Light-responsive self-assembly of a cationic azobenzene surfactant at high concentration.

The formation of high-concentration mesophases by a cationic azobenzene photosurfactant is described for the first time. Using a combination of polarised optical microscopy and small-angle X-ray scattering, optically anisotropic, self-assembled structures with long-range order are reported. The mesophases are disrupted or lost upon UV irradiation

Controlling the properties of the micellar and gel phase by varying the counterion in functionalised-dipeptide systems

The micellar aggregates formed at high pH for dipeptide-based gelators can be varied by using different alkali metal salts to prepare the solutions. The nature of the micellar aggregates directly affects the properties of the resulting gels

Isotopic control over self-assembly in supramolecular gels

It is common to switch between H2O and D2O when examining peptide-based systems with the assumption being that there are no effects from this change. Here, we describe the effect of changing from H2O to D2O in a number of low molecular weight dipeptide-based gels. Gels are formed by decreasing the pH. In most cases, there is little dif-ference in the structures formed at high pH, but this is not universally true. On lowering the pH, the ki-netics of gelation are affected and, in some cases, the structures underpinning the gel network are dif-ferent. Where there are differences in the self-assembled structures, the resulting gel properties are different. We therefore show isotopic control over gel properties is possible

Design of a multipurpose sample cell holder for the Diamond Light Source high-throughput SAXS beamline B21

The design of a multipurpose sample cell holder for the high-throughput (HT) beamline B21 is presented. The device is compatible with the robot bioSAXS sample changer currently installed on BM29, ESRF, and P12 Petra IV synchrotrons. This work presents an approach that uses 3D-printing to make hardware alterations which can expand the versatility of HT beamlines at low cost

Self-assembly and antimicrobial activity of lipopeptides containing lysine-rich tripeptides

The conformation and self-assembly of two pairs of model lipidated tripeptides in aqueous solution are probed using a combination of spectroscopic methods along with cryogenic-transmission electron microscopy (cryo-TEM) and small-angle X-ray scattering (SAXS). The palmitoylated lipopeptides comprise C16-YKK or C16-WKK (with two l-lysine residues) or their respective derivatives containing d-lysine (k), i.e., C16-Ykk and C16-Wkk. All four molecules self-assemble into spherical micelles which show structure factor effects in SAXS profiles due to intermicellar packing in aqueous solution. Consistent with micellar structures, the tripeptides in the coronas have a largely unordered conformation, as probed using spectroscopic methods. The molecules are found to have good cytocompatibility with fibroblasts at sufficiently low concentrations, although some loss of cell viability is noted at the highest concentrations examined (above the critical aggregation concentration of the lipopeptides, determined from fluorescence dye probe measurements). Preliminary tests also showed antimicrobial activity against both Gram-negative and Gram-positive bacteria

Controlling the formation and alignment of low molecular weight gel ‘noodles’

We show how to control the formation and alignment of gel ‘noodles’. Nanostructure alignment can be achieved reproducibly by extensional deformation as the filaments form. Using a spinning technique, very long and highly aligned filaments can be made. The Young’s moduli of the gel noodles are similar to that of a bulk gel. By using two syringe pumps in a concentric flow setup, we show that a filament-in-filament morphology can be created

Controlling photocatalytic activity by self-assembly – Tuning perylene bisimide photocatalysts for the hydrogen evolution reaction

Amino acid functionalized perylene bisimides (PBIs) form self-assembled structures in solution, the nature of which depends on the local environment. Using a high-throughput photocatalysis setup, five PBIs are studied for the hydrogen evolution reaction (HER) under a range of conditions (pH and hole scavenger concentration) across 350 experiments to explore the relationship between supramolecular structure and photocatalytic activity. Using small angle X-ray scattering (SAXS), NMR spectroscopy and ultraviolet-visible (UV-vis) absorption spectroscopy, it is shown that photocatalytic activity is determined by the nature of the self-assembled aggregate that is formed, demonstrating the potential of self-assembly to tune activity. There is a clear correlation between the presence of charged flexible cylindrical aggregates and the occurrence of photocatalytic H2 production, with UV–vis spectroscopy indicating that the most active structure type has a distinctive form of π-aggregation which is proposed to enable efficient charge separation across multiple PBI units

Using Small angle X-ray acattering (SAXS) to characterise the solution conformation and flexibility of matrix metalloproteinases (MMPs)

Small angle X-ray scattering (SAXS) provides information about the conformation and flexibility of proteins in solution, and hence provides complementary structural information to that obtained from X-ray crystallography and nuclear magnetic resonance spectroscopy. In this chapter, we describe the methods for the preparation of matrix metalloproteinase (MMP) samples for SAXS analyses, and for the acquisition, processing and interpretation of the SAXS data

Research data supporting "Light-responsive self-assembly of a cationic azobenzene surfactant at high concentration"

Data files contain the raw data for the Figures in the manuscript and ESI. Figure 1 contains the UV-Vis absorption XY data for both photostationary states as wavelength (nm), trans-PSS absorption, cis-PSS absorption. Figure 2 contains the raw SAXS data for the trans-PSS state at 10, 15 and 20 wt%. Columns are q (A^-1), 20 wt%, yError, 10 wt%, y error, 15 wt%, y error. Figure 3 contains the raw SAXS data for the cis-PSS state at 10, 15 and 20 wt%. Columns are q (A^-1), 20 wt%, yError, 15 wt%, y error, 10 wt%, y error. Figure S1 contains the UV-Vis absorption XY data for the 100% trans-assembly as wavelength (nm) and absorption. Figure S2a contains the UV Vis absorption and kinetics of the trans to cis photoisomerisation XY data, as wavelength (nm) and absorption at fixed intervals over 90 seconds. Figure S2a_inset contains the XY data for the calculated rate constant (trans-cis) as a function of time (s). Figure S2b contains the UV Vis absorption and kinetics of the cis to trans photoisomerisation XY data, as wavelength (nm) and absorption at fixed intervals over 180 seconds. Figure S2b_inset contains the XY data for the calculated rate constant (cis - trans) as a function of time (s). Figure S4a contains the SAXS data for the trans state (20 wt%) as a function of temperature, as q (A^-1), and scattering intensity at T = 20 degrees Celcius, 30 degrees, 40 degrees, 50 degrees, 60 degrees. Figure S4b contains the DSC XY data for the heat flow thermograms at 20 and 30 wt% across 10-90 degrees Celcius

Controlling Activity by Self-Assembly – Tuning Perylene Bisimide Photocatalysts for the Hydrogen Evolution Reaction

Amino acid functionalised perylene bisimides (PBIs) form self-assembled structures in solution, the nature of which depends on the local environment. Using a high throughput photocatalysis set-up, we have studied five PBIs for the hydrogen evolution reaction (HER) under a range of conditions (pH and hole scavenger concentration) across 350 experiments to explore the relationship between supramolecular structure and photocatalytic activity. Using small angle X-ray scattering (SAXS), we show that photocatalytic activity is determined by the nature of the self-assembled aggregate that is formed with a correlation between the presence of charged flexible cylindrical aggregates and high levels of H2. Our work highlights the complexity of designing supramolecular photocatalysts, and also the power of tuning activity by the type of aggregate that is formed