scholarly journals Exploring the in meso crystallization mechanism by characterizing the lipid mesophase microenvironment during the growth of single transmembrane α-helical peptide crystals

2016 ◽  
Vol 374 (2072) ◽  
pp. 20150125 ◽  
Author(s):  
Leonie van 't Hag ◽  
Konstantin Knoblich ◽  
Shane A. Seabrook ◽  
Nigel M. Kirby ◽  
Stephen T. Mudie ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Self Assembly ◽  
Lamellar Phase ◽  
Cubic Phase ◽  
Supporting Evidence ◽  
X Ray ◽  
X Ray Scattering ◽  
Standard Procedures ◽  
Helical Peptide ◽  
Saxs Analysis

The proposed mechanism for in meso crystallization of transmembrane proteins suggests that a protein or peptide is initially uniformly dispersed in the lipid self-assembly cubic phase but that crystals grow from a local lamellar phase, which acts as a conduit between the crystal and the bulk cubic phase. However, there is very limited experimental evidence for this theory. We have developed protocols to investigate the lipid mesophase microenvironment during crystal growth using standard procedures readily available in crystallography laboratories. This technique was used to characterize the microenvironment during crystal growth of the DAP12-TM peptide using synchrotron small angle X-ray scattering (SAXS) with a micro-sized X-ray beam. Crystal growth was found to occur from the gyroid cubic mesophase. For one in four crystals, a highly oriented local lamellar phase was observed, providing supporting evidence for the proposed mechanism for in meso crystallization. A new observation of this study was that we can differentiate diffraction peaks from crystals grown in meso , from peaks originating from the surrounding lipid matrix, potentially opening up the possibility of high-throughput SAXS analysis of in meso grown crystals. This article is part of the themed issue ‘Soft interfacial materials: from fundamentals to formulation’.

scholarly journals Synchrotron X-ray Observations of a Monolayer Template for Mineralization

2001 ◽  
Vol 711 ◽  
Author(s):  
E. DiMasi ◽  
L. B. Gower
Keyword(s):  
Crystal Growth ◽  
Stearic Acid ◽  
Self Assembly ◽  
Langmuir Trough ◽  
X Ray ◽  
X Ray Scattering ◽  
Calcium Bicarbonate ◽  
Bicarbonate Solutions ◽  
Film Interface

ABSTRACTMineral nucleation at a Langmuir film interface has been studied by synchrotron x-ray scattering. Diluted calcium bicarbonate solutions were used as subphases for arachidic and stearic acid monolayers, compressed in a Langmuir trough. Self-assembly of the monolayer template is observed directly, and subsequent crystal growth monitored in-situ.

scholarly journals Microfluidics for Time-Resolved Small-Angle X-Ray Scattering

2020 ◽  
Author(s):  
Susanne Seibt ◽  
Timothy Ryan
Keyword(s):  
Self Assembly ◽  
Structural Evolution ◽  
Time Resolved ◽  
X Ray ◽  
Structural Characterisation ◽  
X Ray Scattering ◽  
Saxs Analysis ◽  
Kinetics Of ◽  
Ray Scattering

With the advent of new in situ structural characterisation techniques including X-ray scattering, there has been an increased interest in investigations of the reaction kinetics of nucleation and growth of nanoparticles as well as self-assembly processes. In this chapter, we discuss the applications of microfluidic devices specifically developed for the investigation of time resolved analysis of growth kinetics and structural evolution of nanoparticles and nanofibers. We focus on the design considerations required for spectrometry and SAXS analysis, the advantages of using a combination of SAXS and microfluidics for these measurements, and discuss in an applied fashion the use of these devices for time-resolved research.

