxicity in HepG2 cells over HUVECs. Therefore, our approach to fine-tune the oxidation sensitivity of the micelles has potential for improving therapeutic efficacy and safety of drugs in cancer treatment.

Illuminating the Imperceptible, Researching Mina'i Ceramics with Digital Imaging Techniques.

Mina’i ceramics dating to the late 12th and early 13th century made in the Kashan region of Iran represent a novel period of overglaze enamelling technology in ceramic history. New colours were used to produce stylistically attractive and dynamic polychrome motifs. Due to their archaeological context, and popularity in the art market since the mid-20th century, these objects often have complex conditions involving reconstruction and overpainting. The aesthetic and technological significance of these pieces warrants further study, but in practice, removing restorations can lead to structural destabilisation, requiring time-consuming and potentially unplanned for conservation treatment. To determine if it is possible to gain useful information from the study of these artworks without disturbing existing restorations, a group of objects were drawn from the Sarikhani and Ashmolean Museum of Art and Archaeology collections. The objective of this project was twofold, first to assess the merits of the imaging techniques for understanding condition, and second to propose a protocol for imaging with the aim of encouraging collaborative projects with international partners. The techniques used in this study include digital photography under visible and ultraviolet light, infrared reflectography, and radiography. The results show that important information invisible to the naked eye can be obtained about the decorative surfaces, using ultraviolet light and infrared reflectography. Digital radiography proved to be equally effective when studying the condition of the ceramic body. The results of this project were used to produce guidance on these techniques as a collaborative documentation package for the study of Mina’i ceramics.

Electrochemical Performance of Na3V2(PO4)2F3 Electrode Material in a Symmetric Cell.

A NASICON-based Na3V2(PO4)2F3 (NVPF) cathode material is reported herein as a potential symmetric cell electrode material. The symmetric cell was active from 0 to 3.5 V and showed a capacity of 85 mAh/g at 0.1 C. With cycling, the NVPF symmetric cell showed a very long and stable cycle life, having a capacity retention of 61% after 1000 cycles at 1 C. The diffusion coefficient calculated from cyclic voltammetry (CV) and the galvanostatic intermittent titration technique (GITT) was found to be ~10−9–10−11, suggesting a smooth diffusion of Na+ in the NVPF symmetric cell. The electrochemical impedance spectroscopy (EIS) carried out during cycling showed increases in bulk resistance, solid electrolyte interphase (SEI) resistance, and charge transfer resistance with the number of cycles, explaining the origin of capacity fade in the NVPF symmetric cell. Finally, the postmortem analysis of the symmetric cell after 1000 cycles at a 1 C rate indicated that the intercalation/de-intercalation of sodium into/from the host structure occurred without any major structural destabilization in both the cathode and anode. However, there was slight distortion in the cathode structure observed, which resulted in capacity loss of the symmetric cell. The promising electrochemical performance of NVPF in the symmetric cell makes it attractive for developing long-life and cost-effective batteries.

Destabilization of the surface structure of Ni-rich layered materials by water-washing process

Washing Ni-rich layered materials with water is a simple and effective way to reduce gas evolution by eliminating the gas generation factors. However, the water-washing process itself degrades the electrochemical performances; hence additional treatments such as heating and coating are undertaken. Thus, most studies for the post-process mainly focus on the relationship between additional treatments and electrochemical performances, not paying much attention to the water-washing effect. Here, we focused on the effect of water-washing on the Ni-rich layered materials by studying bare and water-washed LiNi0.88Co0.054Mn0.066O2(NCM) cathodes. The results of synchrotron-based X-ray analysis indicate that the crystal and electronic structures are the same in the bulk aspect after the water-washing process, but differences occur in the surface environment. The amount of Li2CO3 decreases while NiO-like rock-salt phase increases on the surface of the water-washed NCM, and it deteriorates the rate performances by elevating the surface resistances. Furthermore, the surface layer reconstruction of water-washed NCM, which has lower capacity retention during 200 cycles, is much more severe than the bare NCM; this indicates that the water-washing process makes the surface of Ni-rich layered materials more vulnerable to the side reaction, facilitating the formation of NiO-like rock-salt phase by the reconstruction.

Reconstructing Vanadium Oxide with Anisotropic Pathways for a Durable and Fast Aqueous K-Ion Battery.

