Lipid‐like Peptides can Stabilize Integral Membrane Proteins for Biophysical and Structural Studies

A crucial bottleneck in membrane protein structural biology is the difficulty in identifying a detergent that can maintain the stability and functionality of integral membrane proteins (IMPs). Detergents are poor membrane mimics, and their common use in membrane protein crystallography may be one reason for the challenges in obtaining high‐resolution crystal structures of many IMP families. Lipid‐like peptides (LLPs) have detergent‐like properties and have been proposed as alternatives for the solubilization of G protein‐coupled receptors and other membrane proteins. Here, we systematically analyzed the stabilizing effect of LLPs on integral membrane proteins of different families. We found that LLPs could significantly stabilize detergent‐solubilized IMPs in vitro. This stabilizing effect depended on the chemical nature of the LLP and the intrinsic stability of a particular IMP in the detergent. Our results suggest that screening a subset of LLPs is sufficient to stabilize a particular IMP, which can have a substantial impact on the crystallization and quality of the crystal.     

Intensified and safe ozonolysis of fatty acid methyl esters in liquid CO2 in a continuous reactor

We demonstrate a continuous reactor for performing the ozonolysis of fatty acid methyl esters (FAMEs) using liquid CO₂ as solvent. The fast reaction kinetics allows the use of small‐volume reactors to completely convert the FAMEs, forming secondary ozonides as the primary products. The short residence times also help maximize the yields of the secondary ozonides by minimizing over‐oxidation and the formation of oligomeric products. The liquid CO₂ medium promotes safe reactor operation by providing an essential fraction of overall reactor cooling and by diluting the vapor phase organics. We also demonstrate a continuous stirred reactor for the safe thermal decomposition of the secondary ozonides to their corresponding acids and aldehydes. Using a lumped kinetic model for the thermal decomposition of the ozonolysis products, we estimate activation energy values of 108.6 ± 0.6 kJ mol^?1 for the decomposition of secondary ozonides and 122 ± 3 kJ mol^?1 for the decomposition of the undesired oligomeric species. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2819–2826, 2017     

Imaging of Extracellular pH Using Hyperpolarized Molecules

Many diseases can overrule natural pH regulatory mechanisms and alter the extracellular pH (pH_e). A non-invasive method that resolves pH_e in vivo with high spatial and temporal resolution could therefore improve diagnosis and monitoring of diseases, contributing to the concept of precision medicine. During the last decades, several techniques have been proposed to image pH_e non-invasively. The majority of these methods rely on magnetic resonance because of its good spatial resolution, high penetration depth, non-ionizing radiation and excellent complimentary soft tissue contrast. Dissolution dynamic nuclear polarization (DNP) is an emerging concept to enhance nuclear magnetic resonance (NMR) signals by more than four orders of magnitude, making it possible to observe in vivo metabolic processes in real-time. Here, we summarize and review recent developments in pH_e imaging techniques based on hyperpolarization methods and give an overview of recently discovered hyperpolarized pH sensor molecules that have been applied in vitro and in vivo.     

Modification of cotton fabrics with a hydrolysed organotrialkoxysilane/metal alkoxide system: multifunctionalisation and mordant dyeing

Untreated cotton fabrics and cotton samples pretreated with 1,2,3,4-butanetetracarboxylic acid were functionalised with an organotrialkoxysilane [(3-glycidyloxy)propyltrimethoxysilane] in conjunction with a metal alkoxide (aluminium isopropoxide, titanium tetraisopropoxide, or zircon tetrabutoxide). Evaluation of the physicomechanical properties revealed that the dry crease recovery angle was significantly increased in the case of aluminium isopropoxide, whereas the tensile strength and the tear strength were reduced. The application of alkyltrialkoxysilanes resulted in an enhanced contact angle. As the cotton samples were treated with hydrolysed metal alkoxides, which can function as mordants, the cotton fabrics were dyed with alizarin. The dyeing behaviour was determined from colorimetric data.     

Microwave-specific heating of crystalline species in nuclear waste glass

The microwave heating of a crystal-free and a partially trevorite-crystallized nuclear waste glass simulant was evaluated. Our results show that a 500-mg monolith of partially crystallized waste glass can be heated from room temperature to above 1600°C within 2 minutes using a single-mode, highly focused, 2.45-GHz microwave, operating at 300 W. Using X-ray diffraction measurements, we show that trevorite is no longer detectable after irradiation and thermal quenching. When a crystal-free analog of the same waste glass simulant composition was exposed to the same microwave radiation, it could not be heated above 450°C regardless of the heating time. The reduction in crystalline content achieved by selectively heating spinels in the presence of glass suggests that microwave-specific heating should be further explored as a technique for remediating crystal accumulation in a glass melt.     