In situ Time-Resolved Small-Angle X-ray Scattering Reveals the Formation Kinetics of Polyelectrolyte Complex Micelles

2019 ◽  
Author(s):  
Hao Wu ◽  
Jeffrey Ting ◽  
Siqi Meng ◽  
Matthew Tirrell
Keyword(s):  
Small Angle ◽  
Self Assembly ◽  
Electrostatic Interactions ◽  
Polyelectrolyte Complex ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Scattering ◽  
Kinetics Of ◽  
Ray Scattering

We have directly observed the <i>in situ</i> self-assembly kinetics of polyelectrolyte complex (PEC) micelles by synchrotron time-resolved small-angle X-ray scattering, equipped with a stopped-flow device that provides millisecond temporal resolution. This work has elucidated one general kinetic pathway for the process of PEC micelle formation, which provides useful physical insights for increasing our fundamental understanding of complexation and self-assembly dynamics driven by electrostatic interactions that occur on ultrafast timescales.

scholarly journals Pilot study on the effects of preservatives on corneal collagen parameters measured by small angle X-ray scattering analysis

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Susyn Joan Kelly ◽  
Lizette duPlessis ◽  
John Soley ◽  
Frazer Noble ◽  
Hannah Carolyn Wells ◽  
...  
Keyword(s):  
Small Angle ◽  
Collagen Fibril ◽  
Diameter Distribution ◽  
X Ray ◽  
X Ray Scattering ◽  
Saxs Analysis ◽  
Triton X ◽  
Fibril Diameter ◽  
Corneal Collagen ◽  
Ray Scattering

Abstract Objective Small angle X-ray scattering (SAXS) analysis is a sensitive way of determining the ultrastructure of collagen in tissues. Little is known about how parameters measured by SAXS are affected by preservatives commonly used to prevent autolysis. We determined the effects of formalin, glutaraldehyde, Triton X and saline on measurements of fibril diameter, fibril diameter distribution, and D-spacing of corneal collagen using SAXS analysis. Results Compared to sections of sheep and cats’ corneas stored frozen as controls, those preserved in 5% glutaraldehyde and 10% formalin had significantly larger mean collagen fibril diameters, increased fibril diameter distribution and decreased D-spacing. Sections of corneas preserved in Triton X had significantly increased collagen fibril diameters and decreased fibril diameter distribution. Those preserved in 0.9% saline had significantly increased mean collagen fibril diameters and decreased diameter distributions. Subjectively, the corneas preserved in 5% glutaraldehyde and 10% formalin maintained their transparency but those in Triton X and 0.9% saline became opaque. Subjective morphological assessment of transmission electron microscope images of corneas supported the SAXS data. Workers using SAXS analysis to characterize collagen should be alerted to changes that can be introduced by common preservatives in which their samples may have been stored.

scholarly journals Modeling of the Resonant X-ray Response of a Chiral Cubic Phase

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 214
Author(s):  
Timon Grabovac ◽  
Ewa Gorecka ◽  
Damian Pociecha ◽  
Nataša Vaupotič
Keyword(s):  
Absorption Edge ◽  
Unit Cell ◽  
Resonant Peak ◽  
Cubic Phase ◽  
Tensor Form ◽  
Resonant Enhancement ◽  
X Ray ◽  
X Ray Scattering ◽  
Thermotropic Liquid Crystals ◽  
Carbon Absorption

The structure of a continuous-grid chiral cubic phase made of achiral constituent molecules is a hot topic in the field of thermotropic liquid crystals. Several structural models have been proposed so far. Resonant X-ray scattering (RXS), which gives information on the molecular orientation in the unit cell, could be applied to select the most appropriate model. We modeled the RXS response for the recently proposed chiral cubic phase structure with an all-hexagon chiral continuous grid. A tensor form factor of a unit cell is constructed, which enables calculation of intensities of peaks for all Miller indices. We find that all the symmetry allowed peaks are resonantly enhanced, and their intensity is much stronger than the intensity of the symmetry forbidden (resonant) peaks. In particular, we predict that a strong resonant enhancement of the symmetry allowed peaks (011) and (002), not observed in a nonresonant scattering, could be observed by RXS at the carbon absorption edge. By RXS at the sulfur absorption edge, one might observe a resonant peak (113) and resonantly enhanced peak (233), and resonant enhancement of all the peaks that are observed in a nonresonant scattering, which probably hide the rest of the predicted resonant peaks.

