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Beamline B21 at the Diamond Light Source synchrotron in the UK is a small-angle X-ray scattering (SAXS) beamline that specializes in high-throughput measurements via automated sample delivery systems. A system has been developed whereby a sample can be illuminated by a focused beam of light coincident with the X-ray beam. The system is compatible with the highly automated sample delivery system at the beamline and allows a beamline user to select a light source from a broad range of wavelengths across the UV and visible spectrum and to control the timing and duration of the light pulse with respect to the X-ray exposure of the SAXS measurement. The intensity of the light source has been characterized across the wavelength range enabling experiments where a quantitative measure of dose is important. Finally, the utility of the system is demonstrated via measurement of several light-responsive samples.

Beamline B21 at the Diamond Light Source synchrotron in the UK is a small‐angle X‐ray scattering (SAXS) beamline that specializes in high‐throughput measurements via automated sample delivery systems. A system has been developed whereby a sample can be illuminated by a focused beam of light coincident with the X‐ray beam. The system is compatible with the highly automated sample delivery system at the beamline and allows a beamline user to select a light source from a broad range of wavelengths across the UV and visible spectrum and to control the timing and duration of the light pulse with respect to the X‐ray exposure of the SAXS measurement. The intensity of the light source has been characterized across the wavelength range enabling experiments where a quantitative measure of dose is important. Finally, the utility of the system is demonstrated via measurement of several light‐responsive samples. [ABSTRACT FROM AUTHOR]

Pluronic F127 dimethacrylate (F127-DM) inks exhibit potential for 3D printing biomaterials due to their combined gelation and photo-crosslinking capabilities. Previous studies have explored their application in extrusion 3D printing of medical devices, relying on their long-range micellar ordering to impart mechanical stability, stretchability, and control over drug delivery. However, there is a lack of information regarding the impact of the extrusion and photo-crosslinking processes on the micellar ordering of F127-DM. Herein, we employed in operando 3D printing synchrotron small-angle X-ray scattering (SAXS) to analyze the influence of various printing parameters, including nozzle shape, nozzle size, extrusion rate, ink composition, and photo-crosslinking, on the micellar ordering of F127-DM. Our findings from 2D SAXS patterns indicate orientation of the micellar packing clusters along the flow direction. The nozzle diameter and shape emerged as crucial parameters, leading to increased disruption of long-range ordering. Furthermore, 1D SAXS curves during UV-Vis light exposure and photo-crosslinking revealed a partial preservation of the micellar packing structure, with cluster size reduction, and coexisting with randomly distributed micelles and unimers. These results underscore the importance of in operando synchrotron experiments for the systematic study of 3D printing parameters from a nanostructure perspective. [ABSTRACT FROM AUTHOR]

Pluronic F127 dimethacrylate (F127-DM) inks exhibit potential for 3D printing biomaterials due to their combined gelation and photo-crosslinking capabilities. Previous studies have explored their application in extrusion 3D printing of medical devices, relying on their long-range micellar ordering to impart mechanical stability, stretchability, and control over drug delivery. However, there is a lack of information regarding the impact of the extrusion and photo-crosslinking processes on the micellar ordering of F127-DM. Herein, we employed in operando 3D printing synchrotron small-angle X-ray scattering (SAXS) to analyze the influence of various printing parameters, including nozzle shape, nozzle size, extrusion rate, ink composition, and photo-crosslinking, on the micellar ordering of F127-DM. Our findings from 2D SAXS patterns indicate orientation of the micellar packing clusters along the flow direction. The nozzle diameter and shape emerged as crucial parameters, leading to increased disruption of long-range ordering. Furthermore, 1D SAXS curves during UV-Vis light exposure and photo-crosslinking revealed a partial preservation of the micellar packing structure, with cluster size reduction, and coexisting with randomly distributed micelles and unimers. These results underscore the importance of in operando synchrotron experiments for the systematic study of 3D printing parameters from a nanostructure perspective.

