HBV─C基因探针的制备及应用

应用ＰＣＲ技术扩增出ＨＢＶＤＮＡＣ基因片段并与ｐＡＴ１５３质粒重组,转化到Ｅ．ｃｏｌｉＲＲＩ中,经体内扩增,提纯,用光生物素标记,制备了Ｃ基因的重组质粒探针。该探针检测灵敏度在Ｓｏｕｔｈｅｒｎ印迹中达１ｐｇ,在点印迹中为５ｐｇ。用此探针以Ｓｏｕｔｈｅｒｎ印迹方式配合ＰＣＲ技术检测乙肝病人血清中的ＨＢＶＤＮＡ,在５３例ＰＣＲ产物电泳检测阴性的样品中,Ｓｏｕｔｈｅｒｎ杂交又检出１８例阳性。     

PCR法快速检测临床标本中结核杆菌DNA

应用聚合酶链反应（ＰＣＲ）快速检测临床标本（脑脊液、胸水、腹水、血、痰液）中的结核杆菌ＤＮＡ,特异性扩增片段１２３ｂｐ,为结核杆菌的特异性重复序列ＩＳ６１１０部分基因。ＰＣＲ检测人型结核杆菌的敏感性达１０ｆｇＤＮＡ。临床标本的ＰＣＲ检测阳性率（２３．３％）明显高于抗酸染色涂片（２．９％）和细菌培养（５．７％）的阳性率（Ｐ〈０．０５）。通过设立对照系统及对扩增产物酶切分析,表明该法无假阴性结果（特异     

Encephalitozoon cuniculi Isolated from the Urine of an AIDS Patient, which Differs from Canine and Murine Isolates

ABSTRACT. A species of Encephalitozoon has been isolated from the urine of a patient with the acquired immunodeficiency syndrome and maintained in vitro in Madin Darby Canine Kidney cells. When examined by random amplified polymoprhic DNA polymerase chain reaction the new isolate was found to differ from E. hellem and to have amplified products in common with murine and canine E. cuniculi . However, it more closely resembled the canine than the murine isolate. Sodium dodecylsulphate polyacrylamide gel electrophoresis differentiated between all three isolates of E. cuniculi , with a band at 42–45 kDa present in the murine isolate only, bands at 52 kDa present in the canine and human isolates but not the murine, and a single band at 60 kDa (murine) and 65 kDa (canine) replaced by two bands at 55 and 70 kDa in the human isolate. The 55 kDa and 70 kDa antigens were also revealed as characteristic bands of the human isolate by Western blotting. The study has thus revealed that the species Encephalitozoon cuniculi is not a homogeneous entity.     

Increased reliability of selective PCR by using additionally mutated primers and a commercialTaq DNA polymerase enhancer

A reliable selective PCR procedure that combines the use of additionally mutated primers with the specificity-enhancing properties of a commercial preparation (Perfect Match, Stratagene) is described. The human immunodeficiency virus type 1pol gene point mutations known to confer in vitro resistance to azidothymidine were examined as a model for optimization of the assay. The usual strategy of deliberately introducing an additional mismatch 1 residue from the 3′ end in the wild-type and mutant primers did not allow reproducible discrimination between wild-type and mutant target sequences. Addition of minimal amounts of Perfect Match to the same PCR mixtures resulted in a significantly enlarged range of selective annealing temperatures, providing a valuable and cost-effective means for reliable detection of known mutations by selectivePCR.     

Comparative studies on the dynamics of crosslinked insulin

Molecular dynamics simulations were carried out on an insulin crosslinked between the N-terminal A chain and the C-terminal B chain to form a so-called mini-proinsulin: N -^A1-N -^B29-diaminosuberoyl insulin (DASI). To investigate the influence of crosslinking on the dynamics of the insulin moiety, the bridge was removed from a transient DASI structure and simulation was carried on independently with the then unlinked (ULKI) as well as with the crosslinked species. The effects of crystal packing and quaternary interactions were checked by simulating both types of monomers and dimers known from the hexamer structure. All simulations were compared to previous ones of native insulin. DASI shows general similarity to the native simulations in most parts of the structure. Deviations are visible in the segments to which the bridge is directly connected, i.e. their flexibility is reduced. Upon removal of the bridge the ULKI simulations reapproach those of native insulin. The influence of the bridge spreads over the whole molecule, but all of its main structural features remain intact. The simulations suggest that the displacement of the C-terminal B chain of native insulin, considered important for receptor interaction, is prevented by the bridge, which also partially shields some binding residues. This is in accordance with the poor biological potency of A1-B29-crosslinked insulins.Abbreviations DASI-insulin(DASI) bovineN -^A1-N -^B29-di-aminosuberoyl insulin - ULK-insulin (ULKI) Native beef insulin with the bridge of DASI removed     

Ricin B chain fragments expressed inEscherichia coli are able to bind free galactose in contrast to the full length polypeptide

