Characteristic Steroids from the South China Sea Gorgonian Muricella sibogae and Their Cytotoxicities

Twenty‐four steroid‐based natural products, 9,10‐secosteroids ( 1 – 10 ), 1,4‐dien‐3‐one steroids ( 11 – 19 ), and 4‐en‐3‐one steroids ( 20 – 24 ), containing varying side‐chains, were isolated from the South China Sea gorgonian Muricella sibogae. The structures of one new 9,10‐secosteroid, sibogol D ( 1 ), and two new 1,4‐dien‐3‐one steroids, sibogols E and F ( 11 and 12 ), were elucidated by extensive spectroscopic analyses and by comparison with the literature data. Cytotoxicities for all the isolates were evaluated against four selected tumor cell lines, HL‐60, HCT116, K562, and P388. Compounds 3, 9 , and 13 exhibited potent cytotoxic activities against the HL‐60 cell line, with IC₅₀ values ranging from 1.27 to 10.05 μM , and compound 3 was also cytotoxic against HCT116 with an IC₅₀ value of 5.8 μM . The bioassay results also indicated a potential relationship between structural patterns and activity. The newly presented series of 1,4‐dien‐3‐one and 4‐en‐3‐one types of steroids relating to the unique 9,10‐secosteroids in biogenesis were found in this species for the first time, which is of considerable chemotaxonomic significance.     

Gene expression profiles in different stem internodes reveal the genetic regulation of primary and secondary stem development in <Emphasis Type="Italic">Betula platyphylla</Emphasis>

Secondary growth of stems is an important process for the radial increase of trees. To gain an insight into the molecular mechanisms underlying stem development from primary to secondary growth and to provide information for molecular research and breeding in Betula platyphylla (birch), the gene expression profiles of material from the first, third, and fifth internodes (IN) of 3-month-old seedlings were analyzed. Compared with the first IN, 177 genes were up-regulated and 157 genes down-regulated in the third IN; in the fifth IN, 180 genes were up-regulated and 275 genes were down-regulated. The expressions of 24 genes were up-regulated and 6 genes were down-regulated in the fifth IN relative to the third IN. The differentially expressed genes were annotated as having roles in cambium, xylem, and phloem development and formation; including cell wall expansion, cellulose biosynthesis, lignin biosynthesis and deposition, xylem extension, cell wall modification, and growth hormone responses. The expressions of genes related to cell wall expansion and cellulose biosynthesis in the primary cell wall were down-regulated in the third and fifth IN relative to the first IN. Genes involved in lignin biosynthesis, xylem extension, and cellulose synthesis in the secondary cell wall were up-regulated in the third and fifth IN relative to the first IN. These results described the patterns of gene expression during stem development in birch and provided candidate genes for further functional characterization.     

3D‐Printed Cathodes of LiMn1−xFexPO4 Nanocrystals Achieve Both Ultrahigh Rate and High Capacity for Advanced Lithium‐Ion Battery

A 3D‐printing technology and printed 3D lithium‐ion batteries (3D‐printed LIBs) based on LiMn_0.21Fe_0.79PO₄@C (LMFP) nanocrystal cathodes are developed to achieve both ultrahigh rate and high capacity. Coin cells with 3D‐printed cathodes show impressive electrochemical performance: a capacity of 108.45 mAh g^?1 at 100 C and a reversible capacity of 150.21 mAh g^?1 at 10 C after 1000 cycles. In combination with simulation using a pseudo 2D hidden Markov model and experimental data of 3D‐printed and traditional electrodes, for the first time deep insight into how to achieve the ultrahigh rate performance for a cathode with LMFP nanocrystals is obtained. It is estimated that the Li‐ion diffusion in LMFP nanocrystal is not the rate‐limitation step for the rate to 100 C, however, that the electrolyte diffusion factors, such as solution intrinsic diffusion coefficient, efficiency porosity, and electrode thickness, will dominate ultrahigh rate performance of the cathode. Furthermore, the calculations indicate that the above factors play important roles in the equivalent diffusion coefficient with the electrode beyond a certain thickness, which determines the whole kinetic process in LIBs. This fundamental study should provide helpful guidance for future design of LIBs with superior electrochemical performance.     

Integrated Intercalation‐Based and Interfacial Sodium Storage in Graphene‐Wrapped Porous Li4Ti5O12 Nanofibers Composite Aerogel

Sodium storage in both solid–liquid and solid–solid interfaces is expected to extend the horizon of sodium‐ion batteries, leading to a new strategy for developing high‐performance energy‐storage materials. Here, a novel composite aerogel with porous Li₄Ti₅O₁₂ (PLTO) nanofibers confined in a highly conductive 3D‐interconnected graphene framework (G‐PLTO) is designed and fabricated for Na storage. A high capacity of 195 mA h g^?1 at 0.2 C and super‐long cycle life up to 12 000 cycles are attained. Electrochemical analysis shows that the intercalation‐based and interfacial Na storage behaviors take effect simultaneously in the G‐PLTO composite aerogel. An integrated Na storage mechanism is proposed. This study ascribes the excellent performance to the unique structure, which not only offers short pathways for Na⁺ diffusion and conductive networks for electron transport, but also guarantees plenty of PLTO–electrolyte and PLTO–graphene interfacial sites for Na⁺ adsorption.