scholarly journals Alpha helical surfactant-like peptides self-assemble into pH-dependent nanostructures

Soft Matter ◽  
2021 ◽  
Vol 17 (11) ◽  
pp. 3096-3104
Author(s):  
Valeria Castelletto ◽  
Jani Seitsonen ◽  
Janne Ruokolainen ◽  
Ian W. Hamley
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Small Angle ◽  
Self Assembly ◽  
X Ray ◽  
Cryogenic Transmission Electron Microscopy ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
Ph Dependent ◽  
Ray Scattering

A designed surfactant-like peptide is shown, using a combination of cryogenic-transmission electron microscopy and small-angle X-ray scattering, to have remarkable pH-dependent self-assembly properties.

scholarly journals Controlling water evaporation through self-assembly

2016 ◽  
Vol 113 (37) ◽  
pp. 10275-10280 ◽  
Author(s):  
Kevin Roger ◽  
Marianne Liebi ◽  
Jimmy Heimdal ◽  
Quoc Dat Pham ◽  
Emma Sparr
Keyword(s):  
Self Assembly ◽  
Feedback Loop ◽  
Ambient Air ◽  
Underlying Mechanism ◽  
Water Evaporation ◽  
Air Humidity ◽  
X Ray ◽  
X Ray Scattering ◽  
Composition And Structure ◽  
Living Organisms

Water evaporation concerns all land-living organisms, as ambient air is dryer than their corresponding equilibrium humidity. Contrarily to plants, mammals are covered with a skin that not only hinders evaporation but also maintains its rate at a nearly constant value, independently of air humidity. Here, we show that simple amphiphiles/water systems reproduce this behavior, which suggests a common underlying mechanism originating from responding self-assembly structures. The composition and structure gradients arising from the evaporation process were characterized using optical microscopy, infrared microscopy, and small-angle X-ray scattering. We observed a thin and dry outer phase that responds to changes in air humidity by increasing its thickness as the air becomes dryer, which decreases its permeability to water, thus counterbalancing the increase in the evaporation driving force. This thin and dry outer phase therefore shields the systems from humidity variations. Such a feedback loop achieves a homeostatic regulation of water evaporation.

scholarly journals REGALS: a general method to deconvolve X-ray scattering data from evolving mixtures

2020 ◽  
Author(s):  
Steve P. Meisburger ◽  
Da Xu ◽  
Nozomi Ando
Keyword(s):  
A Priori ◽  
Scattering Data ◽  
Biological Macromolecules ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Scattering ◽  
Open Source Software Package ◽  
Saxs Analysis ◽  
Structural Methods ◽  
Ray Scattering

AbstractMixtures 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, we introduce the REGALS method (REGularized Alternating Least Squares), 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, which makes it well-suited for exploring datasets with unknown species. Here we apply REGALS to analyze 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, we anticipate 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.

scholarly journals In Situ Synchrotron X-ray Study of the Mechanical Properties of Pure Mg Produced by Powder Metallurgy

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1198
Author(s):  
Li Li ◽  
Leyun Wang ◽  
Jie Wang ◽  
Huan Zhang ◽  
Qingchun Zhu ◽  
...  
Keyword(s):  
Powder Metallurgy ◽  
Tensile Deformation ◽  
Line Broadening ◽  
X Ray ◽  
X Ray Scattering ◽  
Type Dislocation ◽  
Diffraction Patterns ◽  
Saxs Analysis ◽  
Ray Scattering

In this study, in situ synchrotron X-ray experiments with wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) detectors were performed on two pure magnesium materials produced by powder metallurgy. According to SAXS analysis, each of the two materials has a porosity of less than 0.5%. Line broadening analysis was performed on diffraction patterns collected by WAXS to analyze the dislocation evolution during material deformation. In both materials, <a>-type dislocation activities dominate the tensile deformation. The influence of grain size and texture on the different tensile behaviors of these two materials is also discussed.

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