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Over the last decade, Macromolecular crystallography (MX) has advanced significantly by developing brilliant micro-focus beamlines, highly sensitive and rapid-readout detectors, and sophisticated data collection systems. Automated data collection has made it possible to efficiently collect large amounts of diffraction data from microcrystals, which would be impossible to achieve manually. This has enabled high-resolution structural analysis of ultra-small crystals, efficient screening of compounds, and new MXs for structural dynamics analysis in crystal fields.

The diffusion limitations on gas storage and catalytic reaction of microporous materials can often be overcome if they are incorporated into a mesoporous structure with much larger pores. Shen et al. grew ordered arrays of microcrystals of the ZIF-8 metal-organic framework, in which zinc ions are bridged by 2-methylimidazole linkers, inside a porous polystyrene template. These materials showed higher reaction rates for the Knoevenagel reaction between benzaldehydes and malononitriles and better catalyst recyclability. Science , this issue p. 206 A double-solvent method and templating are used to grow ordered arrays of metal-organic framework microcrystals. We constructed highly oriented and ordered macropores within metal-organic framework (MOF) single crystals, opening up the area of three-dimensional–ordered macro-microporous materials (that is, materials containing both macro- and micropores) in single-crystalline form. Our methodology relies on the strong shaping effects of a polystyrene nanosphere monolith template and a double-solvent–induced heterogeneous nucleation approach. This process synergistically enabled the in situ growth of MOFs within ordered voids, rendering a single crystal with oriented and ordered macro-microporous structure. The improved mass diffusion properties of such hierarchical frameworks, together with their robust single-crystalline nature, endow them with superior catalytic activity and recyclability for bulky-molecule reactions, as compared with conventional, polycrystalline hollow, and disordered macroporous ZIF-8.

Controlling the upconversion luminescence (UCL) intensity ratio, especially pumped at 808 nm, is of fundamental importance in biological applications due to the water molecules exhibiting low absorption at this excitation wavelength. In this work, a series of β-NaYbF4:Er microrods were synthesized by a simple one-pot hydrothermal method and their intense green (545 nm) and red (650 nm) UCL were experimentally investigated based on the single-particle level under the excitation of 808 nm continuous-wave (CW) laser. Interestingly, the competition between the green and red UCL can be observed in highly Yb3+-doped microcrystals as the excitation intensity gradually increases, which leads to the UCL color changing from green to orange. However, the microcrystals doped with low Yb3+ concentration keep green color which is independent of the excitation power. Further investigations demonstrate that the cross-relaxation (CR) processes between Yb3+ and Er3+ ions result in the UCL competition.

Thermal management is the most critical technology challenge for modern electronics. Recent key materials innovation focuses on developing advanced thermal interface of electronic packaging for achieving efficient heat dissipation. Here, for the first time we report a record-high performance thermal interface beyond the current state of the art, based on self-assembled manufacturing of cubic boron arsenide (s-BAs). The s-BAs exhibits highly desirable characteristics of high thermal conductivity up to 21 W/m·K and excellent elastic compliance similar to that of soft biological tissues down to 100 kPa through the rational design of BAs microcrystals in polymer composite. In addition, the s-BAs demonstrates high flexibility and preserves the high conductivity over at least 500 bending cycles, opening up new application opportunities for flexible thermal cooling. Moreover, we demonstrated device integration with power LEDs and measured a superior cooling performance of s-BAs beyond the current state of the art, by up to 45 °C reduction in the hot spot temperature. Together, this study demonstrates scalable manufacturing of a new generation of energy-efficient and flexible thermal interface that holds great promise for advanced thermal management of future integrated circuits and emerging applications such as wearable electronics and soft robotics. Well-developed prototype interface materials for electronics thermal management are limited to a low thermal conductivity or high elastic modulus. Here, the authors report flexible thermal interfaces through self-assembled manufacturing of polymetric composites based on the high thermal conductivity of cubic boron arsenide.