Polarized recombination of acoustically transported carriers in GaAs nanowires

ABSTRACT: : The oscillating piezoelectric field of a surface acoustic wave (SAW) is employed to transport photoexcited electrons and holes in GaAs nanowires deposited on a SAW delay line on a LiNbO3 crystal. The carriers generated in the nanowire by a focused light spot are acoustically transferred to a second location where they recombine. We show that the recombination of the transported carriers occurs in a zinc blende section on top of the predominant wurtzite nanowire. This allows contactless control of the linear polarized emission by SAWs which is governed by the crystal structure. Additional polarization-resolved photoluminescence measurements were performed to investigate spin conservation during transport.     

Near-field optical microscopy of femtosecond-laser-reshaped silver nanoparticles in dielectric matrix

ABSTRACT: : Samples containing single silver nanoparticles have been irradiated by intense femtosecond laser pulses to gain a persistent transformation of their shape to ellipsoidal forms. Irradiated and non-irradiated regions of these samples have been analyzed by microscope spectrometry as well as near-field scanning optical microscopy (NSOM) with several wavelengths and different linear polarizations. The results show the outstanding capability of NSOM technique to detect the individual shape of transformed metallic nanoparticles and to analyze their orientation and aspect ratio.     

Polymer anion-selective membranes for electrolytic splitting of water. Part II: Enhancement of ionic conductivity and performance under conditions of alkaline water electrolysis

An attempt was made to increase the ionic conductivity of novel, heterogeneous, anion-selective membranes by increasing the porosity of their surface skin. This was based on the addition of a water-soluble component, namely poly(ethylene-ran-propylene glycol), to an inert polymer matrix, based on low-density polyethylene, while mixing it with the ion-exchange particles. A series of membranes was prepared, consisting of 66 wt% of anion-exchange phase represented by a styrene-divinyl benzene copolymer matrix with quaternary ammonium functional groups and an inert polymer matrix in a mixture with variable amounts of water-soluble component added. The membranes were subsequently tested with respect to their morphology, mechanical properties, apparent ion-exchange capacity, ionic conductivity, and performance under conditions of alkaline water electrolysis. When added in the appropriate amount, the addition of a water-soluble component was found to improve the electrochemical properties of the resulting membrane efficiently, while at the same time not reducing its mechanical properties to below a critical level.     

Controlled reversible debundling of single-walled carbon nanotubes by photo-switchable dendritic surfactants

Stimulus responsive surfactants based on dendritic glycerol azobenzene conjugates were used to solubilize and debundle single-walled carbon nanotubes in aqueous media. Their debundling property as well as their reaggregation behavior upon irradiation with light was examined and light triggered reversible bundling and precipitation are shown.     

Thermally reduced graphenes exhibiting a close relationship to amorphous carbon

Graphene is an important material for sensing and energy storage applications. Since the vast majority of sensing and energy storage chemical and electrochemical systems require bulk quantities of graphene, thermally reduced graphene oxide (TRGO) is commonly employed instead of pristine graphene. The sp(2) planar structure of TRGO is heavily damaged, consisting of a very short sp(2) crystallite size of nanometre length and with areas of sp(3) hybridized carbon. Such a structure of TRGO is reminiscent of the key characteristic of the structure of amorphous carbon, which is defined as a material without long-range crystalline order consisting of both sp(2) and sp(3) hybridized carbons. Herein, we describe the characterization of TRGO, its parent graphite material and carbon black (a form of amorphous carbon) via transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry experiments. We used the data obtained as well as consideration of practical factors to perform a comparative assessment of the relative electrochemical performances of TRGO against amorphous carbon. We found out that TRGO and amorphous carbon exhibit almost identical characteristics in terms of density of defects in the sp(2) lattice and a similar crystallite size as determined by Raman spectroscopy. These two materials also exhibit similar amounts of oxygen containing groups as determined by XPS and nearly indistinguishable cyclic voltammetric response providing almost identical heterogeneous electron transfer constants. This leads us to conclude that for some sensing and energy storage electrochemical applications, the use of amorphous carbon might be a much more economical solution than the one requiring digestion of highly crystalline graphite with strong oxidants to graphite oxide and then thermally exfoliating it to thermally reduced graphene oxide.