粗糙脉孢菌(Neurospora crassa)木糖发酵的研究

研究了不同通氧条件和培养基初始pH等对粗糙脉孢菌(Neurospora crassa)AS3．1602木糖发酵的影响。结果表明,粗糙脉孢菌具有较强的发酵木糖产生乙醇及木糖醇的能力。通气量对木糖发酵有较大的影响。乙醇发酵适合在半好氧条件下进行,此时乙醇的转化率达到63．2％。木糖醇发酵适合在微好氧的条件下进行,转化率达到31．8％。木糖醇是在培养基中乙醇达到一定浓度后才开始积累。培养基的初始pH对木糖发酵产物有较大的影响,乙醇产生最适pH5．0,木糖醇产生最适pH4．0。在培养基pH为碱性条件时,木糖发酵受到很大的抑制。初始木糖浓度对产物乙醇及木糖醇的产率有很大的影响。葡萄糖的存在会抑制木糖的利用,对乙醇和木糖醇的产生也有很大的影响。     

木聚糖酶分子的结构区域

多数木聚糖酶分子中含有多个功能区域,这些区域包括催化区、纤维素结合区、木聚糖结合区、连接序列、重复序列、热稳定区、Ｃｅｌｕｌｏｓｏｍｅ－Ｄｏｃｋｉｎｇ区及其它未知功能的非催化区,它们担负着不同的生物功能,不同来源的木聚糖酶分子的功能区域之间同源性或高或低。     

纤维二糖脱氢酶生成羟自由基和还原各种自由基的研究

利用电子顺磁共振（ＥＳＲ）技术和硫代巴比妥酸（ＴＢＡ）反应研究了纤维二糖脱氢酶（ＣＤＨ）生成·ＯＨ和还原各种自由基的能力．以纤维二糖为电子供体时,ＣＤＨ可以生成·ＯＨ．·ＯＨ生成量与ＣＤＨ、Ｆｅ３＋和Ｏ２的浓度有关．加入过氧化氢酶可使·ＯＨ的生成明显减少．ＣＤＨ可以还原自旋加合物［ＰＢＮ－ＯＨ］·、氮氧自由基和天然木素分子中的自由基．结果表明,ＣＤＨ具有生成·ＯＨ和还原各种自由基的能力．对该酶在木质纤维素降解中的作用进行了探讨     

秦岭重点保护植物丰富度空间格局与热点地区

秦岭地区物种资源丰富,是我国重要的生物多样性热点地区之一。以秦岭山系涉及的43个行政县为研究区域,基于重点保护植物的县级分布,并结合垂直分布和生境类型信息获得物种分布区范围,探讨重点保护植物的丰富度空间格局和热点地区。研究结果表明:该地区共包括重点保护植物200种,其中国家一级保护植物20种,国家二级保护植物180种;秦岭重点保护植物丰富度空间格局总体随山体呈东西向递减的条带状分布,东段随着山岭与盆地相间的地形呈扫帚状展开,南坡物种丰富度高于北坡;通过丰富度空间格局确定了3个热点地区,分别是:(1)伏牛-熊耳山地;(2)太白-佛坪山地;(3)天水东南部山地。将热点地区与国家级自然保护区叠加后鉴别出保护空缺地,可为下一步实施科学的生物多样性保护规划提供基础资料。     

The C-terminal Domain of the DNA Polymerase Catalytic Subunit Regulates the Primase and Polymerase Activities of the Human DNA Polymerase α-Primase Complex

The initiation of DNA synthesis during replication of the human genome is accomplished primarily by the DNA polymerase α-primase complex, which makes the RNA-DNA primers accessible to processive DNA pols. The structural information needed to understand the mechanism of regulation of this complex biochemical reaction is incomplete. The presence of two enzymes in one complex poses the question of how these two enzymes cooperate during priming of DNA synthesis. Yeast two-hybrid and direct pulldown assays revealed that the N-terminal domain of the large subunit of primase (p58N) directly interacts with the C-terminal domain of the catalytic subunit of polα (p180C). We found that a complex of the C-terminal domain of the catalytic subunit of polα with the second subunit (p180C-p70) stimulated primase activity, whereas the whole catalytically active heterodimer of polα (p180ΔN-p70) inhibited RNA synthesis by primase. Conversely, the polα catalytic domain without the C-terminal part (p180ΔN-core) possessed a much higher propensity to extend the RNA primer than the two-subunit polα (p180ΔN-p70), suggesting that p180C and/or p70 are involved in the negative regulation of DNA pol activity. We conclude that the interaction between p180C, p70, and p58 regulates the proper primase and polymerase function. The composition of the template DNA is another important factor determining the activity of the complex. We have found that polα activity strongly depends on the sequence of the template and that homopyrimidine runs create a strong barrier for DNA synthesis by polα.     

