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Restriction fragments of HBV-DNA, cleaved by endonuclease HhaI,containing HBcAg gene were trimmed by BAL-31 exonuclease to remove different lengths of the precore sequence.They were inserted into plasmid pUR222 at EcoRI site through synthetic linker ligation. Transformants in E.coli BMH7118 showing different levels of HBcAg gene expression were screened and analyzed for their nucleotide sequences in the junction region both by Maxam and Gilbert's chemical degradation method and by M13 chain termination method. Results of sequence analysis of different transformants revealed a partial palindromic (loop and stem) structure, at -7 to -35 nucleotide with regard to ATG of the HBcAg gene as position +1, which has dramatic effect on the level of expression of the inserted gene using the same promoter,SD sequence and identical N-terminus.The amount of HBcAg synthesized differed from 9% in the high expressing plasmid to less than 0.01% of the total cell proteins in the low expressing transformants.The findings w 相似文献
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为建立一种更为准确、快速、简便的营养流行病学调查的生化检验方法,应用改进的消化方法将血清充分消化,然后应用火焰原子吸收光谱仪测定血清中钙、铁和锌的含量。结果表明,本消化方法所得实验结果空白值低、精密度高、加标回收率在95%-105%之间、质控血清的测定含量与推荐值一致,3种元素的标准回归曲线相关系数r都在0.999以上,1200份健康人血清中钙、铁和锌的测定值与文献相同。该消化方法简单,准确,所需血清量少,适合用于大规模人群的营养流行病学检测。 相似文献
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设f是一个压缩常数为h的压缩映象,T是一个非扩张映象使得F(T)≠Φ。{xn}是由下式xn+1=αnf(xn)+(1-αn)1/n+1 sum Tjxn from j=0 to n,n∈N,定义的迭代序列,其中{αn}(0,1)且满足lim αn=0 n→∞和sum αn=∞ from n=1 to ∞。证明{xn}强收敛于F(T)中某个变分不等式的唯一 相似文献
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为了解淮安地区中小学生血清中钙、铁、锌含量情况,应用改进的火焰原子吸收光谱法对1684名对象的血清中相关元素的含量进行了测定。结果表明,该地区3种元素总体水平在正常范围内,钙、铁、锌血清含量分别为(102.69±26.30)mg/L、(1.01±0.61)mg/L、(0.86±0.45)mg/L;性别、城乡差别无统计学意义(P〉0.05);而年级的差别有统计学意义(P值均〈0.0001),初中组各元素水平明显高于小学组。 相似文献
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本文将含乙型肝炎(以下简称乙肝)病毒(HBV)核心抗原(HBcAg)基因的1kbHhaI酶切HBV·DNA片段用BAL-31外切酶切除两端非编码区,连接EcoRI合成接头后插入到载体pUR222的EcoRI位点,转化受体菌后筛到一系列不同HBcAg表达水平的重组体。分析高表达和低表达重组体工作中,发现在同一乳糖启动子、核糖体结合部位(SD序列)和Lac Z基因N端第5氨基酸后连接的HBcAg基因,由于在ATG5′端上游—7至—35核苷酸区有一呈部分迥文的序列,当转录成mRNA时可形成一环茎二级结构,是否用BAL—31酶切除此结构对表达水平影响极大。高表达重组体HBcAg产量可占菌体总蛋白9%,低表达的只为其千分之一。本文并对此现象在原核细胞中表达真核基因的意义进行了讨论。 相似文献
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