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Articles by Lei Shi
Total Records ( 8 ) for Lei Shi
  Lei Shi , Peijuan Yao , Lin Wei and Yongcai Tao
  Web proxy caching hierarchy is one of the main solutions used to improve Internet QoS. Focusing on the modeling of Web proxy hierarchy caching, this paper applies cost function to analyze Web caching performance. The experiments evaluate the caching performance of different combinations of replacement policy (LRU, LFU, GDS) across different levels within Web hierarchy caching model. The experimental results demonstrate that when the lower level uses the LFU or LRU replacement policy and the upper level uses the GDS, the two-level hierarchical proxy model achieves higher caching performance.
  Suo-Ping Xu , Lei Shi , Peng-Cheng Lv , Rui-Qin Fang and Hai-Liang Zhu
  Two new Schiff bases (2,4-diiodo-6-[(2-morpholin-4-yl-ethylimino)-methyl]-phenol and 2,4-diiodo-6-[(3-morpholin-4-yl-propylimino)-methyl]-phenol), condensed from 3,5-diiodosalicylaldehyde with 2-morpholinoethylamine and 3-morpholinopropylamine, have been designed and synthesized. Reaction of the Schiff bases with Zn(OAc)2 · 2H2O, Cu(OAc)2 · H2O, Ni(OAc)2 · 4H2O, Co(OAc)2 · 4H2O, Cd(OAc)2 · 2H2O, Mn(OAc)2 · 4H2O, Fe(SO4)2 · 7H2O, and Hg(OAc)2 led to the formation of 16 new mononuclear complexes. The complexes were characterized by UV, Infrared, ESI-MS, and elemental analyses, and 3,5-diiodosalicylalidene-2-morpholinoethylaminozinc(II) (1) and 3,5-diiodosalicylalidene-2-morpholinoethylaminocopper(II) (2) were characterized by single crystal X-ray diffraction. Based on crystal structural analysis of 1 and 2, coupled with their spectral similarity with 3-16, it can be concluded that 3-16 have structures similar to 1 and 2. All the complexes were assayed for antibacterial activities against three Gram positive bacterial strains (Bacillus subtilis, Staphylococcus aureus, and Streptococcus faecalis) and three Gram negative bacterial strains (Escherichia coli, Pseudomonas aeruginosa, and Enterobacter cloacae) by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide method. Among the complexes tested, 8 and 16 showed the most favorable antibacterial activity with minimum inhibitory concentration of 0.781, 12.5, 6.25, 3.125, 3.125, 6.25 and 1.562, 6.25, 1.562, 3.125, 3.125, 1.562 µg mL-1 against B. subtilis, S. aureus, S. faecalis, P. aeruginosa, E. coli, and E. cloacae, respectively.
  Lei Shi , Wen-Jun Mao , Ying Yang and Hai-Liang Zhu
  Preparation and crystal structure of {4-chloro-2-[(2-morpholinoethylimino)methyl]phenolato} methanolchlorozinc(II) are reported. The X-ray structure reveals highly distorted square pyramidal geometry around zinc, binding to one phenolate O and two imine N atoms of the Schiff base, one methanol and one chloride. The complex and its ligand were tested in vitro for antibacterial and cytotoxic activity with a wide range of bactericidal activity and significant cytotoxic activity.
  Mei YANG , Lei SHI , Fang-Sen XU , Jian-Wei LU and Yun-Hua WANG
  A field experiment was conducted to study the effects of boron (B), molybdenum (Mo), zinc (Zn) and their interactions on seed yield and yield formation of rapeseed (Brassica napus L. var. Huashuang 4). Application of B fertilizer to a sandy soil increased the seed yield by 46.1% compared to the control and also created a considerably higher seed yield than the two treatments solely applying Mo and Zn fertilizers, which suggested that B was a main constraint for the seed yield of Huashuang 4 in this experiment. The effect of B fertilizer on the seed yield was attributed to an increase in the number of seeds per silique and siliques per plant. The combined application of B with Mo or Zn resulted in higher seed yield than the application of B, Mo or Zn alone, and the seed yield of the B+Mo+Zn treatment was the highest in all treatments, 68.1% above the control. Dry matter accumulation of seed followed a typical S-shaped curve and it was higher in plants supplied with B than in plants without B. A small but significant increase in the seed oil content and an improvement in the oil quality were also observed in all treatments compared with the control. These results suggested that optimal micronutrient application could provide both yield and quality advantages for rapeseed in poor soil.