High efficient degradation of dyes with lignin peroxidase coupled with glucose oxidase

The H(2)O(2) supply strategy was one of crucial factors for high efficient degradation of pollutants with lignin peroxidase (LiP). In this paper, an attempt was made to couple a H(2)O(2) producing enzymatic reaction to the LiP catalyzed oxidation of dyes. H(2)O(2) needed was generated by glucose oxidase (GOD) and its substrate glucose. The generation rate of H(2)O(2) could be easily controlled by adjusting the pH of the degradation system and the amount of GOD added. Due to the controlled release of H(2)O(2), a sustainable constant activity of LiP was observed. The inhibition of LiP by high level H(2)O(2) supplied externally by a single addition at the beginning of the experiments could be avoided. Degradation of three dyes (xylene cyanol, fuchsine and rhodamine B) with LiP coupled with GOD indicated that the present H(2)O(2) supply strategy was very effective for improvement of the efficiency of the decolourization of dyes.     

Studies on cellulosic ethanol production for sustainable supply of liquid fuel in China

As the biggest developing country, China faces a serious challenge in satisfying its need for huge amounts of energy resources, especially for liquid fuel. The Chinese government has recently started a bioethanol project, and has produced about 1 million tons of ethanol fuel from corn and wheat in 2005. As it has the largest population in the world and limited lands for food production, cellulosic ethanol would be a more suitable choice for China. Many research projects in China on biodegradation and biotransformation of lignocellulosics have been carried out. Furthermore, understanding the biodegradation mechanism of lignocellulosics and developing practical processes for ethanol production have been ongoing. After more than 30 years of research, several pilot scale facilities have been set up, and lots of experience has been acquired. However, the calculated production cost of cellulosic ethanol is still higher than that of corn ethanol. To overcome this problem, the biorefinery conception has been introduced into research on lignocellulosics transformation. A corncob biorefinery process has been developed in Shandong University. By combining the cellulase and ethanol production with a xylose-related products production, the total production cost can be reduced. A scale of 50,000-ton/year cellulosic ethanol biorefinery is being planned to be built at Yucheng.     

DNA polymerase δ and ζ switch by sharing accessory subunits of DNA polymerase δ

Translesion DNA synthesis is an important branch of the DNA damage tolerance pathway that assures genomic integrity of living organisms. The mechanisms of DNA polymerase (Pol) switches during lesion bypass are not known. Here, we show that the C-terminal domain of the Pol ζ catalytic subunit interacts with accessory subunits of replicative DNA Pol δ. We also show that, unlike other members of the human B-family of DNA polymerases, the highly conserved and similar C-terminal domains of Pol δ and Pol ζ contain a [4Fe-4S] cluster coordinated by four cysteines. Amino acid changes in Pol ζ that prevent the assembly of the [4Fe-4S] cluster abrogate Pol ζ function in UV mutagenesis. On the basis of these data, we propose that Pol switches at replication-blocking lesions occur by the exchange of the Pol δ and Pol ζ catalytic subunits on a preassembled complex of accessory proteins retained on DNA during translesion DNA synthesis.     

固氮红细菌(Rhodobacter azotoforman)色素蛋白复合体的分离纯化与特性

【目的】为揭示不产氧光合细菌产氢菌株色素蛋白复合体(PPC)色素组成和含量与光合放氢的关系奠定基础。【方法】以PPC特征光谱为检测指标,采用硫酸铵分级分离、DEAE-纤维素层析、吸收光谱和SDS-PAGE等方法进行了固氮红细菌(Rhodobacter azotoformans,R.azotoformans)R7产氢菌株PPC的分离纯化、纯度分析和鉴定;采用表面增强激光解吸电离离子飞行时间质谱、HPLC-MS和荧光光谱法对其中一种PPC进行了组成分析和能量传递活性测定。【结果】从R7菌株获得了3种纯化的PPC,1种为反应中心与中心捕光色素蛋白复合体(RC-LH1),2种为外周捕光色素蛋白复合体(LH2),其中一种LH2的吸收光谱具有异常的423nm强吸收峰,其蛋白的两种亚基的分子量分别为5356.8Da和5697.8Da,类胡萝卜素属球形烯系,分子量为562Da,激发光能够从类胡萝卜素向细菌叶绿素以及细菌叶绿素向细菌叶绿素传递。【结论】固氮红细菌产氢菌株含有2种不同光谱特性的LH2,其中一种具有新光谱特性。     

Asn64-glycosylation affects Hypocrea jecorina (syn. Trichoderma reesei) cellobiohydrolase Cel7A activity expressed in Pichia pastoris

In this study, four N-glycosylation sites, Asn45, Asn64, Asn270 and Asn384 of Hypocrea jecorina (syn. Trichoderma reesei) Cel7A (family 7 cellobiohydrolase I) were replaced by serines using site-directed mutagenesis. These four mutants and wild type H. jecorina Cel7A gene were transformed into P. pastoris, and the recombinant enzymes were purified and analyzed. The enzymatic activities of recombinant Cel7A (rCel7A), and mutants N45S, N270S and N384S were very low while mutant N64S displayed about seven times higher activity than that of rCel7A, and about 10% of the wild-type Cel7A activity from H. jecorina. The results indicate that N-glycosylation of Asn64 had an effect on the activity of the Cel7A enzyme expressed in P. pastoris, and that glycosylation at this site would be only a subordinate reason for the low activity of the recombinant enzyme.