Small-angle X-ray Diffraction Research Articles

Fast myosin binding protein C knockout in skeletal muscle alters length-dependent activation and myofilament structure.

In striated muscle, the sarcomeric protein myosin-binding protein-C (MyBP-C) is bound to the myosin thick filament and is predicted to stabilize myosin heads in a docked position against the thick filament, which limits crossbridge formation. Here, we use the homozygous Mybpc2 knockout (C2-/-) mouse line to remove the fast-isoform MyBP-C from fast skeletal muscle and then conduct mechanical functional studies in parallel with small-angle X-ray diffraction to evaluate the myofilament structure. We report that C2-/- fibers present deficits in force production and calcium sensitivity. Structurally, passive C2-/- fibers present altered sarcomere length-independent and -dependent regulation of myosin head conformations, with a shift of myosin heads towards actin. At shorter sarcomere lengths, the thin filament is axially extended in C2-/-, which we hypothesize is due to increased numbers of low-level crossbridges. These findings provide testable mechanisms to explain the etiology of debilitating diseases associated with MyBP-C.

Differences in thick filament activation in fast rodent skeletal muscle and slow porcine cardiac muscle.

There is a growing appreciation that regulation of muscle contraction requires both thin filament and thick filament activation in order to fully activate the sarcomere. The prevailing mechano-sensing model for thick filament activation was derived from experiments on fast-twitch muscle. We address the question whether, or to what extent, this mechanism can be extrapolated to the slow muscle in the hearts of large mammals, including humans. We investigated the similarities and differences in structural signatures of thick filament activation in porcine myocardium as compared to fast rat extensor digitorum longus (EDL) skeletal muscle under relaxed conditions and sub-maximal contraction using small angle X-ray diffraction. Thick and thin filaments were found to adopt different structural configurations under relaxing conditions, and myosin heads showed different changes in configuration upon sub-maximal activation, when comparing the two muscle types. Titin was found to have an X-ray diffraction signature distinct from those of the overall thick filament backbone, and its spacing change appeared to be positively correlated to the force exerted on the thick filament. Structural changes in fast EDL muscle were found to be consistent with the mechano-sensing model. In porcine myocardium, however, the structural basis of mechano-sensing is blunted suggesting the need for additional activation mechanism(s) in slow cardiac muscle. These differences in thick filament regulation can be related to their different physiological roles where fast muscle is optimized for rapid, burst-like, contractions, and the slow cardiac muscle in large mammalian hearts adopts a more finely tuned, graded response to allow for their substantial functional reserve. KEY POINTS: Both thin filament and thick filament activation are required to fully activate the sarcomere. Thick and thin filaments adopt different structural configurations under relaxing conditions, and myosin heads show different changes in configuration upon sub-maximal activation in fast extensor digitorum longus muscle and slow porcine cardiac muscle. Titin has an X-ray diffraction signature distinct from those of the overall thick filament backbone and this titin reflection spacing change appeared to be directly proportional to the force exerted on the thick filament. Mechano-sensing is blunted in porcine myocardium suggesting the need for additional activation mechanism(s) in slow cardiac muscle. Fast skeletal muscle is optimized for rapid, burst-like contractions, and the slow cardiac muscle in large mammalian hearts adopts a more finely tuned graded response to allow for their substantial functional reserve.

Heterogeneous micellar solubilization within lyotropic liquid crystals interfaces

