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Alternaria alternata is a common plant pathogen that can infect crops and reduce their production. In this work, an antagonism experiment between A. alternata and the essential oil of arborvitae ( Platycladus orientalis ) was performed, and it was proven that A. alternata had developed resistance to this plant-derived fungicide. A. alternata facilitated the biotransformation of hinokitiol ( 1 ), the main antifungal compound in the essential oil of arborvitae, into ( R )-2-hydroxy-β-methylbenzeneethanol ( 2 ), which does not have antifungal activity against A. alternata . This biotransformation is an unusual ring-contraction reaction that was verified to be catalyzed by P450 enzyme hydroxylation and Baeyer-Villiger oxidation. In addition, the P450 enzyme inhibitors 1-aminobenzotriazole and piperonyl butoxide effectively prevented the destruction of the hinokitiol structure by A. alternata , and the combined use of these P450 enzyme inhibitors significantly increased the antifungal activity of hinokitiol. This work provides a theoretical reference for the further development of botanical fungicides.

The electrochemical CO 2 reduction reaction (CO 2 RR) into high-value carbon compounds such as CO and HCOOH is a promising strategy for the utilization and conversion of emitted CO 2 . However, the selectivity of the CO 2 RR for HCOOH is typically less than 90% and operates within a narrow voltage range, which limits its practical application. Herein, we propose a novel heterostructural aerogel as a highly efficient electrocatalyst for CO 2 RR to HCOOH. This catalyst consists of Cu-Sn-O x solid solutions embedded in a reduced graphene oxide matrix (Cu-Sn-O x /rGO). The incorporation of Cu 2+ into the SnO 2 matrix enhances HCOOH production by improving the adsorption of the *OCHO intermediate and inhibiting H 2 evolution, as confirmed by in situ measurements and computational studies. As a result, Cu-Sn-O x /rGO achieves a remarkable Faradaic efficiency (FE) of up to 91.4% for HCOOH and maintains high selectivity over a broad operating voltage range (-0.8 to -1.1 V). Additionally, the assembled Zn-CO 2 batteries demonstrated an excellent power density of 1.14 mW/cm 2 and exceptional stability for over 25 h.

In vivo drug monitoring is crucial for evaluating the effectiveness and safety of drug treatment. Blood sampling and analysis is the current gold standard but needs professional skills and cannot meet the requirements of point-of-care testing. Dermal interstitial fluid (ISF) showed great potential to replace blood for in vivo drug monitoring; however, the detection was challenging, and the drug distribution behavior in ISF was still unclear until now. In this study, we proposed surface-enhanced Raman spectroscopy (SERS) microneedles (MNs) for the painless and real-time analysis of drugs in ISF after intravenous injection. Using methylene blue (MB) and mitoxantrone (MTO) as model drugs, the innovative core-satellite structured Au@Ag SERS substrate, hydrogel coating over the MNs, rendered sensitive and quantitative drug detection in ISF of mice within 10 min. Based on this technique, the pharmacokinetics of the two drugs in ISF was investigated and compared with those in blood, where the drugs were analyzed via liquid chromatography-mass spectrometry. It was found that the MB concentration in ISF and blood was comparable, whereas the concentration of MTO in ISF was 2-3 orders of magnitude lower than in blood. This work proposed an efficient tool for ISF drug monitoring. More importantly, it experimentally proved that the penetration ratio of blood to ISF was drug-dependent, providing insightful information into the potential of ISF as a blood alternative for in vivo drug detection.

This study explored the potential to improve the storage quality and prolong the shelf life of truffles by storing them in a modified atmosphere fresh-keeping box with sealed gas components of Active Modified Atmosphere Packaging (AMAP, 40% O 2 + 60% CO 2 ) at 4 °C. During the storage period, a total of 63 volatile components in 10 categories were detected, with aldehydes being the most abundant and the relative content of ethers being the highest. The relative odor activity value and principal component analysis revealed that isovaleraldehyde, 1-octen-3-ol, 1-octen-3-one, and dimethyl sulfide were the characteristic flavor components of fresh truffles. However, 3-methylthiopropionaldehyde and (E, E)-2,4-nonadienal were the components that caused the deterioration of truffle flavor and could potentially serve as markers of truffle decay characteristics. 16S rDNA high-throughput sequencing showed that Leuconostoc and Lactococcus were dominant in the truffle samples stored for 14 days, but the abundance of putrefactive pathogenic bacteria showed an increasing trend in the truffle samples stored for 28 days. During the whole storage period, the common fungi detected in the different treatment groups were Candida and Aspergillus . The relative abundance of the former decreased, while the relative abundance of the latter decreased initially and then increased. The correlation between volatile components and the microbial flora was further analyzed, which indicated that Lactococcus and Lactobacillus had the same contributions to the same flavor, while Pseudomonas and Glutamicibacter had the opposite contributions to the same flavor. The results provide a reference for the storage and preservation of truffles., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Unprecedented regioselective electrochemical tandem selenation/cyclization of alkynyl phosphonates with diselenide is described here. These obtained selenoether products can be chemo-selectively converted into halogen-functionalized cyclic enol phosphonates under our electrochemical conditions. These protocols provide straightforward access to valuable cyclic enol phosphonate or phosphaisocoumarins under the electrochemical and transition-metal-free conditions. The robustness of these transformations was illustrated by their compatibility with various complex natural products and bioactive molecules. The selenoether and halogen functional groups allow the further diversification of the phosphorus heterocycles thus obtained.

