Solving the Jigsaw puzzle of phytosterol diversity by a novel sterol methyltransferase from Zea mays.

Phytosterols are vital structural and regulatory components in plants. Zea mays produces a series of phytosterols that are specific to corn. However, the underline biosynthetic mechanism remains elusive. In this study, we identified a novel sterol methyltransferase from Z. mays (ZmSMT1-2) which showed a unique feature compared with documented plant SMTs. ZmSMT1-2 showed a substrate preference for cycloartenol. Using S-adenosyl-L-methionine (AdoMet) as a donor, ZmSMT1-2 converted cycloartenol into alkylated sterols with unique side-chain architectures, including Δ25(27) (i.e., cyclolaudenol and cycloneolitsol) and Δ24(25) (i.e., cyclobranol) sterols. Cycloneolitsol is identified as a product of SMTs for the first time. Our discovery provides a previously untapped mechanism for phytosterol biosynthesis and adds another layer of diversity of sterol biosynthesis.

Serum fat-soluble vitamin levels may be related to sudden sensorineural hearing loss.

BACKGROUND: Few related studies reported yet the association between vitamins and the onset of sudden sensorineural hearing loss (SSNHL). OBJECTIVE: To explore the relationship between the serum levels of fat-soluble vitamins A, D, and E and the risk of SSNHL. METHODS: This retrospective analysis included 310 SSNHL patients and 154 people without risk of hearing loss. The demographic information of all participants like age, gender, body mass index, occupation, cigarette smoking or drinking status, etc. were recorded. The serum levels of vitamins A, D, and E were determined using the electrochemical method. RESULTS: The results indicated that serum vitamin D levels in SSNHL patients were significantly lower. Vitamin D deficiency was only observed in SSNHL group. Similarly, serum vitamin A levels in female SSNHL patients were significantly lower than the control group. Meanwhile, serum vitamin E levels in male SSNHL patients were significantly lower than the control group. CONCLUSION AND SIGNIFICANCE: Our results revealed that the serum levels of fat-soluble vitamins A, D, and E in SSNHL patients were lower than those in the control group with normal hearing, indicating that the decrease of serum fat-soluble vitamins may be related to SSNHL pathogenesis.

Sequential Modifications of Metal-Organic Layer Nodes for Highly Efficient Photocatalyzed Hydrogen Atom Transfer.

Herein, we report the synthesis of a bifunctional photocatalyst, Zr-OTf-EY, through sequential modifications of metal cluster nodes in a metal-organic layer (MOL). With eosin Y and strong Lewis acids on the nodes, Zr-OTf-EY catalyzes cross-coupling reactions between various C-H compounds and electron-deficient alkenes or azodicarboxylate to afford C-C and C-N coupling products, with turnover numbers of up to 1980. In Zr-OTf-EY-catalyzed reactions, Lewis acid sites bind the alkenes or azodicarboxylate to increase their local concentrations and electron deficiency for enhanced radical additions, while EY is stabilized by site isolation on the MOL to afford a long-lived catalyst for hydrogen atom transfer. The proximity between photostable EY sites and Lewis acids on the nodes of Zr-OTf-EY enhances the catalytic efficiency by approximately 400 times over the homogeneous counterpart in the cross-coupling reactions.

Modulating Energy Transfer and Light-Emitting Colors by Chiral Dye Exchange and Achiral-to-Chiral Dye Conversion.

New chiral and achiral dyes were synthesized by using clean, highly efficient Diels-Alder 'click' reactions. We prepared pure endo- and exo- stereoisomers and blue-light-emitting single crystal of an exo-isomer. 1 H NMR spectroscopy and single-crystal X-ray diffraction reveal the precise spatial configurations of endo- and exo-dye stereoisomers. Single-crystal X-ray diffraction results reveal the dynamic nature of Diels-Alder covalent bonds. By reversible formation and cleavage of dynamic covalent bonds, an achiral dye was converted to a chiral dye, where achiral dansyl dye moiety was replaced by chiral moiety. Before achiral-to-chiral dye conversion, the dye system displayed dansyl acceptor green light-emitting color due to intramolecular fluorescence resonance energy transfer, where the blue emission of pyrene donor fluorophore was not observed. After achiral-to-chiral dye conversion, light-emitting colors of dye system change from green to blue, where the pyrene-to-dansyl fluorophore energy transfer was suppressed, and pyrene fluorophore blue emission was restored. Chiral transfer occurs in a chiral dye solid from non-chromophore alky chirality to pyrene chromophore. Thus, the chiral dye solid displayed chiral optical behaviors, i. e., circular dichroism and circularly polarized luminescence.