Aqueous potassium-ion batteries are long-term pursued, due to their excellent performance and intrinsic superiority in safe, low-cost storage for portable and grid-scale applications. However, the notorious issues of K-ion battery chemistry are the inferior cycling stability and poor rate performance, due to the inevitably destabilization of the crystal structure caused by K-ions with pronouncedly large ionic radius. Here, we resolve such issues by reconstructing commercial vanadium oxide (α-V2O5) into the bronze form, i.e., δ-K0.5V2O5 (KVO) nanobelts, as cathode materials with layered structure of enlarged space and anisotropic pathways for K-ion storage. Specifically, it can deliver a high capacity as 116 mAh g-1 at the 1 C-rate, an outstanding rate capacity of 65 mAh g-1 at 50 C, and a robust cyclic stability with 88.2% capacity retention after 1,000 cycles at 1 C. When coupled with organic anode in a full-cell configuration, the KVO electrodes can output 95 mAh g-1 at 1 C and cyclic stability with 77.3% capacity retention after 20,000 cycles at 10 C. According to experimental and calculational results, the ultradurable cyclic performance is assigned to the robust structural reversibility of the KVO electrode, and the ultrahigh-rate capability is attributed to the anisotropic pathways with improved electrical conductivity in KVO nanobelts. In addition, applying a 22 M KCF3SO3 water-in-salt electrolyte can impede the dissolving issues of the KVO electrode and further stabilize the battery cyclic performance. Lastly, the as-designed AKIBs can operate with superior low-temperature adaptivity even at -30 °C. Overall, the KVO electrode can serve as a paradigm toward developing more suitable electrode materials for high-performance AKIBs.

Effects of Ionic Liquids on Laccase from Trametes versicolor

Interactions between ionic liquids and biomolecules are of great interest due to the intrinsic properties of ionic liquids and the flexibility allowed by mixing and matching cations and anions to create unique ionic liquids. A number of ionic liquid–biomolecule studies have focused on interactions with proteins, including industrially relevant enzymes. One of these, laccase from Trametes versicolor, is a naturally derived enzyme used in the breakdown of phenolic compounds in a wide variety of industries, especially useful in breakdown of lignocellulosic materials. Here, a combination of experiments and molecular dynamics (MD) simulations was used to investigate the interactions of ionic liquids with laccase. Enzyme kinetics assays indicated that ionic liquids composed of tetramethylguanidine (TMG) and either serine or threonine caused significant reduction in enzymatic activity, while kinetics was not impacted by TMG-Asp or TMG-Glu ionic liquids. Similarly, intrinsic fluorescence of laccase in the presence of TMG-Ser and TMG-Thr exhibited a shift in spectral properties consistent with structural destabilization, but again TMG-Asp and TMG-Glu had no impact. MD simulations of laccase and ABTS with/without TMG-Ser ionic liquid provided insight into the deactivation mechanism of laccase. The simulations indicated that TMG-Ser disrupts laccase’s electron transfer mechanism.

Transformation of oil dispersed systems during operation

Abstract: Using the example of oil road bitumen grades BND 100/130, BND 130/200 and BND 70/100, this article studies the transformation of oil dispersed systems under various logistic schemes of operation. This research focuses on the influence of the conditions for storing road bitumens of different grades on their physical and mechanical properties and group hydrocarbon composition during transportation from the manufacturer to the consumer. The results show that a change in the physical and mechanical properties of road bitumens during high-temperature storage is related to the changes in the group hydrocarbon composition due to the hydrocarbons autooxidation and destabilization of the colloidal structure of dispersal systems. The conditions for storing bitumen with a minimum change in its quality indicators have been determined. It has been established that storage of bitumen under atmospheric conditions allows preserving its original properties without significant changes. There is evidence that nitrogen purging significantly reduces the effect of homolytic processes leading to the transformation of oil dispersed systems during further transportation from the manufacturer to the consumer. Experimental data confirm that of all basic physical and mechanical properties of bitumen, “the depth of penetration of needle” is the most sensitive index, while the “softening temperature” index, frequently used for quality control of bitumen, is inertial. Determining the change in penetration, depending on the duration of storing bitumen, has required formulating a special equation. It has been established that when storing road bitumen at a temperature of 180 ºС, for each hour the index of the penetration depth of the needle at 25 º decreases by 0.8 units. Organizational and technical measures have been determined to ensure the stability of the road bitumen quality during manufacture, storage and transportation to consumers.