Carbon supports containing single-atomically dispersed metal-N x (denoted as M SAC -N x C y , x , y : coordination number) have attracted increasing attention due to their superb performance in heterogeneous catalysis. However, large-scale controllable preparation of single-atom catalysts (SACs) with high concentration of supported metal-N x is still a big challenge because of the metal atom agglomeration during synthesis at high density and temperatures. Herein, we report a stepwise anchoring strategy from a 1,10- o -phenanthroline Pt chelate to an N x -doped carbon (N x C y ) with isolated Pt single-atom catalysts (Pt SAC -N x C y ) containing Pt loadings up to 5.31 wt % measured via energy-dispersive X-ray spectroscopy (EDS). The results show that 1,10- o -phenanthroline Pt chelate predominantly contributes to the formation of chelate single metal sites that bind tightly to platinum ions to prevent metal atoms from aggregating, resulting in high metal loading. The high-loading Pt SAC -N x C y exhibits a low hydrogen evolution (HER) overpotential of 24 mV at 0.010 A cm -2 current density with a relatively small Tafel gradient of 60.25 mV dec -1 and excellent stable performance. In addition, the Pt SAC -N x C y catalyst shows excellent oxygen reduction reaction (ORR) catalytic activity with good stability, represented by the fast ORR kinetics under high-potential conditions. Theoretical calculations show that Pt SAC -NC 3 ( x = 1, y = 3) offers a lower H 2 O activation energy barrier than Pt nanoparticles. The adsorption free energy of a H atom on a Pt single-atom site is lower than that on a Pt cluster, which is easier for H 2 desorption. This study provides a potentially powerful cascade anchoring strategy in the design of other stable M SAC -N x C y catalysts with high-density metal-N x sites for the HER and ORR.

Graphene is an ideal platform to study the coherence of quantum interference pathways by tuning doping or laser excitation energy. The latter produces a Raman excitation profile that provides direct insight into the lifetimes of intermediate electronic excitations and, therefore, on quantum interference, which has so far remained elusive. Here, we control the Raman scattering pathways by tuning the laser excitation energy in graphene doped up to 1.05 eV. The Raman excitation profile of the G mode indicates its position and full width at half-maximum are linearly dependent on doping. Doping-enhanced electron-electron interactions dominate the lifetimes of Raman scattering pathways and reduce Raman interference. This will provide guidance for engineering quantum pathways for doped graphene, nanotubes, and topological insulators.

Skin interstitial fluid (ISF)-based microneedle (MN) sensing has recently exhibited wide promise for the minimally invasive and painless diagnosis of diseases. However, it is still a great challenge to diagnose more disease types due to the limited in situ sensing techniques and insufficient ISF biomarker sources. Herein, ISF is employed to pioneer the tracking of acute peritonitis progression via surface-enhanced Raman scattering (SERS) tags labeled MNs patch technique. Densely deposited core-satellite gold nanoparticles and 3-mercaptophenylboronic acid as a Raman reporter enable the developed MNs patch with high sensitivity and selectivity in the determination of H 2 O 2 , an indicator of peritonitis development. Importantly, the MNs patch not only reliably tracks the different states of peritonitis but also evaluates the efficacy of drugs in the treatment of peritonitis, as evidenced by the altered SERS signal consistent with plasma pro-inflammatory factor (TNF-α) and peritoneum pathological manifestations. Interestingly, the major source of H 2 O 2 in ISF of acute peritonitis investigated may not be through conventional blood capillary filtration pathway. This work provides a new route and technique for the early diagnosis of acute peritonitis and the evaluation of drug therapy effects. The developed MNs patch is promising to serve as a universal sensing tool to greatly enrich the variety and prospect of ISF-based disease diagnosis.

