猴头菌原生质体制备条件的研究

比较了不同酶液、酸碱度，渗透压稳定剂，菌龄和菌丝培养基成分等因素对猴头菌菌丝释放原生质体作用的影响。结果表明：在土豆培养基（ＰＤＰ）上静止浅层培养９６小时的菌丝，用２％的溶壁酶液，以０．６ｍｏｌ／ＬＭｇＳＯ４为渗透压稳定剂，在ＰＨ５．５的条件下酶解，获得的原生质体数最大。     

稗弯孢菌（Curvularis lunata）原生质体的制备

研究了不同菌龄、酶浓度、渗透压稳定剂、缓冲液pH值以及酶解温度和时间等因素对稗弯孢菌(Curvularia lunata)原生质体形成的影响。将培养18h的菌丝,以0.7mol/L KCl作为渗透压稳定剂,30℃下,经过2％溶壁酶和4％纤维素酶混合酶液(pH5.8)酶解4h,原生质体在静止条件下最大释放量达到 1.7×10~6/mL,再生率为0.76％。     

脉孢菌纤溶酶的纯化和性质初步研究

应用超滤、盐析、凝胶过滤和疏水相互作用层析对脉孢菌产纤溶酶初步纯化后,活性电泳证实获得单一的纤溶活性组分。对该纤溶组分的基本酶学性质作了进一步的研究,结果表明该纤溶酶的最适作用温度和最适pH分别是46℃和7.8,在40℃以下和pH6.2~7.8时稳定,该纤溶酶具有直接和间接的纤溶活性。     

溶菌酶高产链霉菌RX-17的筛选及其特性研究

在添加变链球菌(Strephtococcus mutans)菌体的双层平板上，筛选到一株产溶菌酶能力较高的放线菌RX-17，将其初步归为链霉菌黄色类群，对产酶进程监测表明，该菌产酶与生长密切相关，72h酶活力可达185U／mL．RX-17所产溶菌酶溶菌谱广泛，能够溶解多种卵清溶菌酶不能作用的革兰氏阳性与阴性细菌，对金黄色葡萄球菌(Staphylococcus aureus)及变链球菌族细菌溶解能力较强．通过CM-Sephadex C-50离子交换层析，对RX-17溶菌酶粗制品进行了初步分离，得到了3个有溶菌活力的组分.     

灵芝良种选育Ⅰ：影响灵芝原生质体形成的因素

对灵芝的原生质体形成条件进行了研究。结果表明,合适的在生质体形成条件为酶组成蜗牛酶４ｇ／Ｌ,溶壁酶５ｇ／Ｌ;ｐＨ７．１７的磷酸缓冲液;酶解温度３０℃;酶解时间４ｈ;菌龄７２ｈ;稳定剂０．６ｍｏｌ／Ｌ的ＫＣｌ。原生质体最高产量为５．２×１０＾６个（ｇ·Ｌ＾－１）。灵芝菌丝释放原生质有顶端的边上二种方式。     

超声波在食品行业的利用

高磁场对各种微生物代谢的影响，促进或抑制生长，或磁场对噬菌体的蛋白质作用后；噬菌体感染细菌“溶原化”而向“溶菌化”转化的比例增加的现象已见于报告。虽然温度、pH值、营养源、氧、光等是控制微生物反应的因子，但是声波的磁场也是全新的控制手段。特别是后者，人们甚至已在考虑利用生物预测地震等特殊的应用。另一方面，在比较温和的超声波照射下，通过酶和微生物的反应，可以促进酶的反应促进作用和微生物反应系，放出菌体内积聚的醇和二次代谢产物。例如：（l）利用蔗糖酶使蔗糖水解时，随着基质蔗糖浓度增高而产生基质阻碍，结…     

一种新型血栓溶酶的分离纯化及其性质

中国根霉23＃的发酵液经离心除菌、硫酸铵分级盐析、SephadexG-25凝胶过滤、SephdexG-75凝胶过滤层析、DEAE-纤维素柱层析等步骤，得到一种凝胶电泳均一的血栓溶酶。通过等电聚焦实验测得其等电点pI＝4.2。该酶在pH7.0～8.0较稳定。50 ℃保持30 min血检溶酶活力无明显变化。     

发酵液中纤溶酶盐析法分离纯化的研究

作者分离出一株能产纤溶酶的芽孢杆菌菌株，用液体发酵法将其发酵，对纤溶酶的纯化方法进行了初步的研究。产生的纤溶酶采用硫酸铵盐析法进行粗提纯，使用超滤脱盐的方法纯化。结果如下：硫酸铵盐在70％饱和度时提纯效果较好，工作压力为0．11MPa超滤脱盐后，粗纤溶酶纯化倍数达到12．41，活性回收率为74．35％。     