Reactive binder and aggregate interfacial zones in the mortar of Tomb of Caecilia Metella concrete, 1C BCE, Rome

AbstractIntegrated spectroscopic analyses and synchrotron X‐ray microdiffraction investigations provide insights into the long‐term reactivity of volcanic aggregate components and calcium‐aluminum‐silicate‐hydrate (C‐A‐S‐H) binder in mortar samples from the robust concrete of the sepulchral corridor of the Tomb of Caecilia Metella, 1st C BCE, Rome. The results of innovative micrometer‐scale analytical maps indicate that Pozzolane Rosse tephra components–scoria groundmass, clinopyroxene, and leucite crystals–contributed to pozzolanic production of C‐A‐S‐H binder and then remained reactive long after hydrated lime (Ca(OH)2) was fully consumed. The C‐A‐S‐H binding phase is reorganized into wispy halos and tendril‐like strands, some with nanocrystalline preferred orientation or, alternatively, split into elongate features with short silicate chain lengths. These microstructures apparently record chemical and structural destabilization of C‐A‐S‐H during excessive incorporation of Al3+and K+released through leucite dissolution. Resistance to failure may result from the intermittent toughening of interfacial zones of scoriae and clinopyroxene crystals with post‐pozzolanic strätlingite and Al‐tobermorite mineral cements and from long‐term remodeling of the pozzolanic C‐A‐S‐H binding phase. Roman builders’ selection of a leucite‐rich facies of Pozzolane Rosse tephra as aggregate and construction of the tomb in an environment with high surface and ground water exposure apparently increased beneficial hydrologic activity and reactivity in the concrete.

Deep blue autofluorescence reveals the instability of human transthyretin

Wild-type human transthyretin (TTR) is a tetrameric protein that transports thyroxine and retinol in the blood and brain. However, a number of mutations or aging leads to destabilization of the quaternary structure of TTR, which results in dissociation of TTR tetramers to monomers, followed by oligomerization and subsequent amyloid formation. TTR amyloid is a pathogenic factor underlying several diseases. It has recently been documented that destabilization of the structure of TTR is driven by Ca2+. The present work shows that the in vitro redox conditions contribute to the destabilization and formation of the highly unstable substoichiometric population(s) of TTR molecules. Importantly, destabilized TTR forms acquire the ability to emit fluorescence in the blue range of the light spectrum. Dithiothreitol (DTT), in the presence of Ca2+, enhances the formation of complex autofluorophore which displays maxima at 417 nm and 438 nm in the emission spectrum of TTR.

The role of intrinsic stacking fault in facilitating the pressure-induced phase transition in CoCrFeMnNi high entropy alloys

The pressure-induced phase transitions in CoCrFeNi and CoCrFeMnNi high entropy alloys (HEAs) at ambient temperature at pressure up to 24.0(2) and 19.4(2) GPa, respectively, were investigated using angle-dispersive X-ray diffraction (ADXRD). Structurally at ambient pressure, both CoCrFeNi and CoCrFeMnNi HEAs consist of face-centered cubic (fcc) structure with different lattice constants which are arisen primarily from the cellular growth of alloy during solidification. In-situ ADXRD measurements revealed no evidence of structural transformation in CoCrFeNi HEAs up to 24.0(2) GPa. The intrinsic stacking fault (ISF) begins to appear at 1.7(1) GPa and sustains up to 19.4(2) GPa. Moreover, an fcc to hexagonal close-packed (hcp) structural phase transition emerges at around 7.0(1) GPa in CoCrFeMnNi HEAs. The pressure dependent lattice constants and volume compression yield the zero-pressure isothermal bulk moduli of 187(4) GPa while the normalized c/a ratio 1.636(1) for the resultant hcp phase. The quantitative correlation of the ISF diffraction intensity shows that the appearance of ISF disrupts the crystal lattice to trigger, at around 7.0(1) GPa, fcc-to-hcp phase transition which persists sluggishly to the highest experiment pressure. Neutron powder diffraction (NPD) at pressure up to 8.9(2) GPa was performed in CoCrFeMnNi HEAs at ambient temperature to clarify the significance of pressure induced suppression of local magnetic moment on destabilization of the initial fcc structure. The results, however, suggest that the magnetism may only play a minor role, if not none, in facilitating the pressure-induced fcc-to-hcp phase transition in CoCrFeMnNi HEAs.