Tailoring magnetic orders in topological insulators is critical to the realization of topological quantum phenomena. An outstanding challenge is to find a material where atomic defects lead to tunable magnetic orders while maintaining a nontrivial topology. Here, by combining magnetization measurements, angle-resolved photoemission spectroscopy, and transmission electron microscopy, we reveal disorder-enabled, tunable magnetic ground states in MnBi 6 Te 10 . In the ferromagnetic phase, an energy gap of 15 meV is resolved at the Dirac point on the MnBi 2 Te 4 termination. In contrast, antiferromagnetic MnBi 6 Te 10 exhibits gapless topological surface states on all terminations. Transmission electron microscopy and magnetization measurements reveal substantial Mn vacancies and Mn migration in ferromagnetic MnBi 6 Te 10 . We provide a conceptual framework where a cooperative interplay of these defects drives a delicate change of overall magnetic ground state energies and leads to tunable magnetic topological orders. Our work provides a clear pathway for nanoscale defect-engineering toward the realization of topological quantum phases.

Microneedles (MNs) are currently one of the most promising tools for skin interstitial fluid (ISF)-based biosensing, while it is still a challenge to expand the detectable biomarkers in ISF due to limited MNs types and detection techniques. Herein, highly sensitive internal-standard surface-enhanced Raman scattering microneedles (IS-SERS-MNs) were developed, which enabled the reliable detection of bacterial metabolites in ISF as new detectable biomarkers for infection diagnosis. The developed IS-SERS-MNs can not only directly detect pyocyanin (a representative bacterial metabolite) present in mouse dermal ISF but also indirectly detect pyocyanin in the hypodermis via its diffusion into the dermis, revealing a new possible pathway for the source of biomarkers in dermal ISF. Moreover, the SERS signal of pyocyanin was also clearly detected at real mouse wounds, indicating that the developed IS-SERS-MNs have great potential in minimally invasive and painless diagnosis of bacterial infection via a new ISF route. This work not only develops IS-SERS-MNs as a powerful tool for expanding the application of SERS-based MNs but also provides a new chance for ISF-related infection diagnosis.

Exosomes serve as a promising therapeutic nanoplatform. However, the exosomes produced by donor cells are a heterogeneous group, with only a small portion having high therapeutic efficacy. Specific isolation of the subpopulation with high efficacy is important for lowering the dose and minimizing toxicity. In this study, we loaded target mRNA and displayed specific Flag in engineered exosomes simultaneously. Briefly, the donor cells were transfected with plasmid expressing a fusion protein Flag-TCS-PTGFRN-CTSL-MCP, namely, exosome sorter. During biogenesis, the RNA-binding motif MCP can specifically bind with MS2-containing RNA and sort the target RNA into the lumen of exosomes. Anti-Flag magnetic beads can capture and thus purify the engineered exosomes via recognition of the Flag on the surface of exosomes. After purification, the Flag could be cleaved by thrombin treatment while MCP can be separated from the fusion protein by CTSL autocleavage upon exosome acidification, minimizing the side effects and augmenting the therapeutic effects. By the proof-of-concept experiment, the exosome sorter-based "all-in-one" strategy was confirmed effective in both the encapsulation of therapeutic mRNA ( Ldlr-MS2 ) into exosomes and the subsequent purification. The purified Ldlr-MS2 -containing exosomes had much higher efficacy in alleviating atherosclerosis, in comparison with the bulk exosomes, confirming the advantage of the proposed "all-in-one" strategy.

Immigration has been recently recognized as an important ecological process that affects the microbial community structure in diverse ecosystems. However, the fate of microbial immigrants in the new environment and their involvement in the local biochemical network remain unclear. In this study, we performed meta-omics-supervised characterization of immigrants' activities in anaerobic sludge digesters. Metagenomic analyses revealed that immigrants from the feed sludge accounted for the majority of populations capable of anaerobic respiration in a digester. Electron acceptors that were predicted to be respired, including nitrate, nitrite, sulfate, and elemental sulfur, were added to digester sludge in batch tests. Consumption of up to 91% of the added electron acceptors was observed within the experiment period. 16S rRNA sequencing detected populations that were stimulated by the electron acceptors, largely overlapping with respiration-capable immigrants identified by metagenomic analysis. Metatranscriptomic analysis of the batch tests provided additional evidence for upregulated expression of respiration genes and concomitant suppressed expression of methanogenesis. Anaerobic respiration activity was further evaluated in full-scale digesters in nine wastewater treatment plants. Although nitrate and sulfate respiration were ubiquitous, the expression level of respiration genes was generally 2-3 orders of magnitude lower than the expression of methanogenesis in most digesters, suggesting marginal ecological roles by immigrants in full-scale digester ecosystems.

