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Streptovaricin C is a naphthalenic ansamycin antibiotic structurally similar to rifamycins with potential anti-MRSA bioactivities. However, the formation mechanism of the most fascinating and bioactivity-related methylenedioxy bridge (MDB) moiety in streptovaricins is unclear. Based on genetic and biochemical evidences, we herein clarify that the P450 enzyme StvP2 catalyzes the MDB formation in streptovaricins, with an atypical substrate inhibition kinetics. Furthermore, X-ray crystal structures in complex with substrate and structure-based mutagenesis reveal the intrinsic details of the enzymatic reaction. The mechanism of MDB formation is proposed to be an intramolecular nucleophilic substitution resulting from the hydroxylation by the heme core and the keto-enol tautomerization via a crucial catalytic triad (Asp89-His92-Arg72) in StvP2. In addition, in vitro reconstitution uncovers that C6-O-methylation and C4-O-acetylation of streptovaricins are necessary prerequisites for the MDB formation. This work provides insight for the MDB formation and adds evidence in support of the functional versatility of P450 enzymes., Streptovaricin C is an antibiotic containing a methylenedioxy bridge (MDB) moiety essential for its activity. Here, the authors show that a P450 monooxygenase StvP2 catalyses MDB formation, report its crystal structure in complex with the substrate, and elucidate mechanistic details of MDB formation.

Rechargeable aqueous Zn-ion battery has been considered as a key complement to the existing battery technologies due to its intrinsic merits such as operational safety and cost saving. However, issues of dendrite growth and accompanied water consumption hinder its further development. In this work, we utilize a chelating agent, 2-Bis(2-hydroxyethyl) amino-2-(hydroxymethyl)-1,3-propanediol (BIS-TRIS), to regulate the solvation sheath structure of Zn2+. Benefiting from such zinc-chelating coordination, Zn2+ 2D diffusion can be restricted and the altered deposition kinetic has contributed to the inhibition of the dendrite growth. In addition, partial substitution of water in solvation shell with chelator can also greatly suppress the competitive hydrogen evolution reaction (HER). Consequently, a stable symmetric Zn cell with lifetime more than 1000 h at a current density of 1 mA cm−2 is achieved. Moreover, the aqueous Zn/MnO2 battery with BIS-TRIS as electrolyte additive delivers an 86% capacity retention after 600 cycles at 500 mA g−1. This zinc-chelating coordination based facile strategy opens a new window for the future development in dendrite-free Zn anode.

Four new hydroxamate-containing natural product cyclopeptides designated acremonpeptides A-D (1-4), together with Al(III)-acremonpeptide D (5) were obtained from the marine fungus Acremonium persicinum SCSIO 115. The planar structures of 1-5 were established on the basis of HRMS as well as 1D and 2D NMR data sets. Moreover, the amino acid absolute configurations were determined using Marfey's method. Compounds 1-5 all feature three 2-amino-5-(N-hydroxyacetamido)pentanoic acid (N5-hydroxy-N5-acetyl-l-ornithine) metal ion chelating moieties. Beyond their discovery and structure elucidation, in vitro bioassays revealed acremonpeptides A (1), B (2), and Al(III)-acremonpeptide D (5) as moderate antiviral agents for herpes simplex virus 1 with EC50 values of 16, 8.7, and 14 μM, respectively.

Two new ansamycin derivatives, damavaricin H (1) and protostreptovaricin VI (2) were isolated from the Streptomyces spectabilis CCTCC M2017417 derived mutants of ΔstvP5 and ΔstvA2, respectively. The structures of 1 and 2 were established by analysis of the HRESIMS as well as 1D and 2D NMR datasets. The minimum inhibitory concentration (MIC) results showed that compounds 1 and 2 possessed the corresponding anti-MRSA bioactivities of 4 ∼ 8 μg/ml and 8 ∼ 16 μg/ml, which confirmed the structure-activity relationships of streptovaricins reported previously and also revealed that addition of the hydroxyl group at C-8 increased the anti-MRSA activity.

The ether extract ofArtemisia integrifoliawas separated by chromatography and afforded a new iridoid, arteintegin A (6), together with five known compounds, namely chamazulene (1) , acetylenes (E)-2, (E)-3, (Z)-4, eugenol (5). The structure elucidation of the new compound was carried out by 1D ( 1H NMR and 13C NMR) and 2D-NMR (COSY, HSQC and NOESY) spectral analysis .

In this work, garnet-framework Li3Nd3W2O12 as a novel insertion-type anode material has been prepared via a facile sol–gel method and examined as a lithium container for lithium ion batteries (LIBs...