Advances in time-resolved structural techniques, mainly in macromolecular crystallography and small-angle X-ray scattering (SAXS), allow for a detailed view of the dynamics of biological macromolecules and reactions between binding partners. Of particular promise, are mix-and-inject techniques, which offer a wide range of experimental possibility as microfluidic mixers are used to rapidly combine two species just prior to data collection. Most mix-and-inject approaches rely on diffusive mixers, which have been effectively used within crystallography and SAXS for a variety of systems, but their success is dependent on a specific set of conditions to facilitate fast diffusion for mixing. The use of a new chaotic advection mixer designed for microfluidic applications helps to further broaden the types of systems compatible with time-resolved mixing experiments. The chaotic advection mixer can create ultra-thin, alternating layers of liquid, enabling faster diffusion so that even more slowly diffusing molecules, like proteins or nucleic acids, can achieve fast mixing on timescales relevant to biological reactions. This mixer was first used in UV–vis absorbance and SAXS experiments with systems of a variety of molecular weights, and thus diffusion speeds. Careful effort was also dedicated to making a loop-loading sample-delivery system that consumes as little sample as possible, enabling the study of precious, laboratory-purified samples. The combination of the versatile mixer with low sample consumption opens the door to many new applications for mix-and-inject studies.

This article presents the recent progress of synchrotron scattering methods for elucidating the self-assembly pathways in dilute surfactant systems. An order of magnitude increases in the source brilliance, together with advanced detectors enable time-resolved structural investigations of relatively low contrast and dilute surfactant solutions in the millisecond range. This is demonstrated by monitoring the structural evolution in mixtures of cationic and anionic surfactants well below their individual critical micelle concentration, upon rapid mixing using a stopped-flow device. Despite the low concentration of surfactants in these samples, well-defined nanostructures were detected within in the mixing time of the stopped-flow device (ca. 2 ms). These transient structures have a more elongated morphology than spherical unilamellar vesicles and they grow over the subsequent seconds. The results demonstrate that the spontaneous self-assembly occurs even in dilute solutions without any pre-existing motifs, which may be relevant in applications where high surfactant concentrations are inappropriate. [ABSTRACT FROM AUTHOR]

The function of biomolecules is tightly linked to their structure, and changes therein. Time-resolved X-ray solution scattering has proven a powerful technique for interrogating structural changes and signal transduction in photoreceptor proteins. However, these only represent a small fraction of the biological macromolecules of interest. More recently, laser-induced temperature jumps have been introduced as a more general means of initiating structural changes in biomolecules. Here we present the development of a setup for millisecond time-resolved X-ray solution scattering experiments at the CoSAXS beamline, primarily using infrared laser light to trigger a temperature increase, and structural changes. We present results that highlight the characteristics of this setup along with data showing structural changes in lysozyme caused by a temperature jump. Further developments and applications of the setup are also discussed.

Mixtures of biological macromolecules are inherently difficult to study using structural methods, as increasing complexity presents new challenges for data analysis. Recently, there has been growing interest in studying evolving mixtures using small-angle X-ray scattering (SAXS) in conjunction with time-resolved, high-throughput or chromatography-coupled setups. Deconvolution and interpretation of the resulting datasets, however, are nontrivial when neither the scattering components nor the way in which they evolve are known a priori. To address this issue, the REGALS method (regularized alternating least squares) is introduced, which incorporates simple expectations about the data as prior knowledge, and utilizes parameterization and regularization to provide robust deconvolution solutions. The restraints used by REGALS are general properties such as smoothness of profiles and maximum dimensions of species, making it well suited for exploring datasets with unknown species. Here, REGALS is applied to the analysis of experimental data from four types of SAXS experiment: anion-exchange (AEX) coupled SAXS, ligand titration, time-resolved mixing and time-resolved temperature jump. Based on its performance with these challenging datasets, it is anticipated that REGALS will be a valuable addition to the SAXS analysis toolkit and enable new experiments. The software is implemented in both MATLAB and Python and is available freely as an open-source software package.

