γ-聚谷氨酸高产菌株的选育和发酵培养基的初步优化

以实验室保藏的一株枯草芽孢杆菌为出发菌株,采用紫外、亚硝基胍以及60Coγ射线对其进行复合诱变,获得一株γ-聚谷氨酸高产突变株,在基础培养基中产量是出发菌株的3.11倍,并且突变株经过传代10次,发酵能力稳定;通过正交试验对突变株的发酵培养基进行了初步优化,突变株在一组培养基上的γ-聚谷氨酸产量可达到33.81g/L,是优化前的1.11倍。该突变株的摇瓶发酵产量较高,值得深入开发研究。     

丝裂霉素诱变黑曲霉产植酸酶过程模型化

用均匀设计分析方案,进行丝裂霉素C对黑曲霉化学诱变菌丝体和原生质体诱导产植酸酶选育,并以诱变时间(X_1)和丝裂霉素C的浓度(X_2)建立回归方程．实验筛选出具有4株较高酶活的菌株,诱变菌丝体得到2株酶活是始发菌株183．89％和147．55％;诱变原生质体得到2株酶活是始发菌株395．52％和381． 98％．由响应面模型初步判断,在丝裂霉素C浓度为5～30 mg·L-1和诱变时间45～60 min时,丝裂霉素C 对黑曲霉诱变原生质体选育产植酸酶菌株的效果比对菌丝体诱变效果好．用均匀设计对丝裂霉素C诱变菌丝体和原生质体的效果进行回归分析,所得模型调整后的相关系数分别为89．02％和99．13％,模型拟合程度好,实验误差小,可以用此模型较好的对丝裂霉素C的黑曲霉菌丝体诱变进行分析和预测．     

Important amino acid in the hemagglutinin glycoprotein of measles virus (MV) that governs hemadsorption

Two strains of measles virus IMA and SMD that were isolated using B95a cell line show hemadsorption negative. After adaptation to Vero cells, these strains gain the ability to agglutinate AGM-RBC and show hemadsorption positive. Sequence analysis of these two kinds of virus reveals that the two strains all have a Ser (HAD negative) to Gly (HAD positive) mutation at position 546 in the H protein. Site-directed mutagenesis and expression in COS cells were used to confirm that the mutation Ser→Gly is responsible for hemadsorption alteration. Then the monoclonal antibody against CD46 was used to identify that this mutation also governs the binding function of MV H protein to CD46 receptor. The data provide a new important amino acid of MV H protein that governs the hemadsorption and binding to CD46 receptor.     

紫红曲的原生质体紫外线诱变育种

对紫红曲原生质体进行不同时间紫外线照射诱变,实验表明,采用紫外线（ＵＶ）照射６０ｓ,可获得高产突变株,该突变株Ｍ１－１的红曲色素产量是亲本株的红曲色素产量的２．２７倍,说明原生质体进行诱变处理是简单易行的较好方法。     

Genetically engineered avidins and streptavidins

Chicken avidin and bacterial streptavidin, (strept)avidin, are proteins widely utilized in a number of applications in life science, ranging from purification and labeling techniques to diagnostics, and from targeted drug delivery to nanotechnology. (Strept)avidin-biotin technology relies on the extremely tight and specific affinity between (strept)avidin and biotin (dissociation constant, K_d≈10⁻¹⁴–10⁻¹⁶ M). (Strept)avidins are also exceptionally stable proteins. To study their ligand binding and stability characteristics, the two proteins have been extensively modified both chemically and genetically. There are excellent accounts of this technology and chemically modified (strept)avidins, but no comprehensive reviews exist concerning genetically engineered (strept)avidins. To fill this gap, we here go through the genetically engineered (strept)avidins, summarizing how these constructs were designed and how they have improved our understanding of the structural and functional characteristics of these proteins, and the benefits they have provided for (strept)avidin-biotin technology. Received 22 June 2006; received after revision 1 August 2006; accepted 21 September 2006     

Evidence for essential catalytic determinants for human erythrocyte pyrimidine 5′-nucleotidase

Human erythrocyte pyrimidine 5′-nucleotidase, PN-I, catalyzes the dephosphorylation of pyrimidine nucleoside monophosphates. The enzyme also possesses phosphotransferase activity, transferring phosphate groups between pyrimidine nucleoside monophosphates and various pyrimidine nucleosides. Deficiency of the enzyme activity is associated with a hemolytic anemia. PN-I cDNA has been expressed in Escherichia coli, yielding a fully active recombinant enzyme, which was purified to homogeneity and extensively characterized. Multiple sequence alignment of PN-I and homologues proteins revealed the existence of conserved regions, whose importance in catalysis was examined by performing experiments designed to intercept covalent intermediates as strongly suggested by our previous kinetic studies. Furthermore, a functional analysis of the enzyme was carried out through site-directed mutagenesis designed on the basis of the sequence of the identified conserved regions as well as mutations observed in PN-I-deficient patients.Received 25 March 2005; received after revision 3 May 2005; accepted 13 May 2005     

On the structure of AP-4 responsive element in the LTR of Jembrana disease virus

As a bovine lentivirus,Jembrana disease virus (JDV) is genetically similar to the bovine immunodeficiency virus (BIV). Unlike other lentiviruses which always have a long incubation period, e.g. 8—10 years for HIV, JDV infection causes an acute illness with shorter incubationpreriod and higher mortality. In the experimentally inocu-lated cattle, the incubation period varied from 8 to 12 d before the onset of clinical symptoms, which is very simi-lar to bovine plague with a high titer of J…     

用细小病毒H-1探测人细胞中的直接诱变与间接诱变途径

用细小病毒H-1为探针,可在人细胞中检测由紫外线照射诱导的三种不同致突变途径.直接突变产生于细胞的结构性复制(或修复)功能对受损DNA模板的复制;间接无靶突变和间接有靶突变分别产生于紫外线诱导的易错修复功能对完整模板和模板上的靶损伤的作用.在低剂量范围内,间接无靶突变在某些DNA毒剂诱导的细胞突变中起主要作用.某些DNA损伤,如烷化剂诱导的次级损伤(无碱基位损伤)可作为诱导性易错修复功能的靶损伤.