Modulating hierarchical self-assembly in thermoresponsive intrinsically disordered proteins through high-temperature incubation time.

The cornerstone of structural biology is the unique relationship between protein sequence and the 3D structure at equilibrium. Although intrinsically disordered proteins (IDPs) do not fold into a specific 3D structure, breaking this paradigm, some IDPs exhibit large-scale organization, such as liquid-liquid phase separation. In such cases, the structural plasticity has the potential to form numerous self-assembled structures out of thermal equilibrium. Here, we report that high-temperature incubation time is a defining parameter for micro and nanoscale self-assembly of resilin-like IDPs. Interestingly, high-resolution scanning electron microscopy micrographs reveal that an extended incubation time leads to the formation of micron-size rods and ellipsoids that depend on the amino acid sequence. More surprisingly, a prolonged incubation time also induces amino acid composition-dependent formation of short-range nanoscale order, such as periodic lamellar nanostructures. We, therefore, suggest that regulating the period of high-temperature incubation, in the one-phase regime, can serve as a unique method of controlling the hierarchical self-assembly mechanism of structurally disordered proteins.

Modulating Hierarchical Self-Assembly In Thermoresponsive Intrinsically Disordered Proteins Through High-Temperature Incubation Time.

The cornerstone of structural biology is the unique relationship between protein sequence and the 3D structure at equilibrium. Although intrinsically disordered proteins (IDPs) do not fold into a specific 3D structure, breaking this paradigm, some IDPs exhibit large-scale organization, such as liquid-liquid phase separation. In such cases, the structural plasticity has the potential to form numerous self-assembled structures out of thermal equilibrium. Here, we report that high-temperature incubation time is a defining parameter for micro and nanoscale self-assembly of resilin-like IDPs. Interestingly, high-resolution scanning electron microscopy micrographs reveal that an extended incubation time leads to the formation of micron-size rods and ellipsoids that depend on the amino acid sequence. More surprisingly, a prolonged incubation time also induces amino acid composition-dependent formation of short-range nanoscale order, such as periodic lamellar nanostructures. We can correlate the lamellar structures to \b{eta}-sheet formation and demonstrate similarities between the observed nanoscopic structural arrangement and spider silk. We, therefore, suggest that regulating the period of high-temperature incubation, in the one-phase regime, can serve as a unique method of controlling the hierarchical self-assembly mechanism of structurally disordered proteins.

Modulating Hierarchical Self-Assembly In Thermoresponsive Intrinsically Disordered Proteins Through High-Temperature Incubation Time.

The cornerstone of structural biology is the unique relationship between protein sequence and the 3D structure at equilibrium. Although intrinsically disordered proteins (IDPs) do not fold into a specific 3D structure, breaking this paradigm, some IDPs exhibit large-scale organization, such as liquid-liquid phase separation. In such cases, the structural plasticity has the potential to form numerous self-assembled structures out of thermal equilibrium. Here, we report that high-temperature incubation time is a defining parameter for micro and nanoscale self-assembly of resilin-like IDPs. Interestingly, high-resolution scanning electron microscopy micrographs reveal that an extended incubation time leads to the formation of micron-size rods and ellipsoids that depend on the amino acid sequence. More surprisingly, a prolonged incubation time also induces amino acid composition-dependent formation of short-range nanoscale order, such as periodic lamellar nanostructures. We can correlate the lamellar structures to ß-sheet formation and demonstrate similarities between the observed nanoscopic structural arrangement and spider silk. We, therefore, suggest that regulating the period of high-temperature incubation, in the one-phase regime, can serve as a unique method of controlling the hierarchical self-assembly mechanism of structurally disordered proteins.

Correction: Understanding the role of co-surfactants in microemulsions on the growth of copper oxalate using SAXS.

Correction for 'Understanding the role of co-surfactants in microemulsions on the growth of copper oxalate using SAXS' by Sunaina et al., Phys. Chem. Chem. Phys., 2019, 21, 336-348.

Hydrotrope-Driven Self-Assembly in CTAB/ n-Hexanol/Water/Heptane Reverse Micellar System.

