Double - mutations trp215ala / his217ala and leul6his / his217leu cause completely desensitization with no decrease in enzymatic activity . these results suggest that mutations at these residues cause the destruction of the symmetry , and interfere with the signal transmission of feedback regulation , which leads to the partially or completely relief of feedback inhibition 这些结果说明“ dz ”对称性相关氨基酸残基的点突变和双突变导致了对称性的变化，影响了反馈抑制信号的传递，因此能够部分或完全解除户曲g的反馈抑制。
Fourth , the theoretical model of optimum technological growth rate under discrete change is erected . technology is a unique production factor because technological growth experiences a mutation when technological increase accumulates to a certain extent . under this condition , the point - mutation model in tom ’ s mutation theory is applied to explain the phenomenon of technological 将技术作为不同于劳动和资本的特殊生产要素进行考察，即当技术量的积累达到一定程度时，技术增长会产生突变，在此条件下，运用汤姆突变理论中的尖点突变模型，解释了技术突变现象，讨论了劳动和资本的不同组合变化下，在临界点附近技术突然跃升或下降的突变性质；构建了技术突变完成后的技术增长率优化理论模型。
The comparative analysis of sequences indicated that the sequences of meq in different pathotypes are relatively conserved and the homology of the amino acid sequences is very high . the significant differences include two mutations in both mdv - 1 vaccine strains cvi988 / rispens and 814 strain : the deletion of a proline ( no . l93aa ) , and this mutation is just exactly located in a 15 - amino - acid ( eelcaqlcstppppi ) repeat sequence within the c - terminal transactivation domain of meq protein ; and a point mutation with a shift from alanine ( a ) of all virulent strains to serine ( s ) was occurred on the no . 71 aa 结果发现， mdv不同致病型的meq基因序列相对比较保守，它们相互间核苷酸和氨基酸序列的同源性均很高；但是，与所有七个致瘤性的mdv毒株相比，二个型弱毒疫苗cv1988 rispens株和814株均出现了两个特征性的突变：即第194位的p缺失性突变和第71位氨基酸由a变成了s的位点突变；缺失性突变恰恰位于meq基因中转录激活域内的一个多脯氨酸的重复序列( pppp )之中。
We successfully construct the eukaryotic expression vector of gfp - eif - 5a and its mutational vector using genetic engineering techniques . we found that eef - 5 a localized in nucleus as well as in cytoplasm just for a short time after its transient expression , then distributed only in cytoplasm Eif - 5a的hypusine修饰是其活性和功能发挥所必需的，我们通过pcr方法实现了hypusine位点的定点突变，并进一步构建了含gfp标签的eif - 5a及其hypusine位点突变的真核表达载体。
The strain softening of dam body and foundation is the necessary condition for dam instability . according to observation data of dam cracks , a gray cusp catastrophe model is established to judge the stability of the crack . according to the slope observation data of a certain hydropower plant , a nonlinear dynamic model is developed by means of reversion and the lyapunov exponent spectrum , and the lyapunov information dimension are calculated for judgement of the stability of the slope （ 5 ）基于变分原理，研究建立了能量形式的失稳准则，并说明坝体、岩基的材料具有应变软化的性质，是大坝失稳的必要条件；并利用大坝的裂缝实测资料，建立了相应的灰色尖点突变模型，由此判断裂缝的稳定性；根据某水电站库区滑坡体的变形实测资料，反演其非线性动力学模型，进而计算lyapunov指数谱、 lyapunov信息维来判定边坡的稳定性及稳定程度。
The fusion protein was bactericidal active against staphylococcus aureus . in present study , we will truncate the none channel - forming do main , then attach the agrd to the pore - forming region ( k544 - i626 ) to construct a new engineered multidqmain protein machine - compact engineered peptide targeting staphylococcus aureus . such engineered peptide was constructed by linking the gene of staphylococcal agrd pheromone with the gene of c - terminal ( 1626 ) of colicin la pore - forming region ( k544 - i626 ) with site - directed mutation 利用点突变方法将金黄色葡萄球菌信息素agrd ( i型， ystcdfim )的基因引入到大肠菌素fa梭基端1626基因上，并将限制性内切酶sacl酶切位点基因分别引入到大肠菌素fa的p4和k544上，通过酶切、胶回收、连接获得含大肠菌素ia水性孔道结构域和金黄色葡萄球菌信息素agrd基因的重组质粒。