The solubilization of sodium diclofenac (Na-DFC) in a glycerol mono-oleate-based emulsion triggers structural changes. A reverse hexagonal mesophase forms at 2–5 wt% Na-DFC. Above 6 wt%, the hexagonal symmetry gradually transitions to a disordered lamellar mesophase at 9 wt%. These structural shifts impact the storage modulus, structuring enthalpy, and structural diffusivity of the system. Despite these transitions, the driving force for Na-DFC release remains consistent, leading to hypothesize that the interfacial structure remains unchanged during Na-DFC release.The nano-structural modifications imposed by the Na-DFC load and release were assessed by small-angle X-ray diffraction (SAXD), spin-probe electron paramagnetic resonance (EPR), and nuclear quadrupole resonance (NQR).The selective solubilization of Na-DFC was demonstrated in the SAXD peak fittings, revealing an increase in hexagonally oriented rods at the expense of non-oriented micelles, rather than gradual micellar elongation. Computation of the EPR spectra also showcased the selective solubilization of Na-DFC at an enhanced free energy interface (γ), evidenced by step-wise variations in polarity, microviscosity, and order parameters. Additionally, NQR analysis highlighted a higher anisotropy for sodium compared to deuterium, linking the selective solubilization of Na-DFC to heterogeneous structural transformations. These findings underscore the heterogeneous nature of solubilization-release processes, driven by locally increased micellar free energy. Consequently, the loaded Na-DFC interfaces maintain a constant γ, ensuring a consistent release driving force despite structural transitions affecting the matrix. The ability to selectively solubilize guest molecules may herald a new era in the utilization of selective molecular interfacial loading.

Preparation and Corrosion Resistance of OMMT/EP Composite Coatings in Sulfur-Containing Sodium Aluminate Solution

Organic montmorillonite (OMMT) was prepared from Na-montmorillonite (MMT) by Hexadecylamine (HDA) modification. The composite material has good smoothness, acidity, and salt resistance. OMMT was characterized using small-angle X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and a video optical contact angle measuring instrument. The results showed that the layer spacing was enlarged from 1.44 nm to 2.87 nm after the modification, and the hydrophobicity performance was greatly improved. The organic modification of MMT was successful. The surface morphology, roughness, and anticorrosion properties of the organic montmorillonite/epoxy (OMMT/EP) composite coating were investigated and compared with those of the epoxy (EP) coating. The OMMT/EP composite coating had a flatter surface than the EP coating. The roughness was reduced from 65.5 nm to 10.3 nm. The electrochemical impedance spectroscopy showed that the composite coating’s thickness positively affected its anticorrosion performance, the corrosion current density (Icorr) decreased with the increase in thickness, and its maximum impedance was much larger than that of EP coating. The protection efficiency of the OMMT/EP composite coating was 77.90%, which is a significant improvement over the EP’s 31.27%. In addition, the corrosion resistance of the composite coating gradually decreased with increasing immersion time, but the change was insignificant.

Development of Low-Molecular-Weight Gelator/Polymer Composite Materials Utilizing the Gelation and Swelling Process of Polymeric Materials.

The creation of polymer composite materials by compositing fillers into polymer materials is an effective method of improving the properties of polymer materials, and the development of new fillers and their novel composite methods is expected to lead to the creation of new polymer composite materials. In this study, we develop a new filler material made of low-molecular-weight gelators by applying a gelation process that simultaneously performs the swelling (gelation) of crosslinked polymer materials and the self-assembly of low-molecular-weight gelators into low-dimensional crystals in organic solvents within polymer materials. The gelation process of crosslinking rubber-based polymers using alkylhydrazides/toluene as the low-molecular-weight gelator allowed us to composite self-assembled sheet-like crystals of alkylhydrazides as fillers in polymeric materials, as suggested by various microscopic observations, including infrared absorption measurements, small-angle X-ray diffraction measurements and thermal analysis, microscopy, and infrared absorption measurements. Furthermore, tensile tests of the composite materials demonstrated that the presence of fillers improved both the Young's modulus and the tensile strength, as well as the elongation at yield. Additionally, heat treatment was shown to facilitate filler dispersion and enhance the mechanical properties. The findings demonstrate the potential of self-assembled sheet-like crystals of low-molecular-weight gelators as novel filler materials for polymers. The study's composite method utilizing gelators via gelation proved effective.

