Pattern formation in an immobilized bienzyme system. A morphogenetic model.

Experimental and theoretical studies of a reaction-diffusion model of two immobilized enzymes participating in the cellular acid-base metabolism, namely glutaminase and urease, are presented. The system shows an unstable steady state at pH 6.0, where any perturbation will drive the system towards a more alkaline or more acidic pH, owing to the autocatalytic behaviour with respect to pH exhibited by both enzymes. When diffusion is coupled to reaction by means of immobilization, different patterns of the internal pH profile appear across the membrane. If the bienzymic membrane is subjected to a perturbation at its boundaries, of the same amplitude but in opposite directions, the internal pH evolves through an asymmetric pattern to attain a nearly symmetric distribution of pH. The pH value at the final steady state is more acidic or more alkaline than the initial state according to the initial and boundary conditions. The final nearly symmetric state is attained more rapidly when less enzyme is immobilized (1.8 x 10(-4) M.s-1 as against 3.3 x 10(-4) M.s-1 of total enzyme activity in the membrane volume). The experimental results agree rather well qualitatively with numerical predictions of the model equations.     

东北白眉蝮蛇毒细胞毒组分的分离制备及活性鉴定

用离子交换层析和凝胶过滤法从东北白眉蝮蛇毒中分离出一种具有较强的细胞毒活性的蛋白质。这种蛋白质对肿瘤细胞的细胞毒作用元选择性,但各种肿瘤细胞的敏感性有一定差别。对正常人体细胞也有一定的细胞毒性作用,与肿瘤细胞相比,敏感性较低。这种蛋白质加热到56℃,30分钟,细胞毒活性稳定。4℃及-20℃保存4个月,细胞毒活性稳定。PH值低于4及高于9时,可使其完全失活。     

Initiation of minus-strand RNA synthesis by the brome mosaicvirus RNA-dependent RNA polymerase: use of oligoribonucleotide primers.

Various DNA- and RNA-dependent RNA polymerases have been reported to use oligoribonucleotide primers to initiate nucleic acid synthesis. For the brome mosaic virus RNA-dependent RNA polymerase (RdRp), we determined that in reactions performed with limited GTP concentrations, minus-strand RNA synthesis can be stimulated by the inclusion of guanosine monophosphate or specific oligoribonucleotides. Furthermore, guanylyl-3',5'-guanosine (GpG) was incorporated into minus-strand RNA and increased the rate of minus-strand RNA synthesis. In the presence of GpG, RdRp's Km for GTP decreased from 50 microM to approximately 3 microM while the Kms for other nucleotides were unaffected. These results have implications for the mechanism of initiation by RdRp.     

Resuscitation of Vibrio cholerae O1 strain TSI-4 from a viable but nonculturable state by heat shock

Abstract Vibrio cholerae strain TSI-4 was incubated in an M9 salt solution at 15 °C for more than 100 days. The plate counts showed no viable cells on day 30, but a broth culture from that day showed the growth of bacteria. However, after 35 days the bacteria entered the nonculturable state, based on the assessment of both the plate counts and broth culture. A portion of the culture was heated at 45 °C for 1 min in a water bath and subsequently plated onto a nutrient agar plate. More than 1000 colonies were recovered after this heat-shock treatment. The recovered cells showed the same chromosomal DNA pattern in the restriction map and the same outer membrane protein pattern in SDS-PAGE. Recovery of viable cells by heat-shock was achieved in cultures grown on M9 salt but not from cultures grown in phosphate-buffered saline. This suggests that the presence of NH₄Cl in the M9 salt solution may support the growth of the bacteria in a low nutrient medium, while also playing an important role in resuscitation.     