Development of biocompatible electrostatic‐repulsive microparticles for local tumor treatment

AbstractIn this study, we reported pH‐responsive microparticles consisting of poly(D,L‐lactide‐co‐glycolide) (PLGA), aminated hyaluronic acid (aHA) conjugated with 2,3‐dimethylmaleic anhydride (DMA, as a pH‐responsive cleavable molecule) (aHA‐DMA), and doxorubicin (DOX, as an antitumor drug) for local tumor treatment. The DOX‐loaded microparticles, denoted as PLGA(aHA‐DMA)/DOX MPs, were fabricated using the W1/O/W2 multi‐emulsification method. These PLGA(aHA‐DMA)/DOX MPs (~10 μm in diameter) accelerated the rate of DOX release at pH 6.8 due to the acidic pH‐responsive cleavage of the DMA moieties followed by electrostatic‐repulsion between aHA and DOX. This event caused the structural destabilization and collapse of the MPs, leading to the rapid release of DOX. Consequently, the PLGA(aHA‐DMA)/DOX MPs resulted in significant inhibition of tumor growth, demonstrating their ability for acidic tumor‐specific treatment.

Structural and functional effects of single nucleotide polymorphism on canine cytochrome b 5 reductase - in silico

The objectives of this study were to investigate the effects of single nucleotide polymorphism in Canine cytochrome b5 reductase using computational methods. Data was obtained from database of National Centre for Biotechnology Information (db SNP) and computational software was used for the analysis. The 3D protein structure was predicted using phyre 2 server. PANTHER analysis predicted the effect of single nucleotide polymorphism (substitution of Isoleucine for Leucine at position 194) as damaging. Analysis using the Mutpred 2 web application also indicated deleterious effects of the amino acid substitution. Molecular mechanisms of structural changes in the amino acid were determined using Mutpred 2 to be altered ordered interface, gain of allosteric sites and altered metal binding. The study indicated that the substitution of Isoleucine by Leucine at position 194 of the amino acid sequence (Ile 194 Leu) resulted in the destabilization of the amino acid structure leading to functional deviation in canine cytochrome b5 reductase.

Novel bioengineered MBenes for the treatment of Alzheimer's disease: An in-Sillico study

Alzheimer's disease is a neurodegenerative disease caused by the deposition and accumulation of amyloid-β (Aβ) peptides in the brain neurons. Current medications are not a definitive cure for this disease, but they can hamper the signs and symptoms of Alzheimer's disease. Therefore, prevention is the best way to deal with this disease. In this study, the novel structures based on MBenes (such as Cd2B, Mo2B, Cu2B, and Ta2B) are proposed to prevent amyloid-β accumulation in Alzheimer's disease. Regarding the remarkable MBene properties such as tunability, biocompatibility, and low manufacturing cost, the effect of these structures on amyloid-β deformation was explored using molecular dynamics simulation. To provide an atomic analysis of Beta-amyloid behavior in the presence of these structures, the compaction, contact area, and stability of Beta-amyloid were investigated. The results indicated the satisfactory performance of MBenes on the destabilization of amyloid-β structures. Moreover, given the higher interactions between Cd2B and amyloid-β, the instability, compaction, and the contact area of amyloid-β particles were investigated in this complex. The findings confirmed Cd2B as the best structure to prevent amyloid-β accumulation. The results of this investigation paved the way for the development of these structures as a medicinal agent to prevent Alzheimer's disease.

Interaction of water soluble cationic gallium(III) phthalocyanines with different G-quadruplex DNAs

Small molecule-G-quadruplex DNA interaction has been gained considerable interest due to existence of G-quadruplex structures in telomeres and promotor regions of proto-oncogenes. In the present study, the interaction of 2(3), 9(10), 16(17), 23(24)-tetrakis-[(N-methyl-3-pyridyloxy)phthalocyaninato]chloro gallium (III) sulphate (TGaPc) and 2, 3, 9, 10, 16, 17, 23, 24-octakis-[(N-methyl-3-pyridyloxy) phthalocyaninato]chloro gallium (III) sulphate (OGaPc) with different DNA forms (ctDNA and G-quadruplex DNAs) was investigated. The interactions of compounds with DNA was extensively investigated by different methods, such as capillary gel electrophoresis (CGE) integrated with a high sensitivity LED-induced fluorescence detector, UV–Vis and circular dichroism spectroscopy, competitive dialysis experiments. UV–Vis. titrations and CGE studies showed that the two phthalocyanine compounds interacted with the G-quadruplex and ctDNA, but the binding affinity of TGaPc was high for AS1411. Dialysis experiments also supported the higher affinity of TGaPc to AS1411. CD studies showed that both TGaPc and OGaPc caused destabilization of Tel21 structure even at low concentrations. This was more or less observed in other G-quadruplex DNAs other than AS1411. The structure of AS1411 remained intact at binding stoichiometric ratios. The viscosimetric studies and gel electrophoresis studies have been used to explore the interaction of TGaPc and OGaPc with ctDNA. The viscosity experiments along with gel electrophoresis confirmed the intercalation binding for ctDNA with OGaPc and groove binding for TGaPc. All results show that these molecules interact with different DNA types at different strengths and different mechanisms and the binding affinity of TGaPc was high for AS1411. Therefore, these compounds have the potential for cancer treatment.