Controlled release of foam from mesoporous silica-surfactant nanocomposite for enhanced natural gas production

Foam generated from solid foam sticks plays a crucial role in enhancing natural gas production by mitigating liquid accumulation in gas wells. Traditional solid foam sticks dissolve rapidly, releasing foam instantly, particularly at high downhole temperatures in gas wells. This necessitates frequent addition of surfactants to sustain foam generation. To address this issue, this study investigates the use of mesoporous silica nanocomposite to encapsulate the surfactant, cetyltrimethylammonium bromide (CTAB), as foam sticks, allowing for extended foam release. Mesoporous silica was synthesized through a sol–gel process involving a silica precursor and surfactant, utilizing alkali-acid catalysts in two steps. The resulting nanocomposite solid sticks were formed through aging and drying in a mold. The silica-surfactant nanocomposite was characterized by infrared spectroscopy (IR), scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), and small angle X-ray diffraction (SAXD). Experimental results demonstrated the successful encapsulation of 68.2 % surfactant into an average size of 50 nm nanosized silica capsules with a mesoporous structure. Quantitative determination of surfactant release over time in brine at a high temperature (130 °C) was determined through thermogravimetric analysis (TGA), which showed 6.3 % surfactant remained in nanocomposite after 3 days. Foam performance from the released surfactants was evaluated using a dynamic foam apparatus and blender test. The study showed that foam could be control-released over a period of 7 days through surfactant diffusion from mesoporous nanoparticles. The release of CTAB follows the first-order release kinetic model. This research provides a sustainable solution by utilizing mesoporous silica nanoparticles as carriers for surfactants, resulting in longer-lasting foam for the gas well deliquification and the enhancement of gas production.

Myosin-binding protein C regulates the sarcomere lattice and stabilizes the OFF states of myosin heads

Muscle contraction is produced via the interaction of myofilaments and is regulated so that muscle performance matches demand. Myosin-binding protein C (MyBP-C) is a long and flexible protein that is tightly bound to the thick filament at its C-terminal end (MyBP-CC8C10), but may be loosely bound at its middle- and N-terminal end (MyBP-CC1C7) to myosin heads and/or the thin filament. MyBP-C is thought to control muscle contraction via the regulation of myosin motors, as mutations lead to debilitating disease. We use a combination of mechanics and small-angle X-ray diffraction to study the immediate and selective removal of the MyBP-CC1C7 domains of fast MyBP-C in permeabilized skeletal muscle. We show that cleavage leads to alterations in crossbridge kinetics and passive structural signatures of myofilaments that are indicative of a shift of myosin heads towards the ON state, highlighting the importance of MyBP-CC1C7 to myofilament force production and regulation.

Emergent properties of magnetic ions and nanoparticles in micellar solutions of surfactants: Use in fine technologies

Objectives. To establish expected emergent (unexpected) properties of magnetic materials when obtained in aqueous micellar solutions of surfactants (aqueous quantum materials), and their use in fine technologies.Methods. Chemical synthesis of magnetic nanoparticles in aqueous micellar solutions of surfactants of various nature. Characterization of magnetic solutions and nanoparticles by magnetic measurements, spectroscopy, diffractometry, small-angle X-ray diffraction, scanning probe microscopy, and others.Results. The term “water quantum material” refers to materials (micellar solutions) whose properties are mainly determined by the nuclear quantum effect on macroscopic scales (emergent property). Micellar solutions exhibit phenomena and functionality not always consistent with the classical theory of micellization. The article presents in detail the experimental results that suggest the manifestation of the emergent properties of magnetic materials obtained in aqueous micellar solutions of surfactants. In particular, Gd3+ ions in an aqueous micellar solution of sodium dodecyl sulfate exhibit paramagnetic properties, possibly indicating their random arrangement in solution contrary to the classical theory of micellization with an ordered adsorption layer on micelles. Hybrid Pt–Gd nanoparticles are formed in a quantum material with cetylpyridinium chloride as a matrix, although Gd3+ ions must be repelled by CP+ ions on micelles. Nanosized powders of cobalt ferrite and nickel ferrite obtained in a micellar solution of sodium dodecyl sulfate have superparamagnetic properties, although the presence of their precursor ions in the adsorption layer in classical micelles should lead to ferromagnetic properties.Conclusions. The synthesis of nanoparticles in a quantum material opens up the possibility of reducing ions of different signs in one stage during the processing of metallurgy waste, in order to obtain nanoparticles of various metals and their composites. Magnetic nanoparticles obtained in a quantum surfactant material self-assemble on various substrates, enabling the creation of materials whose residual magnetization and coercive field can be controlled at room temperatures.