Deleted forms of ricin B chain (RTB) containing only one of the two galactose binding sites were produced inE. coli and targeted to the periplasm by fusion to theompA orompF signal sequences. The proteins were then isolated from the periplasm and their sugar binding properties assessed. Previous studies investigating the properties of such proteins produced inXenopus laevis oocytes suggested that deleted forms of RTB, when not glycosylated, retain their ability to bind simple sugars, unlike the full-length unglycosylated proteins. When produced inE. coli however we found that only one, EB733, of a number of deleted forms of RTB closely related to those previously produced inXenopus laevis oocytes, bound to simple sugars. All of the deletion forms of RTB were found to bind in the asialofetuin binding assay; an assay which has been previously utilized to measure binding of lectins to the terminal galactose residues of glycoprotein oligosaccharides. However, in contrast to glycosylated RTB, binding of the deletion mutants could be competed to only a small degree or not at all with galactose. The only deletion mutant observed to bind to free galactose when produced inE. coli corresponded closely to the complete domain 2 of RTB. It is assumed that this mutant forms a stable structure similar to that of the C-terminal domain in the full-length protein. The structural integrity of EB733 was not only suggested by its sugar binding properties and solubility but also by its consistently higher level of expression and the absence of any apparent susceptibility toE. coli proteases.Abbreviations RTA ricin toxin A chain - RTB ricin toxin B chain - ER endoplasmic reticulum - SDS-PAGE sodium dodecyl sulphate-polyacrylamide gel electrophoresis - IPTG isopropyl -d-thiogalactopyranoside     

Poly(ADP-ribose) polymerase: Structural conservation among different classes of animals and its implications

Poly(ADP-ribose) polymerase cDNAs have been isolated from different classes of animals. Cloning of genes from lower eukaryotes has allowed us to investigate directly the biological functions of poly(ADP-ribosyl)ationin vivo. The conservation of specific regions among mammals, chicken,Xenopus laevis, andDrosophila melanogaster reveals the essential structural elements required for recognition of breaks in DNA and for catalytic activity. Cys, His and basic residues in the zinc-finger consensus region are conserved. The carboxyl terminal region corresponding to an NAD-binding domain is strongly conserved. The dinucleotide-binding consensus sequence and 1-A-2, Rossmann fold structure, and -sheet structures are completely conserved from mammals to insect. InDrosophila, a putative leucine-zipper motif has been identified, and other poly(ADP-ribose) polymerases also contain an -helical, amphipathic structure in the auto-modification domain. In this article, we review the recent structural analyses of the functional domains of poly(ADP-ribose) polymerase in phylogenetically divergent species, and discuss the implications of structural conservation for its biological functions.Abbreviations aa amino acid(s) - D. melanogaster Drosophila melanogaster - PARP poly(ADP-ribose) polymerase [EC 2.4.2.30] - PCR polymerase chain reaction - X. laevis Xenopus laevis     

Chaos in three species food chains

We study the dynamics of a three species food chain using bifurcation theory to demonstrate the existence of chaotic dynamics in the neighborhood of the equilibrium where the top species in the food chain is absent. The goal of our study is to demonstrate the presence of chaos in a class of ecological models, rather than just in a specific model. This work extends earlier numerical studies of a particular system by Hastings and Powell (1991) by showing that chaos occurs in a class of ecological models. The mathematical techniques we use are based on work by Guckenheimer and Holmes (1983) on co-dimension two bifurcations. However, restrictions on the equations we study imposed by ecological assumptions require a new and somewhat different analysis.     

PCR detection of MLOs in quick decline-affected pear trees in Italy

Polymerase chain reaction (PCR) amplification, using primers derived from the 16S rRNA gene, followed by restriction fragment length polymorphism (RFLP) analysis with Alu I restriction endonuclease was used to detect myc-oplasma-like organisms (MLOs) associated with pear decline. MLOs were consistently detected in pear trees that suddenly wilted and died within a few days during summer, as well as in pears of the same orchards with symptoms similar to the slow form of pear decline. In both cases the same RFLP pattern was obtained. Declining pear trees were 5 to 8-yr-old cvs Williams, Kaiser and Max Red Bartlett grafted on to Pyrus communis seedling rootstocks. All the orchards affected by quick decline had severe attacks of pear psyllid (Cacopsylla pyri) during the year this study was performed and during the previous year. The results showed the suitability of DNA amplification by the polymerase chain reaction for the detection of pear decline MLOs and established that MLOs can be detected in infected tissues of dead trees.     

精子介导鱼类基因转移和聚合酶链反应检测技术

金鱼精子与美洲大绵ｗｅｉ的抗冻蛋白基因一起保温３０分钟后,再与卵子受精,共获得１４５尾成鱼和若干胚胎。从胚胎和成鱼中提取ＤＮＡ经聚合酶链反应（ＰＣＲ法）扩增和Ｓｏｕｔｈｅｒｎ ｂｌｏｔ分子杂交表明,外源的抗冻蛋白基因进入了部分受体鱼的染色体组内。测定了４５尾一年龄实验鱼中,有１２尾显示出明确的杂交带,阳性率为２６％。