Self-organization of nanoparticles into one-dimensional (1D) nanochains leads to new unpredicted physiochemical properties, which are further exploited to develop photonic or electronic devices. Thus, the controlled fabrication of 1D nanochains requires nanotemplate, which acts as building blocks for the self-assembly of nanoparticles. To address this issue, we designed a hydrotrope (sodium salicylate)-based CTAB/ n-hexanol/water/heptane reverse micellar system. Hydrotrope, herein, modulates electrostatic interactions between reverse micellar droplets and paves the way for the formation of self-assembled structures. Small-angle X-ray scattering studies were performed on the CTAB/heptane reverse micellar system by varying hydrotrope concentrations and water-to-surfactant ratios (W x). The aqueous content of the reverse micellar pool is determined from the W x value, where W x = [H2O]/[CTAB] and [CTAB] = 0.05 M. SAXS studies were performed for CTAB/heptane reverse micellar systems at three different W x values, that is, 6, 12, and 16 and represented by W6, W12, and W16, respectively. All SAXS profiles were modeled with a spherical form factor and a Baxter sticky hard sphere structure factor. The interaction between droplets was predicted in terms of stickiness parameter. The effect of W x on the formation of self-assembled structures and forces governing the assembly has been discussed in detail. For the W6 system, the electrostatic repulsion between reverse micellar droplets decreases, resulting in the formation of the 1D chain-like assembly of nanodroplets. In the case of the W12 system, the dual feature of the hydrotrope has been observed, it increases the size of the reverse micellar system and reduces electrostatic repulsion between droplets because of which the formation of chain-like assemblies cannot be determined with accuracy. For the W16 system, the decrease in micellar size with the increase in the hydrotrope concentration has been observed. Thus, our reverse micellar templates may provide a comprehensive method for the fabrication of high aspect ratio 1D nanochains of a variety of materials and harnessing their collective properties for magnetic, catalytic, and opto-electronic applications.

Understanding the role of co-surfactants in microemulsions on the growth of copper oxalate using SAXS.

This study is an effort to understand the mechanism of the effect of the chain length of co-surfactants on the growth of copper oxalate inside the core of reverse micelles using small angle X-ray scattering (SAXS). In this study, we have used two different kinds of co-surfactants viz. 1-butanol (C4) and 1-octanol (C8) for the formation of the microemulsions. Time-dependent SAXS studies were carried out for these two systems. The data were analyzed using both the model-independent approach and model-dependent approach. For microemulsions containing only water inside the core of reverse micelles (no ions), the shape of the reverse micelles was observed to be ellipsoid and spherical in nature for 1-butanol and 1-octanol respectively. For a system containing copper oxalate nanostructures, the fitting was carried out using the ellipsoidal core-shell model for reverse micelles and spheres, ellipsoids and cylinders for copper oxalate nanostructures with 1-butanol as the co-surfactant. With 1-octanol as the co-surfactant, the two contributions that were used were the spherical core-shell model for reverse micelles and spheres for copper oxalate nanostructures. Based on the analysis of SAXS data, a growth mechanism has been proposed. The study discussed here could open the field of understanding the growth mechanism of complex nanostructures formed using the microemulsion route.

Hydrotrope induced structural modifications in CTAB/butanol/water/isooctane reverse micellar systems.

Designing nanostructures of desired morphology calls for development of new synthetic protocols to stimulate structural alterations in templates, modulating the architecture of nano-metric structures. The present study is an endeavor to investigate structural modifications in reverse micellar nanotemplates of a cationic surfactant system, CTAB/butanol/water/isooctane, as a function of hydrotrope concentration (sodium salicylate) and amount of water loading, Wx, in the micellar pool by synchrotron small-angle X-ray scattering. The micellar structural transition from a one-dimensional cylinder to a prolate ellipsoid can be controlled by tuning the water-to-surfactant molar ratio while the hydrotrope modulates growth of the micellar droplets. The inter-micellar interactions in these systems could be best represented by the Polymer Reference Interaction Site (PRISM) model at lower water content in the reverse micellar pool and by the Macroion model at higher water loadings. The location of the hydrotrope inside the micellar assembly and its interaction with different components of the reverse micellar system is probed with the help of 1H NMR studies. The formation and tuning of anisotropic cylindrical/ellipsoidal reverse micellar droplets suggest promising application of such aggregates as "tunable soft templates" for fabricating fascinating nanostructures.

Exchange relaxometry of flow at small Péclet numbers in a glass bead pack.

In this paper we consider low Péclet number flow in bead packs. A series of relaxation exchange experiments has been conducted and evaluated by ILT analysis. In the resulting correlation maps, we observed a collapse of the signal and a translation towards smaller relaxation times with increasing flow rates, as well as a signal tilt with respect to the diagonal. In the discussion of the phenomena we present a mathematical theory for relaxation exchange experiments that considers both diffusive and advective transport. We perform simulations based on this theory and discuss them with respect to the conducted experiments.