DS 9701菌株的紫外诱变及PHB解聚酶高产菌株的筛选

以青霉(Penicillium.sp)DS 9701为出发菌株,通过紫外线诱变分生孢子,采用透明圈初筛和摇瓶培养复筛的方法,获得一突变株,编号DS 9701-M 09.该突变株的PHB解聚酶活力是原始菌株的2.3倍,经传代培养,该菌株的PHB解聚酶高产特性稳定遗传.     

饲用菜籽饼微生物脱毒研究

从霉菌（Ｍｏｕｌｄ）、酵母菌（Ｙｅａｓｔ）、乳酸细菌（Ｌａｃｔｉｃｂａｃｔｅｒｉａ）中选育出对菜籽饼粕中的抗营养因子具有强降解能力的根霉（Ｒｈｉｚｏｐｕｓ ｓｐｐ．）、白地霉（Ｇｅｏｔｒｉｃｈｕｍ ｃａｎｄｉｄｕｍ）、酿酒酵母（Ｓａｃｃｈａｒｏｍｙｃｅｓ ｃｅｒｅｖｉｓｉａｅ）、乳酸杆菌（Ｌａｃｔｏｂａｃｉｌｌｕｓ ｓｐｐ．）。采用纯培养、混种固态发酵法对菜籽粕进行微生物脱毒试验,初步研究结果表明     

Electrostatic effect on electron transfer between cytochrome b5 and cytochrome c

The binding and electron transfer between wild type, E44A, E56A, E44/56A, E44/48/56A/D60A and F35Y variants of cytochrome b5 and cytochrome c were studied. When mixed with cytochrome c, the cytochrome b, E44/48/56A/D60A did not show the typical UV-vis difference spectrum of absorption, indicating that the alteration of the surface electrostatic potential obviously influenced the spectrum. The electron transfer rates of wild type cytochrome bj, its variants and cytochrome c at different temperature and ionic strength exhibited an order of F35Y > wild type > E56A > E44A > E44/48/56A/D60A. The enthalpy and entropy of the reaction did not change obviously, suggesting that the mutation did not significantly disturb the electron transfer conformation. The investigation of electron transfer rate constants at different ionic strength demonstrated that electrostatic interaction obviously affected the electron transfer process. The significant difference of Cyt b, F35Y and E44/48/56A/D60A from the wild type protein further confirmed the great importance of the electrostatic interaction in the protein electron transfer.     

蛋白质分子的定点突变和化学修饰

回顾蛋白质工程研究及应用技术、手段和方法,分析定点突变及化学修饰在改造蛋白质分子结构与功能方面的异同。定点突变技术可以随心所欲地在已知DNA序列中取代、插入或缺失一定长度的核苷酸片段。该方法与使用化学因素导致突变的方法相比,具有突变率高、简单易行、重复性好的特点。     

黑曲霉外切葡聚糖酶基因密码子的优化及表达

通过NCBI(美国国立生物技术信息中心)对黑曲霉的来源外切葡聚糖酶基因(cbh1)的氨基酸序列进行分析,发现其16个活性部位中有6个位点附近的氨基酸为毕赤酵母(Pichia pasto-ris)表达的稀有密码子。利用反向长距离PCR技术将这些活性位点附近的稀有密码子定点突变为毕赤酵母表达偏爱密码子。将优化后的表达载体pPICZαA-cbh1m转入毕赤酵母KM71H菌株中进行诱导表达。经密码子优化后的cbh1m基因较未优化前cbh1基因的表达量提高了17%。     

小麦蜡质突变体Wx蛋白突变基因的分子鉴定

蜡质型小麦面粉对于改善面食品的加工品质、适口性、风味特点和延长货架寿命具有重要意义.淀粉粒结合型淀粉合酶I被称为蜡质蛋白(Waxy Protein,简称为Wx蛋白),是决定胚乳中直链/支链淀粉比例的关键酶.Wx基因发生突变并不影响产量等其它性状的表现.小麦三个Wx基因位点中Wx-D1的天然突变型遗传资源非常稀有.本实验对EMS诱导扬麦158的6个蜡质型突变体及其子代系进行了基于PCR的遗传多态性分析、单粒种子Wx蛋白SDS-PAGE电泳鉴定、PCR产物的克隆分析.利用自行设计的引物为5个突变体子代找到了STS标记;查明了两个突变体突变位点及其突变方式,是新的突变方式.     

紫外诱变原生质体提高脂肪酶活力

以粗壮假丝酵母CJ-1为出发菌株,对其进行原生质体紫外诱变选育.筛选得到10株脂肪酶活力比出发菌株高的突变株,其中菌株CJ-1-09的酶活达35.78 U/mL,比CJ-1提高了4.58倍.突变株CJ-1-09经10次传代,其脂肪酶活性保持稳定.     

电磁辐照诱发家蚕变异的实验研究

电磁场辐照家蚕卵,能使家蚕产生明显的变异。比较试验的研究结果显示,经过电场刺激后的蚕种,茧质和茧量均有所提高;此外,也观察到生物大分子的局部结构变化的表现型变异。     

胡萝卜素产生菌原生质体诱变育种的研究

采用原生质体制备技术与单一因素多次诱变育种相结合的育种技术，对产胡萝卜素酵母原生质体进行诱变处理，选育出一株比亲株胡萝卜素产量高１．６倍的新菌株     

Structure/function analysis of a critical disulfide bond in the active site of l-xylulose reductase

l-Xylulose reductase (XR) is involved in water re-absorption and cellular osmoregulation. The crystal structure of human XR complemented with site-directed mutagenesis (Cys138Ala) indicated that the disulfide bond in the active site between Cys138 and Cys150 is unstable and may affect the reactivity of the enzyme. The effects of reducing agents on the activities of the wild-type and mutant enzymes indicated the reversibility of disulfide-bond formation, which resulted in three-fold decrease in catalytic efficiency. Furthermore, the addition of cysteine (>2 mM) inactivated human XR and was accompanied by a 10-fold decrease in catalytic efficiency. TOF-MS analysis of the inactivated enzyme showed the S-cysteinylation of Cys138 in the wild-type and Cys150 in the mutant enzymes. Thus, the action of human XR may be regulated by cellular redox conditions through reversible disulfide-bond formation and by S-cysteinylation. Received 25 January 2009; received after revision 12 February 2009; accepted 16 February 2009 H.-T. Zhao, S. Endo: These two authors contribute equally to this work.