The function of biomolecules is tightly linked to their structure, and changes therein. Time‐resolved X‐ray solution scattering has proven a powerful technique for interrogating structural changes and signal transduction in photoreceptor proteins. However, these only represent a small fraction of the biological macromolecules of interest. More recently, laser‐induced temperature jumps have been introduced as a more general means of initiating structural changes in biomolecules. Here we present the development of a setup for millisecond time‐resolved X‐ray solution scattering experiments at the CoSAXS beamline, primarily using infrared laser light to trigger a temperature increase, and structural changes. We present results that highlight the characteristics of this setup along with data showing structural changes in lysozyme caused by a temperature jump. Further developments and applications of the setup are also discussed. [ABSTRACT FROM AUTHOR]

Time-resolved small-angle X-ray experiments (TR-SAXS) are reported here that capture and quantify a previously unknown rapid collapse of the unfolded oligonucleotide as an early step in G4 folding of hybrid 1 and hybrid 2 telomeric G-quadruplex structures. The rapid collapse, initiated by a pH jump, is characterized by an exponential decrease in the radius of gyration from 20.6 to 12.6 Å. The collapse is monophasic and is complete in less than 600 ms. Additional hand-mixing pH-jump kinetic studies show that slower kinetic steps follow the collapse. The folded and unfolded states at equilibrium were further characterized by SAXS studies and other biophysical tools, to show that G4 unfolding was complete at alkaline pH, but not in LiCl solution as is often claimed. The SAXS Ensemble Optimization Method (EOM) analysis reveals models of the unfolded state as a dynamic ensemble of flexible oligonucleotide chains with a variety of transient hairpin structures. These results suggest a G4 folding pathway in which a rapid collapse, analogous to molten globule formation seen in proteins, is followed by a confined conformational search within the collapsed particle to form the native contacts ultimately found in the stable folded form.

Viruses have been of interest to mankind since their discovery as small infectious agents in the nineteenth century. Because many viruses cause diseases to humans and agriculture, they were rigorously studied for biological and medical purposes. Viruses have remarkable properties such as the symmetry and self-assembly of their protein envelope, maturation into infectious virions, structural stability, and disassembly. Solution X-ray scattering can probe structures and reactions in solutions, down to subnanometer spatial resolution and millisecond temporal resolution. It probes the bulk solution and reveals the average shape and average mass of particles in solution and can be used to study kinetics and thermodynamics of viruses at different stages of their life cycle. Here we review recent work that demonstrates the capabilities of solution X-ray scattering to study in vitro the viral life cycle. [ABSTRACT FROM AUTHOR]

Small-angle X-ray scattering (SAXS) is an established technique that provides low-resolution structural information on macromolecular solutions. Recent decades have witnessed significant progress in both experimental facilities and in novel data-analysis approaches, making SAXS a mainstream method for structural biology. The technique is routinely applied to directly reconstruct low-resolution shapes of proteins and to generate atomistic models of macromolecular assemblies using hybrid approaches. Very importantly, SAXS is capable of yielding structural information on systems with size and conformational polydispersity, including highly flexible objects. In addition, utilizing high-flux synchrotron facilities, time-resolved SAXS allows analysis of kinetic processes over time ranges from microseconds to hours. Dedicated bioSAXS beamlines now offer fully automated data-collection and analysis pipelines, where analysis and modelling is conducted on the fly. This enables SAXS to be employed as a high-throughput method to rapidly screen various sample conditions and additives. The growing SAXS user community is supported by developments in data and model archiving and quality criteria. This review illustrates the latest developments in SAXS, in particular highlighting time-resolved applications aimed at flexible and evolving systems.