Polymeric carbon nitride (PCN) shows great potential applications in the areas of sustainable energy (photocatalysis and photoelectric conversion, as well as other important catalytic reactions), biosensing, biomedicine, devices, and more, but efficient phosphorescence is very scarce because of the lack of an effective synthetic method and an unsettled phosphorescent mechanism. Herein, we report a strategy to promote efficient phosphorescence to activate triplet exciton release by introduction of S and N elements. PCN could be synthesized by thiourea or urea (named S,N-PCN and N-PCN, respectively) at a relatively low reaction temperature (260 °C). S,N-PCN exhibits phosphorescence quantum yield (4.15%) higher than that (0.41%) for N-PCN. The introduction of C=S and C≡N groups in S,N-PCN networks could boost the intersystem crossing (ISC), leading to small singlet-triplet energy (Δ E ST ) up to more triplet exciton generation. Considering the excellent optical stability of PCN, a preliminary application of visible-light-excited PCN in advanced anticounterfeiting is proposed.

Understanding the in vivo behavior of photothermal nanomedicines (PTNMs) is important for drug development and evaluation. However, it is still very challenging. Herein, two key parameters, i.e., the depth of PTNMs under biological tissue and the drug release ratio of PTNMs in vivo, can be revealed by a near-infrared (NIR) light-responsive surface-enhanced Raman scattering (SERS) strategy. The fabricated PTNMs were composed of waxberry-like gold nanoparticles, model drug curcumin, and an elaborately selected NIR light-responsive Raman reporter (3,3'-diethylthiatricarbocyanine iodide, DTTC). The response mechanism of DTTC to NIR light was investigated as photodegradation. NIR light irradiation heated the gold nanoparticles, triggered the release of a model drug, and simultaneously decreased the SERS intensity of the PTNMs. In vitro experiment results revealed that the SERS intensity decrease could well reflect the depth of PTNMs with a correlation coefficient of more than 0.99. On this basis, after in situ SERS detection, the depth of PTNMs in a tumor could be revealed with satisfactory accuracy. Moreover, the decrease in the SERS intensity of PTNMs showed a highly similar trend to the increase in the drug release, suggesting that it could be used for real-time monitoring of drug release of PTNMs. This study not only opens a new avenue for the release study of many inactive fluorescent and Raman drugs of PTNMs but also provides an effective way for reporting the depth, which greatly promotes the application of PTNMs in vivo.

Recently, MnBi 2 Te 4 has been demonstrated to be an intrinsic magnetic topological insulator and the quantum anomalous Hall (QAH) effect was observed in exfoliated MnBi 2 Te 4 flakes. Here, we used molecular beam epitaxy (MBE) to grow MnBi 2 Te 4 films with thickness down to 1 septuple layer (SL) and performed thickness-dependent transport measurements. We observed a nonsquare hysteresis loop in the antiferromagnetic state for films with thickness greater than 2 SL. The hysteresis loop can be separated into two AH components. We demonstrated that one AH component with the larger coercive field is from the dominant MnBi 2 Te 4 phase, whereas the other AH component with the smaller coercive field is from the minor Mn-doped Bi 2 Te 3 phase. The extracted AH component of the MnBi 2 Te 4 phase shows a clear even-odd layer-dependent behavior. Our studies reveal insights on how to optimize the MBE growth conditions to improve the quality of MnBi 2 Te 4 films.

Herein, we report a highly efficient ruthenium-catalyzed peri -selective C(sp 2 )-H acylmethylation of 1-naphthols with α-carbonyl sulfoxonium ylides by utilizing hydroxyl as a weakly coordinating directing group. This new method imparts good reactivity, excellent chemo- and regioselectivity, and broad functional group tolerance and involves mild reaction conditions. The C-H acylmethylated products can be readily cyclized into fluorescent annulated pyrans by a one-pot process.

The present study verified that 1,8-dihydroxyanthraquinone ( 1 ), a common component in some industrial raw materials and dyes, could be converted into peniphenone ( 2 ), which possesses immunosuppressive activity and other medicinal potential, by Aleurodiscus mirabilis fermentation. The yield of peniphenone ( 2 ) after 7 days of fermentation was 11.05 ± 2.19%. To reveal the transformation mechanism, two secondary metabolites, emodin ( 3 ) and monodictyphenone ( 4 ), were isolated from the fermentation broth of A. mirabilis , implying that polyketide metabolic pathways from emodin ( 3 ) to monodictyphenone ( 4 ) might exist in A. mirabilis . 1,8-Dihydroxyanthraquinone ( 1 ) was suspected to be converted into peniphenone ( 2 ) via the same pathway since emodin ( 3 ) and 1,8-dihydroxyanthraquinone ( 1 ) share very similar skeletons. The P450 enzyme and Baeyer-Villiger oxidase in A. mirabilis were confirmed to catalyze this biotransformation on the basis of ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) analysis. This novel investigation could shed light on the mechanism and therefore development of peniphenone production from 1,8-dihydroxyanthraquinone by microbial fermentation., Competing Interests: The authors declare no competing financial interest., (© 2020 American Chemical Society.)

