Biosynthesis of 1-alkenes in the defensive secretions ofTribolium confusum (Tenebrionidae); stereochemical implications

Summary The terminally unsaturated hydrocarbons of the defensive secretion ofTribolium confusum are biosynthesized from fatty acids by oxidative decarboxylation. The process involves an enantiospecific cleavage of the C–H bond of thepro-(S) C(3)–H atom and simultaneous decarboxylation of the acid into an 1-alkene and carbon dioxide via ananti-periplanar transition state geometry (anti-elimination). The stereochemistry of this biotranformation is identical in all respects with the same reaction in higher plants. The mechanism seems to be of general importance for the biosynthesis of many vinylic substructures of natural products from oxygen-containing precursors.     

Blocking of lectin-like adhesion molecules on pulmonary cells inhibits lung sarcoma L-1 colonization in BALB/c-mice

Summary Adhesion and inhibition experiments with pulmonary cells of BALB/c-mouse origin and syngeneic sarcoma L-1 cells indicated that L-fucose specific lectin-like adhesion molecules, presumably situated on pulmonary cell surfaces are (at least partly) responsible for the specificity of this cell-cell interaction. Addition of specific sugars and glycoconjugates (L-fucose and fucoidan, respectively) to the incubation medium evidently inhibited the adhesion process as quantified using radiolabelled tumor cells. Unspecific carbohydrates (e.g. D-galactose) did not affect the cellular interaction. In vivo, repeated administration of fucoidan (but not of unspecific glycoconjugates) significantly inhibited the settling of metastatic sarcoma L-1 cells in the lungs of BALB/c-mice. Therefore, when lectin-like adhesion molecules on pulmonary cells were blocked with competitive glycoconjugates, tumor cell colonization of the lung could be significantly inhibited.     

(2+1)维KdV方程的Gramm解及其pfaffian化

给出（2＋1）维KdV方程的Gramm解，并应用P如P faffianization方法，推导出（2＋1）维KdV方程的耦舍系统及其Gramm型pfaffian解。     

人类基因组中L1元件及其5′UTR的研究

讨论了L1在人类染色体中的分布密度与染色体长度以及L1的密度与基因密度之间的关系.发现在大多数染色体上L1的密度和染色体的长度表现为正相关,而L1的密度和染色体中基因的密度表现为负相关;对人类L1的5′UTR进行了详细的研究后,发现在L1元件的5′UTR部分含有许多转录因子结合位点.对基因的转录起始位点上游进行统计分析,发现其中含有大量的L1序列.通过对人类的EST数据库进行BLAST分析,新发现了51条和人类L1 5′UTR相似性较高的EST片断,根据它们分布的组织特异性,说明L1元件可能调控与发育过程有关的基因的表达;最后应用多样性增量的方法对人类和大鼠的L1 5′UTR进行了区分,得到了较好的预测结果,说明大部分L1的5′UTR的调控作用是人类特有的.     

Tier1算法分析及其VLSI编解码复用结构设计

针对JPEG2000中Tier1编解码算法的复杂度高和硬件实现困难,提出一种Tier1编解码复用的VLSI体系结构。该结构改进了传统的位平面扫描方法和Tier1串行解码模式,充分利用了硬件资源,在通道并行处理的基础上实现编解码复用,具有很高的编解码效率和资源利用率。     

体能测试时间安排的优化模型

运用"黑箱思想"、"动态规划"和"0-1规划"的方法建立了一个动态优化模型.研究了如何合理安排各班体能测试时间的问题.     

GM(1,1)模型初始条件和初始点的优化

在对GM(1,1)模型的初始条件进行优化时,由于优化的目标函数为误差平方和最小,而模型的检验标准为平均相对误差最小,两个准则的不一致性导致优化效果不理想.本文以相对误差平方和最小为目标优化GM(1,1)模型,分别对初始条件和初始点进行优化,给出优化的计算公式,并证明在原始序列相对误差平方和最小的准则下,初始条件优化和初始点优化是统一的.实例表明运用优化公式与数值最优解计算得到的模型平均相对误差非常接近,且运用优化公式比数值解求解更方便.     

拟南芥翻译延伸因子EF1A的亚细胞定位研究

探讨了拟南芥的翻译延伸因子EF1A的亚细胞定位.以Col野生型拟南芥的cDNA为模板,通过高保真KOD扩增酶获得2 363bp的拟南芥转录延伸因子EF1A基因片段,将其与GFP融合后共同连入p1300表达载体,利用农杆菌侵染法将p35S∶GFP和p35S∶EF1A∶∶GFP转入野生型拟南芥中,观察转基因植物细胞中GFP的表达情况.结果显示:p35S∶GFP转基因植物中,细胞核中GFP荧光强度显著高于细胞质中荧光强度,但是在p35S∶EF1A∶∶GFP转基因植物中,细胞核中荧光强度与细胞质中荧光强度无显著差异,说明在进行蛋白翻译时细胞质中的EF1A含量显著高于细胞核中,这也为翻译延伸因子EF1A的亚细胞定位提供了实验依据.