The current challenges of structural biophysics include determining the structure of large self-assembled complexes, resolving the structure of ensembles of complex structures and their mass fraction, and unraveling the dynamic pathways and mechanisms leading to the formation of complex structures from their subunits. Modern synchrotron solution X-ray scattering data enable simultaneous high-spatial and high-temporal structural data required to address the current challenges of structural biophysics. These data are complementary to crystallography, NMR, and cryo-TEM data. However, the analysis of solution scattering data is challenging; hence many different analysis tools, listed in the SAS Portal (http://smallangle.org/), were developed. In this review, we start by briefly summarizing classical X-ray scattering analyses providing insight into fundamental structural and interaction parameters. We then describe recent developments, integrating simulations, theory, and advanced X-ray scattering modeling, providing unique insights into the structure, energetics, and dynamics of self-assembled complexes. The structural information is essential for understanding the underlying physical chemistry principles leading to self-assembled supramolecular architectures and computational structural refinement. [ABSTRACT FROM AUTHOR]

CoSAXS is a state-of-the-art SAXS/WAXS beamline exploiting the high brilliance of the MAX IV 3 GeV synchrotron. By coupling advances in sample environment control with fast X-ray detectors, millisecond time-resolved scattering methods can follow structural dynamics of proteins in solution. In the present work, four sample environments are discussed. A sample environment for combined SAXS with UV-vis and fluorescence spectroscopy (SUrF) enables a comprehensive understanding of the time evolution of conformation in a model protein upon acid-driven denaturation. The use of microfluidic chips with SAXS allows the mapping of concentration with very small sample volumes. For highly reproducible sequences of mixing of components, it is possible using stopped-flow and SAXS to access the initial effects of mixing at 2 millisecond timescales with good signal to noise to allow structural interpretation. The intermediate structures in a protein are explored under light and temperature perturbations by using lasers to "pump" the protein and SAXS as the "probe". The methods described demonstrate that features at low q, corresponding to cooperative motions of the atoms in a protein, could be extracted at millisecond timescales, which results from CoSAXS being a highly-stable, low background, dedicated SAXS beamline., (Copyright © 2024. Published by Elsevier Inc.)

Self-assembled DNA structures enable creation of specific shapes at the nanometer–micrometer scale with molecular resolution. The construction of functional DNA assemblies will likely require dynamic structures that can undergo controllable conformational changes. DNA devices based on shape complementary stacking interactions have been demonstrated to undergo reversible conformational changes triggered by changes in ionic environment or temperature. An experimentally unexplored aspect is how quickly conformational transitions of large synthetic DNA origami structures can actually occur. Here, we use time-resolved small-angle X-ray scattering to monitor large-scale conformational transitions of a two-state DNA origami switch in free solution. We show that the DNA device switches from its open to its closed conformation upon addition of MgCl2 in milliseconds, which is close to the theoretical diffusive speed limit. In contrast, measurements of the dimerization of DNA origami bricks reveal much slower and concentration-dependent assembly kinetics. DNA brick dimerization occurs on a time scale of minutes to hours suggesting that the kinetics depend on local concentration and molecular alignment. [ABSTRACT FROM AUTHOR]

Block copolymer-based nanoproducts including particles, fibers and films show promise in high-end applications including nanotemplating, nanolithography, and nanoporous membranes due to their advantageous self-assembled structure. However, few studies probe the nanofabrication process in detail and monitor the concomitant self-assembled structural transitions. Herein, time-resolved small-angle X-ray scattering (SAXS) is exploited to follow such nanostructural changes. Evaporation-induced casting, electrospraying or electrospinning, followed by a final solvent vapor annealing step, have been used to create a series of nanoproducts with reversibly tunable morphologies from a model block copolymer, polystyrene- b -poly(ethylene- co -butylene)- b -polystyrene (SEBS). During evaporation-induced casting, which is considered as an unconfined system, a selective (co)solvent system composed of tetrahydrofuran (THF) and dimethylformamide (DMF) can lead to the formation of various SEBS structures. For DMF-based unconfined systems, the final SEBS lamellar structures were found to be different from the structure formed from THF only, demonstrating the critical role of solvent selection in evaporation-induced casting. The comparison of SEBS electrospun fibers reveals the unique and complex self-assembled structural transition occurring in a confined system. Time-resolved SAXS studies of our model triblock copolymer provide guidelines for a more general approach to access various nanostructures from self-assembling block copolymers. [Display omitted] • Successfully monitor triblock copolymer self-assembled structural transitions via either evaporation-induced method or vapor annealing by time-resolved small-angle X-ray scattering studies. • Mechanism insights of triblock copolymer self-assembled structural transitions by small-angle X-ray scattering modelling. • Detailed comparisons of nano-scale block copolymer self-assembled structures between different nanofabrication methods. [ABSTRACT FROM AUTHOR]

