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Concept: X-ray crystallography


During the beer brewing process, bitter tasting cis and trans iso-α-acids are generated from the precursor α-acids found in hops. The absolute configurations of the α-acid (-)-humulone and several of its derivatives have now been elucidated by X-ray crystallography, thus resolving decades of confusion over the humulone isomerization mechanism.

Concepts: X-ray, X-ray crystallography, Brewing, Beer, Hops, Brewery


Cyan variants of green fluorescent protein are widely used as donors in Förster resonance energy transfer experiments. The popular, but modestly bright, Enhanced Cyan Fluorescent Protein (ECFP) was sequentially improved into the brighter variants Super Cyan Fluorescent Protein 3A (SCFP3A) and mTurquoise, the latter exhibiting a high-fluorescence quantum yield and a long mono-exponential fluorescence lifetime. Here we combine X-ray crystallography and excited-state calculations to rationalize these stepwise improvements. The enhancement originates from stabilization of the seventh β-strand and the strengthening of the sole chromophore-stabilizing hydrogen bond. The structural analysis highlighted one suboptimal internal residue, which was subjected to saturation mutagenesis combined with fluorescence lifetime-based screening. This resulted in mTurquoise2, a brighter variant with faster maturation, high photostability, longer mono-exponential lifetime and the highest quantum yield measured for a monomeric fluorescent protein. Together, these properties make mTurquoise2 the preferable cyan variant of green fluorescent protein for long-term imaging and as donor for Förster resonance energy transfer to a yellow fluorescent protein.

Concepts: DNA, Protein, Fluorescence, Oxygen, Green fluorescent protein, X-ray crystallography, Linus Pauling, Yellow fluorescent protein


Scanning small and wide angle X-ray scattering (scanning SWAXS) experiments were performed on healthy and pathologic human bone sections. Via crystallographic tools the data were transformed into quantitative images and as such compared with circularly polarized light (CPL) microscopy images. SWAXS and CPL images allowed extracting information of the mineral nanocrystalline phase embedded, with and without preferred orientation, in the collagen fibrils, mapping local changes at sub-osteon resolution. This favorable combination has been applied for the first time to biopsies of dwarfism syndrome and Paget’s disease to shed light onto the cortical structure of natural bone in healthy and pathologic sections.

Concepts: Optics, Electromagnetic radiation, Scattering, X-ray crystallography, Polarization, Circular polarization, Linear polarization


The recent elucidation of the X-ray structure of several class A GPCRs clearly indicates that the amphipathic helix 8 (H8) is a conserved structural domain in most crystallized GPCRs. Very little is known about the presence and the possible role of an analogous H8 domain in the distantly related class C GPCRs. In this study, we investigated the structural properties for the H8 domain of the mGluR2 receptor, a class C GPCR, by applying extended molecular dynamics simulations. Our study indicates that the amphipathic H8 adopts membrane-sensitive conformational states, which depend on the membrane composition. Cholesterol-rich membranes stabilize the helical structure of H8 whereas cholesterol-depleted membranes induce a disruption of H8. The observed link between membrane cholesterol levels and H8 conformational states suggests that H8 behaves as a sensor of cholesterol concentration.

Concepts: Protein structure, Cell membrane, Receptor, Membrane biology, Metabotropic glutamate receptor, X-ray crystallography, Knowledge, Alpha helix


Ordered CuIn(1 - x)GaxSe2 (CIGS) nanopore films were prepared by one-step electrodeposition based on porous anodized aluminum oxide templates. The as-grown film shows a highly ordered morphology that reproduces the surface pattern of the substrate. Raman spectroscopy and X-ray diffraction pattern show that CIGS nanopore films had ideal chalcopyrite crystallization. Energy dispersive spectroscopy reveals the Cu-Se phases firstly formed in initial stage of growth. Then, indium and gallium were incorporated in the nanopore films in succession. Cu-Se phase is most likely to act as a growth promoter in the growth progress of CIGS nanopore films. Due to the high surface area and porous structure, this kind of CIGS films could have potential application in light-trapping CIGS solar cells and photo electrochemical water splitting.

Concepts: DNA, Spectroscopy, Diffraction, X-ray, Electromagnetic radiation, Hydrogen, X-ray crystallography, Copper indium gallium selenide


We have investigated the influences of aluminum and gallium dopants (0 to 2.0 mol%) on zinc oxide (ZnO) thin films regarding crystallization and electrical and optical properties for application in transparent conducting oxide devices. Al- and Ga-doped ZnO thin films were deposited on glass substrates (corning 1737) by sol–gel spin-coating process. As a starting material, AlCl3.6H2O, Ga(NO3)2, and Zn(CH3COO)2.2H2O were used. A lowest sheet resistance of 3.3 x 103 [greek capital letter omega]/[white square] was obtained for the GZO thin film doped with 1.5 mol% of Ga after post-annealing at 650 [degree sign]C for 60 min in air. All the films showed more than 85 % transparency in the visible region. We have studied the structural and microstructural properties as a function of Al and Ga concentrations through X-ray diffraction and scanning electron microscopy analysis. In addition, the optical bandgap and photoluminescence were estimated.

