上海高重复频率硬X射线自由电子激光装置(Shanghai HIgh repetition rate XFEL aNd Extreme light facility,SHINE)使用低温超导高频腔加速电子,电子能量可以到达8 GeV。对于SHINE的电子束团横向截面测量将使用丝扫描这种半拦截式的截...上海高重复频率硬X射线自由电子激光装置(Shanghai HIgh repetition rate XFEL aNd Extreme light facility,SHINE)使用低温超导高频腔加速电子,电子能量可以到达8 GeV。对于SHINE的电子束团横向截面测量将使用丝扫描这种半拦截式的截面测量方法,产生的次级粒子数量较拦截式测量方法(如截面靶小)可以减小超导腔失超的风险,但需要实现束损探测器的信号与电机位置同步采集。本文基于Zynq-UltraScale+型片上系统设计与实现了丝扫描系统数据采集系统,首先对该数据采集系统的实现方式作了详细描述,然后利用实验平台检验了电机位置测量的正确性,并验证了同步采集探测器信号和扫描丝位置的功能。实验结果表明:该数据采集系统可以满足SHINE丝扫描截面测量系统的运行要求。展开更多
B.Subtilis expression plasmids generally require a stringent Shine Dalgarno Sequence(SDS). Site directed mutagenesis was explored to change the Shine Dalgarno Sequence from AAAAATGGGG (mutant type) to AAAAAGGGGG (...B.Subtilis expression plasmids generally require a stringent Shine Dalgarno Sequence(SDS). Site directed mutagenesis was explored to change the Shine Dalgarno Sequence from AAAAATGGGG (mutant type) to AAAAAGGGGG (wild type) in recombinant plasmid PSM604. The single base substitution made the plasmid with wild SDS unstable in structure and segregation. The interaction of SDS with subtilisin leader sequence of PSM604 might be responsible for the instability of plasmid.展开更多
The Shine-Dalgarno (SD) sequence, when present, is known to promote translation initiation in a bacterial cell. However, the thermodynamic stability of the messenger RNA (mRNA) through its secondary structures has an ...The Shine-Dalgarno (SD) sequence, when present, is known to promote translation initiation in a bacterial cell. However, the thermodynamic stability of the messenger RNA (mRNA) through its secondary structures has an inhibitory effect on the efficiency of translation. This poses the question of whether bacterial mRNAs with SD have low secondary structure formation or not. About 3500 protein-coding genes in <i>Rhodobacter sphaeroides</i> were analyzed and a sliding window analysis of the last 100 nucleotides of the 5’ UTR and the first 100 nucleotides of ORFs was performed using <i>RNAfold</i>, a software for RNA secondary structure analysis. It was shown that mRNAs with SD are less stable than those without SD for genes located on the primary chromosome, but not for the plasmid encoded genes. Furthermore, mRNA stability is similar for genes within each chromosome except those encoded by the accessory chromosome (second chromosome). Results highlight the possible contribution of other factors like replicon-specific nucleotide composition (GC content), codon bias, and protein stability in determining the efficiency of translation initiation in both SD-dependent and SD-independent translation systems.展开更多
文摘上海高重复频率硬X射线自由电子激光装置(Shanghai HIgh repetition rate XFEL aNd Extreme light facility,SHINE)使用低温超导高频腔加速电子,电子能量可以到达8 GeV。对于SHINE的电子束团横向截面测量将使用丝扫描这种半拦截式的截面测量方法,产生的次级粒子数量较拦截式测量方法(如截面靶小)可以减小超导腔失超的风险,但需要实现束损探测器的信号与电机位置同步采集。本文基于Zynq-UltraScale+型片上系统设计与实现了丝扫描系统数据采集系统,首先对该数据采集系统的实现方式作了详细描述,然后利用实验平台检验了电机位置测量的正确性,并验证了同步采集探测器信号和扫描丝位置的功能。实验结果表明:该数据采集系统可以满足SHINE丝扫描截面测量系统的运行要求。
文摘B.Subtilis expression plasmids generally require a stringent Shine Dalgarno Sequence(SDS). Site directed mutagenesis was explored to change the Shine Dalgarno Sequence from AAAAATGGGG (mutant type) to AAAAAGGGGG (wild type) in recombinant plasmid PSM604. The single base substitution made the plasmid with wild SDS unstable in structure and segregation. The interaction of SDS with subtilisin leader sequence of PSM604 might be responsible for the instability of plasmid.
文摘The Shine-Dalgarno (SD) sequence, when present, is known to promote translation initiation in a bacterial cell. However, the thermodynamic stability of the messenger RNA (mRNA) through its secondary structures has an inhibitory effect on the efficiency of translation. This poses the question of whether bacterial mRNAs with SD have low secondary structure formation or not. About 3500 protein-coding genes in <i>Rhodobacter sphaeroides</i> were analyzed and a sliding window analysis of the last 100 nucleotides of the 5’ UTR and the first 100 nucleotides of ORFs was performed using <i>RNAfold</i>, a software for RNA secondary structure analysis. It was shown that mRNAs with SD are less stable than those without SD for genes located on the primary chromosome, but not for the plasmid encoded genes. Furthermore, mRNA stability is similar for genes within each chromosome except those encoded by the accessory chromosome (second chromosome). Results highlight the possible contribution of other factors like replicon-specific nucleotide composition (GC content), codon bias, and protein stability in determining the efficiency of translation initiation in both SD-dependent and SD-independent translation systems.