By means of time-resolved small-angle X-ray scattering, we developed an analysis methodology to assess the void volume fraction ϕv in high-density polyethylene ( HDPE) during tensile testing. The specimens were first drawn up to different imposed strains, and subsequently were subjected to stress unloading and strain recovery stages. During the loading stage, ϕv progressively increased with the strain level, starting from a well-defined onset strain prior to the yield point. In particular, ϕv reached a maximum of 8.75 vol% for a strain of 12.5% in the case of a HDPE grade with a molecular weight of 105 000 g mol−1. Stress unloading and strain recovery caused a decrease in ϕv attained at the end of the loading stage. For a HDPE grade with a molecular weight of 55 000 g mol−1, ϕv was more important during the loading stage and the decrease in ϕv was less marked during the stress unloading stage when compared to the HDPE with molecular weight of 105 000 g mol−1. The residual and reversible components of void volume fraction were revealed. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Soft nanoarchitectures created by biomimetic self-assembly offer unexploited potential for therapeutic drug delivery applications, tissue engineering, and diagnostics. The lipid bilayer building blocks impart biocompatible properties and low toxicity of the resulting nanoassemblies. Our work provides a survey of the recent advances in design and structural studies of functional bicontinuous soft porous nanoarchitectures created from amphiphilic bilayer membrane building blocks. Depending on the packing symmetries and the densities of the curved lipid bilayers, organized in membrane-type nanoparticles, a class of multicompartment nanoobjects involving cubosomes, spongosomes, onion-like liposomes, or vesicles arranged in hierarchical supramolecular architectures, can be obtained. High resolution structural investigations by cryo-transmission electron microscopy microscopy and time-resolved small-angle X-ray scattering (SAXS) have demonstrated that binding and complexation of rigid protein molecules to flexible membrane-vesicle building blocks may generate significant changes in the curvature of the membrane interfaces and may induce formation of bicontinuous cubic nanoarchitectures. Enzyme-mediated cubic nanoarchitecture generation represents another low-energy fabrication method of nanoporous liquid crystalline assemblies. The kinetic pathway of packing ready-to-assemble membrane building blocks (vesicles, nanocubosomes) into nanoarchitectonic vehicles has been revealed by rapid-mixing stopped-flow SAXS experiments. [ABSTRACT FROM AUTHOR]

This review covers recent studies on the characterization of the dynamics of lipidic nanostructures formed via self-assembly processes. The focus is placed on two main topics: First, an overview of advanced experimental small-angle X-ray scattering (SAXS) setups combined with various sample manipulation techniques including, for instance, stop-flow mixing or rapid temperature-jump perturbation is given. Second, our recent synchrotron SAXS findings on the dynamic structural response of gold nanoparticle-loaded vesicles upon exposure to an ultraviolet light source, the impact of rapidly mixing negatively charged vesicles with calcium ions, and in situ hydration-induced formation of inverted-type liquid-crystalline phases loaded with the local anesthetic bupivacaine are summarized. These in situ time-resolved experiments allow real-time monitoring of the dynamics of the structural changes and the possible formation of intermediate states in the millisecond to second range. The need for investigating self-assembled systems, mainly stimuli-responsive drug nanocarriers, under nonequilibrium conditions is discussed. For pharmaceutically relevant applications, it is essential to combine these investigations with appropriate in vitro and in vivo studies. [ABSTRACT FROM AUTHOR]

A kinetic study was carried out to monitor the time-dependent formation of surfactant-stabilized polymeric nanoparticles prepared by controlled phase separation. The nanoparticles were made of poly(methylmethacrylate) or polystyrene and several ionic and nonionic surfactants. The dispersion was prepared by fast mixing a solution of the polymers in organic solvents with a solution of a surfactant in water. We observed the formation of well-defined nanoparticles measured by time-resolved small-angle x-ray scattering (TR-SAXS). Our results suggest that the kinetics for the formation of nanoparticles comprising ionic surfactants is much faster (in the range of milliseconds) than that for nanoparticles comprising nonionic surfactants (on the time scales of several seconds). We were able to observe the transformation of particle surface from transient structure to hard sphere one in real time. Some systems manifest a plethora of structural changes that demands further experimental research. [ABSTRACT FROM AUTHOR]