白腐丝状真菌Phanerochaete chrysosporium原生质体形成条件的研究

白腐菌P.chrysosporium能产生具有广泛用途的木质素酶,制备该菌的原生质体对业已兴起的木质素酶基因工程具重要意义。白腐菌原生质体还可直接用于脉冲场电泳及转化等研究。对白腐菌原生质体形成条件的研究还将有助于其它丝状真菌原生质体的制备。在文[1—2]的基础上,我们采用溶壁酶(Lywallzyme)研究了白腐菌原生质体的制备。     

产纤溶酶菌种的鉴定及纤溶酶的分离纯化

为了获得纯纤溶酶并探讨其酶学性质,从广泛收集的豆豉中筛选到一株具有高产纤溶酶能力的菌株,经鉴定为枯草芽孢杆菌.将该菌突变株DC-12N8的发酵液经离心除菌、硫酸铵分级沉淀、DEAE-Sepharose Fast Flow和CM-Sepharose Fast Flow离子交换层析、Sephadex G-75凝胶过滤,获得电泳纯的豆豉纤溶酶,每升发酵液可得到4.5mg活性酶蛋白,每克酶蛋白活力达1.18mol/s,纯度为发酵原液的53.6倍,回收率为11.7%.SDS-聚丙烯酰胺凝胶电泳表明,该酶是单链蛋白质,其分子质量约为28ku.     

基于SVM的革兰氏阴性菌分泌系统蛋白识别方法

本文提出了一种基于SVM快速识别革兰氏阴性菌分泌系统蛋白的方法.该方法以氨基酸组成和位置特异性得分矩阵为最优特征集,充分考虑了蛋白质的序列信息及进化信息.实验结果表明,本文提出的方法对革兰氏阴性菌分泌系统蛋白具有较好的预测性能,可作为细菌分泌系统研究的有益补充.     

Antibacterial agents based on the cyclic D,L-alpha-peptide architecture

The rapid emergence of bacterial infections that are resistant to many drugs underscores the need for new therapeutic agents. Here we report that six- and eight-residue cyclic d,l-alpha-peptides act preferentially on Gram-positive and/or Gram-negative bacterial membranes compared to mammalian cells, increase membrane permeability, collapse transmembrane ion potentials, and cause rapid cell death. The effectiveness of this class of materials as selective antibacterial agents is highlighted by the high efficacy observed against lethal methicillin-resistant Staphylococcus aureus infections in mice. Cyclic d,l-alpha-peptides are proteolytically stable, easy to synthesize, and can be derived from a potentially vast membrane-active sequence space. The unique abiotic structure of the cyclic peptides and their quick bactericidal action may also contribute to limit temporal acquirement of drug resistant bacteria. The low molecular weight d,l-alpha-peptides offer an attractive complement to the current arsenal of naturally derived antibiotics, and hold considerable potential in combating a variety of existing and emerging infectious diseases.     

Monoclonal antibodies demonstrate protection of polymorphonuclear leukocytes against complement attack

Studies on erythrocytes have shown that the formation of the membrane attack complex on a cell surface inevitably results in lysis. However, it is known that nucleated cells are much more difficult to kill with complement, although the molecular basis of this resistance has never been established. We have shown that a very early intracellular event, occurring within seconds of formation of the attack complex in the membrane, is a rise in cytoplasmic Ca2+, which can activate cell responses without cell death 5,6. Here we report the use of a monoclonal antibody to the terminal complement component C9, quantified by 125I and visualized by fluorescein, to demonstrate a protection mechanism in polymorphonuclear leukocytes (PMNs) attacked by complement, involving removal of the attack complex by vesiculation. Concomitantly, there is a Ca2+-dependent activation of reactive oxygen metabolite production without cell lysis. These findings have important implications in the evolutionary and pathological significance of the terminal components of the complement pathway.     

大肠杆菌不依赖特异性抗体激活补体系统经典途径的研究

除已被公认的两条补体激活途径，即经典途径和替代途径外，还存在着一条不依赖抗原──抗体复合物而激活补体的经典途径。用Ｅ．ｃｏｌｉＢ、Ｅ．ｃｏｌｉＫ１２ｇａｌ＋的细胞壁加入到补体参与的溶血实验中发现有明显的溶血抑制作用，从而说明大肠杆菌的细胞壁对不依赖抗体而激活补体经典途径有密切关系。     

不依赖特异性抗体激活补体经典途径的机理探讨

实验证实了Ｅ．ｃｏｌｉＢ和Ｅ．ｃｏｌｉｋ１２ ｇａｌ＾＋的细胞壁可直接激活补本，去壁扣的细菌球形体或原生质体加入补体后可裂解，说明在不依赖特异抗体激活补体经典途径中，补体的激活部位是细胞壁，作用靶子似乎是细胞膜。     

细菌细胞壁肽聚糖的研究

肽聚糖是真细菌细胞壁中特有的成分,因其在细菌细胞壁的生理功能中发挥着主要作用,而成为目前细菌细胞壁方面研究的主题.介绍了细菌细胞壁肽聚糖的化学组成、结构特点、分类、分离纯化、生物合成、生物学功能及应用前景等.     

