海枣曲霉β-半乳糖苷酶的提纯与性质

 通过过聚乙二醇6000-磷酸钾缓冲液双相分离、Sephadex G-100凝胶过滤、DEAE-Sephadex A-50离子交换层析、羟基磷灰石层析及SephadexG-100凝胶过滤等提纯步骤,从海枣曲霉(Aspergillus phoenicis)麦麸培养物抽提液中提纯得到凝胶电泳均一的β-半乳糖苷酶。该酶的最适pH为3.5—4.0,最适温度为60℃(反应15分钟),在pH5.0—8.5之间及60℃以下稳定。在65℃和70℃保温时失活50％的时间分别为27和2分钟。用SDS凝胶电泳法和梯度凝胶电泳法分别测得该酶的分子量为115,000和118,000。薄层凝胶等电聚焦法测得其等电点为pH4.6。     

FPC-ICAD: an intelligent CAD for fermentation process control

The paper presents an Intelligent CAD system for Fermentation Process Control (FPC-ICAD) based on a hierarchical architecture possessing three levels: real-time supervision level, CAD level and learning level. The aims of the learning are mainly composed of the aspects fermentation process modelling, determination of appropriate control and estimation methods, determination of the corresponding parameters and fermentation monitoring through measurement and software management. Three independent, but interactive software packages allow user to organize his system for different purposes: on-line control system (with only supervision), off-line CAD as a teaching software, off-line intelligent CAD (CAD+learning package), and on-line intelligent CAD.     

Phosphorylation of the carotenoid droplet protein p57 by the catalytic subunit of cyclic adenosine monophosphate-dependent protein kinase and the effect of fluoride

We have previously shown that the dispersion and aggregation of carotenoid droplets in goldfish xanthophores are regulated, respectively, by phosphorylation and dephosphorylation of a carotenoid droplet protein p57. There is a basal level of p57 phosphorylation of p57 in unstimulated cells, which is greatly stimulated by adrenocorticotropic hormone (ACTH) or cyclic adenosine monophosphate (cAMP) acting via cAMP-dependent protein kinase. We have also observed that, in permeabilized xanthophores, pigment dispersion can be induced when cAMP is replaced by fluoride. Since p57 has multiple phosphorylation sites, there is the question of whether all p57 phosphorylation is by cAMP-dependent protein kinase or whether phosphorylation by cAMP-independent protein kinase coupled with inhibition of phosphatase activity by fluoride can replace cAMP-dependent protein kinase and that the ability of fluoride to replace cAMP for pigment dispersion in permeabilized cells is probably due to activation of adenylcyclase. We also show that ACTH causes an approximately threefold increase in the level of cAMP in these cells.     

Pleiotropic resistance to glycoprotein processing inhibitors in Chinese hamster ovary cells. The role of a novel mutation in the asparagine-linked glycosylation pathway

In order to obtain a better understanding of the control mechanisms involved in asparagine-linked glycosylation, we developed conditions under which the glucosidase I and II inhibitor castanospermine and the mannosidase II inhibitor swainsonine were toxic to Chinese hamster ovary (CHO) cells when cultured in the presence of low concentrations of the plant lectin concanavalin A. Cells resistant to castanospermine (CsR cells) and swainsonine (SwR cells) were obtained by gradual stepwise selections. These cells had normal levels of glucosidase II and mannosidase II and appeared to have no major structural alterations in their surface asparagine-linked oligosaccharides. Interestingly, the CsR and SwR cells were each pleiotropically resistant to castanospermine, swainsonine, and deoxymannojirimycin, an inhibitor of mannosidase I. This resistance was not due to the multiple-drug resistance phenomenon. Both the CsR and SwR cell populations synthesized Man5GlcNAc2 in place of Glc3Man9GlcNAc2 as the major dolichol-linked oligosaccharide. This defect was not due to a loss of mannosylphosphoryldolichol synthetase. Furthermore, the Man5GlcNAc2 oligosaccharide was transferred to protein and appeared to give rise to normal mature oligosaccharides. Thus, the CsR and SwR cells achieved resistance to castanospermine, swainsonine, and deoxymannojirimycin by synthesizing altered dolichol-linked oligosaccharides that reduced or eliminated the requirements for glucosidases I and II and mannosidases I and II during the production of normal asparagine-linked oligosaccharides. We propose that this phenotype be termed PIR, for processing inhibitor resistance.     

2,3-Butanediol production by Enterobacter aerogenes in continuous culture: role of oxygen supply

Summary The influence of oxygen on growth and production of 2,3-butanediol and acetoin by Enterobacter aerogenes was studied in continuous culture. At all dilution rates (D) studied cell mass increased steadily with increasing oxygen uptake rate (OUR), hence the micro-aerobic cultivation was energy-limited. The biomass yield on oxygen increased with D which suggests that cells need more energy for maintenance functions at lower D. At each D an optimal OUR giving highest volumetric productivity for the sum of butanediol and acetoin was found. The optimal OUR increased with D. The occurrence of optimal OURs results from the various effects of O₂ on growth and specific productivity. The latter was found to be a linear function of the specific OUR irrespective of D. At optimal OUR the cells proved to have equal specific OURs and equal specific productivities representing a fixed relationship between fermentative and respiratory metabolism. The product yield based on glucose and corrected for biomass formation was 80%. A product concentration as high as 43 g/l was obtained at D =0.1 h^–1 while the volumetric productivity was the highest at D =0.28 h^–1 (5.6 g/l and hour). The findings further indicate that growth and product generation are obviously non-associated phenomena. Hence, high productivities may be achievable by cell recycling and cell immobilisation systems. Offprint requests to: W.-D. Deckwer     

应用纯化的重组Epstein-Barr病毒早期抗原建立检测鼻咽癌病人血清IgA/EA抗体的ELISA方法

利用凝胶和离子交换柱(Mono Q)两次层析,将大肠杆菌表达的EB病毒早期抗原P138片段多肽纯化。以此P138为抗原,增加鼠抗人IgA单克隆抗体以扩大IgA的反应,建立了三步ELISA法。用本法检查了100例鼻咽癌病人和63例正常人血清中抗EB病毒IgA/EA抗体,病人血清的阳性检出率为86％,正常人有3例阳性(4.7％)。此结果表明,三步ELISA法较常用的间接ELISA法(阳性检出率为71％)敏感。     

大兴安岭林区针叶林的生长方程及火灾林木死亡率

本文用随机模拟的方法建立了北方针叶林的生长方程及其受到火灾侵害后的林木死亡率,定量地研究了火灾对这种林分变动的影响．