Commonly, the interbacterial transfer of circular plasmids is initiated by nicking at an internal sequence, oriT, followed by transferring one strand as single-stranded DNA through a type Ⅳ secretion channel on cell membrane. In contrast, Streptomyces conjugative linear plasmids, containing a free 3'-end but a protein-capped 5'-end, can potentially undergo cell-to-cell transfer by transfer of non-nicked DNA. It was reported that circular derivatives of the Streptomyces lividans linear plasmid SLP2, as well as the parental linear plasmid itself can transfer efficiently. And the genetic requirements for such transfer was described. Efficient transfer of plasmid requires six co-transcribed SLP2 genes, encoding a Tra-like DNA translocase, cell wall hydrolase, two cell membrane proteins that interact with an ATP binding protein, and a protein of unknown function. Reduced transfer efficiency of plasmid from SalⅠ R-/M-to Sal Ⅰ R/M hosts argues that transfer of both the circular and linear forms of the plasmid involves double-stranded DNA. These results suggest that conjugal transfer occurs by a similar mechanism for SLP2-derived linear and circular plasmids, and cellular membrane/wall functions in the transfer process.

Though Runx2 and Osterix are both key transcription factors in the pathway of osteoblast differentiation, whether Runx2 positively regulates Osterix being unknown. It was showed that Runx2 induced the gene expression of Osterix both in the non-osteoblastic cell lines, either pluripotent or differentiated, and in the osteoblastic cell lines. At the same time, the results also indicated that Runx2 up-regulated the activity of the 3.2 kb human Osterix promoter. Further experiments identified a highly conserved and functional Runx2 binding site "AGTGGTT" within the promoter. Thus the results support the hypothesis that Runx2 is involved in the regulation of the Osterix gene expression. Moreover, the transient transfection and dual-luciferase assay showed Osterix up-regulated the activity of the 2.3 kb type Ⅰ collagen promoter in the non-osteoblastic cells, but Runx2 did not. This difference implies that Osterix, the down stream transcription factor of Runx2 during osteoblast differentiation, is needed to stimulate the osteoblast-specific gene expression of type Ⅰ collagen.

Glechoma hederocea agglutinin (Gleheda) is a novel glycosylated lectin isolated from the leaves of G. hederacea. Like other glycosylated proteins, the detection of Gleheda by immunological methods is often hampered by the cross-reactivity of the polyclonal antibodies with unrelated glycoproteins. Hence a protocol to purify monospecific polyclonal antibodies from a crude antiserum raised against Gleheda was developed. After selective ammonium sulfate precipitation and successive affinity chromatography on columns of Sepharose 4B with immobilized Gleheda and Robinia pseudoacacia agglutinin (RPA), respectively, ion-exchange chromatography on a column of Q Fast Flow was used for further purification. The specificity of the antibody fractions from each step was tested by double immunodiffusion assay and analyzed by Western blot. Results revealed that affinity chromatography of the immunoglobulin fraction on the immobilized Gleheda antigen yielded an antibody preparation that still cross-reacted with many proteins in leaf extracts. Depletion of nonspecific cross-reacting antibodies directed against the glycan part of the glycoprotein by affinity chromatography on immobilized RPA removed most but not all nonspecifically reacting antibodies. Only upon further purification by ion exchange chromatography an IgG fraction of monospecific antibodies that reacted exclusively with Gleheda could be obtained and accordingly was suitable for immunodetection studies. This antibody purification procedure promises simplicity and efficiency. In addition, this method does not require expensive facilities.

The hippocampus plays a critical role during the consolidation of trace eyeblink conditioned responses (CRs). However, the role of its related structure such as dentate gyms (DG) remains unclear. The present study was aimed at monitoring the activity of single granule cell in the DG during the consolidation of trace eyeblink CRs, and elucidating the possible role of DG during this hippocampus-dependent task. Guinea pigs (n=8) were trained on a trace eyeblink conditioning paradigm using a 200-ms tone conditioned stimulus (CS), a 200-ms corneal airpuff unconditioned stimulus (US) and a 600-ms trace interval. Controls consisted of pseudo- conditioned guinea pigs (n=8). Extracellular single unit recordings in vivo were performed in the DG of learner animals during the consolidation of trace eyeblink CRs. The results revealed that all the trace-conditioned animals acquired the trace eyeblink CRs over 14 training days, however, none of the pseudo-conditioned animals did. Furthermore, 23 of 40 single granule cells in the DG of learner animals exhibited heterogeneous activity patterns during the consolidation of trace eyeblink CRs such as increases in activities to the tone CS, trace interval or airpuff US. The results suggested that the DG might participate in the neural circuit important for the consolidation of trace eyeblink CRs, and that the granule cells might encode different information during the consolidation of trace eyeblink CRs.

Glutathione S-transferase (GST) gene, PcgstA was cloned from the penicillin producing strain Penicillium chrysogenum,which is important for understanding the industrial fermentation process. PcgstA gene has an open-reading-frame of 840 bp in length,which is interrupted by two introns. The deduced amino acid sequence shows about 50% identity to several characterized filamentous fungi GSTs. The recombinant PcGSTA in Escherichia coli were overexpressed and purified. Enzymatic assays showed that the recombinant PcGSTA had a specific activity with 1-chloro-2, 4-dinitrobenzene of (0.159±0.031) μmol/(min· mg). It was found that the expression level of PcgstA in the penicillin producing medium supplemented with phenylacetic acid, the side chain precursor of penicillin G, was significant down regulated than that in medium without phenylacetic acid. This result suggested that PcGST may be related to phenylacetic acid metabolism in the penicillin producing strain.

