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Articles by Lei Li
Total Records ( 6 ) for Lei Li
  Lei Li , Yuwan Gu , Yanyan Guo , Kemeng He , Yan Chen and Yuqiang Sun
  Research a master-slave duplex layer structure exact string matching parallel algorithm on the homogeneous PC cluster platform. Making use of the KMP main string mismatching irrelevant feature to construct secondary KR substring and then calculate the value of next function quickly. Using PC Cluster Message Passing Interface (MPI) parallel platforms and for the balanced load of each node processes which involved in computing, an anti-missing methods was proposed to do overlapped block with the target dictionary. The paralleled implementation process of hierarchical nested exact string matching algorithm was discussed in detail. The experiment demonstration is conducted on the homogeneous PC cluster platform, analyzing the parallel processing efficiency of data traffic on different levels under the condition of the intervention of multi nodes. Experimental results show that the algorithm has a high parallel efficiency and linear acceleration was obtained and has good scalability.
  Yuwan Gu , Zhiyuan Shi , Lei Li and Yuqiang Sun
  Mashup can facilitate using the retrieved content from external data source to create new services. Using the feature in the study, Mashup technique is applied in network shopping search strategy, through the opening of the API, screen capture etc method, the different content sources is integrated. The merchandises in different websites can be displayed and redundance is eliminated using filters, change of the resource information is notified in time through the warning apparatus. This method can be convenient online shopping user, saving the user time, constructing a more efficient network shopping environment.
  Lei Li , Wei Deng , Jie Song , Wei Ding , Qun- Fei Zhao , Chao Peng , Wei- Wen Song , Gong -Li Tang and Wen Liu
  Saframycin A (SFM-A), produced by Streptomyces lavendulae NRRL 11002, belongs to the tetrahydroisoquinoline family of antibiotics, and its core is structurally similar to the core of ecteinascidin 743, which is a highly potent antitumor drug isolated from a marine tunicate. In this study, the biosynthetic gene cluster for SFM-A was cloned and localized to a 62-kb contiguous DNA region. Sequence analysis revealed 30 genes that constitute the SFM-A gene cluster, encoding an unusual nonribosomal peptide synthetase (NRPS) system and tailoring enzymes and regulatory and resistance proteins. The results of substrate prediction and in vitro characterization of the adenylation specificities of this NRPS system support the hypothesis that the last module acts in an iterative manner to form a tetrapeptidyl intermediate and that the colinearity rule does not apply. Although this mechanism is different from those proposed for the SFM-A analogs SFM-Mx1 and safracin B (SAC-B), based on the high similarity of these systems, it is likely they share a common mechanism of biosynthesis as we describe here. Construction of the biosynthetic pathway of SFM-Y3, an aminated SFM-A, was achieved in the SAC-B producer (Pseudomonas fluorescens). These findings not only shed new insight on tetrahydroisoquinoline biosynthesis but also demonstrate the feasibility of engineering microorganisms to generate structurally more complex and biologically more active analogs by combinatorial biosynthesis.
  Lei Li , Elizabeth A. Monckton and Roseline Godbout
  DEAD box proteins are a family of putative RNA helicases associated with all aspects of cellular metabolism involving the modification of RNA secondary structure. DDX1 is a member of the DEAD box protein family that is overexpressed in a subset of retinoblastoma and neuroblastoma cell lines and tumors. DDX1 is found primarily in the nucleus, where it forms two to four large aggregates called DDX1 bodies. Here, we report a rapid redistribution of DDX1 in cells exposed to ionizing radiation, resulting in the formation of numerous foci that colocalize with γ-H2AX and phosphorylated ATM foci at sites of DNA double-strand breaks (DSBs). The formation of DDX1 ionizing-radiation-induced foci (IRIF) is dependent on ATM, which was shown to phosphorylate DDX1 both in vitro and in vivo. The treatment of cells with RNase H prevented the formation of DDX1 IRIF, suggesting that DDX1 is recruited to sites of DNA damage containing RNA-DNA structures. We have shown that DDX1 has RNase activity toward single-stranded RNA, as well as ADP-dependent RNA-DNA- and RNA-RNA-unwinding activities. We propose that DDX1 plays an RNA clearance role at DSB sites, thereby facilitating the template-guided repair of transcriptionally active regions of the genome.
  Hong-Chuang Song , Li-Mei Wang , Kai-Ze Shen , Rong Sun , Guo-Hong Li , Lei Li and Ke-Qin Zhang
  From cultural filtrates of the freshwater fungus Ophioceras dolichostomum YMF1.00988 a novel neolignan with an unprecedented dibenzo-1,6-dioxacyclodecane carbon skeleton, ophiocerol (1), was isolated, and the known compounds isoamericanoic acid A (2) and caffeic acid (3) were identified. The structure of the novel compound was determined by interpretation of its spectroscopic data, including 1D and 2D, 1H and 13C NMR (COSY, HMQC, HMBC, NOESY), and MS. Compounds 1-3 were assayed for their nematicidal activity against Bursaphelenchus xylophilus as well as their antifungal activity against several plant pathogen fungi.
  Ping Li , Shyam S. Chaurasia , Yan Gao , Aprell L. Carr , P. Michael Iuvone and Lei Li
  In zebrafish, the expression of long-wavelength cone (LC) opsin mRNA fluctuated rhythmically between the day and night. In a 24-h period, expression was high in the afternoon and low in the early morning. This pattern of fluctuation persisted in zebrafish that were kept in constant darkness, suggesting an involvement of circadian clocks. Functional expression of Clock, a circadian clock gene that contributes to the central circadian pacemaker, was found to play an important role in maintaining the circadian rhythms of LC opsin mRNA expression. In zebrafish embryos, in which the translation of Clock was inhibited by anti-Clock morpholinos, the circadian rhythms of LC opsin mRNA expression diminished. CLOCK may regulate the circadian rhythms of LC opsin mRNA expression via cyclic adenosine monophosphate (cAMP)-dependent signaling pathways. In control retinas, the concentration of cAMP was high in the early morning and low in the remainder of the day and night. Inhibition of Clock translation abolished the fluctuation in the concentration of cAMP, thereby diminishing the circadian rhythms of opsin mRNA expression. Transient increase of cAMP concentrations in the early morning (i.e. by treating the embryos with 8-bromo-cAMP) restored the circadian rhythms of LC opsin mRNA expression in morpholino-treated embryos. Together, the data suggest that Clock plays important roles in regulating the circadian rhythms in photoreceptor cells.
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