The preparation and characterization of Pb1-xBaxLi2Ti6O14 (x = 0, 1/4, 1/2, 3/4, 1) as anode materials for lithium ion batteries are investigated in this research. The structure, morphology and electrochemical properties are compared with each other by changing the Pb/Ba atomic ratio in Pb1-xBaxLi2Ti6O14. It can be observed that each sample shows the same orthorhombic structure with Cmca space group. Moreover, it can also be found that the working potential, conductivity, cycling and rate performances of as-received samples gradually change along with the evolution of x in Pb1-xBaxLi2Ti6O14 (x = 0, 1/4, 1/2, 3/4, 1). Electrochemical evaluation shows that the operating potential of the as-received sample gradually decreases with increasing x value in Pb1-xBaxLi2Ti6O14 and its initial charge capacity increases reversely. Moreover, different Pb/Ba atomic ratio also brings different cycling stability for Pb1-xBaxLi2Ti6O14. Especially for Pb3/4Ba1/4Li2Ti6O14, it presents better electrochemical properties than other samples. After 120 cycles, the reversible capacity of Pb3/4Ba1/4Li2Ti6O14 is maintained at 129.7 mAh g−1 with capacity retention of 88.3%. In addition, its electrochemical reversibility is also demonstrated by in-situ X-ray investigation.

Emodacidamides A–H (1–8), natural products featuring anthraquinone–amino acid conjugates, have been isolated from a marine-derived fungus, Penicillium sp. SCSIO sof101, together with known anthraquinones 9 and 10. The planar structures of 1–8 were elucidated using a combination of NMR spectroscopy and mass spectrometry. The absolute configurations of the amino acid residues were confirmed using Marfey’s method and chiral-phase HPLC analyses. Additionally, isolates were evaluated for possible immunomodulatory and cytotoxic activities. Emodacidamides A (1), C (3), D (4), and E (5) inhibited interleukin-2 secretion from Jurkat cells with IC50 values of 4.1, 5.1, 12, and 5.4 μM, respectively.

Isostructural LiMTiO 4 (M = Mn, Fe, Co) have been successfully synthesized by a facile sol-gel route and evaluated their possibility as an anode materials for lithium ion batteries (LIBs). All the samples exhibit high operating potential plateaus (>1.7 V vs. Li + /Li), which can prevent the formation of the solid electrolyte interphase (SEI) film on the electrode surface effectively. In addition, electrochemical investigations show that LiCoTiO 4 has a superior cycling performance, better rate capability, lower charge transfer resistance and higher lithium-ion diffusion coefficient than those of LiMnTiO 4 and LiFeTiO 4 . These electrochemical results indicate that LiCoTiO 4 is the most promising lithium storage material among all the examined spinel-type LiMTiO 4 samples.

Metal doping is an effective way to improve the electrochemical properties of titanates. In this work, Ba-site substituted Ba 0.9 M 0.1 Li 2 Ti 6 O 14 (M = K, Zn, La) are synthesized to fabricate high performance titanate anode for lithium-ion batteries. Electrochemical evaluations reveal that introducing metal doping at Ba-site can result in higher ionic/electronic conductivity. As a result, Ba 0.9 M 0.1 Li 2 Ti 6 O 14 exhibits enhanced lithium storage capability. Especially for Ba 0.9 La 0.1 Li 2 Ti 6 O 14 , it shows the best electrochemical performance with a high reversible charge capacity of 151.3 mAh g −1 and high capacity retention of 94.21% at a current density of 100 mA g −1 . For comparison, the pristine BaLi 2 Ti 6 O 14 only exhibits a reversible charge capacity of 128.5 mAh g −1 with the capacity retention of 80.06% after 100 cycles. Further, the lithium storage process is investigated in detail by in-situ structural observation, which reveals a maximum volume expansion of 1.9% for Ba 0.9 La 0.1 Li 2 Ti 6 O 14 during charge-discharge cycle. It shows that Ba 0.9 La 0.1 Li 2 Ti 6 O 14 is a possible material with high structural reversibility for lithium storage.

In order to investigate the lithiation-delithiation kinetics in BaLi2Ti6O14 anode material, BaLi2Ti6O14 is achieved by a solid-state reaction process in this work. The as-prepared BaLi2Ti6O14 is high purity titanate and well crystallized with a particle size distribution in the range of 0.5–1.5 μm. Electrochemical analysis shows that BaLi2Ti6O14 can deliver a reversible capacity of 126.1 mAh g− 1 at 5C, and the capacity retention is 74.1% after 1000 cycles. In addition, the electrochemical kinetics of BaLi2Ti6O14 is investigated by cyclic voltammetry (CV), in-situ electrochemical impedance spectroscopy (in-situ EIS) and galvanostatic intermittent titration (GITT) techniques. The DLi + values calculated from CVs are located in the range of 10− 13–10− 12 cm2 s− 1. For comparison, the average DLi + values received from EIS and GITT methods are located in the range of 10− 14–10− 12 cm2 s− 1 and 10− 14–10− 11 cm2 s− 1, respectively. Although the DLi + differs by several orders of magnitude from different measurement techniques, it still reveals higher value than that of Li4Ti5O12. Owing to the rapid diffusion kinetics of BaLi2Ti6O14, symmetrical structural evolutions can be observed via in-situ X-ray diffraction (XRD) study, which indicates that BaLi2Ti6O14 is a promising high-power anode candidate.