The effect of fluorination on the liquid crystal and optical behaviors of amphiphilic cyanostilbene-based mesogens

Three series of amphiphilic mesogens containing a cyanostilbene core with zero, one or two lateral fluorine atoms, which attach one polar glycerol group at one end and three lipophilic alkyl chains at the other end were synthesized by Suzuki coupling and Knoevenagel reactions. The thermodynamics, liquid crystalline and photophysical properties of these amphiphilic mesogens were evaluated by polarized optical microscopy, differential scanning calorimetry, small-angle X-ray diffraction, density functional theory calculation, absorption and emission spectra. The non-fluoro and mono-fluoro amphiphilic mesogens display a mesophase transition from hexagonal columnar phase to three-dimensional micellar cubic phase with Im3¯m lattice by the increase of temperature or the elongation of terminal lipophilic alkyl chains. The bi-fluoro amphiphilic mesogens can only self-organize into hexagonal columnar mesophase. Similar spectral properties and weak solvatochromism in these amphiphilic mesogens are observed attributed to the weak intramolecular charge transfer and weak influence of fluorine atom on the electronic properties in both ground and excited states. In addition, aggregation-induced emission behavior could be achieved in these amphiphilic mesogens due to the twisted molecular configuration. Therefore, complex self-assembly structures and interesting photophysical properties may be altered by varying the degree of fluorination of amphiphilic mesogens, which could promote the application of liquid crystalline materials.

Synthesis, liquid crystalline self-assembly, organogel behavior, and DFT investigation of first phenolphthalein-based hexacatenar

ABSTRACT Different building blocks in organic molecules could induce complex intermolecular interactions to lead to different supramolecular micro/nanostructures in bulk and solution states. Herein, the first new phenolphthalein-based hexacatenar containing a central phenolphthalein fluorochrome functionalized with two dendritic wings is synthesized by click reaction. The polarized optical microscopy, differential scanning calorimetry, and small-angle X-ray diffraction data demonstrated that the reported phenolphthalein-based hexacatenar could self-assemble into hexagonal columnar mesophase in the bulk state and could form organogel with distinct morphologies in some common organic solvents due to intermolecular interactions. Density functional theory calculation results showed highly twisted molecular conformation, distinct charge distribution, and asymmetrical electronic property, which might be essential for the stabilization of columnar mesophase and organogel. Therefore, this work provides a method to develop soft materials containing different functional building blocks with complex self-assemblies.

Disruption of Z-Disc Function Promotes Mechanical Dysfunction in Human Myocardium: Evidence for a Dual Myofilament Modulatory Role by Alpha-Actinin 2.

The ACTN2 gene encodes α-actinin 2, located in the Z-disc of the sarcomeres in striated muscle. In this study, we sought to investigate the effects of an ACTN2 missense variant of unknown significance (p.A868T) on cardiac muscle structure and function. Left ventricular free wall samples were obtained at the time of cardiac transplantation from a heart failure patient with the ACTN2 A868T heterozygous variant. This variant is in the EF 3-4 domain known to interact with titin and α-actinin. At the ultrastructural level, ACTN2 A868T cardiac samples presented small structural changes in cardiomyocytes when compared to healthy donor samples. However, contractile mechanics of permeabilized ACTN2 A868T variant cardiac tissue displayed higher myofilament Ca2+ sensitivity of isometric force, reduced sinusoidal stiffness, and faster rates of tension redevelopment at all Ca2+ levels. Small-angle X-ray diffraction indicated increased separation between thick and thin filaments, possibly contributing to changes in muscle kinetics. Molecular dynamics simulations indicated that while the mutation does not significantly impact the structure of α-actinin on its own, it likely alters the conformation associated with titin binding. Our results can be explained by two Z-disc mediated communication pathways: one pathway that involves α-actinin's interaction with actin, affecting thin filament regulation, and the other pathway that involves α-actinin's interaction with titin, affecting thick filament activation. This work establishes the role of α-actinin 2 in modulating cross-bridge kinetics and force development in the human myocardium as well as how it can be involved in the development of cardiac disease.

Feasibility of the preparation of cochleate suspensions from naturally derived phosphatidylserines.