Concepts: Electron, X-ray, Optical fiber, Aluminium, Zinc, X-ray crystallography, Scanning electron microscope, Zinc oxide


Serial femtosecond crystallography (SFX) takes advantage of extremely bright and ultrashort pulses produced by x-ray free-electron lasers (XFELs), allowing for the collection of high-resolution diffraction intensities from micrometer-sized crystals at room temperature with minimal radiation damage, using the principle of “diffraction-before-destruction.” However, de novo structure factor phase determination using XFELs has been difficult so far. We demonstrate the ability to solve the crystallographic phase problem for SFX data collected with an XFEL using the anomalous signal from native sulfur atoms, leading to a bias-free room temperature structure of the human A2A adenosine receptor at 1.9 Å resolution. The advancement was made possible by recent improvements in SFX data analysis and the design of injectors and delivery media for streaming hydrated microcrystals. This general method should accelerate structural studies of novel difficult-to-crystallize macromolecules and their complexes.

Concepts: Diffraction, X-ray, Crystallography, Fundamental physics concepts, Laser, X-ray crystallography, Neutron diffraction, Free electron laser


CeB2O4F is the first cerium fluoride borate, which is exclusively built up of one-dimensional, infinite chains of condensed trigonal-planar [BO3](3-) groups. This new cerium fluoride borate was synthesized under high-pressure/high-temperature conditions of 0.9 GPa and 1450 °C in a Walker-type multianvil apparatus. The compound crystallizes in the orthorhombic space group Pbca (No. 61) with eight formula units and the lattice parameters a=821.63(5), b=1257.50(9), c=726.71(6) pm, V=750.84(9) Å(3), R 1=0.0698, and wR 2=0.0682 (all data). The structure exhibits a 9+1 coordinated cerium ion, one three-fold coordinated fluoride ion and a one-dimensional chain of [BO3](3-) groups. Furthermore, IR spectroscopy, Electron Micro Probe Analysis and temperature-dependent X-ray powder diffraction measurements were performed.

Concepts: Diffraction, Crystallography, Materials science, X-ray crystallography, Crystal system, Powder diffraction, Neutron diffraction, Crystallographic database


In the present study, novel ultradeformable liposomes (menthosomes; MTS), deformable liposomes (transfersomes; TFS) and conventional liposomes (CLP) were compared in their potential for transdermal delivery of meloxicam (MX). MTS, TFS and CLP were investigated for size, size distribution, zeta potential, elasticity, entrapment efficiency and stability. In vitro skin permeation using hairless mice skin was evaluated. Vesicular morphology was observed under freeze-fractured transmission electron microscopy (FF-TEM). Intrinsic thermal properties were performed using differential scanning calorimetry (DSC) and X-ray diffraction. The skin permeation mechanism was characterized using confocal laser scanning microscopy (CLSM). The results indicated that the difference in physicochemical characteristics of MTS, TFS and CLP affected the skin permeability. MTS and TFS showed higher flux of MX than CLP. CLSM image showed deformable vesicles mechanism for delivery of MX across the hairless mice skin. Our study suggested that ultradeformable and deformable liposomes (MTS and TFS) had a potential to use as transdermal drug delivery carriers for MX.

Concepts: Electron, Diffraction, X-ray, Transdermal patch, X-ray crystallography, Differential scanning calorimetry, Scientific techniques, Transmission electron microscopy


Increasing the data acquisition rate of X-ray diffraction images for macromolecular crystals at room temperature at synchrotrons has the potential to significantly accelerate both structural analysis of biomolecules and structure-based drug developments. Using lysozyme model crystals, we demonstrated the rapid acquisition of X-ray diffraction datasets by combining a high frame rate pixel array detector with ultrasonic acoustic levitation of protein crystals in liquid droplets. The rapid spinning of the crystal within a levitating droplet ensured an efficient sampling of the reciprocal space. The datasets were processed with a program suite developed for serial femtosecond crystallography (SFX). The structure, which was solved by molecular replacement, was found to be identical to the structure obtained by the conventional oscillation method for up to a 1.8-Å resolution limit. In particular, the absence of protein crystal damage resulting from the acoustic levitation was carefully established. These results represent a key step towards a fully automated sample handling and measurement pipeline, which has promising prospects for a high acquisition rate and high sample efficiency for room temperature X-ray crystallography.

Concepts: DNA, Diffraction, X-ray, Crystallography, X-ray crystallography, Powder diffraction, Neutron diffraction, Bragg's law