  Lei SHI , Yun-Hua WANG , Fu-Zhao NIAN , Jian-Wei LU , Jin-Ling MENG and Fang-Sen XU
  Field experiments were conducted to study the inheritance of boron efficiency in oilseed rape (Brassica napus L.) by evaluating the boron (B) efficiency coefficient (BEC, the ratio of the seed yield at below the critical boron level to that at the boron-sufficient level) with 657 F2:3 lines of a population derived from a cross between a B-efficient cultivar, Qingyou 10, and a B-inefficient cultivar, Bakow. Qingyou 10 had high BEC as well as high seed yield at low available soil B. On the contrary, Bakow produced low seed yield at low B status. Boron deficiency decreased the seed yield of the F2:3 lines to different extents and the distribution of BEC of the population showed a bimodal pattern. When the 657 F2:3 lines were grouped into B-efficient lines and B-inefficient lines according to their BEC, the ratio of B-efficient lines to B-inefficient lines fitted the expected ratio (3:1), indicating that one major gene controlled the B-efficiency trait. 127 F2:3 lines selected from the population at random, with distribution of BEC similar to that of the overall population, were used to identify the target region for fine mapping of the boron efficiency gene.
  Yupeng Chen , Lei Shi , Lirong Zhang , Ruifang Li , Jing Liang , Wenhua Yu , Luyang Sun , Xiaohan Yang , Yan Wang , Yu Zhang and Yongfeng Shang
  SOX genes encode a family of high-mobility group transcription factors that play critical roles in organogenesis. The functional specificity of different SOX proteins and the tissue specificity of a particular SOX factor are largely determined by the differential partnership of SOX transcription factors with other transcription regulators, many of which have not yet been discovered. Virtually all members of the SOX family have been found to be deregulated in a wide variety of tumors. However, little is known about the cellular and molecular behaviors involved in the oncogenic potential of SOX proteins. Using cell culture experiments, tissue analysis, molecular profiling, and animal studies, we report here that SOX2 promotes cell proliferation and tumorigenesis by facilitating the G1/S transition and through its transcription regulation of the CCND1 gene in breast cancer cells. In addition, we identified β-catenin as the transcription partner for SOX2 and demonstrated that SOX2 andβ-catenin act in synergy in the transcription regulation of CCND1 in breast cancer cells. Our experiments not only determined a role for SOX2 in mammary tumorigenesis but also revealed another activity of the multifunctional protein, β-catenin.
  Juan M. Pascual , Dong Wang , Ru Yang , Lei Shi , Hong Yang and Darryl C. De Vivo
  Exon IV of SLC2A1, a multiple facilitator superfamily (MFS) transporter gene, is particularly susceptible to mutations that cause GLUT1 deficiency syndrome, a human encephalopathy that results from decreased glucose flux through the blood-brain barrier. Genotyping of 100 patients revealed that in a third of them who harbor missense mutations in the GLUT1 transporter, transmembrane domain 4 (TM4), encoded by SLC2A1 exon IV, contains mutant residues that have the periodicity of one face of a kinked α-helix. Arg-126, located at the amino terminus of TM4, is the locus for most of the mutations followed by other arginine and glycine residues located elsewhere in the transporter but conserved among MFS proteins. The Arg-126 mutants were constructed and assayed for protein expression, targeting, and transport capacity in Xenopus oocytes. The role of charge at position 126, as well as its accessibility, was investigated in R126H by determining its activity as a function of extracellular pH. The results indicate that intracellular charges at the MFS TM2–3 and TM8–9 signature loops and flanking TMs 3, 5, and 6 are critical for the structure of GLUT1 as are TM glycines and that TM4, located at the catalytic core of MFS proteins, forms a helix that surfaces into the extracellular solution where another proton facilitates transport.
  Julie Kniazeff , Lei Shi , Claus J. Loland , Jonathan A. Javitch , Harel Weinstein and Ulrik Gether
  Neurotransmitter:sodium symporters (NSS)1 mediate sodium-dependent reuptake of neurotransmitters from the synaptic cleft and are targets for many psychoactive drugs. The crystal structure of the prokaryotic NSS protein, LeuT, was recently solved at high resolution; however, the mechanistic details of regulation of the permeation pathway in this class of proteins remain unknown. Here we combine computational modeling and experimental probing in the dopamine transporter (DAT) to demonstrate the functional importance of a conserved intracellular interaction network. Our data suggest that a salt bridge between Arg-60 in the N terminus close to the cytoplasmic end of transmembrane segment (TM) 1 and Asp-436 at the cytoplasmic end of TM8 is stabilized by a cation-π interaction between Arg-60 and Tyr-335 at the cytoplasmic end of TM6. Computational probing illustrates how the interactions may determine the flexibility of the permeation pathway, and mutagenesis within the network and results from assays of transport, as well as the state-dependent accessibility of a substituted cysteine in TM3, support the role of this network in regulating access between the substrate binding site and the intracellular milieu. The mechanism that emerges from these findings may be unique to the NSS family, where the local disruption of ionic interactions modulates the transition of the transporter between the outward- and inward-facing conformations.
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