Abstract: Nanocomposites composed of palladium (Pd) nanoparticles, (Pd)n, and a symmetric diblock copolymer (dibcp) of poly(styrene)-block-poly(isoprene) (PS-b-PI) were prepared via thermal reduction of palladium acetylacetonate, Pd(acac)2, by isothermal heat treatments of the as-cast dibcp films containing Pd(acac)2 by 1wt%, at temperatures below and above the order–disorder transition temperature (T ODT) of the dibcp. Effects of the reaction field on the thermal reduction process of Pd(acac)2 were studied by setting the field either in the disordered state or the ordered state of the dibcp. The reduction process was studied in situ and at real time by time-resolved small-angle X-ray scattering. In the as-cast films, a larger fraction of Pd(acac)2 is preferentially incorporated in PS lamellar microdomains, seemingly due to stronger interactions of Pd(acac)2 with PS than with PI. The spatial concentration fluctuations of (Pd)n in the final stage of the reduction reflect the memory of the concentration fluctuations of the dibcp before the reduction, either in the disordered state or in the ordered state. We found that the scaled scattering form factor of (Pd)n is universal with time and temperature of the reduction. This reveals that the reduction mechanism of Pd(acac)2 and the growth mechanism of (Pd)n do not depend on temperature; they are same below and above T ODT. However, the reduction rate and the growth rate as well as the concentration of (Pd)n in the final stage depend on temperature: the higher the temperature is, the larger are the rate and the concentration. [Copyright &y& Elsevier]

Abstract: Phase behavior and structure formation in liquid crystallization of a side-chain liquid crystalline (LC) block copolymers composed of poly[11-(4′-cyanophenyl-4″-phenoxy)undecyl acrylate] (PA11OCB) and polystyrene (PSt) were investigated by using a time-resolved small-angle X-ray scattering technique (SAXS), differential scanning calorimetry and polarizing optical microscopy. PA11OCB homopolymer formed smectic (Sm) liquid crystal. Liquid crystallization behavior of the block copolymers depended on the molecular weight and the block composition. When molecular weight was relatively low, order–disorder transition (ODT) was observed. In cooling of such block copolymers, liquid crystallization seemed to wait for the formation of LC-rich microphase by ODT. For the block copolymers with relatively high molecular weight, liquid crystallization slightly enlarged the domain spacing without changing the microphase separation structure in the melt. The order of the LC phase was lowered with decreasing dimensionality of the LC microdomains, that is, the LC blocks formed smectic liquid crystal in the matrix or lamellar microphase while liquid crystallization in the cylindrical microdomains did not show smectic but maybe nematic liquid crystal. Moreover, the LC blocks within the spherical microdomains did not liquid crystallize. From the 2-D SAXS with applying shear flow, the Sm layers were orientated perpendicularly to the interface of the microphase separation. The relation between the layer thickness of the LC phase and the molecular weight suggested that the main chain was extended normally to the interface of the microphase separation. [Copyright &y& Elsevier]

Abstract: Third generation synchrotron sources such as the Advanced Photon Source at Argonne National Laboratory, Argonne, IL, are outstanding tools for X-ray diffraction (XRD) and scattering studies of non-crystalline biological materials. However, these studies are hindered by the lack of adequate detectors that can provide multiple frames of detailed structural information on the required millisecond time scale at the extremely high count rates available at the APS. RMD is developing a cost effective detector for time-resolved small angle X-ray scattering (SAXS), using a cooled, 512×512 pixel electron multiplying CCD (EMCCD). This paper describes the detector design, its efficacy for time-resolved SAXS studies, and its imaging performance with frame rates of 30–500fps. [Copyright &y& Elsevier]