On the basis of displacement - time series of the slope , a nonlinear dynamic model is set up according to backus generalized linear inversion theory in this paper . due to the equivalence beween autonomous gradient system and catastrophe model , a standard cusp catastrophe model can be obtained through variable substitution . the method is used in analysis of displacement data of huangci landslide and wolongsi landslide and in understanding how slopes evolve before sliding . the result shows that the nonlinear dynamic model can make satisfactory prediction result . is it most important that there is a sudden fall of d , which indicates the occurrence of catastrophe ( when d = 0 ) 研究表明，滑坡变形失稳过程具有混沌和分维特性，可以用分形理论来研究滑坡预测问题，基于对任一连续函数，至少在较小的邻域内可以用多项式任意逼近的数学理论，运用改进的backus广义线性反演理论，以斜坡位移时间序列为基础，反演了斜坡演化的非线性动力学模型。并利用自治梯度系统与突变模型的等价性，通过变量代换得到标准的尖点突变模型。
It was interested that there was an extra six nucleosides insertion between 1647 - 1652nt ( according to the genomic sequence of la sota strain ) , and the sequence were cccccc in f48e9 strain , and tcccac in zj1 strain . in order to test if insertion of this six nucleosides is related with the virulence of nd , two primers were designed to amplify the same fragment of another ten ndv strains . the result of sequence comparison of 16 strains showed that the six nucleoside was absent in lentogenic strain . this suggested that the six nucleosides insertion might have relationship with the ndv virulence . compared with all known sequence of ndv . there was a special sequence ( 5 ' tctctctcctctctcctcc3 " ) in the genomic cdna of ndv f48e9 strain 通过rt - pcr方法扩增获得了另外10个背景清楚毒株的np - p基因间隔区片段，将这些序列与f48e9 、 lasota 、 clone30 、 b1 、 zj1和v4的相应序列进行了比较，结果在参比的16个ndv毒株中在该区段中除了有多个点突变外，个别毒株有碱基插入和缺失，所有以lasota株为代表的弱毒株均无6碱基的插入，而以f48e9株为首的强毒株均有此6碱基的插入，但有一个中等毒力的毒株dp没有6碱基的插入，不过它的基因序列和lasota的几乎相同，对于所克隆到的基因的代表性还有待确定。
We summed up and analyzed the polymorphisms of the fut2 gene of three groups in the world with references to other published data . further discussion was made for the hypotheses of origin and generation of special point mutations of fut2 gene . master candidate : zhang ying major : microbiology and immunology supervisor : prof 综合目前已发表文献报道的其它地区人群fut2等位基因的分布状况，我们对世界三大人群fut2基因的多态性进行了整理分析，并对fut2基因特定点突变的可能的起源及形成进行了讨论。
The n - terminus truncated mutant can not form tight dimeric and tetrameric structure , and leads to the destruction of the quaternary structure , which is quite the contrary to wild type arog . these data indicate that n - terminus of arog is not only involved in the feedback inhibition , but also plays a role in the formation of stable dimer which is an essential structure for its enzymatic activity . according to the 3d structure , " d2 " symmetry of arog , to which contributed by leu 16 , trp215 and his217 , is essential for the feedback inhibition 对“ dz ”对称性相关的氨基酸leul6 、 trpz15和hisz17进行点突变和双突变研究结果表明: l )在1mm苯丙氨酸的存在下， leul6ala 、 trpz15ala和hisz17ala能解除35一70 %的反馈抑制， t印2巧ala的比活降低65 %以上，其余两者的比活与野生型相近; 2 )在lmm苯丙氨酸的存在下，导入双点突变trpz1sai洲isz17ala和leul6hi撇isz17leu后能够完全解除arog的反馈抑制，同时保持与野生型相当的比活。