Surface-enhanced Raman resonant scattering (SERRS) tags encoded with near-infrared (NIR) Raman reporters showed great potential for in vivo detection owing to their ultrasensitivity. However, in vivo signal stability of such tags is a remaining problem due to the lack of suitable silica coating method because the weakly adsorbed NIR reporters tend to detach from traditional gold nanosubstrates in the ethanol-rich and high pH conditions, which are commonly used for silica coating. Herein, we propose a silica coating method for NIR SERRS tags by using waxberry-like gold nanoparticles (NPs) as substrates. The lipid bilayer of the NPs played a crucial role in the coating, which can encapsulate the NIR Raman reporter via hydrophobic interactions and prevent the interference from a harsh medium. Thus, the silica-coated tags well preserved ultrasensitivity of bare tags and simultaneously gained satisfactory signal stability in vivo . Moreover, the coating method is compatible for the encapsulation of a variety of thiol group-free NIR reporters (as exemplified by DTTC, Cy7, IR792, and DIR), relying on which a tag-pair with distinguishable peaks can be screened (labeling with DTTC and Cy7, respectively). In vivo duplexing detection revealed that the tag-pair-labeled liposome was cleared faster in the liver than polydopamine NPs within one mouse. The developed method paves an easy way for gaining high-quality SERRS tags and will promote their in vivo multiplex analysis and diagnostics applications.

Bimetallic gold core-silver shell (Au@Ag) surface-enhanced Raman scattering (SERS) tags draw broad interest in the fields of biological and environmental analysis. In reported tags, silver coating tended to smooth the surface and merge the original hotspot of Au cores, which was disadvantageous to signal enhancement from the aspect of surface topography. Herein, we developed gold nanorod (AuNR)-bridged Au@Ag SERS tags with uniform three-dimensional (3D) topography for the first time. This unique structure was achieved by selecting waxberry-like Au nanoparticles (NPs) as cores, which were capped by vertically oriented AuNR arrays. Upon selective surface blocking with thiol-ligands, Ag NPs were controlled to anisotropically grow on the tips of the AuNRs, producing high-density homo- (Ag-Ag) and hetero- (Au-Ag) hotspots in a single NP. The 3D hotspots rendered this NP extraordinary SERS enhancement ability (an analytical enhancement factor of 3.4 × 10 6 ) 30 times higher than the counterpart with a smooth surface, realizing signal detection from a single NP. More importantly, multiplexing signals ("blank" or multiplex "internal standard") can be achieved by simply changing thiol-ligands, as exemplified in the synthesis of NPs with 8 signatures. Furthermore, the multifunctionality has been demonstrated in living cell/in vivo imaging, photothermal therapy, and SERS substrates for ratiometric quantitative analysis, relying on the inherent internal standard signal. The prepared Au@Ag NPs have great potential as standard tools in many SERS-related fields.

An efficient electro-oxidative C-H/N-H activation with 1,3-diynes has been achieved with a robust earth-abundant cobalt catalyst. The electrochemical C-H functionalization was accomplished with ample scope and remarkable functional group compatibility in a simple undivided cell. This protocol avoids the utilization of stoichiometric and cost-intensive chemical oxidants in C-H activation, thus forming hydrogen as the only byproduct.

Surface coating determined the sensitivity and stability of surface-enhanced Raman scattering (SERS) tags in bioanalysis. The reported various coatings suffered from the drawbacks of a lack of rigidity, stability, or synthesis versatility. Herein, we demonstrated robust polystyrene (PS) coated SERS tags that could be prepared by an easy and universal approach. Taking advantages of biocompatible, transparent, compact properties of PS shell, the coated tags showed satisfactory sensitivity, biocompatibility, and superior structural stability in cell and in vivo imaging applications. More importantly, the PS coating strategy allowed for the encapsulation of SERS tags encoded with not only thiolated but also nonthiolated Raman reporters without loss of sensitivity, as exemplified in the synthesis of 9 different resonant dye-encoded tags. Moreover, the coating of SERS tags with various kinds of substrates was achieved via the same standard protocol. Comparing with widespread silica coated tags, the PS coated ones were more stable in harsh conditions and had an easily expanded ultrasensitive (resonant) tags library with much lower cost (no need of expensive sulfhydryl/isothiocyano reporters with limited types), illustrating great promise as standard analytical tools of commercialized value for bioanalysis, medical diagnostics, and environmental science studies.