Confined Ir single sites with triggered lattice oxygen redox: Toward boosted and sustained water oxidation catalysis

Confined Ir single sites with triggered lattice oxygen redox: Toward boosted and sustained water oxidation catalysis

Biomimetic Strontium Substituted Calcium Phosphate Coating for Bone Regeneration

Cellulose acetate (CA)/strontium phosphate (SrP) hybrid coating has been proposed as an effective strategy to build up novel bone-like structures for bone healing since CA is soluble in most organic solvents. Strontium (Sr2+) has been reported as a potential agent to treat degenerative bone diseases due to its osteopromotive and antibacterial effects. Herein, bioactive hybrid composite SrP-based coatings (CASrP) were successfully produced for the first time. CASrP was synthesized via a modified biomimetic method (for 7—CA7dSrP, and 14 days—CA14dSrP), in which the metal ion Sr2+ was used in place of Ca2+ in the simulated body fluid. Energy-dispersive X-ray (EDX) and Fourier transform infrared spectroscopy (FTIR) analysis confirmed the SrP incorporation chemically in the CASrP samples. Atomic absorption spectroscopy (AAS) supported EDX data, showing Sr2+ adsorption into CA, and its significant increase with the augmentation of time of treatment (ca. 92%—CA7dSrP and 96%—CA14dSrP). An increment in coating porosity and the formation of SrP crystals were evidenced by scanning electron microscopy (SEM) images. X-ray diffraction (XRD) evidenced a greater crystallinity than CA membranes and a destabilization of CA14dSrP structure compared to CA7dSrP. The composites were extremely biocompatible for fibroblast and osteoblast cells. Cell viability (%) was higher either for CA7dSrP (48 h: ca. 92% and 115%) and CA14dSrP (48 h: ca. 88% and 107%) compared to CA (48 h: ca. 70% and 51%) due to SrP formation and Sr2+ presence in its optimal dose in the culture media (4.6–9 mg·L−1). In conclusion, the findings elucidated here evidence the remarkable potential of CA7dSrP and CA14dSrP as bioactive coatings on the development of implant devices for inducing bone regeneration.

Na0.5Bi0.5TiO3 phase relations: Thermodynamics and phase equilibria in the systems Bi2O3 – TiO2, Na2O – TiO2, and Na2O – Bi2O3 – TiO2

The lead-free piezoelectric material sodium bismuth titanate (NBT, Na0.5Bi0.5TiO3) has attracted considerable attention owing to its promising dielectric, piezoelectric, and electrical properties. However, the literature on the binary subsystems is contradictory and there are only limited data for the ternary system. The present work surveys all of the reports of the binary subsystems Bi2O3 – TiO2 and Na2O – TiO2 and synthesizes these data into inclusive revised versions. The compatibilities for the ternary system Na2O – Bi2O3 – TiO2 were determined experimentally, thus enabling the construction of a complete isothermal section at 800 °C. The compatibilities associated with the problematic binary subsystem Na2O – Bi2O3, which experiences extreme volatilisation, were determined through the generation of the absent standard-state thermodynamic functions for the relevant binary and ternary phases, thus providing a full suite of thermodynamic data for this system. The thermodynamic stability diagrams for Na2O, Bi2O3, and TiO2 thus were calculated. The isothermal section also addresses the contradictions in the literature concerning the formation of solid solutions of Bi12TiO20-x / Bi12-xTi1+xO20+0.5x, pyrochlore (Bi2Ti2O7 / NawBi2-xTi2-yO7-z), BTO (Bi4Ti3O12 / NaxBi4Ti3O12+0.5x), and NBT (Na0.5Bi0.5TiO3 / Bi1±xNaxTiO3.5±x). Further, it was observed that the congruent melting point of NBT, which was determined to be 1225 °C, was preceded by the onset of gradual structural destabilization at 940 °C. Also, the NBT rhombohedral → tetragonal phase transformation was observed at an onset temperature of ∼250 °C. The present work thus provides platform data for the fabrication and reactivities of materials in the ternary system Na2O – Bi2O3· TiO2 and its binary subsystems.