Cardiac PDGFRα+ interstitial cells generate spontaneous inward currents that contribute to excitability in the heart.

The cell types and conductance that contribute to normal cardiac functions remain under investigation. We used mice that express an enhanced green fluorescent protein (eGFP)-histone 2B fusion protein driven off the cell-specific endogenous promoter for Pdgfra to investigate the distribution and functional role of PDGFRα+ cells in the heart. Cardiac PDGFRα+ cells were widely distributed within the endomysium of atria, ventricle, and sino-atrial node (SAN) tissues. PDGFRα+ cells formed a discrete network of cells, lying in close apposition to neighboring cardiac myocytes in mouse and Cynomolgus monkey (Macaca fascicularis) hearts. Expression of eGFP in nuclei allowed unequivocal identification of these cells following enzymatic dispersion of muscle tissues. FACS purification of PDGFRα+ cells from the SAN and analysis of gene transcripts by qPCR revealed that they were a distinct population of cells that expressed gap junction transcripts, Gja1 and Gjc1. Cardiac PDGFRα+ cells generated spontaneous transient inward currents (STICs) and spontaneous transient depolarizations (STDs) that reversed at 0 mV. Reversal potential was maintained when ECl = -40 mV. [Na+ ]o replacement and FTY720 abolished STICs, suggesting they were due to a non-selective cation conductance (NSCC) carried by TRPM7. PDGFRα+ cells also express ß2 -adrenoceptor gene transcripts, Adrb2. Zinterol, a selective ß2 -receptor agonist, increased the amplitude and frequency of STICs, suggesting these cells could contribute to adrenergic regulation of cardiac excitability. PDGFRα+ cells in cardiac muscles generate inward currents via an NSCC. STICs generated by these cells may contribute to the integrated membrane potentials of cardiac muscles, possibly affecting the frequency of pacemaker activity.

Molecular Engineering of Metal-Organic Layers for Sustainable Tandem and Synergistic Photocatalysis.

Metal-organic layers (MOLs), a monolayered version of metal-organic frameworks (MOFs), have recently emerged as a novel two-dimensional molecular material platform to design multifunctional catalysts. MOLs inherit the intrinsic molecular tunability of MOFs and yet have more accessible and modifiable building blocks. Here we report molecular engineering of six MOLs via modulated solvothermal synthesis between HfCl4 and three photosensitizing ligands followed by postsynthetic modification with two carboxylate-containing cobaloximes for tandem and synergistic photocatalysis. Morphological and structural characterization by transmission electron microscopy and atomic force microscopy and compositional analysis by inductively coupled plasma-mass spectrometry and nuclear magnetic resonance spectroscopy establish the MOLs as flat nanoplates with a periodic lattice structure of hexagonal symmetry. The MOLs efficiently catalyze tandem dehydrogenative coupling reactions and synergistic Heck-type coupling reactions. The most active MOL catalyst was used for the gram-scale synthesis of vesnarinone, a cardiotonic agent, in 80% yield with a turnover number of 400 and in eight consecutive reaction cycles without significant loss of activities.

Suppressing Nonradiative Recombination by Electron-Donating Substituents in 2D Conjugated Triphenylamine Polymers toward Efficient Perovskite Optoelectronics.

Highly efficient perovskite optoelectronics (POEs) have been limited by nonradiative recombination. We report a strategy to inhibit the nonradiative recombination of 2D triphenylamine polymers in the hole transport layer (HTL) via introducing electron-donating groups to enhance the conjugation effect and electron cloud density. The conjugated systems with electron-donating groups present smaller energy level oscillation compared to the ones with electron-absorbing groups, as confirmed by nonadiabatic molecular dynamics (NAMD) calculation. Further study reveals that the introduction of low-frequency phonons in the electron-donating group systems shortens the nonadiabatic coupling and inhibits the nonradiative recombination. Such electron-donating groups can decrease the valence band maximum of 2D polymers and promote hole transport. Our report provides a new design strategy to suppress nonradiative recombination in HTL for application in efficient POEs.

