Hidden smectic properties of a chiral side-chain co-oligomer

We recently showed that a side-chain industrial co-oligosiloxane presents a quenchable enlarged blue phase behaviour at the cholesteric-isotropic phase transition. In this paper, we present the results of a structural study based on X-ray diffraction, differential scanning calorimetry and optical measurements. In particular, the smectic A organisation is demonstrated in the lower temperature domain, which was hitherto understood as a cholesteric phase. A structural model for this phase is proposed on the basis of the analysis of the anisotropic scattering of stretched fibers. Our results also suggest that the observed glass transition is indeed a rather complex phenomenon, which seems to involve not only the freezing of the main chains, but also smectic correlations at the side-chain level. Moreover, the calorimetric study indicates that, notwithstanding the conservation of the processed film's optical properties, low kinetic reorganisations occur at room temperature.     

Characterization of a human cervical carcinoma-associated antigen by lectin binding and immuno-electron microscopy

Summary The specific binding and nature of the epitope recognized by monoclonal antibody (Mab) 1H10, which binds an antigen expressed on human cervical tumors, was characterized by enzyme digestion, lectin competition assay and immuno-electron microscopy. Membrane homogenates of CaSki cervical carcinoma cells were digested with various enzymes, then analysed by SDS-PAGE and immunoblotting. Cells grown on coverslips were treated with various enzymes and in situ binding of Mab 1H10 to cells was analysed by electron microscopy. The ability of lectin-conjugates to block Mab 1H10 binding to CaSki cells was also examined. Treatment of samples with sodium periodate abrogated antigen recognition by Mab 1H10. Neuraminidase and hyaluronidase digestion decreased but did not eliminate Mab 1H10 binding to cells in situ. Chondroitinase ABC digestion, in contrast, removed Mab 1H10 binding sites both in vitro and in situ. Trypsin and chymotrypsin digestion of cell membrane homogenates decreased the molecular weight of the Mab 1H10 antigen but did not decrease the binding intensity. Wheat germ agglutinin (WGA) strongly bound to CaSki cells and partially blocked Mab 1H10 binding, indicating that the antigen contains N-acetyl-galactosamine residues at or near the epitope recognized by Mab 1H10. Ricinus communis agglutinin (RCA) exhibited a similar binding pattern to WGA. However, concanavalin A bound only weakly to CaSki cells and was ineffective at blocking Mab 1H10 binding. The tumor-associated antigen recognized by Mab 1H10 is concluded to be a chondroitin sulphate glycoprotein or proteoglycan rather than a mucopolysaccharide or lipoprotein.     

点状气单胞菌引起虹鳟感染症及其病原学机制的初步研究

对山西省朔县省虹鳟试验场1987年8月在亲鱼中爆发的一次流行病进行了病原菌分离、培养、毒力试验和详细的生理生化测定,确定点状气单胞菌为其病原菌。并对该菌胞外产物的致病性进行了研究,通过测定其溶血活性、酪蛋白酶活性、对鱼致死性以及对其引起的组织病理学变化的观察,初步确定了胞外产物与该菌侵袭力的相关性。     

高原低氧对机体无氧代谢阈值的影响

为了探讨高原低氧对机体无氧代谢阈值(AT)的影响,本研究采用Wasserman无创性方法,分别测定了11名新兵在平原(四川淮口,海拔500m)和经空运进驻高原 (西藏错那,海拔4370m)后的第3、5、7和14天的AT。结果表明:新兵进驻高原后AT由平原的813.6±147.4kg·m/min降低到395.5±194.5 kg·m/min(P<0.01);高原低氧引起AT的降低幅度与受试者平原AT的高低呈正相关(r=0.933,P<0.01);进驻高原后第3、5、7天AT维持在较低水平,随后呈上升趋势。但移居高原1年战士的AT仍低于平原水平(P<0.05)。提示,高原低氧能够显著地降低机体的AT,并且AT越高的个体进驻高原后受低氧环境的影响程度越大。     

甜菜坏死黄脉病毒的分离提纯及其生物化学特性的研究

本研究工作中,建立了一个有效的甜菜坏死黄脉病毒的分离提纯程序,解决了该病毒粒体易于聚集难以提纯的问题,其操作要点是,(1)通过Sepharose 2B柱层析代替超离心,有效地除去一些小分子量核酸杂质;(2)经PEG再次沉淀浓缩后,调整pH至酸牲(pH3.0),使病毒充分悬浮以减少凝聚;(3)在病毒等电点(pH4.8～4.9)条件下,进一步沉淀以纯化病毒。根据病毒提取物的OD260/OD280比值,算出核酸含量约4.5％。核酸电泳出现4条带,分子量分别为:2.25×10~(?),1.8×10~(?),1.05×10~(?),0.75×10~(?)道尔顿。病毒提取物经超速离心出现4个界面,沉淀系数分别为,200.8S,165S,125.8S,100S。说明甜菜坏死黄脉病毒可能是4组分病毒粒体。病毒粒体含一蛋白亚基,分子量约为2.05±0.05×10~4道尔顿,由16种共199个氨基酸组成。     

慢性蜜蜂麻痹病病毒核酸与蛋白质组分的研究

从自然感染的意大利麻痹病蜂(APis mellifera)头部,经二次差速离心与蔗糖梯度离心获得纯化的慢性蜜蜂麻痹病病毒(CBPV)。纯化的CBPV制备物感染正常蜜蜂,4天后出现典型的麻痹症状,接着死亡,平均死亡率分别为95％与100％。SDS-聚丙烯酰胺凝胶电泳分析,二次差速离心初步纯化的病毒制备物含有多条蛋白带,而蔗糖密度梯度纯化的病毒制备物仅含有单一的多肽带。5％、7.5％与10％SDS-聚丙烯酰胺凝胶电泳分析,均检测出一种病毒蛋白质,分子量大约为24,200道尔顿,而且不同凝胶浓度检测的蛋白质分子量相近。慢性蜜蜂麻痹病病毒核酸也用SDS-聚丙烯酰胺凝胶电泳分析,结果表明,凝胶中有5条带,对核酸酶敏感,证明该病毒含有5个单股RNA组分。对慢性蜜蜂麻痹病病毒的基因组结构进行了讨论。