Cochleates are cylindrical particles composed of dehydrated phospholipid bilayers. They are typically prepared by addition of calcium ions to vesicles composed of negatively charged phospholipids such as phosphatidylserines (PS). Due to their high physical and chemical stability, they provide an interesting alternative over other lipid-based drug formulations for example to improve oral bioavailability or to obtain a parenteral sustained-release formulation. In the present study, the feasibility to prepare cochleate suspensions from soy lecithin-derived phosphatidylserines (SPS) was investigated and compared to the "gold standard" dioleoyl-phosphatidylserine (DOPS) cochleates. The SPS lipids covered a large range of purities between 53 and >96% and computer-controlled mixing was evaluated for the preparation of the cochleate suspensions. Electron microscopic investigations were combined with small-angle x-ray diffraction (SAXD) and Laurdan generalized polarization (GP) analysis to characterize particle structure and lipid organization. Despite some differences in particle morphology, cochleate suspensions with similar internal lipid structure as DOPS cochleates could be prepared from SPS with high headgroup purity (≥96%). Suspensions prepared from SPS with lower purity still revealed a remarkably high degree of lipid dehydration and well-organized lamellar structure. However, the particle shape was less defined, and the typical cochleate cylinders could only be detected in suspensions prepared with higher amount of calcium ions. Finally, the study proves the feasibility to prepare suspensions of cochleates or cochleate-like particles directly from a calcium salt of soy-PS by dialysis.

Transient of flow regimes and slip boundary analysis of water and gas in nano clay pores

ABSTRACT Nanoscale two-phase flow is important during shale gas production. In this work, molecular dynamics simulations are employed to investigate fluid flow regimes of water and methane under different pressure gradients inside the nanoscale slit pores. The illite mineral is selected to model the clay pores based on the Small-Angle X-ray Diffraction (SAXD) experiment. The different flow regimes of gas-water two-phase are visualised and the structures are analysed. As the driving pressure gradient increases, it is observed that the two-phase flow in the slit undergoes transitions from intermittent flow to a transition stage between intermittent flow and annular flow, and finally fully converts to annular flow. The slip conditions during the two-phase flow on the hydrophilic illite surface are investigated. We found that the negative slip length stays around 0.25 nm within the range of practical production pressure gradients, which can be used for accurate production prediction. This work provides detailed insights into the nanoscale water and gas two-flow inside the clay nanopores during shale gas exploration.

Abstract P1026: Structural And Biochemical Effects Of Missense MyBP-C Mutations On The Myofilament In Human Hypertrophic Cardiomyopathy

Significance: While the disease mechanisms of truncating MyBP-C variants in HCM have been well defined, the mechanisms by which missense MyBP-C variants cause HCM are largely unknown. Recent studies show that unlike truncating variants that push myosin into an active high energy state due to their overall reduction in MyBP-C, missense MyBP-C properly incorporates into the sarcomere without affecting protein abundance. The consequences of missense MyBP-C on myosin have not been explored and may have implications for the treatment of HCM patients with missense MyBP-C variants. Results: We performed small angle X-ray diffraction (XrD) on human HCM tissue from patients with missense MyBP-C, and healthy control hearts. When healthy tissue was moved from relaxing pCa 8 to activating pCa 5 the I 1,1 /I 1,0 equatorial intensity ratio increased (p<0.001) indicating myosin is moving away from the backbone and adopting an active conformation. However, in missense hearts I 1,1 /I 1,0 is lower than healthy hearts at pCa 8 meaning more myosin is localized to the backbone. This is contrary to other HCM mutations which are proposed to push myosin to an active conformation under relaxing conditions. I 1,1 /I 1,0 does not increase at pCa 5 (p>0.05) indicating that at activating Ca myosin remains in the inactive conformation suggesting the thick filament Ca response is impaired in missense hearts. Ongoing Experiments: We are planning to perform XrD on more samples and Mant-ATP assays to determine if the structural inactivation of myosin in missense tissue also results in myosin remaining in the low energy super relaxed state (SRX). We expect the structural state to correlate with the biochemical state meaning missense hearts will demonstrate an equivalent percentage of SRX myosin compared to control hearts. Conclusions: Our finding that the transition of myosin to a structurally active conformation does not occur in human MyBP-C missense hearts distinguishes these variants from other HCM causing mutations such as truncating MyBP-C and missense MYH7 which have been shown to shift myosin to the active disordered relaxed state. If Mant-ATP assays show myosin is maintaining SRX along with an inactive conformation this suggests MyBP-C missense mutations act through a different mechanism.