Design of an Intron-Retained Bioluminescence Reporter and its Application in Imaging of Pre-mRNA Splicing in Living Subjects.

Aberrant splicing of precursor messenger RNA (pre-mRNA) can generate abnormal transcripts, and most of the human diseases have been shown to associate with abnormal splicing of pre-mRNA. Conventional methods require sample lysis and thus cannot be used for monitoring pre-mRNA splicing in real time. This chapter guides how to develop an intron-retained bioluminescence (BL) reporter, which simulates the splicing process of pre-mRNA in vitro and in vivo noninvasively. In the following, we illustrate the design and construction of RLuc-intron and the methods of BL experiments in vitro and in vivo. The exemplified results show that our reporter is suitable for high-throughput screening of splicing inhibitors for the therapies of the diseases caused by aberrant splicing.

Site Isolation in Metal-Organic Layers Enhances Photoredox Gold Catalysis.

Herein, we report the synthesis of a metal-organic layer, Hf-Ru-Au, containing Ru(bipyridine)32+-type photosensitizers and (phosphine)-AuCl catalysts for photoredox Au-catalyzed cross-coupling of allenoates, alkenes, or alkynes with aryldiazonium salts to afford furanone, tetrahydrofuran, or aryl alkyne derivatives, respectively. Site isolation of (phosphine)-AuCl complexes in Hf-Ru-Au prevents Au catalyst deactivation via ligand redistribution, Au(I) disproportionation, and aryl-phosphine reductive elimination, while the proximity between the Ru photosensitizers and Au catalysts enhances catalytic efficiency, with 14-200 times higher activity over those of the homogeneous controls in the cross-coupling reactions.

Endoscopic type 1 tympanoplasty: comparison of the effects of three different thicknesses grafts.

BACKGROUND: The effects of graft thickness on tympanoplasty is uncertain. OBJECTIVE: To compare the results of endoscopic tympanoplasty using different thicknesses of autologous tissues. METHODS: This retrospective analysis included 186 patients who received type I tympanoplasty, divided into three main groups based of grafting material: perichondrium (A), cartilage-perichondrium (B), or cartilage-perichondrium plus additional perichondrium (C). Group A was subdivided based on whether the placement was inside (A1) or outside (A2) of the malleus. The hearing improvement, graft success rate, and surgery duration were analysed. RESULTS: Statistical analysis showed significant hearing improvement in the three main groups (p < .001); recovery in group A occurred the earliest. Six months postoperatively, group A1 showed significantly greater hearing recovery compared with groups B and C (p < .05). There were no statistical differences the other groups (p > .05) or in the graft success rate among the three main groups (p = .235). The surgery duration of group A was significantly longer than that of groups B and C (p < .001). CONCLUSION AND SIGNIFICANCE: Our results suggest that graft thickness affects hearing recovery; however, graft thickness does not affect the rate of grafting success. Endoscopic transplantation of the perichondrium is more difficult and requires more time.

Dynamic visualization of mRNA splicing variants with a transactivating reporter.

Dynamic changes in intron sequences, with their loss and gain, are poorly detected due to the limited methods for the non-invasive monitoring of the pre-mRNA splicing process. Here, we describe the design of a two-step transcriptional activation (TSTA) reporter for the real-time imaging of the splicing process in living subjects. By taking advantage of the strong transactivating properties of the GAL4-VP16 fusion protein, which can target upstream activation sequence (UAS) elements to boost subsequent firefly luciferase reporter gene expression, we successfully and consistently detected the dynamic pre-mRNA splicing activity in response to exogenous splicing modulators in living cells and animals. Our findings provide a valuable tool for the high-throughput screening of splicing modulators, which could speed up the development of new drugs for the treatment of disordered splicing diseases.

Brønsted Acid Catalyzed Oxocarbenium-Olefin Metathesis/Rearrangements of 1H-Isochromene Acetals with Vinyl Diazo Compounds.