Herein, we presented waxberry-like core-satellite (C-S) nanoparticles (NPs) prepared by an in situ growth of satellite gold NPs on spherical phospholipid bilayer-coated gold cores. The fluidic lipid bilayer cross-linker was reported for the first time, which imparted several novel morphological and optical properties to the C-S NPs. First, it regulated the anisotropic growth of the satellite NPs into vertically oriented nanorods on the core NP surface. Thus, an interesting waxberry-like nanostructure could be obtained, which was different from the conventional raspberry-like C-S structures decorated with spherical satellite NPs. Second, the satellite NPs were "soft-landed" on the lipid bilayer and could move on the core NP surface under certain conditions. The movement induced tunable plasmonic features in the C-S NPs. Furthermore, the fluidic lipid bilayer was capable of not only holding an abundance of reporter molecules but also delivering them to the hotspots at the junctions between the core and satellite NPs, which made the C-S NPs an excellent candidate for preparing ultrasensitive surface-enhanced Raman scattering (SERS) tags. The bioimaging capabilities of the C-S NP-based SERS tags were successfully demonstrated in living cells and mice. The developed SERS tags hold great potential for bioanalysis and medical diagnostics.

Electrochemical oxidative C-H/N-H activations have been accomplished with a versatile cobalt catalyst in terms of [4 + 2] annulations of internal alkynes. The electro-oxidative C-H activation manifold proved viable with an undivided cell setup under exceedingly mild reaction conditions at room temperature using earth-abundant cobalt catalysts. The electrochemical cobalt catalysis prevents the use of transition metal oxidants in C-H activation catalysis, generating H 2 as the sole byproduct. Detailed mechanistic studies provided strong support for a facile C-H cobaltation by an initially formed cobalt(III) catalyst. The subsequent alkyne migratory insertion was interrogated by mass spectrometry and DFT calculations, providing strong support for a facile C-H activation and the formation of a key seven-membered cobalta(III) cycle in a regioselective fashion. Key to success for the unprecedented use of internal alkynes in electrochemical C-H/N-H activations was represented by the use of N-2-pyridylhydrazides, for which we developed a traceless electrocleavage strategy by electroreductive samarium catalysis at room temperature.

C-H alkynylations with weakly coordinating acids were accomplished by the aid of an expedient ruthenium(II) catalysis manifold. The user-friendly C-H alkynylation occurred under mild conditions with the weak base K 2 CO 3 . The versatility of the ruthenium(II) catalysis was reflected by providing step-economical access to phthalides as well as enabling unprecedented decarboxylative ortho-C-H alkynylations.

Aprotic lithium-air batteries have recently drawn considerable attention due to their ultrahigh specific energy. However, the chemical and electrochemical instability of the electrolyte is one of the most critical issues that need to be overcome. To increase the stability and maintain a relatively high conductivity of the lithium ion, a mixed electrolyte of sulfolane (TMS) and N , N -dimethylacetamide (DMA) was evaluated and tested in an aprotic lithium-air battery. The physical and chemical characterizations showed that the mixed electrolyte exhibited a relatively low viscosity, high ionic conductivity and oxygen solubility, and good stability. In addition, it was found that lithium-air batteries with an optimized electrolyte composition (DMA/TMS = 20:80, % v/v) showed a better cycle life and lower charge overpotential as compared to those with electrolytes with a single solvent, either DMA or TMS., Competing Interests: The authors declare no competing financial interest.

The first total synthesis of the Myrioneuron alkaloids (±)-α,β-myrifabral A and B has been accomplished in only four steps from conveniently available starting materials. This short synthesis relied on the use of a key tandem Mannich/amidation reaction to rapidly construct the core framework and two carbon stereocenters. The synthetic route allows for large scale preparation of these promising natural products against the hepatitis C virus (HCV).