In Situ and Ex Situ Studies of Ring-Like Assembly of Silica Nanoparticles in the Presence of Poly(propylene oxide)-Poly(ethylene oxide) Block Copolymers.

Block copolymer-mediated self-assembly of colloidal nanoparticles has attracted great attention for fabricating various nanoparticle arrays. We have previously shown that silica nanoparticles (SNPs) assemble into ring-like nanostructures in the presence of temperature-responsive block copolymers poly[(2-ethoxyethyl vinyl ether)-block-(2-methoxyethyl vinyl ether)] (PEOVE-PMOVE) in an aqueous phase. The ring-like nanostructures formed within an aggregate of PEOVE-PMOVE when the temperature was increased to 45 °C, at which the polymer is amphiphilic. Herein, we report that SNPs assemble into ring-like nanostructures even with a different temperature-responsive, amphiphilic block copolymer poly(propylene oxide)-block-poly(ethylene oxide) (PPO-PEO) at 45 °C. Field-emission scanning electron microscopy for SNP assemblies that were spin-coated on a substrate indicated that SNP first assembled into chain-like nanostructures and then bent into closed loops over several days. In contrast, in situ small-angle X-ray diffraction measurements revealed the formation of SNP nanorings within 75 s at 45 °C in the liquid phase. These results indicated that ring-like assembly of SNPs occurs quickly in the liquid phase, but the slow formation of Si-O-Si bonds between SNPs leads to their structure being destroyed by spin-coating. Intriguingly, SNPs with a diameter of 15 nm form a well-defined nanoring structure, with five SNPs located at the vertex points of a regular pentagon. Additionally, small-angle neutron scattering, where the contrast of the solvent (a mixture of H2O and D2O) matches that of SNPs, clarified that SNPs are contained within the spherical micelle formed from PPO-PEO. This work offers a facile and versatile approach to preparing ring-like arrays from inorganic colloidal nanoparticles, leading to applications including sensing, catalysis, and nanoelectronics.

Non-destructive estimation of conductive network constructed by 1D fillers in polymer composites via small angel X-ray scattering

Efficient and non-destructive estimation of conductive network in conductive polymer composites is now becoming an urgent issue than ever owing to the rapid rise of modern electronic industry. Nevertheless, traditional observation and estimation method inevitably cause damage and distortion to sample, demanding urgent development of a non-destructive fidelity detection methodology. In this study, the degree of network formation of carbon nano-fibers in polymer matrix was calculated based on small-angle X-ray diffraction (SAXS). The degree of fiber network construction based on the power law coefficient (A) has been proved to be valid and effective in comparison with other testing methods. Moreover, a mathematical model was established to predict the electrical conductivity of the conductive polymer composite. This study not only solves the problem of non-destructive testing of fiber network construction, but also provides theoretical guidance for the design of conductive polymer composites.

The correlations between the molecular core structure and mesomorphic behaviour for chiral liquid crystals with several (S)-lactate groups

To contribute to better understanding of the structure–property relationship for chiral liquid crystalline materials a series of new liquid crystalline (LC) materials possessing several (S)-lactate groups as chiral centres have been designed and investigated. All the materials possess the orthogonal paraelectric smectic A* phase stable over a broad temperature range. For the specific lengths of the chiral and non-chiral alkyl chains the ferroelectric tilted smectic C* phase have been detected at lower temperatures. The mesomorphic behaviour and structural properties of new multilactate materials have been studied by polarizing optical microscopy, differential scanning calorimetry, small angle X-ray diffraction and dielectric spectroscopy. The obtained results are discussed and compared to that of the structurally similar lactic acid derivatives. The main objective of the present work is to establish the molecular structure – mesomorphic property relationship for this specific class of multilactate-based LC materials, which can be further successfully utilized as chiral dopants for the design of smart multicomponent LC mixtures targeted for application in optoelectronics and photonics.