Chiral phonons are concerted mirror-symmetric movements of atomic groups connected by covalent and intermolecular bonds. Such lattice vibrations in crystals of biomolecules should be highly specific to their short- and long-range organizations, but their chiroptical signatures and structure–property relationships remain uncertain. Here we show that terahertz chiroptical spectroscopy enables the registration and attribution of chiral phonons for microscale and nanoscale crystals of amino acids and peptides. Theoretical analysis and computer simulations indicate that sharp mirror-symmetric bands observed for left- and right-handed enantiomers originate from the collective vibrations of biomolecules interconnected by hydrogen bonds into helical chains. The sensitivity of chiral phonons to minute structural changes can be used to identify physical and chemical differences in seemingly identical formulations of dipeptides used in health supplements. The generality of these findings is demonstrated by chiral phonons observed for amyloid nanofibrils of insulin. Their spectral signatures and polarization rotation strongly depend on their maturation stage, which opens a new door for medical applications of terahertz photonics.Chiral phonons—long-range lattice vibrations with rotational motion of atoms—are observed by terahertz chiroptical spectroscopy in biocrystals. Terahertz circular dichroism peaks between 0.2 and 2.0 THz clearly identify the chirality of these phonons in various microcrystalline and nanofibrils of biomolecules.

Zinc oxide is an essential ingredient of many enzymes, sun screens, and ointments for pain and itch relief. Its microcrystals are very efficient light absorbers in the UVA and UVB region of spectra due to wide bandgap. Impact of zinc oxide on biological functions depends on its morphology, particle size, exposure time, concentration, pH, and biocompatibility. They are more effective against microorganisms such as Bacillus subtilis , Bacillus megaterium , Staphylococcus aureus , Sarcina lutea , Escherichia coli , Pseudomonas aeruginosa , Klebsiella pneumonia , Pseudomonas vulgaris , Candida albicans , and Aspergillus niger . Mechanism of action has been ascribed to the activation of zinc oxide nanoparticles by light, which penetrate the bacterial cell wall via diffusion. It has been confirmed from SEM and TEM images of the bacterial cells that zinc oxide nanoparticles disintegrate the cell membrane and accumulate in the cytoplasm where they interact with biomolecules causing cell apoptosis leading to cell death.

In this work, a novel crystal growth method termed suspended drop crystallization has been developed. Unlike traditional methods, this technique involves mixing protein and precipitant directly on an electron microscopy grid without any additional support layers. The grid is then suspended within a crystallization chamber designed in-house, allowing for vapor diffusion to occur from both sides of the drop. A UV-transparent window above and below the grid enables the monitoring of crystal growth via light, UV or fluorescence microscopy. Once crystals have formed, the grid can be removed and utilized for X-ray crystallography or microcrystal electron diffraction (MicroED) directly without having to manipulate the crystals. To demonstrate the efficacy of this method, crystals of the enzyme proteinase K were grown and its structure was determined by MicroED following focused ion beam/scanning electron microscopy milling to render the sample thin enough for cryoEM. Suspended drop crystallization overcomes many of the challenges associated with sample preparation, providing an alternative workflow for crystals embedded in viscous media, sensitive to mechanical stress and/or subject to preferred orientation on electron microscopy grids.

In 2013 we established a cryo-electron microscopy (cryo-EM) technique called microcrystal electron diffraction (MicroED). Since that time, data collection and analysis schemes have been fine-tuned, and structures for more than 40 different proteins, oligopeptides and organic molecules have been determined. Here we review the MicroED technique and place it in context with other structure-determination methods. We showcase example structures solved by MicroED and provide practical advice to prospective users.This paper reviews the cryo-EM technique of microcrystal electron diffraction (MicroED), providing a broad overview of the technique, the unique structures determined, and the opportunities for future development.

A structure of the murine voltage-dependent anion channel (VDAC) was determined by microcrystal electron diffraction (MicroED). Microcrystals of an essential mutant of VDAC grew in a viscous bicelle suspension, making it unsuitable for conventional X-ray crystallography. Thin, plate-like crystals were identified using scanning-electron microscopy (SEM). Crystals were milled into thin lamellae using a focused-ion beam (FIB). MicroED data were collected from three crystal lamellae and merged for completeness. The refined structure revealed unmodeled densities between protein monomers, indicative of lipids that likely mediate contacts between the proteins in the crystal. This body of work demonstrates the effectiveness of milling membrane protein microcrystals grown in viscous media using a focused ion beam for subsequent structure determination by MicroED. This approach is well suited for samples that are intractable by X-ray crystallography. To our knowledge, the presented structure is a previously undescribed mutant of the membrane protein VDAC, crystallized in a lipid bicelle matrix and solved by MicroED.