The structural characterization of polydisperse systems consisting of multiple coexisting species or conformations is very challenging or impossible with classical approaches. As a consequence, the structural bases of relevant questions related to protein folding, transient partner recognition, conformational transitions or fibrillation remain poorly understood. Small-Angle Scattering (SAS) techniques structurally probe species present in solution in a population-weighted manner, enabling the inspection of polydisperse systems. However, decomposition of these data to derive the contribution of individual components is not straightforward and requires the acquisition of large SAS datasets and adapted mathematical tools. Here, we present a detailed procedure for the usage of the program COSMiCS for the decomposition of SAS datasets. COSMiCS adapts the popular MCR-ALS chemometrics routine to the specificities of scattering data. Through the use of multiple SAS representations, the appropriate scaling of the data and the possibility to simultaneously decompose multiple orthogonal datasets, COSMiCS efficiently disentangles mixtures and provides species-specific structural and thermodynamic/kinetic information of the process under investigation. Although exemplified for a transient biomolecular interaction, our chemometrics strategy can be applied to many other biological processes that can be straightforwardly probed in last generation SAS beamlines. Indeed, recent experimental setups, including microfluidics and stop-flow devices, coupled to fast-reading detectors can yield large concentration or time-dependent datasets that can be decomposed with COSMiCS. Importantly, as an open-source code, previously known features of the system of interest can be introduced as constraints in the optimization, producing robust solutions for biological systems of increasing complexity., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Understanding and controlling defect formation during the assembly of nanoparticles is crucial for fabrication of self-assembled nanostructured materials with predictable properties. Here, time-resolved small-angle X-ray scattering was used to probe the temporal evolution of strain and lattice contraction during evaporation-induced self-assembly of oleate-capped iron oxide nanocubes in a levitating drop. We show that the evolution of the strain and structure of the growing mesocrystals is related to the formation of defects as the solvent evaporated and the assembly process progressed. Superlattice contraction during the mesocrystal growth stage is responsible for the rapidly increasing isotropic strain and the introduction of point defects. The crystal strain, quantified by the Williamson-Hall analysis, became more anisotropic due to the formation of stress-relieving dislocations as the mesocrystal growth was approaching completion. Understanding the formation of the transformation of defects in mesocrystals and superlattices could assist in the development of optimized assembly processes of nanoparticles with multifunctional properties.

Morphological change of in situ generated silica particles was investigated by a time-resolved two-dimensional small-angle X-ray scattering technique and a simultaneous tensile measurement. The in situ silica particles with diameter ca 34 nm were homogeneously dispersed in a rubbery matrix and the morphological change of the particles was followed up to the elongation ratio α = 2 during stretching and from α = 2.5 during retracting. The observed two-dimensional small-angle X-ray scattering patterns agreed with the simulation results by Rharbi et al. [ Europhys. Lett. (1999), 46, 472–478] where a shear displacement model was proposed for the deformation mode of their soft nanocomposite. [ABSTRACT FROM AUTHOR]

Structural changes occurring on a millisecond time scale during uptake of DNA by cationic lipid nanocarriers are monitored by time-resolved small-angle X-ray scattering (SAXS) coupled to a rapid-mixing stopped-flow technique. Nanoparticles (NPs) of nanochannel organization are formed by PEGylation, hydration, and dispersion of a lipid film of the fusogenic lipid monoolein in a mixture with positively charged (DOMA) and PEGylated (DOPE-PEG2000) amphiphiles and are characterized by the inner cubic structure of very large nanochannels favorable for DNA upload. Ultrafast structural dynamics of complexation and assembly of these cubosome particles with neurotrophic plasmid DNA (pDNA) is revealed thanks to the high brightness of the employed synchrotron X-ray beam. The rate constant of the pDNA/lipid NP complexation is estimated from dynamic roentgenograms recorded at 4 ms time resolution. pDNA upload into the vastly hydrated channels of the cubosome carriers leads to a fast nanoparticle-nanoparticle structural transition and lipoplex formation involving tightly packed pDNA.