Two Classes of Eruptive Events During Solar Minimum

During solar minimum, the Sun is relatively inactive with few sunspots observed on the solar surface. Consequently, we observe a smaller number of highly energetic events such as solar flares or coronal mass ejections (CMEs), which are often associated with active regions on the photosphere. Nonetheless, our magnetofrictional simulations during the minimum period suggest that the solar corona is still dynamically evolving in response to the large-scale shearing velocities on the solar surface. The non-potential evolution of the corona leads to the accumulation of magnetic free energy and helicity, which is periodically shed in eruptive events. We find that these events fall into two distinct classes: One set of events are caused by eruption and ejection of low-lying coronal flux ropes, and they could explain the origin of occasional CMEs during solar minimum. The other set of events are not driven by destabilisation of low-lying structures but rather by eruption of overlying sheared arcades. These could be associated with streamer blowouts or stealth CMEs. The two classes differ significantly in the amount of magnetic flux and helicity shed through the outer coronal boundary. We additionally explore how other measurables such as current, open magnetic flux, free energy, coronal holes, and the horizontal component of the magnetic field on the outer model boundary vary during the two classes of event. This study emphasises the importance and necessity of understanding the dynamics of the coronal magnetic field during solar minimum.

Structure elucidation and docking analysis of 5M mutant of T1 lipase Geobacillus zalihae.

5M mutant lipase was derived through cumulative mutagenesis of amino acid residues (D43E/T118N/E226D/E250L/N304E) of T1 lipase from Geobacillus zalihae. A previous study revealed that cumulative mutations in 5M mutant lipase resulted in decreased thermostability compared to wild-type T1 lipase. Multiple amino acids substitution might cause structural destabilization due to negative cooperation. Hence, the three-dimensional structure of 5M mutant lipase was elucidated to determine the evolution in structural elements caused by amino acids substitution. A suitable crystal for X-ray diffraction was obtained from an optimized formulation containing 0.5 M sodium cacodylate trihydrate, 0.4 M sodium citrate tribasic pH 6.4 and 0.2 M sodium chloride with 2.5 mg/mL protein concentration. The three-dimensional structure of 5M mutant lipase was solved at 2.64 Å with two molecules per asymmetric unit. The detailed analysis of the structure revealed that there was a decrease in the number of molecular interactions, including hydrogen bonds and ion interactions, which are important in maintaining the stability of lipase. This study facilitates understanding of and highlights the importance of hydrogen bonds and ion interactions towards protein stability. Substrate specificity and docking analysis on the open structure of 5M mutant lipase revealed changes in substrate preference. The molecular dynamics simulation of 5M-substrates complexes validated the substrate preference of 5M lipase towards long-chain p-nitrophenyl–esters.

Unveiling the inhibitory mechanism of peptidomimetic inhibitor against Aβ42 aggregation and protofibril disaggregation by molecular dynamics

Alzheimer’s disease (AD) is an irreversible, progressive, and degenerative brain disorder characterized by the aggregation and deposition of amyloid-β (Aβ) oligomers in the brain of patients. A recent study highlighted the peptidomimetic compound (C1) as an inhibitor of Aβ42 aggregation and disassembly of Aβ42 oligomeric structures. However, its molecular mechanism of inhibition remains poorly understood. In this regard, the inhibitory mechanism of C1 against Aβ42 aggregation and disassembly of S-shaped protofibril structure was investigated using molecular docking and molecular dynamics (MD) simulations. MD simulations highlighted that C1 preserved the non-aggregation-prone helical conformation of Aβ42 monomer. C1 destabilized the salt bridge interaction between Asp23 and Lys28 in Aβ42 monomer, which plays a critical role in the formation of the self-assembly prone conformation of Aβ42 monomer. C1 binds with Aβ42 protofibril structure with favourable binding free energy (△Gbinding = –78.2 ± 4.04 kcal/mol) and caused destabilization of the S-shaped protofibril structure. A lower binding affinity between chains C and D of Aβ42 protofibril structure was observed in the presence of C1, which highlighted the destabilization of the Aβ42 protofibril structure. The study provided a complete picture of the inhibitory mechanism of peptidomimetic inhibitor against Aβ42 aggregation and fibril disassembly, which is in accordance with the observed potential in vitro anti-aggregation activity of C1 against Aβ42. The study will be beneficial in the design of potential inhibitors against Aβ42 aggregation and S-shaped protofibril disassembly.