Concentration Effects on the Dynamics of Liquid Crystalline Self-Assembly: Time-Resolved X-ray Scattering Studies

Abstract

A manifold of ordering transitions relevant to chemical and biological systems occur at interfaces from liquids to self-assembled soft solids like membranes or liquid crystals. In the present case, we were interested in understanding the phase transition from the microemulsion phase to the liquid crystal phase in terms of their driving forces, i.e., activation energy and entropy. The purpose of this work was to clarify the influence of concentration effects of the amphiphilic molecules on the nature of these self-assembly processes. By photosensitization of the model system (polyalkylglycolether (C10E4), water, decane, and cyclohexane) with laser dyes, we could effectively induce and control the phase transition through the absorption of optical photons. The photo transformation conditions were chosen in such a way that the system was in thermal equilibrium. By application of time-resolved photo small-angle X-ray scattering we could monitor the conversion process and demonstrate that the surfactant concentration has a direct impact on the activation energy, which is observable through the length of the induction time.

Insights into open/closed conformations of the catalytically active human guanylate kinase as investigated by small-angle X-ray scattering

“…The lack of structural and dynamical information for hGMPK could be due to the purification of recombinant hGMPK in the inactive form and the failures of crystallization (Ardiani et al 2009 ; Brady et al 1996 ; Sekulic et al 2002 ). Small-angle X-ray scattering (SAXS) only requires small amounts of purified hGMPK in solution to provide global structural information, assess structural changes, and derive the three-dimensional surface reconstructions of hGMPK in the absence and presence of its substrates and analogs (Jacques and Trewhella 2010 ; Jain et al 2013 ; Koch et al 2003 ; Mallik et al 2012 ; Petri et al 2011 , 2012 ; Putnam et al 2007 ; Solanki et al 2014 ; Taylor et al 2012 ; Tuukkanen and Svergun 2014 ). We succeeded in purifying the active recombinant hGMPK, which was used to obtain insights into between open/closed hGMPK conformations.…”

Small-Angle X-ray Scattering Investigations of Biomolecular Confinement, Loading, and Release from Liquid-Crystalline Nanochannel Assemblies

“…Small-angle X-ray (SAXS) and neutron (SANS) scattering − are powerful structural methods for establishing the crystallographic space group symmetry and domain topologies of organized nanochannel systems as determined by the materials properties (Figure ). The SAXS method is indispensable for distinguishing topologically random channel networks (e.g., bicontinuous sponge phases) from tubular-type (Figure G) or periodically organized (e.g., gyroid) bicontinuous LC structures of aqueous channels.…”

“…Time-resolved SAXS − (TR-SAXS), especially in the millisecond time scale, has been introduced as a modern method for investigation of the phase transitions in amphiphilic mesophases − as it allows monitoring of the kinetics of stimuli-induced structure conversion processes and the occurrence of intermediate phase states. It is important also for the establishment of size-dependent phase behaviors and the elucidation of the mechanisms of nucleation and formation of new phases.…”

Development of Ultrafast X-ray Free Electron Laser Tools in (Bio)Chemical Research

“….12)[90,[94][95][96][97][98][99][100][101][102][103], X-ray scattering on macromolecules (Fig.17.13) and (Fig. 17.14) [90, 115, 116, 118, 121] and X-ray spectroscopy (Fig.…”