Rapid induction of neutrophil-endothelial adhesion by endothelial complement fixation

The adhesion of neutrophils to vascular endothelium is an early event in their recruitment into acute inflammatory lesions. In evaluating potential neutrophil-endothelial adhesive mechanisms in acute inflammation, important considerations are that adhesion in vivo may occur very rapidly following injury and that the specificity of the reaction resides in altered endothelium. That is, neutrophils adhere only to altered endothelium adjacent to an inflammatory focus, rather than at random as would be expected if activation of neutrophils were the initiator of adhesion. We have explored a possible bridging role for complement in causing early neutrophil-endothelial cell adhesion. The complement system is involved in inflammatory processes, is capable of rapid amplification, and endothelial complement fixation at sites of inflammation could generate an endothelium-restricted signal for neutrophil adhesion. We have now developed a model in which this can be investigated without complicating factors such as immunoglobulin deposition, by constructing a novel molecule, a hybrid of the endothelial binding lectin Ulex europaeus I and of the complement activator cobra venom factor. This molecule has the capacity to cause fixation of complement on human umbilical vein endothelial cells. We show that complement fixation is a potent and rapid stimulus for neutrophil adhesion. Neutrophil adhesion requires only endothelial deposition of C3, and is mediated through the type 3 complement receptor.     

4种动物血清总的补体活性比较

方法:豚鼠、人、鸡、小鼠4种动物的新鲜血清分别以全溶血,CH50为标准,在1,3,5,7,9,11,13,15 d测其总的补体活性.结果:总的补体的活性大小为,豚鼠>人>鸡>小鼠.总的补体活性随着时间的延长呈现下降趋势.豚鼠和人的血清在不稀释条件下,7 d内均能全溶血.人与豚鼠的CH50均在5~9 d出现1个下降的对数期.结论:在短时间内,人血清可以代替豚鼠血清.     

Cloning of decay-accelerating factor suggests novel use of splicing to generate two proteins

Decay-accelerating factor (DAF), a glycoprotein that is anchored to the cell membrane by phosphatidylinositol, binds activated complement fragments C3b and C4b, thereby inhibiting amplification of the complement cascade on host cell membranes. Here, we report the molecular cloning of human DAF from HeLa cells. Analysis of DAF complementary DNAs revealed two classes of DAF messenger RNA, one apparently derived from the other by a splicing event that causes a coding frameshift near the C terminus. The apparent 'intron' sequence contains an Alu family member and encodes contiguous protein sequence. Two DAF proteins are therefore possible, having divergent C-terminal domains which differ in their hydrophobicity. Both mRNAs are found on polysomes, suggesting that both are translated. We propose that the major (90%) spliced DAF mRNA encodes membrane-bound DAF whereas the minor (10%) unspliced DAF mRNA may encode secreted DAF and we present expression data supporting this. The deduced DAF sequence contains four repeating units homologous to a consensus repeat found in a recently described family of complement proteins.     

Structure of C3b reveals conformational changes that underlie complement activity

Resistance to infection and clearance of cell debris in mammals depend on the activation of the complement system, which is an important component of innate and adaptive immunity. Central to the complement system is the activated form of C3, called C3b, which attaches covalently to target surfaces to amplify complement response, label cells for phagocytosis and stimulate the adaptive immune response. C3b consists of 1,560 amino-acid residues and has 12 domains. It binds various proteins and receptors to effect its functions. However, it is not known how C3 changes its conformation into C3b and thereby exposes its many binding sites. Here we present the crystal structure at 4-A resolution of the activated complement protein C3b and describe the conformational rearrangements of the 12 domains that take place upon proteolytic activation. In the activated form the thioester is fully exposed for covalent attachment to target surfaces and is more than 85 A away from the buried site in native C3 (ref. 5). Marked domain rearrangements in the alpha-chain present an altered molecular surface, exposing hidden and cryptic sites that are consistent with known putative binding sites of factor B and several complement regulators. The structural data indicate that the large conformational changes in the proteolytic activation and regulation of C3 take place mainly in the first conversion step, from C3 to C3b. These insights are important for the development of strategies to treat immune disorders that involve complement-mediated inflammation.