Mycophenolic acid (MPA) is a group of metabolite derived from several species of Penicillium, which shows potent bioactivity. In this study, a new derivative of MPA compound named penicacid D (1), was isolated from the marine derived fungus Penicillium sp. SCSIO sof101, along with seven known compounds (2-8). Their structures were elucidated based on the HR-ESI-MS and NMR data. Moreover, the 1H and 13C NMR data of compound 2 and the 13C NMR data of compound 3 are reported. Compounds 1, 4 and 6 exhibited weak activities against Escherichia coli (clinical isolation number 100385570) and Acinetobacter baumannii (clinical isolation number 100069).

Spinel LiCrTiO4 is synthesized via sol-gel pretreatment and subsequent solid state reaction at different calcining temperatures. Structural observation and electrochemical evaluation show that 800 °C is a suitable calcining temperature for LiCrTiO4 preparation. Compared with samples prepared at other temperatures, LiCrTiO4 formed at 800 °C exhibits better electrochemical performance with the capacity retention of 92.2% at 100 mA g−1 after 80 cycles. Even cycled at a higher current density of 500 mA g−1 in 0.0-3.0 V, LiCrTiO4 prepared at 800 °C still shows excellent cycling performance with a reversible capacity of 226.7 mAh g−1 after 80 cycles. Ex-situ valence analysis reveals that the high lithium storage capacity in LiCrTiO4 between 0.0 and 3.0 V is attributed to the reversible redox process of Ti4+/Ti3+ and Cr3+/Cr2+ couples. In addition, quasi zero-strain characteristic of LiCrTiO4 during lithiation is also demonstrated by in-situ and ex-situ structural observations. Therefore, LiCrTiO4 exhibits high structural stability and electrochemical reversibility as anode material for rechargeable lithium-ion batteries.

By using a simple high temperature solid state reaction, LiNi0.6Co0.2Mn0.1Al0.1O2 is prepared via Ni site dual substitution with Mn and Al. Structural observation reveals that the as-prepared sample can be indexed to an α-NaFeO2 type single phase with R-3m space group. Morphology and particle size investigations present that Mn and Al co-doped LiNi0.8Co0.2O2 is composed of micro-sized secondary particles (5–20 μm) agglomerated from highly packed primary particles (1–2 μm). Charge–discharge tests demonstrate that LiNi0.6Co0.2Mn0.1Al0.1O2 can reversibly react with lithium between 2.5 and 4.9 V with a high discharge capacity of 202.0 mAh g−1. This favorable electrochemical performance is attributed to the stable crystal structure after Mn and Al dual doping. This quasi-reversible structural change is also proved by in-situ X-ray diffraction study in this work.

In consideration of the abundance of sodium resources, sodium ion batteries (SIBs) have been revisited recently and are considered as a substitution for lithium ion batteries (LIBs). Among all the proposed anodes for SIBs, metal selenides labeled as high theoretical capacity materials have aroused the interest of battery researchers. However, as conversion/alloying based electrode materials, metal selenides suffer from a severe volume change during cycling, thus leading to kinetic problems and poor electrochemical stability, which restrain their further application in SIBs. Therefore, modification strategies such as coupling with carbonaceous material, designing unique structure, selecting an upper cut-off voltage, optimizing the composition of electrolyte, controlling the composition of the material etc. have been adopted to alleviate the volume change issue of metal selenides electrodes. In this article, the research progresses on the metal selenides as electrodes for SIBs are comprehensively reviewed and the difference and necessity of each metal selenide from the perspectives of structure and conductivity are emphasized. The summarization of metal selenides contains the synthesis methods, modification methods for performance improvement, corresponding reaction mechanism and performance in full-cell system. Finally, a conclusion with the challenges and outlook of metal selenides in the field of SIBs is also presented.

[Song, Xianqin; Luo, Minghe; Lu, Laichun] Third Mil Med Univ, Coll Pharm, Teaching Expt Ctr, Chongqing 400038, Peoples R China; Qingdao Univ, Affiliated Hosp, Cent Lab, 1677 Wutaishan Rd, Qingdao 266003, Peoples R China; [Huang, Hongbo] Chinese Acad Sci, South China Sea Inst Oceanol, RNAM Ctr Marine Microbiol, CAS Key Lab Trop Marine Bioresources & Ecol,Guand, 164 West Xingang Rd, Guangzhou 510301, Guangdong, Peoples R China

A new diketopiperazine (DKP) derivative, (6R,3Z)-3-benzylidene-6-isobutyl-1-methyl piperazine-2,5-dione (1), as well as five known DKPs 2–6 was isolated from a deep sea-derived Streptomyces sp. SCSIO 04496. The structure of 1 was elucidated using a combination of 1D and 2D NMR, HR-ESI-MS and chiral-phase HPLC techniques. Compounds 1–6 did not show cytotoxic activity at a concentration of 100 μM in bioactivity assay.