Preparation, Characterization, and Antibacterial Activity of Silver Nanoparticle-Decorated Ordered Mesoporous Carbon

In this study, Ordered Mesoporous Carbon (OMC) was prepared using resol as a carbon precursor and F127 as a soft template. Small-angle X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) images, and nitrogen adsorption and desorption isotherms revealed that OMC possessed ordered hexagonal mesostructures (p6m) with an ordered pore size of 3.2nm, a high specific surface area (SBET) of 539m2/g, and a large total pore volume (Vtotal) of 0.44cm3/g. Subsequently, silver nanoparticles synthesized from an aqueous AgNO3 solution using glucose as a reducing agent and starch as a stabilizing agent were decorated on OMC, producing Ag/OMC. XRD analysis revealed that the composite contained silver crystals. In addition, the content and size of silver nanoparticles in Ag/OMC were 0.71wt% (AAS) and around 25-50nm (TEM), respectively. Due to the surface cover of silver nanoparticles, SBET and Vtotal of Ag/OMC slightly decreased to 417m2/g and 0.38cm3/g, respectively. Both agar and broth dilution techniques were used to evaluate the antibacterial activity of the material against Staphylococcus aureus. Ag/OMC with a Minimum Inhibitory Concentration (MIC) of 25.0μg/mL is a potential candidate for use against Staphylococcus aureus.

Using Multiscale Simulations as a Tool to Interpret Equatorial X-ray Fiber Diffraction Patterns from Skeletal Muscle.

Synchrotron small-angle X-ray diffraction is the method of choice for nm-scale structural studies of striated muscle under physiological conditions and on millisecond time scales. The lack of generally applicable computational tools for modeling X-ray diffraction patterns from intact muscles has been a significant barrier to exploiting the full potential of this technique. Here, we report a novel "forward problem" approach using the spatially explicit computational simulation platform MUSICO to predict equatorial small-angle X-ray diffraction patterns and the force output simultaneously from resting and isometrically contracting rat skeletal muscle that can be compared to experimental data. The simulation generates families of thick-thin filament repeating units, each with their individually predicted occupancies of different populations of active and inactive myosin heads that can be used to generate 2D-projected electron density models based on known Protein Data Bank structures. We show how, by adjusting only a few selected parameters, we can achieve a good correspondence between experimental and predicted X-ray intensities. The developments presented here demonstrate the feasibility of combining X-ray diffraction and spatially explicit modeling to form a powerful hypothesis-generating tool that can be used to motivate experiments that can reveal emergent properties of muscle.

Role and Effect of Meso-Structuring Surfactants on Properties and Formation Mechanism of Microfluidic-Enabled Mesoporous Silica Microspheres.

We have shown in a previous work that the combination of the emulsion solvent evaporation technique and droplet-based microfluidics allows for the synthesis of well-defined monodisperse mesoporous silica microcapsules (hollow microspheres), whose size, shape and composition may be finely and easily controlled. In this study, we focus on the crucial role played by the popular Pluronic® P123 surfactant, used for controlling the mesoporosity of synthesised silica microparticles. We show in particular, that although both types of initial precursor droplets, prepared with and without P123 meso-structuring agent, namely P123+ and P123- droplets, have a similar diameter (≃30 μm) and a similar TEOS silica precursor concentration (0.34 M), the resulting microparticles exhibit two noticeably different sizes and mass densities. Namely, 10 μm and 0.55 g/cm3 for P123+ microparticles, and 5.2 μm and 1.4 g/cm3 for P123- microparticles. To explain such differences, we used optical and scanning electron microscopies, small-angle X-ray diffraction and BET measurements to analyse structural properties of both types of microparticles and show that in the absence of Pluronic molecules, P123- microdroplets divide during their condensation process, on average, into three smaller droplets before condensing into silica solid microspheres with a smaller size and a higher mass density than those obtained in the presence of P123 surfactant molecules. Based on these results and on condensation kinetics analysis, we also propose an original mechanism for the formation of silica microspheres in the presence and in the absence of the meso-structuring and pore-forming P123 molecules.