Matrix-assisted pulsed-laser evaporation direct-write (MAPLE DW) has been successfully implemented as a promising laser printing technology for various fabrication applications, in particular, three-dimensional bioprinting. Since most bioinks used in bioprinting are viscoelastic, it is of importance to understand the jetting dynamics during the laser printing of viscoelastic fluids in order to control and optimize the laser printing performance. In this study, MAPLE DW was implemented to study the jetting dynamics during the laser printing of representative viscoelastic alginate bioinks and evaluate the effects of operating conditions (e.g., laser fluence) and material properties (e.g., alginate concentration) on the jet formation performance. Through a time-resolved imaging approach, it is found that when the laser fluence increases or the alginate concentration decreases, the jetting behavior changes from no material transferring to well-defined jetting to well-defined jetting with an initial bulgy shape to jetting with a bulgy shape to pluming/splashing. For the desirable well-defined jetting regimes, as the laser fluence increases, the jet velocity and breakup length increase while the breakup time and primary droplet size decrease. As the alginate concentration increases, the jet velocity and breakup length decrease while the breakup time and primary droplet size increase. In addition, Ohnesorge, elasto-capillary, and Weber number based phase diagrams are presented to better appreciate the dependence of jetting regimes on the laser fluence and alginate concentration.

The first asymmetric total syntheses of (+)-dihydrolyfoline and (-)-5-epi-dihydrolyfoline have been achieved in five and six steps with 4.6% and 14% overall yields, respectively, in which the chiral biaryl axes were constructed in a highly regioselective and stereoselective manner via a biogenetic enzymatic oxidative couplings of phenols, and the requisite quinolizidinone cores were prepared by an enzymatic Mannich reaction.

Recently, simultaneous removal of SO2, NOx and oxidized mercury in wet flue gas desulfurization (WFGD) scrubber has become a research focus. Mercury re-emission in traditional WFGD system has been widely reported due to the reduction of oxidized mercury by sulfite ions. However, in multipollutants simultaneous absorption system, the formation of a large quantity of nitrate and nitrite ions as NOx absorption might also affect the reduction of oxidized mercury in the aqueous absorbent. As such, this paper studied the effects of nitrate and nitrite ions on mercury re-emission and its related mechanism. Experimental results revealed that the nitrate ions had neglected effect on mercury re-emission while the nitrite ions could greatly change the mercury re-emission behaviors. The nitrite ions could initially improve the Hg(0)-emission through the decomposition of HgSO3NO2(-), but with a further increase in the concentration, they would then inhibit the reduction of bivalent mercury owing to the formation of Hg-nitrite complex [Hg(NO2)x(2-x)]. In addition, the subsequent addition of Cl(-) could further suppress the Hg(0) emission, where the formation of a stable Hg-SO3-NO2-Cl complex was assumed to be the main reason for such strong inhibition effect.

A novel tandem Mannich/intramolecular aminal formation between tryptamines and salicylaldehydes was reported. This strategy provides a promising approach for the stereoselective synthesis of a range of complex fused spiroindolines, which bear a highly congested contiguous spiro quaternary center and two tertiary stereocenters, in a highly economical and effective fashion.

Self-splicing of Tetrahymena pre-rRNA proceeds in two consecutive phosphoryl transesterification steps. One major difference between these steps is that in the first an exogenous guanosine (G) binds to the active site, while in the second the 3'-terminal G414 residue of the intron binds. The first step has been extensively characterized in studies of the L-21ScaI ribozyme, which uses exogenous G as a nucleophile. In this study, mechanistic features involved in the second step are investigated by using the L-21G414 ribozyme. The L-21G414 reaction has been studied in both directions, with G414 acting as a leaving group in the second step and a nucleophile in its reverse. The rate constant of chemical step is the same with exogenous G bound to the L-21ScaI ribozyme and with the intramolecular guanosine residue of the L-21G414 ribozyme. The result supports the previously proposed single G-binding site model and further suggests that the orientation of the bound G and the overall active site structure is the same in both steps of the splicing reaction. An evolutionary rationale for the use of exogenous G in the first step is also presented. The results suggest that the L-21G414 ribozyme exists predominantly with the 3'-terminal G414 docked into the G-binding site. This docking is destabilized by approximately 100-fold when G414 is attached to an electron-withdrawing pA group. The internal equilibrium with K(int) = 0.7 for the ribozyme reaction indicates that bound substrate and product are thermodynamically matched and is consistent with a degree of symmetry within the active site. These observations are consistent with the presence of a second Mg ion in the active site. Finally, the slow dissociation of a 5' exon analog relative to a ligated exon analog from the L-21G414 ribozyme suggests a kinetic mechanism for ensuring efficient ligation of exons and raises new questions about the overall self-splicing reaction.