An oxocarbenium-olefin cross metathesis occurs during Brønsted acid catalyzed reactions of 1H-isochromene acetals with vinyl diazo compounds. Formally a carbonyl-alkene [2 + 2]-cyclization between isobenzopyrylium ions and the vinyl group of vinyl diazoesters, the retro-[2 + 2] cycloaddition produces a tethered alkene and a vinyl diazonium ion that, upon loss of dinitrogen, undergoes a highly selective carbocationic cascade rearrangements to diverse products whose formation is controlled by reactant substituents. Polysubstituted benzobicyclo[3.3.1]oxocines, benzobicyclo[3.2.2]oxepines, benzobicyclopropane, and naphthalenes are obtained in good to excellent yields and selectivities. Furthermore, isotopic tracer and control experiments shed light on the oxocarbenium-olefin metathesis/rearrangement process as well as on the origin of the interesting substituent-dependent selectivity.

Correction: Dynamic visualization of mRNA splicing variants with a transactivating reporter.

Correction for 'Dynamic visualization of mRNA splicing variants with a transactivating reporter' by Si Chen et al., Chem. Commun., 2021, DOI: 10.1039/d1cc02439f.

Intermolecular [5 + 1]-Cycloaddition between Vinyl Diazo Compounds and tert-Butyl Nitrite to 1,2,3-Triazine 1-Oxides and Their Further Transformation to Isoxazoles.

1,2,3-Triazine 1-oxides are formed by nitrosyl addition from tert-butyl nitrite to the vinylogous position of vinyl diazo compounds. This transformation, which is a formal intermolecular [5 + 1] cycloaddition, occurs under mild conditions, with high functional group tolerance and regioselectivity, and can be employed for late-stage functionalization. Upon heating at refluxing chlorobenzene temperature, these triazine-N-oxides undergo dinitrogen extrusion to form isoxazoles in very high yields.

Formal [4 + 4]-, [4 + 3]-, and [4 + 2]-cycloaddition reactions of donor-acceptor cyclobutenes, cyclopropenes and siloxyalkynes induced by Brønsted acid catalysis.

Brønsted acid catalyzed formal [4 + 4]-, [4 + 3]-, and [4 + 2]-cycloadditions of donor-acceptor cyclobutenes, cyclopropenes, and siloxyalkynes with benzopyrylium ions are reported. [4 + 2]-cyclization/deMayo-type ring-extension cascade processes produce highly functionalized benzocyclooctatrienes, benzocycloheptatrienes, and 2-naphthols in good to excellent yields and selectivities. Moreover, the optical purity of reactant donor-acceptor cyclobutenes is fully retained during the cascade. The 1,3-dicarbonyl product framework of the reaction products provides opportunities for salen-type ligand syntheses and the construction of fused pyrazoles and isoxazoles that reveal a novel rotamer-diastereoisomerism.

Generation of Diazomethyl Radicals by Hydrogen Atom Abstraction and Their Cycloaddition with Alkenes.

A general catalytic methodology for the synthesis of pyrazolines from α-diazo compounds and conjugated alkenes is reported. The direct hydrogen atom transfer (HAT) process of α-diazo compounds promoted by the tert-butylperoxy radical generates electrophilic diazomethyl radicals, thereby reversing the reactivity of the carbon atom attached with the diazo group. The regiocontrolled addition of diazomethyl radicals to carbon-carbon double bonds followed by intramolecular ring closure on the terminal diazo nitrogen and tautomerization affords a diverse set of pyrazolines in good yields with excellent regioselectivity. This strategy overcomes the limitations of electron-deficient alkenes in traditional dipolar [3+2]-cycloaddition of α-diazo compounds with alkenes. Furthermore, the straightforward formation of the diazomethyl radicals provides umpolung reactivity, thus opening new opportunities for the versatile transformations of diazo compounds.

Low-voltage-activated inward current in murine antral smooth muscle cells is an artifact.