Numerous peptides that bind to a given target have been selected by phage display technology. However, some peptides isolated to date do not bind with high affinity to tumor or organ sites, even peptides were selected in vivo. Therefore, the biodistribution of 99mTc-labeled filamentous phage peptide library via MAG3 (mercaptoacetyltriglycine) were investigated to gain a better understanding of phage circulation in vivo. The experimental results showed that the liver and spleen were the organs of the greatest accumulation, while heart, muscle, pancreas and brain retained less radioactivity. In opposite to other tissues and organs, the radioactivity in stomach, intestine and bone gradually went up with time. The clearance of 99mTc-labeled phage in blood was very fast from 5 min to 30 min and then slowed down. When phage in vivo circulated at enough long period of time, some phage particles could extravasate in some organs or tissues and internalized there. In conclusion, the circulation time of phage in vivo should be experimentally determined beforehand according to the targeted organs and the specific location of target peptides in order to panning a peptide with high specificity and affinity to that target.

In hippocampus, numerous studies have shown that N-methyl-D-aspartate (NMDA) receptors are essential for the initiation of long-term potentiation (LTP), whereas the expression of LTP is primarily mediated by the phosphorylation of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and the increased insertion of postsynaptic AMPA receptors. However, in recent years there is also evidence that NMDA receptor channels contribute to the expression of LTP under physiological conditions. It was examined whether NMDA receptor channels contributed to the expression of LTP of C-fiber evoked field potentials in rat spinal dorsal horn by intravenous or spinal application of NMDA receptor antagonists after the establishment of LTP. It was found that MK 801 (a non-competitive NMDA receptor antagonist) at dose of 0.1 mg/kg (iv) had no effect on the spinal LTP and at the dose of 0.5 mg/kg depressed the LTP significantly. However, the inhibitory effect of MK 801 at higher dose (1.0 mg/kg)was not different from that produced by the dose of 0.5 mg/kg. The similar inhibitory effect on spinal LTP was also observed, when MK 801 was applied locally at the recording segments of spinal cord. To confirm the above results, a competitive NMDA receptor antagonist AP V was tested. Spinal application of AP V at a concentration of 100 μmol/L produced a stronger depression than at 50 μmol/L. When the concentration of AP V increased to 200 μmol/L, no further depression was observed. These results indicate that NMDA receptor channels are involved in the expression of LTP of C-fiber evoked field potentials in the rat spinal dorsal horn.

Satellite RNA ofBaMV (satBaMV), a single-stranded positive-sense RNA of 836 nucleotide [excluding 3′ poly(A) tail]containing a single open reading frame which encodes a nonstructural protein of 20 ku (P20), depends on BaMV for its replication and encapsidation. P20 is a nucleic-acid-binding protein, which facilitates the long distance movement of satBaMV in plants.Protein-protein interactions were analyzed by a bacterial two-hybrid system and pull-down assays to investigate whether P20 could self-associate and/or interact with the helper virus proteins. Self-interaction of P20 was the strongest among the viral protein-protein interactions detected in vivo and in vitro. Significant interactions of P20 with methyltransferase (MET) and capsid protein (CP) of BaMV were evidenced. Interactions among triple gene block protein 1, 2 and 3 (TGBp1, TGBp2 and TGBp3) of BaMV were also significant. BaMV CP also exhibited a strong self-interaction and strong affinity to TGBp1, TGBp2 and TGBp3. By deletion analysis,the minimal region delineated for the self-interaction of P20 was the N-terminal 15 amino acids which include the RNA binding motif of P20. N-terminal deletion resulted in the loss of self-interaction of P20. Deletion analysis also confirmed the importance of β-sheet structure of P20 in the P20-P20 interaction. P20 showed significant interactions with two host (Nicotiana benthamiana) proteins,cytochrome-C reductase and β-tubulins. The homotypic and heterotypic interactions of BaMV proteins and P20 in vivo thus suggest that the protein-protein interactions may directly exert an effect on the BaMV and satBaMV RNA movement as a protein complex in the infected host plants.

A new and effective method to produce transgenic animals was established. Without a surgical incision, the recombinant plasmid containing green fluorescence protein (GFP) cDNA was repeatedly injected into male mouse testis at multi-sites. After few weeks of the final injection, the injected male was mated with normal oestrus female to produce transgenic mice. The presence of the GFP cDNA in F1 transgenic individuals were detected by polymerase chain reaction and Southern blot hybridization, which showed that the transgenic rate of mouse F1 offspring was 41%. The transferred gene was integrated into the host genome and could be transmitted to its offspring. When the positive F1 individuals were mated with the wild type ICR mice, the F2 individuals had a transgenic rate of 37%. The results indicate that the high efficiency of gene transfer and the limited number of manipulations make the method suitable for creating a large number of transgenic animals, especially, for producing domestic animals.

Deoxycytidylate (dCMP) deaminase is an enzyme belonged to dCMP cyt deam family. The dCMP deaminase from Streptococcus mutans UA159 was cloned and expressed in E. coli, and purified to homogeneity. The FPLC size exclusion chromatography analysis reveals that the S. mutans dCMP deaminase forms hexamer in solution. The protein was crystallized using hanging drop vapour-diffusion method and diffracted to a resolution of 3.1 (A). The diffraction data were collected at BSRF beamline3W1A. The crystals belong to P213 space group, with unit cell parameters a = b = c = 113.2(A), α =β = γ = 90°. Assuming there are two subunits per asymmetric unit, the Matthews coefficient is 3.6 (A)3 ·Da-1. This is the first crystallization report of the wild-type deoxycytidylate deaminase.