Effects of Impurity Content on the Sintering Characteristics of Plasma-Sprayed Zirconia

Yttria-stabilized zirconia powders, containing different levels of SiO2 and Al2O3, have been plasma sprayed onto metallic substrates. The coatings were detached from their substrates and a dilatometer was used to monitor the dimensional changes they exhibited during prolonged heat treatments. It was found that specimens containing higher levels of silica and alumina exhibited higher rates of linear contraction, in both in-plane and through-thickness directions. The in-plane stiffness and the through-thickness thermal conductivity were also measured after different heat treatments and these were found to increase at a greater rate for specimens with higher impurity (silica and alumina) levels. Changes in the pore architecture during heat treatments were studied using Mercury Intrusion Porosimetry (MIP). Fine scale porosity (<_50 nm) was found to be sharply reduced even by relatively short heat treatments. This is correlated with improvements in inter-splat bonding and partial healing of intra-splat microcracks, which are responsible for the observed changes in stiffness and conductivity, as well as the dimensional changes

Synthesis and anticancer activity of epipolythiodiketopiperazine alkaloids

The epipolythiodiketopiperazine (ETP) alkaloids are a highly complex class of natural products with potent anticancer activity. Herein, we report the application of a flexible and scalable synthesis, allowing the construction of dozens of ETP derivatives. The evaluation of these compounds against cancer cell lines in culture allows for the first expansive structure–activity relationship (SAR) to be defined for monomeric and dimeric ETP-containing natural products and their synthetic cognates. Many ETP derivatives demonstrate potent anticancer activity across a broad range of cancer cell lines and kill cancer cells via induction of apoptosis. Several traits that bode well for the translational potential of the ETP class of natural products include concise and efficient synthetic access, potent induction of apoptotic cell death, activity against a wide range of cancer types, and a broad tolerance for modifications at multiple sites that should facilitate small-molecule drug development, mechanistic studies, and evaluation in vivo.National Institute of General Medical Sciences (U.S.) (Grant GM089732)American Society for Engineering Education. National Defense Science and Engineering Graduate FellowshipCamille & Henry Dreyfus Foundation. Teacher-Scholar Awards Progra

3-Chloro-4-hydroxy­furan-2(5H)-one

In the title compound, C4H3ClO3, mol­ecules are linked via O—H⋯O hydrogen bonds into an infinite chain with graph-set motif C(6) along the c axis

Recent Advances on the Halo- and Cyano-Trifluoromethylation of Alkenes and Alkynes

Incorporation of fluorine into organic molecules is a well-established strategy in the design of advanced materials, agrochemicals, and pharmaceuticals. Among numerous modern synthetic approaches, functionalization of unsaturated bonds with simultaneous addition of trifluoromethyl group along with other substituents is currently one of the most attractive methods undergoing wide-ranging development. In this review article, we discuss the most significant contributions made in this area during the last decade (2012−2021). The reactions reviewed in this work include chloro-, bromo-, iodo-, fluoro- and cyano-trifluoromethylation of alkenes and alkynes

K30, H150, and H168 Are Essential Residues for Coordinating Pyridoxal 5′-Phosphate of O-Acetylserine Sulfhydrylase from Acidithiobacillus ferrooxidans

O-acetylserine sulfhydrylase (OASS) is a key enzyme involved in the pathway of the cysteine biosynthesis. The gene of OASS from Acidithiobacillus ferrooxidans ATCC 23270 was cloned and expressed in E. coli, the soluble protein was purified by one-step affinity chromatography to apparent homogeneity. Colors and UV–vis scanning results of the recombinant protein confirmed that it was a pyridoxal 5′-phosphate (PLP)-containing protein. Sequence alignment and site-directed mutation of the enzyme revealed that the cofactor PLP is covalently bound in Schiff base linkage with K30, as well as the two residues H150 and H168 were the crucial residues for PLP binding and stabilization

Rational Design Principles for De Novo α-Helical Peptide Barrels with Dynamic Conductive Channels

Despite advances in peptide and protein design, the rational design of membrane-spanning peptides that form conducting channels remains challenging due to our imperfect understanding of the sequence-to-structure relationships that drive membrane insertion, assembly, and conductance. Here, we describe the design and computational and experimental characterization of a series of coiled coil-based peptides that form transmembrane α-helical barrels with conductive channels. Through a combination of rational and computational design, we obtain barrels with 5 to 7 helices, as characterized in detergent micelles. In lipid bilayers, these peptide assemblies exhibit two conductance states with relative populations dependent on the applied potential: (i) low-conductance states that correlate with variations in the designed amino-acid sequences and modeled coiled-coil barrel geometries, indicating stable transmembrane α-helical barrels; and (ii) high-conductance states in which single channels change size in discrete steps. Notably, the high-conductance states are similar for all peptides in contrast to the low-conductance states. This indicates the formation of large, dynamic channels, as observed in natural barrel-stave peptide channels. These findings establish rational routes to design and tune functional membrane-spanning peptide channels with specific conductance and geometry