Two types of voltage-dependent inward currents were evoked by depolarization in murine antral smooth muscle cells (SMCs) bathed in Ca2+-containing physiological solution: high-voltage-activated (HVA) and low-voltage-activated (LVA) inward currents. We examined whether the LVA current was due to: 1) T-type Ca2+ channels, 2) Ca2+-activated Cl-channels, 3) nonselective cation channels (NSCC), or 4) voltage-dependent K+ channels. Replacement of external Ca2+ (2 mM) with equimolar Ba2+ increased the amplitude of the HVA current but blocked the LVA current. Nicardipine blocked the HVA current, and in the presence of nicardipine, T-type Ca2+ blockers failed to block LVA current. A Cl- channel antagonist had little effect on LVA current. Cation-free external solution completely abolished both HVA and LVA currents. Addition of Ca2+ to the solution restored only HVA currents. Addition of K+ (5 mM) to otherwise cation-free solution induced LVA current that reversed at -20 mV. These data suggest that LVA current is not due to T-type Ca2+ channels, Ca2+-activated Cl- channels, or NSCC. A-type K+ (KA) currents and delayed rectifying K+ (KDR) currents can be resolved in antral SMCs dialyzed with a solution containing 140 mM K+. When cells were exposed to high K+ external solution and dialyzed with Cs+-rich solution in the presence of nicardipine, LVA current was evoked and reversed at positive potentials. LVA currents were blocked by K+ channel blockers, 4-aminopyridine, and tetraethylammonium. In conclusion, LVA inward currents can be generated by K+ influx via KA channels in murine antral SMCs when cells were dialyzed with Cs+-rich solution.

Litter chemical traits strongly drove the carbon fractions loss during decomposition across an alpine treeline ecotone.

The decomposition of litter carbon (C) fraction is a major determinant of soil organic matter pool and nutrient cycling. However, knowledge of litter chemical traits regulate C fractions release is still relatively limited. A litterbag experiment was conducted using six plant functional litter types at two vegetation type (coniferous forest and alpine shrubland) in a treeline ecotone. We evaluated the relative importance of litter chemistry (i.e. Nutrient, C quality, and stoichiometry) on the loss of litter mass, non-polar extractables (NPE), water-soluble extractables (WSE), acid-hydrolyzable carbohydrates (ACID), and acid-unhydrolyzable residue (AUR) during decomposition. Litter nutrients contain nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sodium (Na), magnesium (Mg), aluminium (Al), manganese (Mn), zinc (Zn), iron (Fe) and copper (Cu), litter C quality contains C, WSE, NPE, ACID, and AUR, and stoichiometry was defined by C:N, C:P; N:P, ACID:N, and AUR:N. The results showed single exponential model fitted decomposition rates of litter mass and C fractions better than double exponential or asymptotic decomposition, and the decomposition rates of C fractions were strongly correlated with initial litter nutrients, especially K, Na, Ca. Furthermore, the temporal dynamics of litter nutrients (Ca, Mg, Na, K, Zn, and Fe) strongly regulated C fractions loss during the decomposition process. Changes in litter C quality had an evident effect on the degradation of ACID and AUR, supporting the concept of "priming effect" of soluble carbon fraction. The significant differences were found in the release of NPE, WSE, and ACID rather than AUR among coniferous forest and alpine shrubland, and the vegetation type effects largely depend on the changes in litter stoichiometry, which is an important implication for the change in plant community abundance regulate decay. Collectively, elucidating the hierarchical drivers of litter chemistry on decomposition is critical to soil C sequestration in alpine ecosystems.

A Secreted Reporter for Blood Monitoring of Pyroptotic Cell Death.

Pyroptotic cell death is a phenomenon that runs through all life activities and plays an important role in physiological and pathological processes of the body's metabolism. It is of big biological significance to understand the phenomenon and nature of cell pyroptosis. In the process of cell pyroptosis, the pore-forming effector gasdermin D (GSDMD) is cleaved to form oligomers, which are inserted into the cell membrane, causing rapid cell death. However, the effective cell death induced by GSDMD complicates our ability to understand the behavior of pyroptosis. In this work, we performed molecular mutagenesis to develop a genetically encoded pyroptotic reporter, where a secreted Gaussia luciferase (Gluc) was strategically placed in the p30-p20 tolerated junction of GSDMD to support natural pyrophosphorylation and promote live imaging of cell pyroptosis. In addition, we demonstrated that this fused Gluc-GSDMD reporter executed inflammatory body-dependent pyroptosis in response to extracellular stimuli, and that the lysed p30-GSDMD can be secreted out of the cell and can be detected in the culture medium and animal blood. Therefore, our study provides a valuable tool that not only noninvasive and real-time monitoring of cell pyroptosis, but also affords a high-throughput functional screening of pyroptosis-targeted compounds in cultured cells and animal models.