Calcium binding to photosystem II slows NH2OH inhibition of O2 evolution; Mn2+ is retained by the O2-evolving complex [Mei, R., & Yocum, C. F. (1991) Biochemistry 30, 7836-7842]. This Ca(2+)-induced stability has been further characterized using the large reductant hydroquinone. Salt-washed photosystem II membranes reduced by hydroquinone in the presence of Ca2+ retain 80% of steady-state O2 evolution activity and contain about 2 Mn2+/reaction center that can be detected at room temperature by electron paramagnetic resonance. This Mn2+ produces a weak enhancement of H2O proton spin-lattice relaxation rates, cannot be easily extracted by a chelator, and is reincorporated into the O2-evolving complex upon illumination. A comparison of the properties of Ca(2+)-supplemented photosystem II samples reduced by hydroquinone or NH2OH alone or in sequence reveals the presence of a subpopulation of manganese atoms at the active site of H2O oxidation that is not accessible to facile hydroquinone reduction. At least one of these manganese atoms can be readily reduced by NH2OH following a noninhibitory hydroquinone reduction step. Under these conditions, about 3 Mn2+/reaction center are lost and O2 evolution activity is irreversibly inhibited. We interpret the existence of distinct sites of reductant action on manganese as further evidence that the Ca(2+)-binding site in photosystem II participates in regulation of the organization of manganese-binding ligands and the overall structure of the O2-evolving complex.

Calcium is required for oxidation of water to molecular oxygen by photosystem II; the Ca2+ demand of the reaction increases upon removal of 23- and 17-kDa extrinsic polypeptides from detergent-derived preparations of the photosystem. Employing the manganese reductant NH2OH as a probe to examine the function of Ca2+ in photosystem II reveals that (1) Ca2+ slows the rate of NH2OH inhibition of O2 evolution activity, but only in photosystem II membranes depleted of extrinsic proteins, (2) other divalent cations (Sr2+, Cd2+) that compete for the Ca2+ site also slow NH2OH inhibition, (3) Ca2+ is noncompetitive with respect to NH2OH, (4) in order to slow inhibition, Ca2+ must be present prior to the initiation of NH2OH reduction of manganese, and (5) Ca2+ appears not to interfere with NH2OH reduction of manganese. We conclude that the ability of Ca2+ to slow the rate of NH2OH inhibition arises from the site in photosystem II where Ca2+ normally stimulates O2 evolution and that the mechanism of this phenomenon arises from the ability of Ca2+ or certain surrogate metals to stabilize the ligation environment of the manganese complex.

The extrinsic 33-kDa protein (P33) was cross-linked covalently to the binding site on P33-depleted PSII preparations which is responsible for reconstitution of photosynthetic water oxidation after PSII preparations have been washed with 1 M CaCl2. Conditions were found in which more than half of the cross-linked protein complexes formed in the PSII preparations retained the ability to catalyze the oxidation of water. The complex is composed of the P33 cross-linked to the D1 and D2 proteins and a 34-kDa protein, which is present in lower abundance than the other three proteins. After solubilization of the membranes with SDS and purification by preparative SDS-PAGE, the complex retains bound manganese and can catalyze the conversion of H2O2 to O2. Calcium and chloride increased the catalase activity of the purified cross-linked complex while lanthanum or hydroxylamine abolished the activity. By use of the specific activity of the H2O2-dependent reaction to follow the extent of purification of the cross-linked complex, the most highly purified complex was determined to contain 0.34 microgram of manganese/180 micrograms of protein. The mole ratio of Mn/protein was calculated to range from 3.6 to 4.5 depending on the assumed stoichiometry of the protein subunits. The results presented here provide direct evidence that one or more of the three proteins that have cross-linked to the P33 are responsible for binding the manganese of the oxygen-evolving complex.

The evolution of O2 from H2O2 catalyzed by the oxygen-evolving complex (OEC) in darkness was examined with photosystem II reaction center complex preparations from spinach. Flash illumination of dark-adapted reaction centers was used to make S0-enriched or S1-enriched complexes. The membranes catalyzed O2 evolution from H2O2 when preset to either the S0 or S1 state. However, only the S0-state reaction was inhibited by carbonyl cyanide m-chlorophenylhydrazone and dependent on chloride. These results indicate that (1) the S0-dependent and S1-dependent catalytic cycles can be separated by flash illumination, (2) the S0-dependent reaction involves the formation of the S2 state, and (3) the S1-dependent reaction does not involve the formation of the S2 or S3 states. A kinetic study of the S1-dependent reaction revealed a rapid equilibrium ordered mechanism in which (1) the binding of Ca(II) must precede the binding of H2O2 to the OEC and (2) the reaction of Ca(II) with the free enzyme is at thermodynamic equilibrium such that Ca(II) does not necessarily dissociate after each catalytic cycle.