Purification and characterization of a gamma-like DNA polymerase from Chlamydomonas reinhardtii

A crude in vitro system which initiates chloroplast DNA synthesis near the D-loop site mapped by electron microscopy [Wu, M., Lou, J. K., Chang, D. Y., Chang, C. H., & Nie, Z. Q. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 6761-6765] consists of soluble proteins and proteins extracted from purified thylakoid membrane. In this paper, a DNA polymerase activity was purified to near homogeneity from the soluble protein fraction of this in vitro system by sequential chromatographic separations on heparin-agarose, DEAE-cellulose, and single-stranded DNA-agarose columns and sedimentation in a glycerol gradient. In the glycerol gradient, the enzyme activity sedimented at a position corresponding to a 110-kDa protein. Electrophoretic analysis of the highly purified fraction on SDS-polyacrylamide gel revealed a major polypeptide band with an apparent molecular mass of approximately 116 kDa. In situ DNA polymerase activity assay shows that the DNA polymerization function is associated with the 116-kDa band and an 80-kDa band which could be a subunit of the enzyme. Polymerization activity is inhibited by N-ethylmaleimide, ethidium bromide, and dideoxycytosine triphosphate and is relatively resistant to aphidicolin. Poly(dA).(dT)10 and gapped double-stranded DNA are preferred templates. The purified enzyme contains no exonuclease activity and can initiate DNA replication in a supercoiled plasmid DNA template containing the chloroplast DNA replication origin.     

人参生理生态的研究

人参是我国极其珍贵的药用植物之一。本文从生理生态的角度对其在生长季的各种环境因子的变化规律及光合生理进程作了较为全面、系统的定位定量研究。根据不同观测点的试验数据,得出了有利于人参生长的最适环境范围,为人参的栽培提供了理论依据及基础资料。     

Achieving stable myocardial regeneration after apical resection in neonatal mice

The neonatal heart completely regenerates after apical resection (AR), providing a desirable research model to study the mechanism of cardiac regeneration and cardiomyocyte proliferation. However, AR-induced neonatal heart regenerative phenomenon is controversial due to the variation of operative details in different laboratories. Here, we provide an optimized AR operation procedure with stable regeneration and high survival rate by achieving heart exposure, normalizing myocardium cut-offs, and reducing operation duration. We also established a whole-heart-slice approach to estimate the myocardial regeneration after the AR operation, which ensures no false-negative/positive results. The combination of the optimized AR operation and the whole-heart-slice analysis provides a stable system to study neonatal heart regeneration and cardiomyocyte proliferation in situ.     

Identification of circRNA and mRNA expression profiles and functional networks of vascular tissue in lipopolysaccharide‐induced sepsis

Sepsis is the most common cause of death in intensive care units. This study investigated the circular RNA (circRNA) and mRNA expression profiles and functional networks of the aortic tissue in sepsis. We established a lipopolysaccharide (LPS)‐induced rat sepsis model. High‐throughput sequencing was performed on the aorta tissue to identify differentially expressed (DE) circRNAs and mRNAs, which were validated by real‐time quantitative polymerase chain reaction (RT‐qPCR). Bioinformatic analysis was carried out and coding and non‐coding co‐expression (CNC) and competing endogenous RNA (ceRNA) regulatory networks were constructed to investigate the mechanisms. In total, 373 up‐regulated and 428 down‐regulated circRNAs and 2063 up‐regulated and 2903 down‐regulated mRNAs were identified. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of mRNAs showed that the down‐regulated genes were mainly enriched in the process of energy generation. CNC and ceRNA regulatory networks were constructed with seven DE circRNAs. The results of functional enrichment analysis of CNC target genes revealed the important role of circRNAs in inflammatory response. The ceRNA network also highlighted the significant enrichment in calcium signalling pathway. Significant alterations in circRNAs and mRNAs were observed in the aortic tissue of septic rats. In addition, CNC and ceRNA networks were established.     

Identification of immune-enhanced molecular subtype associated with BRCA1 mutations,immune checkpoints and clinical outcome in ovarian carcinoma

Ovarian carcinoma has the highest mortality among the malignant tumours in gynaecology, and new treatment strategies are urgently needed to improve the clinical status of ovarian carcinoma patients. The Cancer Genome Atlas (TCGA) cohort were performed to explore the immune function of the internal environment of tumours and its clinical correlation with ovarian carcinoma. Finally, four molecular subtypes were obtained based on the global immune-related genes. The correlation analysis and clinical characteristics showed that four subtypes were all significantly related to clinical stage; the immune scoring results indicated that most immune signatures were upregulated in C3 subtype, and the majority of tumour-infiltrating immune cells were upregulated in both C3 and C4 subtypes. Compared with other subtypes, C3 subtype had a higher BRCA1 mutation, higher expression of immune checkpoints, and optimal survival prognosis. These findings of the immunological microenvironment in tumours may provide new ideas for developing immunotherapeutic strategies for ovarian carcinoma.     

Caesalpanins A–C,Three Dimeric Cassane Diterpenoids from the Seeds of Caesalpinia sappan L.

Three dimeric cassane diterpenoids, caesalpanins A–C, were isolated from the seeds of Caesalpinia sappan L., as well as three known compounds. Their structures were determined via analysis of 1D‐, 2D‐NMR, and HR‐ESI‐MS data. Caesalpanins A and B were the second and third compounds that presented a nitrogen‐containing cassane diterpenoid dimer linked through one ether bond between C‐19 and C‐20′. Caesalpanin B exhibited moderate cytotoxic activity against MCF‐7 cell lines with IC₅₀ value of 29.98 μm . Caesalpanins A and B had weak inhibitory effects against LPS‐induced nitric oxide (NO) production in RAW 264.7 macrophages at 50 μm with inhibitory rate of 36.01 % and 32.93 %, respectively.     

Lead Halide Perovskite Nanocrystals: Room Temperature Syntheses toward Commercial Viability

In this progress report, recent improvements to the room temperaturesyntheses of lead halide perovskite nanocrystals (APbX₃, X = Cl, Br, I) are assessed, focusing on various aspects which influence the commercial viability of the technology. Perovskite nanocrystals can be prepared easily from low‐cost precursors under ambient conditions, yet they have displayed near‐unity photoluminescence quantum yield with narrow, highly tunable emission peaks. In addition to their impressive ambipolar charge carrier mobilities, these properties make lead halide perovskite nanocrystals very attractive for light‐emitting diode (LED) applications. However, there are still many practical hurdles preventing commercialization. Recent developments in room temperature synthesis and purification protocols are reviewed, closely evaluating the suitability of particular techniques for industry. This is followed by an assessment of the wide range of ligands deployed on perovskite nanocrystal surfaces, analyzing their impact on colloidal stability, as well as LED efficiency. Based on these observations, a perspective on important future research directions that can expedite the industrial adoption of perovskite nanocrystals is provided.