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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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]

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]

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]

[Display omitted] In situ formation of high viscous inverse lyotropic non-lamellar liquid crystalline phases is a promising approach for sustained drug delivery in the joint. The in situ forming process on exposure of two diclofenac-loaded preformulations to aqueous media was characterized with respect to depot size and shape, initial release and structural transitions using UV–Vis imaging and spatially and time-resolved synchrotron small-angle X-ray scattering (SAXS). The preformulations consisted of 10 % (w/w) ethanol, 10 % (w/w) water and a binary lipid mixture of glycerol monooleate (GMO):1,2-dioleoyl- sn -glycero-3-phospho- rac -(1-glycerol) (DOPG) or GMO:medium chain triglycerides (MCT). Upon injection of preformulations into an employed injection-cell containing excess of bio-relevant medium, rapid generation of liquid crystalline depots was observed. UV–Vis images and constructed 2D SAXS maps of the injection-cell showed depots with different shapes and sizes, and features with high nanostructural heterogeneity. More extensive swelling of the GMO:DOPG-based preformulation was observed compared to the GMO:MCT-based preformulation. The UV image analysis found that a higher amount of diclofenac was released in the image area after 20 h from the GMO:MCT depot compared to the GMO:DOPG depot. The injection-cell setup employing UV–Vis imaging and synchrotron SAXS constitutes an attractive approach for evaluating the in situ forming processes of liquid crystalline depots. [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]

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]