Alkyne-tag Raman imaging and sensing of bioactive compounds

An alkyne is an unsaturated hydrocarbon characterized by the presence of at least one C≡C bond. Alkyne groups generate a strong Raman peak in the cellular-silent region, a region between 1,800 and 2,800 cm−1 where endogenous molecules do not produce a Raman signal. As a result, alkynes are regularly used as tags to label and visualize small molecules in live cells using Raman microscopy, a method referred to as alkyne-tag Raman imaging (ATRI). ATRI has been applied to various compounds to enable their cellular localization and, recently, alkyne-tagged compounds have been used as Raman sensors to detect intracellular biomolecules, such as metal ions or reactive oxygen species. ATRI has unique advantages over existing methods for localizing small molecules intracellularly, such as enabling super-multiplex detection and incurring a smaller impact on labelled compounds. In this Primer, we describe the principles and key techniques involved in ATRI, including the design of alkyne-tagged molecules, sample preparation and the set-up of Raman microscopes. We showcase the demonstration and application of ATRI, encompassing the development of responsive alkyne-tagged compounds for sensing biomolecules. Finally, we discuss the limitations and potential applications of ATRI, shedding light on the future possibilities of this method

Color-scalable flow cytometry with Raman tags

Flow cytometry is an indispensable tool in biology and medicine for counting and analyzing cells in large heterogeneous populations. It identifies multiple characteristics of every single cell, typically via fluorescent probes that specifically bind to target molecules on the cell surface or within the cell. However, flow cytometry has a critical limitation: the color barrier. The number of chemical traits that can be simultaneously resolved is typically limited to several due to the spectral overlap between fluorescence signals from different fluorescent probes. Here, we present color-scalable flow cytometry based on coherent Raman flow cytometry with Raman tags to break the color barrier. This is made possible by combining a broadband Fourier-transform coherent anti-Stokes Raman scattering (FT-CARS) flow cytometer, resonance-enhanced cyanine-based Raman tags, and Raman-active dots (Rdots). Specifically, we synthesized 20 cyanine-based Raman tags whose Raman spectra are linearly independent in the fingerprint region (400 to 1,600 cm-1). For highly sensitive detection, we produced Rdots composed of 12 different Raman tags in polymer nanoparticles whose detection limit was as low as 12 nM for a short FT-CARS signal integration time of 420 µs. We performed multiplex flow cytometry of MCF-7 breast cancer cells stained by 12 different Rdots with a high classification accuracy of 98%. Moreover, we demonstrated a large-scale time-course analysis of endocytosis via the multiplex Raman flow cytometer. Our method can theoretically achieve flow cytometry of live cells with >140 colors based on a single excitation laser and a single detector without increasing instrument size, cost, or complexity

Total synthesis of natural derivatives and artificial analogs of 13-oxyingenol and their biological evaluation

We have established an efficient synthetic methodology for the 13-oxyingenol natural derivative (13-oxyingenol-13-dodecanoate-20-hexanoate), featuring a ring-closing olefin metathesis reaction for the “direct” construction of a highly strained inside–outside framework and a Mislow–Evans-type [2,3]-sigmatropic rearrangement for the stereoselective introduction of the hydroxy group at C5. We also synthesized artificial analogs of 13-oxyingenol and ingenol by using our synthetic strategy. In vitro activation assays of protein kinase C (PKC) α and δ revealed that the dodecanoyl group at O13 on 13-oxyingenol analogs had a significant role in PKCδ activation. The PKCα- or PKCδ-activating 13-oxyingenol and ingenol analogs induced both distinct morphological changes and increases of CD11b expression in HL-60 cells, which would be typical signs of HL-60 cell differentiation to macrophage-like cells, as expected by previous reports. Intriguingly, however, similar differentiation phenotypes were observed with the use of 13-oxyingenol natural derivatives and 13-oxyingenol-13-dodecanoate showing a remarkably less potent PKCα or PKCδ activation ability, which the PKC inhibitor Gö6983 diminished. This indicated the involvement of other PKC isozymes or related kinase activities. 13-Oxyingenol analogs, which induced HL-60 cell differentiation, also induced HL-60 cell death, similar to the action of a phorbol ester, a strong PKC activator