小麦×玉米杂交后代的蛋白质及酯酶同工酶分析

以８ 个普通小麦（Ｔｒｉｔｉｃｕｍ ａｅｓｔｉｖｕｍ Ｌ．）品种为母本,２ 个栽培玉米（Ｚｅａ ｍ ａｙｓ Ｌ．）品种为父本杂交所获得的Ｆ２ 代在形态上出现了明显变异。对其籽粒进行蛋白质电泳分析,得到了如下主要结果：杂交后代的蛋白质谱带较母本有了很大的变异,主要集中在高分子量麦谷蛋白（ＨＭＷ－Ｇｌｕ）区域。杂交后代的蛋白质谱带由５ 种类型构成：１．母本型,占全部测试籽粒的２２．６％ ;２．附加型,占１４．３％ ;３．互补型,占１５．５％ ;４．杂种型,占３０．９％ ;５．缺失型,占１６．７％ 。对“矮杆早”ד紫粘”的Ｆ２ 代籽粒进行酯酶同工酶电泳分析发现,变异主要发生在ＥＳＴ－１ 区。由此看来,小麦×玉米的杂合子中玉米染色体在被排除前后,可以诱发小麦染色体组发生遗传变异     

细胞分裂素生物合成基因在调节一组烟草病理相关蛋白基因表达中的作用

对一组病理相关蛋白基因在烟草 ( N icotiana tabacum cv. Wisconsin 38)中的表达情况进行了研究 ,包括 :碱性几丁质酶、β- 1 ,3-葡萄糖苷酶、渗透蛋白及伸展蛋白。RNA杂交实验表明在正常烟草植株中上述 4个基因具有发育和器官专一性的表达。在含有细胞分裂素生物合成基因的转基因烟草丛生芽中 ,这 4个基因的表达受过量合成的内源细胞分裂素和载体效应的共同调节 ,细胞分裂素降低这些基因的表达 ,而载体效应则促进它们的表达。热激处理也明显降低这 4种基因的表达水平。上述结果表明这些病理相关蛋白基因具有复杂的调控系统     

生物复苏——大绝灭后生物演化历史的第一幕

生命史是一部生物界短期,快速剧变与长期,慢速稳定相互交替的历史。大绝灭（即集群绝灭）事件反映了全球环境的大突变,点断了地质历史中的生命记录及其发展历程,预示着生物界的演化出现了最有意义的飞跃,近年来尝试研究大绝灭后全球生物界的残存－复苏及其基本型式,并探索复苏的控制因素,标志着地质科学中一个重心的转移（即从大绝灭转向其后的生物残存与复苏的研究）。生物复苏揭示了大绝灭后生物演化历史的第一幕,其研究的     

苏云金芽孢杆菌δ-内毒素基因穿梭质粒的构建

在农业生产中长期使用化学农药已对环境和生态平衡造成一定破坏作用,同时有不少害虫也逐渐产生抗药性从而引起某些害虫的大流行,给农业生产带来巨大损失。应用苏云金杆菌杀虫蛋白基因(Bt基因)可构建具有抗虫作用的抗虫工程菌,这样通过拌种或植物叶面喷雾可达到快速、经济、有效的防治虫害的目的。国际上抗虫工程菌研究应用很快,如美国将BI基因转入到一种正常情况下定居在植物组织中的棒杆菌,将这种工程菌拌玉米种子,这样随植物生长该菌在植物体内大量繁殖,当玉米螟在茎和叶取食时,即因食用表达苏云金杆菌毒蛋白的工程菌而死亡。 田颖川等已克隆了苏云金芽孢杆菌内毒素基因CryIA(b)和CryIA(c)。本文将Bt基因CryIA(c)插入到大肠-枯草穿梭载体pBE-2中构建成Bt毒蛋白基因穿梭质粒pAMY,利用电穿孔法转人大肠杆菌DH5a,枯草芽孢杆菌B.subtilis BR151,IA511,野生型蜡状芽孢杆菌B.cereusa-47,短芽孢杆菌B.brevis A-5和枯草芽孢杆菌90-8,获得了具有较高杀虫活性的工程菌克隆。